This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi).

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Mussel shells are often considered an abundant waste with no use. This study shows that the employment of mussel shells as a biosorbent for ammonium from water environment is completely possible. By using batch experimental method, optimal conditions for the ammonium adsorption onto mussel shells were determined. Specifically, those include a pH level of 8, contact time of 90 min, an initial ammonium concentration of 40 mg/l and the adsorbent dose of 700 mg/25 ml. With such operating conditions, experiments in laboratory aqueous solutions resulted in a maximum adsorption capacity of 2.33 mg/g, corresponded by 46.575% of efficiency. Adsorption isotherms and kinetics were well described with the Freundlich isothermal model, suggesting a heterogeneous adsorption process occurring on multilayers and both the pseudo-first-order and the pseudo-second-order, implying that the operational fundament was based on chemisorption. Analyses regarding SEM, EDS and FTIR were also implemented to identify the morphology, composition and functional groups of the adsorbent.