Adsorptive methylene blue removal using modified agricultural wastes

A magnetic nano biocomposite was developed by coating the surface of pressed Nigella sativa press cakes agricultural waste with Fe3O4 nanoparticles. The uptake of methylene blue from an aqueous solution was evaluated. pH, adsorbent dosage, interaction time, and other parameters were investigated. Equilibrium, kinetic, and thermodynamic models were analyzed. Desorption studies were performed using various solvents. The uptake efficiency of methylene blue reached 93.22% at pH 11. The adsorbent dosage was determined as 0.6 g/L. The uptake efficiency reached 99.40% at 24 h. Adsorption mechanism is found to be both endothermic and spontaneous. The rate-determining step of adsorption is chemical sorption. The adsorption capacity was 454.55 mg/g. Desorption was performed by ethanol and reached 49.21%. The adsorption performances of the adsorbent were also evaluated by real water samples. Toxic and hazardous reagents were not handled in the preparation of the adsorbent. An environmentally friendly, easily prepared, cheap adsorbent has been developed.