The aim of this study was to determine the sorption capacity of biochars obtained from waste biomasses: coffee grounds, banana peels, and marine macroalgae, in relation to phosphate ions. The negatively charged surface of biochar prevented the removal of phosphate ions from the aqueous solution, so its modification using magnesium chloride was performed. The pyrolysis process was performed to obtain modified biochar. Studies were carried out on the characteristics of the modified raw materials and biochars obtained. The influence of the pH of the solution containing phosphate ions on the sorption capacity of biochar was examined and the highest sorption capacity was obtained at pH 7, 8, 10 for modified coffee grounds (16.7 mg/g), marine macroalgae (13.3 mg/g), and banana peels (17.1 mg/g) biochar, respectively. Regarding sorption kinetics, it was determined that the process reached an equilibrium after 4 h and the pseudo-second order kinetic model best explained the process for all modified biochars. Although phosphate ions were effectively removed by all modified biochars, modified banana peels biochar had the highest equilibrium sorption capacity (62.6 mg/g). Further potential applications of biochar produced from waste enriched with phosphorus could be managed as a soil additive.
Niedzbała et al. (Sun,) studied this question.