First investigations on removal of nitrazepam from water using biochar derived from macroalgae low-cost adsorbent: kinetics, isotherms and thermodynamics studies

Abstract

Emerging contaminants such as pharmaceutical compounds offer potential hazards to the aquatic environment and human health. In this paper, the adsorptive removal of the drug Nitrazepam from water was investigated for the first time using biochar prepared from Sargassum macroalgae. The removal efficiency of Nitrazepam using 1 g/L of Sargassum macroalgae-derived biochar was 98% with a maximum adsorption capacity of 143.12 mg/g. Effects of solution pH, adsorbent mass, adsorbate concentration, contact time and temperature on the removal of Nitrazepam were investigated. Different adsorption isotherms and kinetics were also tested. It was found that the solution pH slightly influenced the removal efficiency. The adsorption data fit the Freundlich isotherm model and the adsorption process of Nitrazepam onto Sargassum macroalgae-derived biochar is spontaneous, endothermic and followed the pseudo-second-order kinetics. Based on this work, it was determined that the low-cost Sargassum macroalgae-derived biochar adsorbent could be a promising adsorbent to remove Nitrazepam from water effectively. Highlights A biochar prepared from macroalgae was investigated for Nitrazepam removal from water.; The adsorbent has high efficiency and adsorption capacity for Nitrazepam emerging contaminant.; The kinetics and thermodynamics of Nitrazepam adsorption were studied.; The adsorption process was spontaneous, endothermic and thermodynamically favorable.; Mixed mechanism was dominated by physisorption and followed pseudo second-order kinetics.;

Keywords

• adsorption isotherms
• adsorption kinetics
• pharmaceutical compounds
• water treatment