Application of layered double hydroxides in advanced wastewater remediation processes for the removal of phenol, efavirenz, and nevirapine

Abstract

The global challenge of water contamination necessitates innovative approaches for wastewater treatment. This study explored modified layered double hydroxide (LDH)-based photocatalysts and adsorbents for removing persistent organic pollutants, focusing on antiretroviral drugs (ARVDs) such as efavirenz (EFV) and nevirapine (NVP). These drugs, commonly found in wastewater due to extensive use in HIV/AIDS treatment, resist conventional treatments and pose environmental and health risks. The synthesis and characterization of an Ag-AgBr-LDH photocatalyst revealed a promising combination of LDH’s durability and Ag-AgBr’s superior visible-light absorption. Techniques like X-ray diffraction, scanning electron microscopy, and BET surface area analysis confirmed the material's suitability. Photocatalytic evaluations showed significant degradation of phenol and ARVDs, with EFV and NVP achieving maximum degradation efficiencies of 84% and 100%, respectively. Response surface modeling identified critical interactions among factors such as initial pH, photocatalyst loading, and pollutant concentration. Continuous flow reactor tests highlighted optimal degradation at a photocatalyst loading of 3 g/L, a flow rate of 10 mL/min, and high light intensity. Parallel investigations assessed the adsorption potential of calcined LDH (CLDH). Characterization revealed rapid adsorption kinetics and physisorption as the dominant mechanism, with hydrogen bonding playing a significant role.