Removal of tributyltin from water using a coupled adsorption and electrochemical oxidation process

Organotin compounds, such as tributyltin (TBT), pose significant environmental risks and threaten wildlife, food chain, and human health even years after being banned, highlighting the need for effective removal methods. The Nyex Rosalox™ (NR) process, a novel coupled adsorption and electrochemical oxidation technology, has shown success in removing various organic pollutants. However, its applicability to remove organometallic compounds remains unclear. Therefore, this study evaluated the effectiveness of TBT removal from water using the NR process and investigated the fate of tin and the formation of degradation products. Analyses showed that at high (50 mg/L) concentrations 62 % to 71 % TBT in fresh water and 73 % to 86 % in brackish water could be effectively removed in 1-hour using 6.5 W. The presence of NaCl enhanced conductivity and promoted hypochlorite formation, further improving TBT oxidation. Although direct electrochemical oxidation of TBT (i.e., without adsorption on Nyex™ media) was observed at high concentrations and elevated salinity, at low (0.5 mg/L) concentrations adsorption onto Nyex™ media played a crucial role in enhancing treatment efficiency and stability. No significant production of toxic degradation products such as monobutyltin and dibutyltin was observed, and up to 94 % of the inorganic tin (Sn⁴⁺, the final oxidation product) formed, was immobilised on the Nyex™ media, but could be remobilised by rinsing with a weak acid solution. This is the first study to assess the fate of the inorganic component of an organometallic compound in a coupled adsorption and electrochemical oxidation treatment process. This work demonstrates that the NR process holds promise for treating other organometallic pollutants, potentially at even at lower organotin concentrations.