Photocatalytic degradation of efavirenz and nevirapine using visible light-activated Ag-AgBr-LDH nanocomposite catalyst

Abstract

Antiretroviral drugs (ARVDs) are one of the many classes of emerging pharmaceutical pollutants that have been detected in South African waterbodies in recent years. Efavirenz (EFV) and nevirapine (NVP) are commonly used drugs in antiretroviral therapy (ART) in the region and have been reported to be persistent in wastewater. Their presence in water poses health hazards to human beings and the aquatic environment. It is therefore important that these compounds be remediated from the environment. Visible light activated photocatalysis is one of the sustainable remediation technologies that aptly removes refractory organic contaminants from various water matrices. This study reports for the first time, the synthesis of silver halide doped Mg-Zn-Al LDH clay as a photocatalyst in the degradation of selected ARVDs under visible light irradiation. The physicochemical properties of the photocatalyst were elucidated using a range of characterization techniques. Response surface modelling was used to evaluate the interactions between the independent variables: initial pH of the solution, photocatalyst loading and initial concentration of the pollutants. The results showed that there were significant interactions between initial concentration and photocatalyst loading for EFV degradation while the interactions between photocatalyst loading and initial concentration, and initial pH of the solution and photocatalyst loading were significant for NVP degradation. The highest degradation efficiencies were 84 and 100% for EFV and NVP, respectively. Scavenger tests revealed that the hydroxyl free radicals and photo-induced holes were the dominant active species that promoted the degradation of ARVDs. The synthesized photocatalyst nanocomposite demonstrated its efficacy in degradation of ARVDs in water under visible light irradiation.