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

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 comilled 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.

Automated summary

A novel, solvent-free, simple, fast, and effective oxidation method was successfully developed in this study for preparing oxidized chitosan to remove penicillin G from aqueous solutions. The higher density of oxygen-containing functional groups, shorter polysaccharidic chain, and greater particle surface amorphization in the oxidized chitosan led to its superior adsorption performance compared to pristine chitosan. The proposed mechanochemical method could serve as an economic and rapid approach to synthesize large-scale efficacious adsorbents for removing organic pollutants from wastewater.