Sorption of nonsteroidal anti-inflammatory drugs from aqueous media by aluminosilicate ceramic microspheres

Abstract

Nonsteroidal anti-inflammatory drugs (NSAIDs), along with antifungal, antiepileptic drugs, sex hormones, and beta-blockers, are the most common pharmaceutical preparations that often enter various water bodies through industrial wastewater due to irrational use and improper disposal. The most common NSAIDs used by consumers are ibuprofen (IB), nimesulide (NM), diclofenac (DC), ketoprofen (KT), and piroxicam (PC). The aim of the study is to investigate the sorption of NPVS from aqueous media using aluminosilicate microspheres, including selection of sorption conditions (pH, sorbent mass, time of sorption). Aluminosilicate ceramic microspheres (cenospheres) from INOTEK Holding (Russia) were selected as the sorbent. The efficiency of NSAID sorption, which differs in structure and pKa, depends on the pH of the solution. The extraction degree of DC, IB, and KT decreases with increasing pH, reaching a maximum at pH 1-2, i.e., at values above pKa. pH has a more complex effect on PC sorption: at pH 1-2 it is present in the solution in cationic form, then at pH 3-6 its content decreases, and a mixture of neutral, cationic, and anionic forms is present in the solution. An important parameter affecting sorption efficiency is the ratio of the sorbate solution volume to the sorbent mass. During sorption from a solution volume of 10 cm³, the extraction degree increases in the sorbent mass range from 5 to 15 mg by 40-94%, while in the range of 20-40 mg it increases by only 1-2%. With increasing phase contact time from 0 to 45 min, sorption efficiency smoothly increases from 15-20% (10 min) to 40-69% (45 min). The curve reaches a plateau at 45-90 min. With further increase in phase contact time (120 min), the NSAID extraction degree increases by 1-3%. The pseudo-second-order model is applicable for describing the sorption kinetics (R²=0.951-0.981).