Cross-Linked Cationic Starch Microgranules for Removal of Diclofenac from Aqueous Systems

Abstract

The occurrence of pharmaceuticals, such as anti-inflammatories, antibiotics, antidepressants, antihistamines, and others in the effluents, is a very urgent problem and a big challenge for municipal wastewater treatment companies. Without special treatment, these microcontaminants are retained in discharged water and sewage sludge and this is a high threat to the environment. Cross-linked cationic starch (CLCS) adsorbents with various degrees of substitution (DS) of cationic groups were employed for the removal of diclofenac from aqueous systems. The equilibrium adsorption studies revealed that the driving force of adsorption was the electrostatic interaction between carboxylate groups of diclofenac and quaternary ammonium groups of CLCS. The sorption capacities of CLCS with DS of 0.21 (CLCS-0.21) and DS of 0.33 (CLCS-0.33) varied from 329 to 370 mg/g and from 597 to 684 mg/g, respectively. The release studies revealed that adsorbed diclofenac can be efficiently released into 0.25 mol/L NaCl solution. Adsorbent regeneration studies showed that after four regeneration cycles, the ability of CLCS-0.21 and CLCS-0.33 to remove diclofenac from the aqueous medium decreased by 6% and 3%, respectively. To conclude, CLCS-0.33 exhibited high absorption capacity and sustainability due to good recoverability properties and can be regarded as a promising microcontaminant adsorbent to be used in wastewater treatment processes.