Evaluation of electrochemical regeneration of antibiotic-loaded clay in a single-reactor process

Abstract

This study investigated the in situ electrochemical regeneration of a clay adsorbent loaded with sulfamethoxazole (SMX) using two systems (NaCl/DSA and Na2SO4/BDD), aiming to understand the regeneration process and evaluate the quality of the generated electrolyte solution. The NaCl/DSA system exhibited higher regeneration efficiency (RE: 135–97 %) compared to Na2SO4/BDD (RE: 101–51 %), highlighting the role of active chlorine species in SMX degradation. During regeneration, SMX was not detected in the solution, being degraded into transformation products, or mineralized. The presence of traces of hydrocarbons and the increase in the total organic carbon content in the electrolytic solution suggest partial oxidation of the surfactant present in the clay formulation, possibly generating new active sites and enhancing adsorption capacity (RE > 100 %). However, extended regeneration times appear to promote significant loss of adsorbent integrity. The compounds detected in the solution resulting from the Na2SO4/BDD system indicate more pronounced degradation of the clay matrix, which may have influenced its lower regenerative efficiency. Although the NaCl/DSA system demonstrated greater efficiency, its corresponding electrolyte solution exhibited increased toxicity toward Lactuca sativa seedlings. In contrast, acute toxicity tests using Aliivibrio fischeri indicated that the produced electrolytic solutions did not have any inhibitory effects. Furthermore, photolysis treatment lowered phytoxicity and improved environmental compatibility. Finally, characterization analyses demonstrated preservation of the structural integrity of the clay against the applied processes.