| Summary: | Zinc (Zn) contamination is of environmental concern due to its effect on human health. The purpose of this study was to investigate the use of Calcium Fluoride (CaF2) sludge has been used to investigate its feasibility of using to remove Zn from aqueous solution. The CaF2 sludge produced by AFPD Pte Ltd, one of the world’s largest TFT LCD manufacturing plants (based in Singapore), contains apatite, which have high selectivity for certain toxic metals. The major parameters controlling aqueous Zn removal, viz. initial metal ion concentration, solution pH, ionic strength and metal kinetics were evaluated using batch experiments. Result demonstrated that the capacity of aqueous Zn immobilization by CaF2 was high at low initial Zn aqueous solution. Zn removal efficiency by CaF2 generally increased with decreasing ionic strength. In the pH-controlled study, it was found that removal of Zn is dependent on the cation exchange capacity (CEC) of CaF2. It was also found that the desorption level of Zn from CaF2 sludge is high especially in the acidic condition (pH < 2.88). This implies that Zn laden will have to be stabilized before being disposed into landfill since the maximum allowable limit for zinc in discharged water is 5 mg/L.
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