Co-adsorption of Ammonium, Phosphate, Strontium and Arsenate from Contaminated Water by a Low Cost Biochar. Performance and Mechanisms

Co-adsorption of ammonium, phosphate,strontium and arsenate ions from polluted water sources by alow-cost nut residue biochar, without using any chemicals, wasinvestigated. The adsorption behavior of biochar was examinedfor different experimental parameters and the mechanisms ofadsorption were explored through structural, mineralogicaland chemical analyses, as well as modeling of experimental data.At equilibrium, a higher ionic strength favored the adsorptionprocess, whereas the uptake of each ion by the solid increasedsignificantly when all ions co-existed in the solution, implying nocompetition between them for sorption sites. The experimentaldata were fitted with great accuracy by the Freundlich isothermmodel. The maximum adsorption capacity of the biocharachieved for ammonium, phosphate, strontium and arsenatewas 50.3 mg/g, 121 mg/g, 66.9 mg/g and 62.9 mg/g, respectively.The potential mechanisms of adsorption were the chemicalcomplexation of all ions with the adsorbent, electrostaticattraction for ammonium and strontium cations, ligandexchange for phosphate and arsenate ions and mineral surfaceprecipitation for phosphate, strontium and arsenate ions.