Mercury Decontamination of Dental Clinic Wastewater Using Electrochemical Alloy Formation

This study explores electrochemical alloy formation for mercury removal from dental clinic wastewater. Laboratory-scale experiments using wastewater from a Swedish dental clinic found a total mercury concentration of 0.68 mg/L, with 0.45 mg/L in dissolved or small particulate (<0.45 μm) form and the remainder as larger particulate mercury. Particulate mercury refers to mercury bound to solid-phase materials, including fine particles and fragments of dental amalgam. Electrochemical removal successfully captured 87% of mercury within 150 h by reducing dissolved Hg2+ ions at a platinum cathode, forming a stable Pt–Hg alloy. To investigate the effectiveness of this technique in practical applications, a flow reactor system based on the same electrochemical alloy removal method was installed in four dental clinics across Sweden. The reactors were installed downstream of the existing amalgam separators. While amounts vary, the reactors consistently achieved substantial mercury removal, with an estimated 340 mg to 7.5 g of mercury captured from the wastewater during 1 year of operation at each site. In total, approximately 19 g of mercury was removed, and 125,000 L of wastewater was treated. Thus, this electrochemical method effectively removes mercury not caught by amalgam separators, preventing environmental contamination.