Mechanochemically oxidized chitosan-based adsorbents with outstanding Penicillin G adsorption capacity

Abstract

Despite mild oxidation is a facile and efficacious method to enhance chitosan properties, like adsorption capacity of pollutants, currently developed solvent-based approaches can be hardly scaled up in an economic way because of complicated multi-step process and high solvent separation cost. In this study, a novel, solvent-free, simple, fast, and effective oxidation method was successfully applied to prepare oxidized chitosan by direct mechanochemical solid-state reaction with an oxidant in a high energy ball mill. Reaction products were employed to remove penicillin G from aqueous solutions by adsorption process. Chitosan ball milled for 1 h with 20%w/w potassium persulfate showed the highest adsorption capacity (2165 mg g−1), followed by the polysaccharide co-milled for 2 h with 30%w/w sodium percarbonate (1847 mg g−1) and with 50%w/w calcium peroxide for 2 h (1157 mg g−1). Such performance was likely owed to higher density of oxygen-containing functional groups, shorter polysaccharidic chain, and greater particle surface amorphization, compared to pristine chitosan. The spent adsorbents were successfully regenerated using NaOH solution for five consecutive times before penicillin G uptake loss was observed. The proposed mechanochemical method could serve as an economic and rapid method to synthesize at large-scale efficacious adsorbents to remove organic pollutants from wastewater.