INNOVATIONS: PRESENT&FUTURE
SPECIAL ISSUE ON ARCHITECTURE & DESIGN
Fluoride Removal with FLUORIDITE Edited by ALIT Technologies Srl San Bonifacio (VR) – Italy
M
info@alit-tech.com
any production fields have the technical need to use
A standard purification cycle, based mainly on an acidification phase
particular chemical formulations with high concentrations
(when necessary) followed by a neutralisation phase with lime, is very
of specific elements. For some specialised sectors in the
often not sufficient to achieve such low concentrations of fluorides,
surface treatment of steel, glass, and aluminium, for example, the use
even with considerable dwell times in the line.
of products with high fluoride concentrations is unavoidable.
In order to provide a truly effective solution to this problem without
Fluoride is the monoatomic anion of the fluorine atom. Due to their
necessarily having to intervene at the plant engineering level, ALIT has
high mordanting capacity and their affinity with metals (above all
developed FLUORIDITE, a liquid product that can be used directly on
aluminium and iron) and silica, its salts are key constituents of many
existing waste water treatment systems.
surface finishing products.
For example, in a three-tank purification line with a final sedimentation
However, there exist legal limits for the concentration of fluorides in
tank, a typical process involves adding FLUORIDITE in a concentration
surface and sewage water, which vary from country to country. For
of 500 to 3000 ppm in the first tank, where the acid and possibly
instance, in Italy, except for some stricter local regulations, the limit is
alkaline rinsing water and concentrates are conveyed. In the second
12 ppm for sewage and 6 ppm for shallow discharge.
tank, neutralisation with lime water to about pH 8 takes place. In the
In the specific sector of aluminium coating, however, the continuous
third and last tank, once the anionic polyelectrolyte has been added,
demand for higher productivity and pre-treatment quality has led to an
flocculation occurs.
increase in the use of chemicals, also resulting in critical issue in terms
The treated water then reaches the final sedimentation tank, where
of waste water management.
suspended sludge falls to the bottom and is then sent to the filter press
© ALIT Technologies
FLUORIDITE POLYELECTROLYTE
RINSE WATER
LIME/CHARCOAL
ALKALINE CONC. ACID CONC.
pH
pH
SEDIMENTATION TANK
DRAIN T3
T2
T1
FILTER PRESS Figure 1: Key elements of a standard purification process.
70
N. 75 - MAY/JUNE 2022 - international PAINT&COATING magazine
