Exploitation of bentonite and halloysite fixed bed columns – Removal of organic micropollutants and microbiological regeneration

This study examines the efficacy of bentonite and halloysite in removing caffeine and benzotriazole from aqueous solutions using fixed bed columns. Initially, both micropollutants were removed with high efficiency (98–100 %), but removal degrees decreased markedly after approximately 360 minutes, indicating rapid bed exhaustion and a need for regeneration. Caffeine removal was slightly more effective than benzotriazole, likely due to caffeine's larger molecular weight enhancing its adsorption on clays. The microbial regeneration process, employing Pseudomonas aeruginosa, facilitated significant degradation of adsorbed micropollutants. Benzotriazole was degraded much faster than caffeine, with over 90 % degradation in bentonite within 72 hours and full degradation in halloysite within 96 hours. Caffeine required 168 hours for complete degradation in both materials. The faster degradation of benzotriazole is attributed to its chemical structure and environmental interactions. Post-regeneration, both adsorbents recovered approximately 100 % of their original adsorption capacity. Notably, the BET surface area and density of regenerated adsorbents remained almost consistent with those of their pure, unused forms. This study underscores the effectiveness of microbial regeneration in extending the usability of bentonite and halloysite for continuous purification processes.