Feasibility of Remediation Lead, Nickel, Zinc, Copper, and Cadmium-Contaminated Groundwater by Calcium Sulfide

• Main Authors: Chin-Yuan Huang, Pei-Cheng Cheng, Jih-Hsing Chang, Yu-Chih Wan, Xiang-Min Hong, Shu-Fen Cheng
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Water
• Subjects: metal; polysulfide; groundwater; stabilization; lead
• Online Access: https://www.mdpi.com/2073-4441/13/16/2266

Metal contamination in groundwater often occurs in various industrial processes. Studies have confirmed that polysulfide could reduce hexavalent chromium to trivalent chromium, achieving the effect of in situ stabilization. For other metal contamination in groundwater, whether polysulfide also had a stabilizing ability to achieve in situ remediation. This research focused on metals in addition to chromium that often contaminated groundwater, including lead, nickel, zinc, copper, and cadmium, to explore the feasibility of using calcium polysulfide (CaS_x) as an in situ stabilization technology for these metals’ contamination of groundwater. Results showed that CaS_x had a great removal efficiency for metals lead, nickel, zinc, copper, and cadmium. However, for nickel, zinc, copper, and cadmium, when CaS_x was added excessively, complexes would be formed, causing the result of re-dissolution, in turn reducing the removal efficiency. As it is difficult to accurately control the dosage of agents for in situ groundwater remediation, the concentration of re-dissolved nickel, zinc, copper, and cadmium may not be able to meet the groundwater control standards. CaS_x had high lead removal efficiency and for a concentration of 100 mg/L, the dose of calcium polysulfide was more than the amount of 1/1200 (volume ratio of CaSx to groundwater). In addition, the removal rate was almost 100% and it would not cause re-dissolution due to excessive CaS_x dosing. CaS_x can be used as an in situ stabilization technique for lead-contaminated groundwater.