Selective recovery of nickel ions from wastewater of stainless steel industry via HFSLM

Abstract

High concentration of heavy metal ions in all kinds of effluents, especially in wastewater is of great concern for hazardous pollution due to their high toxicities and wide environmental spreading. The selective stripping or recovery of nickel ions from wastewater of the stainless steel-cold rolled plate process by hollow fiber supported liquid membrane was studied. The optimum conditions were examined in a batch process. The pH of feed, types and concentrations of the extractants, concentration of the stripping solution (sulfuric acid), flow rates of feed and stripping solutions, and volumetric ratio of feed to stripping solutions were investigated. The extractants, i.e., D2EHPA, Cyanex 301, Cyanex 272 and LIX 860-I were dissolved in kerosene as a membrane solution, which was supported by a microporous hydrophobic hollow fiber membrane extractor. Consequently, two consecutive modules of hollow fiber were applied to recover more nickel ions. The results showed that LIX 860-I was the most effective to selectively retrieve nickel ions from wastewater at a feed pH of 4. The percentage of the recovery and selectivity of nickel ions increased in accordance with an increase in the concentration of LIX 860-I and decreased after the concentration of LIX 860-I was higher than 0.8 M. It was found that the percentage of recovery of nickel ions increased with sulfuric acid concentration and lower flow rates of feed and stripping solutions. Higher nickel ions were obtained at the flow rates of feed and stripping solutions of 100 ml/min and reduced when the flow rates increased. In addition, in this study it is recommended to use equal volume of feed and stripping solutions of 3500:3500 (ml:ml) to attain more nickel ions recovery. For a single-module operation, the percentage of recovery of nickel ions was 58%, and 87% by double-module operation.