Evaluation on Heavy Metals Removal Efficiencies in the Plating Factory Wastewater Using Apatite

The purpose of this study is to evaluate heavy metals removal efficiencies of apatite for the plating factory wastewater based on lab experiments. Four different apatite grain sizes such as 2 mm (No. 10 seive) passing-0.84 mm (No. 20 seive) retained, 0.42 mm (No. #40 seive) retained, 0.149 mm (No. 100 seive) retained, and 0.075 mm (No. 200 seive) retained were used and flow rates of industrial waste water were varied from 9.15 x 10(-4) l/min/kg to 60.43 x 10(-4) l/min/kg. The results showed that the dissolution rate of apatite is proportional to the flow rate but is inversely proportional to the grain size of apatite. The pH of the inlet water (the plating factory wastewater) increased from 2.0 to 3.1 - 5.3 at the outlet. It is likely that the apatite grain size between 0.42 mm (No. 40 seive) and 0.149 mm (No. 100 seive) with a flow rate of 60.43 x 10(-4) l/min/kg (reaction time of 165 minutes per one liter of this industrial waste water per one kilo gram of apatite) is the most efficient condition for removing heavy metals. In this case, pH would increase from 1.98 to 5.30 and, the removal efficiencies for Cr, Fe, Cu & Zn would be 77% 100%, 99% and 41%, respectively. But, the experiment used in this study did not show sufficient removal efficiencies for Cr and Zn that could satisfy the wastewater discharge limits. In addition, it was revealed that small apatite particles did not react with the wastewater during the experiment. Therefore, an additional experiment using multiple apatite reaction tanks is suggested for further studies for better removal efficiencies.