Valorization of Moringa oleifera seed husk as biosorbent: isotherm and kinetics studies to remove cadmium and copper from aqueous solutions

Abstract

Moringa oleifera is a plant with multiple uses. Among them, the best-known use of seeds is as natural coagulant for the clarification of turbid water. The process of preparation of the natural coagulant generates different wastes including Moringa seed husk. This work studies the use of this waste as biosorbent for cadmium and copper removal. Adsorption studies were performed using batch test and the effects of contact time, temperature, pH, concentration of metal, and concentration of adsorbent were also analyzed. We have also studied the biosorbent structure through SEM and EDX. Experimental results were analyzed using Langmuir and Freundlich isotherms and the adsorption kinetics by pseudo-first and pseudo-second-order equations. The experimental results showed that the maximum removal of Cu and Cd was observed at pH 6, 1 h contact time, 1 mg/L initial concentration of Cd and 2 mg/L of Cu, and 1 g of biosorbent added. The percentages of metal removal were around 90% for both metals studied. Results indicate that the data of Cu and Cd adsorption onto Moringa seed husk were best fit by the Langmuir model. The adsorption capacity (qm) calculated from the Langmuir isotherm was 13.1 mg g−1 for both metals, higher than observed for other biosorbents prepared from M. oleifera. The results indicate that the adsorption kinetic data were best described by pseudo-second-order model. In summary, Moringa seed husk can be considered as potential and promising biosorbent for heavy metals removal from water or wastewater systems.