Adsorption surface area increases due to fluidization, more free adsorption sites become reachable to the adsorbate Efficient mixing and good contact between adsorbent and adsorbate is ensured Pressure drop is almost constant and thus required pumping energy does not vary Temperature in the system can assumed to be uniform or constant No clogging or channeling takes place Dead zone, gas/ vapor pocket creation inside the bed can also be avoided.

q * → ΑΡ* ……….(1)

or q * → ΑC n ………. (2)

where p = Equilibrium pressure of adsorbate C = Equilibrium concentration of adsorbate in solution. A and n are constants for a given adsorbate and adsorbent at a particular temperature

2.8.2.2 Langmuir equation The Langmuir equation or Langmuir isotherm or Langmuir adsorption equation relates the coverage or adsorption of molecules on a solid surface to gas pressure or concentration of a medium above the solid surface at a fixed temperature. The equation was developed by Irving Langmuir in 1916. The equation is stated as: α.Ρ θ= 1 + σ.Ρ ……….. (3) θ or theta is the fractional coverage of the surface, P is the gas pressure or concentration, α alpha is a constant. The constant α is the Langmuir adsorption constant and increases with an increase in the binding energy of adsorption and with a decrease in temperature. Equation Derivation The equation is derived starting from the equilibrium between empty surface sites (S * ), particles (P) and filled particle sites (SP) S * + Ρ ↔ SΡ ………….(4)

The Equilibrium constant K is thus given by the equation:

K=

[ S Ρ] [[S * ][ Ρ]]

………... (5)

Because the number of filled surface sites (SP) is proportional to θ, the number of unfilled sites (S *) is proportional to 1-θ, and the number of particles is proportional to the gas pressure or concentration (P) the equation can be rewritten as: α=

θ

[1 − θ ] Ρ* …….. (6)

where α is a constant Rearranging this: θ = α(1 − θ)P θ = Pα − Pθα θ + Pθα = Pα θ(1 + Pα) = Pα θ=

α.Ρ ……….. (7) 1 + σ.Ρ

[Equation Fitting The Langmuir equation is expressed here as:

Κc …………….(8) 1+ Κc

φ = φmax

where K = Langmuir equilibrium constant, C* = aqueous concentration (or gaseous partial pressure), φ = amount adsorbed, and φmax = maximum amount adsorbed as c increases. The equilibrium constant is actually given by φmax :

φ (c = Κ

−1

)

φ ΚΚ −1 = φ max = max …………..(9) −1 2 1 + ΚΚ

The Langmuir equation can be fitted to data by linear regression and nonlinear regression methods. Commonly used linear regression methods are: Lineweaver-Burk, Eadie-Hofstee, Scatchard, and Langmuir. The double reciprocal of the Langmuir equation yields the Lineweaver-Burk equation: 1

φ

=

1

φmax

+

1 …………(10) φmax Κc

A plot of (1/ φ) versus (1/c) yields a slope = 1/( φmax K) and an intercept = 1/ φmax . The Lineweaver-Burk regression is very sensitive to data error and it is strongly biased toward fitting the data in the low concentration range. It was proposed in 1934. Another common linear form of the Langmuir equation is the Eadie-Hofstee equation: φ φ = φmax − …………….(11) Κc

A plot of ( φ) versus ( φ/c) yields a slope = -1/K and an intercept = φmax . The EadieHofstee regression has some bias toward fitting the data in the low concentration range. It was proposed in 1942 and 1952. Another rearrangement yields the Scatchard regression: φ = Κφmax − Κφ ……….(12) c

A plot of ( φ/c) versus ( φ) yields a slope = -K and an intercept = K φmax . The Scatchard regression is biased toward fitting the data in the high concentration range. It was proposed in 1949. Note that if you invert the x and y axes, then this regression would convert into the Eadie-Hofstee regression discussed earlier. The last linear regression commonly used is the Langmuir linear regression proposed by Langmuir himself in 1918: c

φ

=

c

φmax

+

1 Κφmax

………….(13)

A plot of (c/ φ) versus (c) yields a slope = 1/ φmax and an intercept = 1/(K φmax ). This regression is often erroneously called the Hanes-Woolf regression. The Hanes-Woolf regression was proposed in 1932 and 1957 for fitting the Michaelis-Menten equation, which is similar in form to the Langmuir equation. Nevertheless, Langmuir proposed this linear regression technique in 1918, and it should be referred to as the Langmuir linear regression when applied to adsorption isotherms. The Langmuir regression has very little sensitivity to data error. It has some bias toward fitting the data in the middle and high concentration range.

There are two kinds of nonlinear least squares (NLLS) regression techniques that can be used to fit the Langmuir equation to a data set. They differ only on how the goodness-of-fit is defined. In the v-NLLS regression method, the best goodness-of-fit is defined as the curve with the smallest vertical error between the fitted curve and the data. In the n-NLLS regression method, the best goodness-of-fit is defined as the curve with the smallest normal error between the fitted curve and the data. Using the vertical error is the most common form of NLLS regression criteria. Definitions based on the normal error are less common. The normal error is the error of the datum point to the nearest point on the fitted curve. It is called the normal error because the trajectory is normal (that is, perpendicular) to the curve. It is a common misconception to think that NLLS regression methods are free of bias. However, it is important to note that the v-NLLS regression method is biased toward the data in the low concentration range. This is because the Langmuir equation has a sharp rise at low concentration values, which results in a large vertical error if the regression does not fit this region of the graph well. Conversely, the n-NLLS regression method does not have any significant bias toward any region of the adsorption isotherm. Whereas linear regressions are relatively easy to pursue with simple programs, such as excel or hand-held calculators, the nonlinear regressions are much more difficult to solve. The NLLS regressions are best pursued with any of various computer programs. 2.9 Fluidized Bed A fluidized bed is formed when a quantity of a solid particulate substance (usually present in a holding vessel) is placed under appropriate conditions to cause the solid/fluid mixture to behave as a fluid. This is usually achieved by the introduction of pressurized fluid through the particulate medium. This results in the medium then having many properties and characteristics of normal fluids; such as the ability to free-flow under gravity, or to be pumped using fluid type technologies. The resulting phenomenon is called fluidization. Fluidized beds are used for several purposes, such as fluidized bed reactors (types of chemical reactors), fluid catalytic cracking, fluidized bed combustion, heat or mass transfer or interface modification, such as applying a coating onto solid items. 2.9.1 Properties of fluidized beds A fluidized bed consists of fluid-solid mixture that exhibits fluid-like properties. As such, the upper surface of the bed is relatively horizontal, which is analogous to hydrostatic behavior. The bed can be considered to be an inhomogeneous mixture of fluid and solid that can be represented by a single bulk density. Furthermore, an object with a higher density than the bed will sink, whereas an object with a lower density than the bed will float, thus the bed can be considered to exhibit the fluid behavior expected of Archimedes' principle. As the "density", (actually the solid volume fraction of the suspension), of the bed can be altered by changing the fluid fraction, objects with different densities comparative to the bed can, by altering either the fluid or solid fraction, be caused to sink or float. In fluidized beds, the contact of the solid particles with the fluidization medium (a gas or a liquid) is greatly enhanced when compared to packed beds. This behavior in fluidized combustion beds enables good thermal transport inside the system and good heat transfer between the bed and its container. Similarly to the good heat transfer, which enables thermal uniformity analogous to that of a well mixed gas, the bed can have a significant heat-capacity whilst maintaining a homogeneous temperature field

2.9.2 Application Fluidized beds are used as a technical process which has the ability to promote high levels of contact between gases and solids. In a fluidized bed a characteristic set of basic properties can be utilised, indispensable to modern process and chemical engineering, these properties include:  Extremely high surface area contact between fluid and solid per unit bed volume  High relative velocities between the fluid and the dispersed solid phase.  High levels of intermixing of the particulate phase.  Frequent particle-particle and particle-wall collisions 2.9.3 Fluidization Fluidization is defined as an operation through which fine solids are transformed into a fluid like state through contact with either a gas or a liquid. 2.9.3.1 The Phenomenon of Fluidization When a fluid is pumped upward through a bed of fine solid particles at a very low flow rate the fluid percolates through the void spaces (pores) without disturbing the bed. This is a fixed bed process. If the upward flow rate is very large the bed mobilizes pneumatically and may be swept out of the process vessel. At an intermediate flow rate the bed expands and is in what we call an expanded state. In the fixed bed the particles are in direct contact with each other, supporting each other’s weight. In the expanded bed the particles have a mean free distance between particles and the particles are supported by the drag force of the fluid. The expanded bed has some of the properties of a fluid and is also called a fluidized bed. First, we consider the behavior of a bed of particles when the upward superficial fluid velocity is gradually increased from zero past the point of fluidization, and back down to zero. At first, when there is no flow, the pressure drop zero, and the bed has a certain height. As we proceed along the right arrow in the direction of increasing superficial velocity, tracing the path ABCD, at first, the pressure drop gradually increases while the bed height remains fixed. This is a region where the Ergun equation for a packed bed can be used to relate the pressure drop to the velocity. When the point B is reached, the bed starts expanding in height while the pressure drop levels off and no longer increases as the superficial velocity is increased. This is when the upward force exerted by the fluid on the particles is sufficient to balance the net weight of the bed and the particles begin to separate from each other and float in the fluid. As the velocity is increased further, the bed continues to expand in height, but the pressure drop stays constant. It is possible to reach large superficial velocities without having the particles carried out with the fluid at the exit. This is because the settling velocities of the particles are typically much larger than the largest superficial velocities used.

Fig 1: Typical curves for a liquid-solid fluidized bed of particles of approximately uniform size. Now, if we trace our path backward, gradually decreasing the superficial velocity, in the direction of the reverse arrows in the figure, we find that the behavior of the bed follows the curves DCE. At first, the pressure drop stays fixed while the bed settles back down, and then begins to decrease when the point C is reached. The bed height no longer decreases while the pressure drop follows the curve CEO. A bed of particles, left alone for a sufficient length of time, becomes consolidated, but it is loosened when it is fluidized. After fluidization, it settles back into a more loosely packed state; this is why the constant bed height on the return loop is larger than the bed height in the initial state. If we now repeat the experiment by increasing the superficial velocity from zero, we’ll follow the set of curves ECD in both directions. Because of this reason, we define the velocity at the point C in the figure as the minimum fluidization velocity. 2.9.3.2 Calculation of fludization velocity the pressure drop over the fluidized bed is:

∆Ρ = ( ρ s − ρ f )(1 − ε ) Ηg …………….(14)

if the bed expand, the product (1- ε) will remain constant. Using the values of each term appropriate to the condition of incipient fluidization: ∆Ρ = ( ρ s − ρ f )(1 − ε mf )Η mf g ………….(15)

For fine particles the pressure drop velocity relationship can be found from Carman-Kozeny equation:

U mf =

ε mf

3

5(1 − ε mf

)

2

∆Ρ 1 …………….(16) S 2 µ Η mf

Hence from equation (14) and (15):

U mf =

ε mf 3

5(1 − ε mf

)

s

− ρ f )g

S 2µ

…..………..(17)

For uniform spherical particles, S = 6/d and taking εmf = 0.4 U mf = 0.00059

d2 g ( ρ s − ρ f ) µ …………….(18)

2.9.3.3 Expansion of a particulately fluidized bed When the superficial velocity of the fluidizing fluid is greater than the incipient velocity i.e. minimum fluidization velocity, the bed expands uniformly to take up the increased flow, the particles spacing themselves out so that the drag on each is equal to the net weight allowing for buoyance. Various authors have measured the expansion of bed. But the most convenient way of showing the variation of sedimentation velocity, or fluidizing velocity, with voidages is by means of correlating the Umf / Ut and ε, because when ε →1, U mf / Ut →1, since ε = 1 we have a single particle in an infinite fluid. According to the Richardson and Zaki the equation is on the basis of fluidization and sedimentation experiments: U mf Ui

= ε n …………………… (19)

Ui is the free falling velocity but it is slightly influenced by the ratio of the diameters of the particle and column (

d ) D

Therefore, for fluidization log U i = log U t −

d …………(20) D

And for index n is given by n = 4.65 +

d D

d   n =  4.4 + 18 ×  Re −0.03 D 

(Re < 0.2) (

0.2< Re < 1)

……. (21)

d   n =  4.4 + 18 ×  Re −0.1 D 

n = 4.4 Re

−0.1

n = 2.4

(1< Re < 200) (200 < Re < 500) (Re > 500)

2.10.4 Ash content It reduces the overall activity of activated carbon. It reduces the efficiency of reactivation. The metals (Fe2O3) can leach out of activated carbon resulting in discoloration. Acid/water soluble ash content is more significant than total ash content. 2.10.5 Apparent density Higher density provides greater volume activity and normally indicates better quality activated carbon.

2.10.6 Hardness/abrasion number It is a measure of the activated carbonâ&#x20AC;&#x2122;s resistance to attrition. It is important indicator of activated carbon to maintain its physical integrity and withstand frictional forces imposed by backwashing, etc. There are large differences in the hardness of activated carbons, depending on the raw material and activity level. 2.10.7 Particle size distribution The finer the particle sizes of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapor phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits. Chapter 3 Theoretical Development The mass transfer in the fluidized bed is characterized by the breakthrough curve, which is the response of an initially fresh bed to an influent containing the solute. The shape of the breakthrough curve depends upon the type of equilibrium isotherm, which in turn is the characteristic of the solute and adsorbent system. In addition, the breakthrough response is influenced by the different transport processes occurring in the bed and within the adsorbent particles. The following assumptions are made in present analysis: a. Perfect mixing of solids occurs and so q does not change with position but is a function of time; b. The adsorption isotherm corresponds to a Freundlich isotherm. CL

C (l) L

dl

F Co

Fig 2 Material balance relation for column

The mass balance over the whole fluidized bed is M

dq = F( C0 − C L ) dt

… … … … (22)

Here M is mass of adsorbent, F is the flow rate of liquid feed, C 0 is the initial feed concentration and CL is the concentration of liquid at the bed exit. The boundary conditions for the above equation are At t = 0, CL = C0, q = 0 The mass transfer processes that are considered here in representing single-component adsorption are (1) film diffusion from the fluid phase to the surface of the particle; (2) adsorption on the surface; (3) pore diffusion in liquid-filled pores on to the particle surface. The average mass flux in the bed across the phases is given by

(

)

N = KF C − C* =

F (C 0 − C L ) ………………….. (23) a

Here, KF is the overall mass transfer coefficient and a is the interfacial area available for mass transfer; C is the average solute concentration in liquid within the bed and is given by l

C=

∫ C (l )dl ; C* is the solute concentration of liquid in equilibrium with the solid phase 0

L and can be estimated from Freundlich isotherm as n

q C * =   ……………..(24)  A

Here C(l) is the liquid concentration along the bed at any moment of time. In absence of C(l) data along the bed length the average concentration within the bed is approximated as C≅

C0 + C L 2

……………………(25)

The overall mass transfer coefficient KF depends on the individual fluid phase and solid phase mass transfer coefficients and can be expressed as 1 1 1 = + KF kf mk s ……………(26)

Where m is the slope of equilibrium curve and can be obtained by rearranging the Freundlich equilibrium isotherm. kf and ks are fluid phase and solid phase mass transfer coefficients, respectively. The parameter kf depends on the Sherwood number which is defined as the ratio of the molecular mass transfer resistance to the convective mass transfer resistance in the fluid. The particle diameter is considered to be the most significant length in the mass transfer operation. The Sherwood number can be expressed by the following equation

kf dp

Sh =

De

… … 

A number of correlations are reported in terms of Sherwood number to estimate kf which are usually in the form of Sh = p ( Re ) ( Sc) x …………(28) q

Here p, q and r are empirical values and d p and De are particle diameter and effective diffusivity of the solute in the adsorbent, respectively. Reynolds number and Schmidt number are defined by the following equations: ρUd p ……… (29) µ µ Sc = ……….. (30) ρDe Re =

The internal or solid phase mass transfer coefficient is commonly expressed in terms of particle diameter and effective diffusivity. ks ≅

10 De …….(31) dp

Equations 22-31 are applicable for both fixed bed and fluidized bed adsorption. In fluidized bed the adsorption particles go into suspension and hence a larger surface area will be exposed to the solution. This will increase the mass transfer rate. Furthermore, the increased fluid velocity will increase the turbulence of the system. As seen from equations (24) – (31), an increase in turbulence results in an increase in the Reynolds number, which in turn increases the Sherwood number. The Sherwood number is directly proportional to the mass transfer coefficient and therefore an increase in the Sherwood number will increase the mass transfer coefficient and the overall mass transfer rate.

Chapter 4 Experimental 4.1 Experimental setup A set of experiments was undertaken to obtain the breakthrough curve and compare different operating conditions. The experimental layout is shown in Figure 3.

Fig 3. Equipment Layout

Fluid Outlet 1"

Sample outlet 5 cm Adsorption Bed 61 cm

1" Activated Carbon

8 cm

Fluid Inlet

Fig 4: Detailed of the fluidized bed The storage tank was used to keep the liquid at a constant initial calculated concentration. The pump supplied a constant flow to the rotameter and the adsorption bed. This flow was controlled by the rotameter which was calibrated before use to determine the flow rate. The calibration curve can be found in Appendix (A). The rotameter measured the flow rate, Q. Using the continuity equation: Q = VA and the cross sectional area of the fluidized bed, the velocity of the water was determined. Figure 3 shows a detailed layout of the adsorption bed. A glass made cylinder of 5 cm diameter and 61 cm height was used as the fluidization column. A dye solution of known concentration was made in 60 dm3 capacity plastic storage tank. This solution was then pumped by a 1 hp pump through the activated carbon bed via a rotameter. The flow rate through the fluidized bed was kept constant by adjusting the valve of the bypass line and the manually controlled valve of the main flow path. Samples were collected at a definite time interval from the exit point and exit solution was stored and then drained out from the tank. The storage tank was then washed to set up for a new run. The minimum fluidization velocity of the bed, Umf, has been determined via the classic plot of bed height (H) versus superficial velocity (U) for decreasing flow rates of water. As was mentioned earlier, the change in exit concentration occurs rapidly in the beginning and then slows down (the breakthrough curve). In order to capture the initial concentration changes,

samples were taken more frequently (every minute) for the first six minutes and less frequently afterwards (every two or five minutes). The parameter altered were the liquid flow rate, particle size of the activated carbon and inlet concentration of the solution. The concentration of the outlet solution was determined by a single cell, Shimadzu UV-1201 V spectrophotometer. 4.2 Adsorbents: Properties of Activated Carbon The activated carbon was collected from Graphics Textiles Ltd. Sreerampur, Dhamrai, Savar, Dhaka, Bangladesh. The carbon is of irregular granular form and made from bituminous coal. It was then grinded and screened to get the desired particle size. The specifications i.e Iodine value, Mithylene Blue, Ash content and Moisture content were supplied. Total surface area and pore volume of the carbon was determined in the laboratory. Some properties of adsorbents are listed in table 1: Table 1: Properties of Activated Carbon (Granular form) Total surface area, av (N2, BET method) Pore volume I.D M.B Ash content

273.80 m2/g 0.2198 m3/g 950 min 150% min 180% max 20% max

Moisture content

17.85 % max

4.3 Adsorbates 4.3.1 Colored Water The experiment was carried out with colored solution of reaction black dye (reactive dye). This dye is commonly used in textile industries as fabric color for cotton, wool and silk. Three concentrations of colored solutions were prepared 29.45 ppm, 23 ppm and 18.45 ppm. Most of the experiment was carried out at 23 ppm and 18.45 ppm. The reactive black dye has been supplied by â&#x20AC;&#x153;Dyesin Chemicalsâ&#x20AC;? located at Bijoynagar, Dhaka, Bangladesh.

The molecular structure of the reactive black dye used in sample solution is given below:

Fig 5: Structure of reactive black dye (Vinyl Sulfone Fiber Reactive Dye) Fig. 4.3.2 Industrial Effluent The experiment was also carried out with industrial effluent. The effluent (wastewater) was collected after the secondary stage effluent treatment section of Graphics Textiles Ltd. Sreerampur, Dhamrai, Savar, Dhaka, Bangladesh. Following parameters of the wastewater were measured before the experiment was done Table 2: Measurement parameters of the wastewater collected from Graphics Textiles Ltd. Parameter

Unit

Raw effluent, pH

Concentration 5.97

Raw effluent temperature

0

C

37

DO

ppm

2.30

Raw effluent BOD

ppm

210.6

Raw effluent COD

ppm

125.87

Total Dissolved Solids

ppm

1990

Total Suspended solids

mg/L

650.2

Turbidity

FAU

81

Color

pt-co

520 over

Conductivity

ms/cm

3.78

Sulphide (S-2)

mg/L

228

Chlorine (Cl2)

mg/L

0.36

NH3-N

mg/L

2.900 over

4.4 Equilibrium isotherms

Adsorption isotherm is established with various initial concentration (10-200 ppm) of dye solution (250 ml) by using a definite amount of activated carbon (5 gm) for different particle sizes. Solutions had been kept for twenty nine days at room temperature to ensure the establishment of equilibrium. 4.5 Analysis The concentration of dye of colored solutions was measured with Shimadzu UV-1201 V spectrophotometer at a wavelength 500nm. For industrial wastewater the calibration of the black reactive dye was used to approximate the total concentration of a number of unknown dyes present in the effluent.

Chapter 5 Results and Discussions 5.1 Isotherm The distribution of dye between the adsorbent and dye solution, at equilibrium, is important to determine the capacity of the granular activated carbon. An adsorption isotherm was generated with three different particle sizes of granular activated carbon as shown in fig. 6. The figure shows that the isotherm rises rapidly initially and flattens at higher equilibrium concentration. The results also indicate that there is no significant effect of particle size on the equilibrium capacities A number of equations exist which enable the equilibrium data to be correlated and two most frequently used, for dilute solutions, are the Langmuir and Freundlich isotherms but in this experiment adsorption equilibrium were described with the Freundlich isotherm (equ.2). The parameters in these equations are very useful for predicting adsorption capacities and also for incorporating into mass transfer relationships in the design of contacting equipment.

Fig 6 : Adsorbtion isotherm for dye solution for different sizes of activated carbon The parameters in the adsorption isotherms were estimated from the experimental equilibrium data. The parameters of the Freundlich model are represents as A = 14.779 (mg g1 (mg dm3)-1/n), n = 0.9477 and R2 = 0.99.

5.2 Fluidized Bed Characteristics The fig. 7 is the bed height (H) versus superficial velocity, (U) for decreasing flow rates of water. According to established convention, minimum fluidization velocity is defined by the intercept of the horizontal line representing the fixed bed height for a bed that has just been defluidized and the extension of the inclined line corresponding to the fall in fluidized bed height for decreasing flow rates.

Fig.7: Bed height of the fluidized bed at different velocity For three particle size Umf and U are calculated by using the equation (17) to (20)

The experimental minimum fluidization velocity (U mf) and velocity at maximum bed height can be read directly from fig.7. Table 3: Fluidized bed properties Particle size (mm) 0.84 mm - 0.71 mm 1 mm - 0.84 mm 1.3 mm - 1.15 mm 1 mm (Theoretical)

Minimum fluidization velocity (m/s) 0.01699 0.01698 0.0194 0.0112

Velocity at Maximum bed height (m/s) 0.0724 0.0726 0.0725 0.0725

Adsorption tests with the fluidized bed were carried out using three arbitrarily selected fluidizing velocities. In practice the fluidizing velocity is chosen to expand the bed to a large enough extent to avoid bed clogging. Both concentration and particle size distribution of the incoming suspended solids affect this choice. 5.3 Breakthrough Curves 5.3.1 Effect of Liquid Velocity Figure 8 shows the effect that changing velocity on the concentration of treated solution. It can be seen that the increase in velocity lowers the slope of the breakthrough curve leading to better initial dye removal and longer saturation time. The slope of the breakthrough curve is highest for 0.0254 m/s and lowest for 0.034 m/s, thus the performance of the fluidized bed was found highest for liquid velocity 0.034 m/s. However, increasing velocity further may or may not improve the color removal capacity of the fluidized bed since it reduces the residence time of the fluid in the bed which affects the mass transfer rate adversely.

Fig 8: Effect of velocity change on the concentration of treated solution 5.3.2 Effect of Adsorbent Particle Size The effect of particle diameter on the concentration of the treated solution at constant velocity is shown in Figure 9. It is observed that a reduction in particle size the range 1.3-1.15 mm to 1-0.84 mm gives a better removal of dye and a prolonged adsorption of material. For smaller particle adsorption is better as exposed surface area to the solution is more for same amount of carbon and also it takes longer time to get exhausted. For comparatively larger sizes (1 -0.84 mm and 1.3-1.15 mm) the effect of size reduction is less prominent.

Fig 9: Effect of particle size on the concentration of treated solution 5.3.3 Effect of Liquid Inlet Concentration Figure 10 shows the effect of the feed solution on colored removal. The initial concentrations used for the feed solutions were 29.45 ppm, 23 ppm and 18.45 ppm. For higher initial concentration decrease in concentration of the treated water is less significance than that for the lower initial concentration.

Fig 10: Effect of Initial Concentration treated solution This would be expected as an increase in concentration means there is more material to be adsorbed. Since the amount of carbon and the velocity were constant for this experiment, the particles would adsorb the same amount of dye before becoming saturated. Thus the experiments were higher concentration reaches saturation before the lower one, as shown in Figure 10.

5.4 Mass Transfer Analysis 5.4.1 Estimation of overall mass transfer co-efficient, KF By rearranging equation (23) following expression for KF is obtained. a  C − CL  ΚF =  o  …………….. (32) F  C − C*  a = av × M

F and Co are known. The data of CL vs. t are obtained from the breakthrough curves. C* is obtained from Freundlich Isotherm equn(2) once the q values for different time are calculated. By integrating equation (22) we get q

q = ∫ dq = 0

F M

t

∫ (C

o

− C L )dt ……..(33)

0

Here Co is constant for a particular run and CL varies with time. Thus by putting in all the values in equation (32) KF for each run are calculated. 5.4.2 Overall mass transfer coefficient at different velocities and particle size Fig. 11-14 presents the overall mass transfer coefficient for different velocities and particle size with respect to time and q (mg of dye solution per gm of activated carbon). As expected from the breakthrough curves K F increases with increasing liquid velocity and decreasing particle size. This can be explained by the equations (26)-(31). K F is a function of kf , ks and slope of the isotherm m. kf is a function of liquid velocity and particle size wheras ks is a function of particle size only. For fixed flow rate and particle size KF decreases with time and q.

Fig 11: Overall mass transfer coefficient at fluid phase vs. amount adsrobed for various velocities of dye solutions

Fig 12: Overall mass transfer coefficient at fluid phase vs. time for various velocities of dye solutions From fig. 11 and 12, it is observed that increased in fluid velocity will increase the turbulence of the system. As seen from equations (24) â&#x20AC;&#x201C; (31), an increase in turbulence results in an increase in the Reynolds number, which in turn increases the Sherwood number. The Sherwood number is directly proportional to the mass transfer coefficient and therefore an increase in the Sherwood number will increase the mass transfer coefficient and the overall mass transfer rate

Fig 13: Overall mass transfer coefficient at fluid phase vs. amount adsrobed for various particle size changes

Fig 14: Overall mass transfer coefficient at fluid phase vs. time for various particle sizes It is observed from fig.13 and 14 that increasing mean particle diameter results in an increase in the overall mass transfer coefficient. The fact is, for small particles a large external surface

area is presented to the adsorbate molecules, which result in a lower driving force per unit surface area for mass transfer than when larger particles are used. Since C is constant and the mass of carbon is constant, the external particle area increases as particle size decrease. If velocity and particle size remain fixed KF depends only on m. As time passes, the average concentration of the colored water as well as the amount of adsorbed solute in the bed increases and corresponding m decreases. Consequently from (equ n 26) overall mass transfer coefficient KF decreases. 5.5 Sample run with industrial wastewater treatment Fig 15 and 16 present the breakthrough curves for industrial wastewater collected after secondary treatment. The curves show similar trend of dye removal to those obtained for the prepared solution of black dye, i.e. the dye removal performance improves with increasing effluent velocity and decreasing particle size of the activated carbon.

Effect of Velocity change (Particle size: 1 mm - 0.84 mm, amount of activated carbon 100 gm) 27

Initial Concentration: 26.45455 ppm

Concentration (ppm)

25

23

21 0.034 m /s 0.0254 m/s 0.017 m /s 19 0

9

18 Tim e (m in)

Fig 15: Effect of velocity change on concentration of exit solution

27

Effect of paticle size (velocity- 0.0254 m/ s, Amount of activated carbon- 100 g)

27

Initical concentration: 26.45455 ppm

26

Concentration, ppm

25 24 23 22 21 20

0.84 m m - 0.71 m m 1m m - 0.84 m m

19

1.3 m m -1.5 m m

18 0

5

10

15

Time, min

20

25

30

Fig 16: Effect of change of particle size on concentration of exit solution Different parameters such as color, turbidity, total suspended solids (TSS) and Total dissolved solids (TDS), BOD; COD etc of the wastewater after the adsorption treatment were measured in the laboratory and are presented in table 4. All the parameters after treatment were found to be within the acceptable limit.

Table 4: Measurement parameters of the treated water collected from Graphics Textiles Ltd.

Parameter

Temp.

Units

0

C

pH

0.84-0.71 mm

1-0.84 mm

1.3-1.15 mm

29.5

28.5

29.5

7.97

8.07

Place of Discharge Subsoil Water

Sewerage Irrigation Canal Land

8.00

6~9

6~9

6~9

DO

ppm

4.5

4.5

4.5

4.5~8

4.5~8

4.5~8

COD

ppm

125.57

125.87

125.87

200

400

400

Total Suspended ppm Solids Total Dissolve ppm Solids (TDS) BOD ppm

142.8

149.4

149.4

150

500

200

1620

1580

1310

2100

2100

2100

17

19

20

50

250

100

Turbidity

FAU

104

94

68

Color

Pt.-Co 520 over

380

397

400

400

400

Conductivity

3.08

3.58

Chlorine (Cl2)

mS/c 3.24 m mg/L 0.16

0.17

0.16

Sulphide ( S-2)

mg/L 120

268

231

NH3

mg/L 2.315 NH3- 1.859 1.642 N NH3-N NH3-N

CHAPTER 6 Conclusion The applicability of fluidized bed in decolorizing wastewater was explored here. The findings and observations of the present study are summarized below. 1. Physical properties and equilibrium isotherm of the activated carbon in reactive black dye, supplied by local wastewater treatment plant, were determined. The isotherm was modeled with Freundlich equation and the constants were determined by fitting the equation in the experimental data. 2. Bed heights at different fluidization velocity of the fluidized bed for three different particle sizes were determined. 3. Breakthrough curves (concentration of the treated solution versus time) for prepared dye solution were obtained. Initial dye concentration, liquid velocity and adsorbent particle size were varied. It was observed that the color removal performance of the fluidized bed system improved with increasing velocity and decreasing particle size. 4. The over all mass transfer coefficients of the fluidized bed for each run were determined and presented with respect to time. 5. Experiment was also carried out using industrial effluent collected after the secondary stage treatment section. Various parameters of the effluent were measured in the laboratory before and after the experiment, which shows that the color removal achieved by the adsorption in the fluidized bed brought the color content of the wastewater from an unacceptable level to a satisfactory level. The main advantage of fluidized bed over fixed bed is the continuous movement of the adsorbent particles that facilitates maximum utilization of the adsorbent surface and leads to less frequent regeneration of it. The present study investigates the adsorption characteristics of commercially available low cost activated carbon currently used by some of the local industries as well as explores the fluidized bed technique for color removal. The investigation shows satisfactory result under the experimental conditions. In order to optimize the process for industrial application further investigation, however, is needed for optimization of different parameters such as the optimum amount of adsorbent per unit volume effluent water, optimum velocity and particle size etc. CHAPTER 7 Recommendations To improve the results of the experiments a double cell spectrophotometer could be used as it compares the sample with a standard for every reading. An on-line monitor can be used to measure the instantaneous concentration over the length of the experiment. This would provide more accurate results as there would be fewer errors in fitting the curve of best fit.

Although this study was concentrating on the use of a fluidized bed, further study could include using a range of different types of adsorbents and dye to determine the most effective way to remove the unwanted color. This could include activated alumina, sawdust and palmfruit bunch particles, tuberose sticks etc. This should be undertaken when removal of a specific dye is required. CHAPTER 8 References Ahsan Habib, Zahidul Hasan, A.S.M. Shajedur Rahman and A.M. Shafiqul Alam, “Tube Rose Sticks as an Adsorbent in the Removal of Mythylene Bluefrom Aquous Solution”, Pak.J.Anal. and Envir. Chem. Vol. 7, No.2, (2006) p. 112-115 A.K. Bhattacharya, C. Venkobachar, J. Environ. Eng. ASCE Vol.110 (1984) p.110. Allen et. al., “Effect of Carbon Surface Chemistry on the Removal of Reactive Dyes from Textile Effluent” Wat. Res. Vol. 34, No. 3,(2000) p. 927-935 Asilian, H.; Moradian fard, Sh.; Rezaei, A.; Mortazavi, S.B., Khavanin, A., “The Removal of Color and COD from wastewater containing water base color by Coagulation Process”, Int. J. Environ. Sci. Tech., Vol.3(2), (2006), p153-157 B.K. Singh, N.S. Rawat, J. Chem. Technol. Biotechnol. Vol.61, (1994), p.307 Carr.K., “Reactive dyes, especially bi-reactive molecules: structure and synthesis”, In: Peters, A.T., Freeman, H.S. (Eds.), Modern Colorants: Synthesis and Structure. Blackie Academic and Professional, London, (1995), p. 87–122. C. Namasivayam, K. Kadirvelu, Bioresource Technol. Vol.48, (1994) p.79. Choy, K.K.H.; McKay, G.; Porter, J.F., “Sorption of acid dyes from effluent using activated carbon”. Resour. Conserv. Recycl., Vol.27, (1999). p.57-62. CoupalB, Lalancette JM. The treatment of waste waters with peat moss. Water Res Vol.10, (1976), p.1071–6. Couillard D. “Appropriate wastewater management technologies using peat.” J Environ Syst Vol.21, (1991), p.1–20. Couillard D. “The use of peat in wastewater treatment”Water Res Vol.28, (1994), p.1261–74. Dimitrios Chatzopoulos and Arvind Varma, “Aqueous-Phase Adsorption and Desorption of Toluene in Activated Carbon Fixed Beds: Experiments and Model”, Chemical Engineering Science, Vol. 50, No. 1, (1994)p. 127 141 F. Kargi and S. Eyiisleyen, “Batch biological treatment of synthetic wastewater in a fluidized bed containing wire mesh sponge particles”, Enzyme and Microbial Technology Vol.17, (1995), p.119-123 Fetting and Sontheimer, “ Kinetics of Adsorption on Activated Carbon”, Journal of environmental engineering 102783, 0733-9372, (1987), p. 764-779, 1987

material,” J. Chem. Tech. Biotech., Vol.32, (1982), p.749-755. Pierce, J., “Colour in Textile Effluents—the origins of the problem” Journal of the Society of Dyers and Colourists, Vol.110,(1994), p.131–133 Qingye Sun and Linzhang Yang, “The Adsorption of Basic Dyes from Aqueous Solution on Modified Peat–Resin particle”, Water Research, Vol.37 (2002), p. 1535–1544 R.S. Juang, R.L. Tseng, F.C. Wu, J. Environ. Sci. Health A, Vol. 31, (1996), p.325 R. Denold, “Technology for dyeing. Wadale, Bombay: Technology of Textile processing” Sevan publications. Vol. XI, (1984). R.A. R. A. Corrêa, L.A. Calçada and R.P. Peçanha, “Development of a Fluidized Bed System for Adsorption of Phenol from Aqueous Solutions with Commercial Microporous resins,” Brazilian J. Chem. Eng., vol. 24, no.1, (2006), p15-18 Rong-Chi Wang, Chien-Chung Kuo and Chja-Cheng Shyu, “Adsorption of Phenols onto Granular Activated Carbon in a Liquid.Solid Fluidized Bed J. Chem. Tech. Biotechnol., Vol.68,(1996), p.187-94 Ruey-Shin, Feng-Chin and Ru-Ling, “Mechanism of Adsorption of Dyes and Phenols from Water Using Activated Carbons Prepared from Plum Kernels”, Journal of Colloid and Interface Science, Vol.227, (2000), p.437–444 S.K. Khare, K.K. Panday, R.M. Srivastava, V.N. Singh, J. Chem. Technol. Biotechnol. Vol.38, (1987), p.99. Steankenrichter, I., Kermer, W.D., “Decolorizing Textile Effluents”, Journal of the Society of Dyers and Colourists, Vol.108,(1992), p.182–186 S. Veeraraghavan, L.T. Fan and A.P.Mathews, “Modeling Adsorption in Liquid-Solid Fluidized Beds”, Chemical Engineering Science. Vol. 44. No. 10, (1989), p.23332344, Song et. al. , “Fundamentals of Hydrodynamics and Mass Transfer in a Three-Phase Fluidized Bed System”, Chemical Engineering Science Vol.54, (1999), p.4967-4973 Tim Robinson, Geo. McMullan, Roger Marchant, Poonam Nigam, “Remediation of Dyes in Textile Effluent: a Critical Review on Current Treatment Technologies with a Proposed Alternative”, Bioresource Technology, Vol.77, (2000), p.247-255 Vinod and Reddy, “Mass Ttransfer Correlation for Phenol Biodegradation in a Fluidized Bed Bioreactor”, Journal of Hazardous Materials, Vol. B136, (2006), p.727–734 Wright and Glasser, “Modeling Mass Transfer and Hydrodynamics in Fluidized-Bed Adsorption of Proteins”, AIChE Journal, Vol. 47, No. 2, (February 2001) Yoshitaka Sudo and Dragoslay M. Misic, “Concentration Dependence of Effective Surface

Diffusion Co-efficients in Aqueous Pase Adsorption on Activated Carbon”, Chemical Engineering Science, Vol. 33, (1977), p.1287-1290 CHAPTER 9 Appendices Appendix A: Calibration Curves Calibration Curve of Spectrophotometer: Data for the calibration curve of UV-VIS spectrophotometer by using reaction black ATM solution for λ= 500 nm Concentration of solution Absorbance (ppm) 100 80 60 50 40 30 20 10 5 4 3 2 1

0.988 0.925 0.667 0.59 0.52 0.387 0.26 0.188 0.145 0.108 0.109 0.102 0.085

Calibration curve of UV-VIS spectrophotometer (UV-1201) for Reaction black ATM solution (For 位-500nm) 1.2

1 y = 0.0111x R2 = 0.9539

Absorbance

0.8

0.6

0.4

0.2

0 0

20

40

60

80

100

Concentration (ppm)

Figure 17: Calibration Curve of UV-VIS Spectrophotometer for Raction Black solution

(a)

120

(b) Fig 18 (a) UV-VIS Spectrophotometer (UV 1201) (b) Cell section of the spectrophotometer Calibration for measuring of total surface area and pore volume Before beginning calibration , ensure that: 1 At least one empty sample holder is in place 2 The SMAPLE SELECT knob is set to the TEST for that location 3 The DELAY knob is on LONG 4 The PATH SELECT knob is on SAMPLE 5 A Dewar of liquid nitrogen or other cryogen is positioned about a loop of the gas delivery tube if the dryness of the 30%N2 /70% He gas is questionable 6 The N2/He gas is flowing such that flowmeter indicates 16 7 The DET, X1 and REL COND. Push buttons are pressed. Now start calibration 1

Fill the 1ml precision syringe wth nitrogen gas by holding the needle tip immediately about the level of liquid nitrogen in Dewar, the evaporating liquid providing an atmosphere of pure nitrogen. Flush the syringe a few times to be sure of obtaining a proper fill. Wipe the needle tip free of accumulated frost and lay the syringe aside, perhaps on the rubber mat of the instrument, allowing the gas inside the syringe to reach room temperature.

2

Zero the instrument display using, as appropriate, the COARSE and FINE ZERO knobs. Observe the display for a few minutes to establish syetem stability.

3 4

Pres the PEAK AREA and CLEAR DISPLAY push buttons. Adjust the syringe to the 1 ml mark and insert the needle in the septum at INJECT, being sure to push it all the way in. Inject the gas at a moderate rate. Withdraw the needle when the syringe is completely dischargerd.

5

The greshold light will begin flashing and the indicator will acumultating surface area information after approxiamately 5 minutes. The rates of flashing will increse and then dercrease. When the THRESHOLD light registers no flash for 15 to 20 seconds, which will typically occure after about 3 minutes, the accumulation may be considered complete. Another check for completeness is the number displayed when the DET. Pursh button is pressed, it should be 0.02 or less. The number displayed by the indicator with the PEAK AREA button pressed is now set with the CALIBRATE contrl knob beside the indicator to read the value for S as calculated by using the following equation:

6

S =V

273.3 Atm. Pr essure 6.023 ×10 2 ×16.2 ×10 −20 RoomTemp. 760 22.414 ×10 3

…………..(33)

 % N 2  Atm. Pr ess  1−   = V .const. ………………..(34)  100  Sat. Pr ess 

Where S is the surface are in square meters. The instrument is now calibrated. Measurement of Total Surface Area and Pore Volume We have used N2 BET method for measuring the total surface area Procedure: At first we sieve the granular activated carbon to a mesh size 16 to 25. Then take 0.5gm from there and dry it to 120 oC approximate at 1 hour for the purposes of remove moisture or water from the carbon pore. Again take weight. There are three sample gas which to be passed in the activated carbon sample for measuring surface area. The three sample gases are: Sample gas 1: He = 85% N2 = 15%

Sample gas 2: He = 70% N2 = 30%

Sample gas 3: He = 50% N2 = 50%

First sample gas 1 is passed through the activated carbon kept in the analyzer. When the Detector is in stable condition we fill liquid N2 in the Dewar and are passing it to the analyzer with 15% N2. Observed how much adsorption takes places and its reading (peak area) are taken from the Detector. Monolayer is form in the sample activated carbon. Now Dewar (liquid N2) reject from the analyzer and passed same amount of liquid N2 into the sample (activated carbon) and observed that how much desorption take places and again its reading are taken (peak area) from the Detector. In this way we passed sample gas 2 and sample gas 3 through the analyzer and collecting peak area from the Detector. From the adsorption and desorption we can calculate total surface area of activated carbon and using the equation 33: Where S is the surface are in square meters. For measuring total pore volume, we passed 100% N2 throughout the analyzer and then passed (95% N2 + 5% He) mixture again. Then we calculate pore volume from the equation: V =

273.2  Atm. Pr ess  ×  × 0.00155 ×100 × v ……………..(35) RoomTemp.  760 

Where v = gas volume

Appendix B: Raw Data For measuring Bed Height: Area, A= Ď&#x20AC;D2/4 D= 5cm Data for bed height of the fluidized bed at different velocity Sr. no. Flow rate Particle size Lit/min 25 mesh 2o mesh 18 mesh

16 mesh

0.701 mm

0.883 mm

0.992 mm

1.18 mm

1

0

4.25

4

3.875

3.75

2

0.5

4.25

4

3.875

3.75

3

0.8

4.25

4

3.875

3.75

4

1

4.25

4

3.875

3.75

5

1.5

4.25

4

3.875

3.75

6

2

4.375

4.25

3.9375

3.75

7

2.5

4.5

4.625

4

3.875

8

3

4.75

4.75

4.125

4.875

9

3.5

5

5

4.375

5

10

4

5.375

5.125

5.25

5.125

11

4.5

6

5.25

5.9375

5.75

12

5

6.75

6.8125

7

6.125

13

5.5

7.75

7.125

7.125

7.625

14

6

8.5

8.1875

8.8125

8.375

15

6.5

10

11.8125

11.625

9.9375

16

7

12.25

14.9375

13.8125

12.125

17

7.5

15.75

16.125

16.9375

15.6875

18

8

18.25

18.125

17.625

17.125

19

8.5

Fluidized

Fluidized

19

19.25

20

9

Fluidized

Fluidized

Adsorption Isotherm Data From Calibration Curve of Spectrophotometer, x=y/0.011 Data taken after 29 days activated carbon = 5.02 gm mesh size: -18+20 ( 1 mm --0.84 mm ) Data for adsorption isotherm for dye solution for different sizes of activated carbon Ce C0 absorbence x=y/0.011 (c0-ce) Q = (c0-ce)/m 11.2792 2.24686 12 0.008 0.720721 8 8 18.7090 3.72689 19.7 0.011 0.990991 1 4 32.6486 6.50371 34 0.015 1.351351 5 5 40.3783 8.04350 42 0.018 1.621622 8 2 48.2882 9.61918 50 0.019 1.711712 9 1 12.5892 65 0.02 1.801802 63.1982 8 13.5458 80 0.022 2 68 2 87.3636 17.4031 90 0.029 2.636364 4 1 106.636 110 0.037 3.363636 4 21.2423 28.6852 150 0.066 6 144 6 181. 34.2031 7 0.11 10 171.7 9 210. 196.254 39.0945 8 0.16 14.54545 5 3 mesh size: -20+25 ( 0.84 mm -- 0.71 mm) Ce C0 absorbence x=y/0.011 (c0-ce) 15

0.009

0.818182

14.18

23.8 34

0.011 0.019

1 1.727273

22.80 32.27

47

0.021

1.909091

45.09

55 65.3

0.023 0.03

2.090909 2.727273

52.91 62.57

Q = (c0-ce)/m 2.82506 3 4.54183 3 6.42883 8.98225 3 10.5396 6 12.4646

81.7 115.4 9

0.037

3.363636

78.34

0.068

6.181818

109.31

140.4

0.089

8.090909

132.31

161.6

0.096

8.727273

152.87

182.3

0.12

10.90909

171.39

200.5

0.15

13.63636

186.86

9 15.6048 5 21.7745 4 26.3563 9 30.4527 3 34.1416 2 37.2238 3

mesh size: -14+16 ( 1.3 mm -- 1.15 mm) Co 12.2 20.8 31 40.9 51 67 82.5 112.4 142.7 167.1 181.6 201.5

Absorbence Ce 0.63063 0.007 1 0.81081 0.009 1 1.17117 0.013 1 1.71171 0.019 2 1.98198 0.022 2 2.61261 0.029 3 3.09090 0.034 9 3.72727 0.041 3 5.36363 0.059 6 8.81818 0.097 2 0.11 10 13.3636 0.147 4

Co-Ce

(Co-Ce)/m

11.56937

2.27439

19.98919

3.92962

29.82883

5.863967

39.18829

7.703918

49.01802

9.636317

64.38739

12.65774

79.40909

15.61327

108.6727

21.36703

137.3364

27.00282

158.2818 171.6

31.12108 33.73968

188.1364

36.99103

Data of Dye Solution: Particle size: -14+16 mesh (U.S standard) Run-1 Amount of activated carbon = 80g Concentration of stock solution = 18.45 ppm Flow rate = 2 dm3/min Time (min) 0.5 1 2 3 4 6 9 12 15 18 21 22

Absorbance 0.177 0.179 0.182 0.179 0.187 0.196 0.2 0.188 0.19 0.197 0.198 0.204

Concentration (g/l) 16.09 16.27 16.55 16.27 17.00 17.82 18.18 17.09 17.27 17.91 18.00 18.55

Particle size: -18+20 mesh (U.S standard) Run-2 Amount of activated carbon = 80g Concentration of stock solution = 18.45 ppm Flow rate = 2 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.115

10.45

1

0.139

12.64

2

0.149

13.55

3

0.16

14.55

4

0.162

14.73

6

0.169

15.36

8

0.172

15.64

10

0.175

15.91

13

0.179

16.27

16

0.174

15.82

19

0.178

16.18

22

0.186

16.91

25

0.187

17.00

31

0.188

17.09

34

0.189

17.18

37

0.189

17.18

Run-3 Amount of activated carbon = 80g Concentration of stock solution = 18.45 ppm Flow rate = 3 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

1 2 3 4 6 8 11 14 15 17 20

0.168 0.172 0.182 0.18 0.189 0.185 0.186 0.194 0.198 0.203 0.2

15.27 15.64 16.55 16.36 17.18 16.82 16.91 17.64 18.00 18.45 18.18

Run-4 Amount of activated carbon = 80g Concentration of stock solution = 23 ppm Flow rate = 2 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.21

19.09

1

0.215

19.55

2

0.217

19.73

3

0.22

20.00

4

0.217

19.73

6

0.221

20.09

8

0.223

20.27

10

0.224

20.36

13

0.224

20.36

16

0.227

20.64

19

0.229

20.82

22

0.236

21.45

25

0.238

21.64

28

0.24

21.82

31

0.245

22.27

34

0.247

22.45

Run-5 Amount of activated carbon = 80g Concentration of stock solution = 23 ppm Flow rate = 3 dm3/min Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.202

18.36

1

0.207

18.82

2

0.211

19.18

3

0.213

19.36

4

0.222

20.18

6

0.225

20.45

9

0.227

20.64

12

0.228

20.73

15

0.236

21.45

20

0.2376

21.6

25

0.2409

21.9

30

0.24354

22.14

34

0.2453

22.3

Time (min)

Run-6 Amount of activated carbon = 80g Concentration of stock solution = 23 ppm Flow rate = 4 dm3/min Time (min)

Absorbance

0.5

0.214

Concentration (ppm) (From calibration curve) 19.45

3

0.232

21.09

6

0.232

21.09

9

0.244

22.18

12

0.234

21.27

15

0.244

22.18

18

0.248

22.55

21

0.25

22.73

24

0.252

22.91

27

0.249

22.64

30

0.252

22.93

Run-7 Amount of activated carbon = 80g Concentration of stock solution = 29.45 ppm Flow rate = 2 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.293

26.64

2

0.293

26.64

3

0.298

27.09

4

0.294

26.73

12

0.3

27.27

15

0.299

27.18

18

0.295

26.82

21

0.297

27.00

24

0.305

27.73

27

0.308

28.00

30

0.308

28.00

Particle size: -20+25 mesh (U.S standard) Run-8 Amount of activated carbon = 80g Concentration of stock solution = 18.45 ppm Flow rate = 3 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.131

11.91

1

0.145

13.18

2

0.145

13.18

3

0.146

13.27

4

0.15

13.64

6

0.161

14.64

9

0.165

15.00

12

0.167

15.18

15

0.169

15.36

18

0.172

15.64

21

0.177

16.09

24

0.188

17.09

27

0.2

18.18

Industrial Effluent Data: Particle size: -14+16 mesh (U.S standard) Run-1 Amount of activated carbon = 100g Industrial Effluent Concentration = 0.291 ppm or 26.45455 mg/l Flow rate = 3 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.231

20.81081

1

0.239

21.53153

2

0.251

22.61261

5

0.263

23.69369

7

0.276

24.86486

9

0.277

24.95495

12

0.284

25.58559

15

0.287

25.85586

18

0.288

25.94595

21

0.29

26.12613

23

0.29

26.12613

Particle size: -18+20 mesh (U.S standard) Run-2 Amount of activated carbon = 100g Industrial Effluent Concentration = 0.291 ppm or 26.45455 mg/l Flow rate = 4 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.22

20

1

0.231

21

2

0.237

21.54545

5

0.241

21.90909

7

0.249

22.63636

9

0.251

22.81818

12

0.253

23

15

0.257

23.36364

18

0.261

23.72727

21

0.269

24.45455

24

0.278

25.27273

26

0.29

26.36364

Particle size: -18+20 mesh (U.S standard) Run-3 Amount of activated carbon = 100g Industrial Effluent Concentration = 0.291 ppm or 26.45455 mg/l Flow rate = 3 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.224

20.36364

1

0.233

21.18182

2

0.243

22.09091

5

0.251

22.81818

7

0.259

23.54545

9

0.263

23.90909

12

0.267

24.27273

15

0.269

24.45455

18

0.275

25

21

0.281

25.54545

23

0.288

26.18182

Particle size: -18+20 mesh (U.S standard) Run-4 Amount of activated carbon = 100g Industrial Effluent Concentration = 0.291 ppm or 26.45455 mg/l Flow rate = 2 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.23

20.72072

1

0.242

21.8018

2

0.253

22.79279

5

0.268

24.14414

7

0.278

25.04505

9

0.281

25.31532

12

0.288

25.94595

15

0.289

26.03604

18

0.289

26.03604

21

0.291

26.21622

0.5

0.23

20.72072

Particle size: -20+25 mesh (U.S standard) Run-5 Amount of activated carbon = 100g Industrial Effluent Concentration = 0.291 ppm or 26.45455 mg/l Flow rate = 3 dm3/min Time (min)

Absorbance

Concentration (ppm) (From calibration curve)

0.5

0.207

18.81818

1

0.211

19.18182

2

0.219

19.90909

5

0.23

20.90909

7

0.237

21.54545

9

0.242

22

12

0.25

22.72727

15

0.249

22.63636

18

0.251

22.81818

21

0.253

23

23

0.263

23.90909

Appendix C: Calculated data Data obtained for mass transfer coefficient calculation: Mesh size: 1 mm -0.84 mm Velocity = 0.034 m/s , Initial concentration = 23 ppm amount of activated carbon: 80 gm time 0.5 3 6 9 12 15 18 21 24 27 30 31 33 34 36 37 38

q 0.391 2.345931 4.690898 7.032423 9.366374 11.68697 13.98677 16.25669 18.48599 20.66228 22.7715 23.45701 24.79797 25.45211 26.72433 27.34096 27.94363

Kf*10-3, m/s 0.071205 0.068586 0.066212 0.06449 0.063283 0.062005 0.062206 0.061716 0.061782 0.061708 0.059176 0.057868 0.056575 0.055124 0.05223 0.050782 0.04933

Velocity = 0.0254 m/s time 0.5 1 2 3 4 6 9 12 15 20 25 30 34

q 0.2921 0.584198 1.16837 1.752446 2.336312 3.502731 5.245301 6.970898 8.666559 11.3792 13.86086 15.98295 17.31708

Kf*10-3, m/s 0.050975 0.050508 0.049662 0.048922 0.048281 0.047269 0.046356 0.046109 0.042621 0.038965 0.037481 0.037094 0.033044

Velocity = 0.017 m/s tim e 0.5 1 2 3 4 6 8 10 13 16 19 22 25 28 31 34

q 0.1955 0.390999 0.781986 1.172931 1.563782 2.344898 3.124518 3.9015 5.058723 6.200294 7.318227 8.402882 9.442969 10.42554 11.33601 12.15811

Kf*10-3, m/s 0.032929 0.032693 0.032256 0.031863 0.031509 0.030901 0.030404 0.029996 0.029508 0.029117 0.028776 0.028438 0.028063 0.027613 0.027058 0.026374

Particle size: 1 mm - 0.84 mm velocity: 0.0254 m/s amount of activated carbon: 80 gm Time (min) 0.5 1 3 4 6 8 11 14 15 17 20

q 0.23431 5 0.46862 5 1.40547 9 1.87322 2.80519 6 3.72823 2 5.08055 4 6.36566 7 6.77227 5 7.54242 3 8.5598

Kf*10-3, m/s 0.030286 0.029958 0.028909 0.028509 0.027891 0.027439 0.026913 0.026378 0.026165 0.02565 0.024587

Particle size:0.84 mm -0.71 mm velocity: 0.0254 m/s amount of activated carbon: 80 gm tim e q Kf*10-3, m/s 0.5 0.234315 0.038153 1 0.468624 0.037505 2 0.937169 0.036404 3 1.405427 0.035517 4 1.873057 0.034808 6 2.804373 0.033825 9 4.180174 0.033167 12 5.505054 0.033173 15 6.740128 0.033478 18 7.835402 0.033578 21 8.729771 0.032784 24 9.65102 0.030509 27 10.49582 0.026825 Particle size: 1.3 mm - 1.15 mm velocity: 0.0254 m/s amount of activated carbon: 80 gm Initial concentration Co = 18.45 ppm tim e q Kf*10-3, m/s 0.5 0.234314 0.029465 1 0.468622 0.029029 2 0.937128 0.028306 3 1.405221 0.027752 4 1.872407 0.027336 6 2.801082 0.02683 9 4.163509 0.026636 12 5.452384 0.026814 15 6.611541 0.027044 18 7.568763 0.026998 21 8.235789 0.026362 22 8.376077 0.025978