Adsorption of anti-inflammatory drugs from aqueous solution using Chitosan-modified waste tire crumb rubber

Abstract

In this research, waste tire crumb rubber was modified by polymeric chitosan to be used as a novel modified adsorbent for the removal of anti-inflammatory drugs including ibuprofen, diclofenac, and naproxen from aqueous solution. The chitosan-modified adsorbent was characterized by infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The appropriated types and amount of chitosan were determined. The pHpzc, investigated by mass titration method, was 6.01. The efficiency of anti-inflammatory drug adsorption using the adsorbent strongly depended on the solution pH. Ibuprofen, diclofenac, and naproxen were greatly adsorbed over pH ranges of 4-9, 5-10, and 3-10, respectively. The optimal solution pH for all three anti-inflammatory drugs removal is 6, at which the adsorption amounts of ibuprofen, diclofenac, and naproxen were 3.20, 10.94, and 0.53 mg/g, respectively. The adsorption equilibria of ibuprofen and diclofenac were reached in one hour while naproxen adsorption took two hours. The adsorption processes of all drugs followed the second-order kinetic model. The adsorption isotherm of these drugs onto the modified adsorbent was fitted with Freundlich isotherm model better than Langmuir isotherm model. Finally, the chitosan-modified adsorbent was applied to remove the anti-inflammatory drugs from real water samples, i.e., Chulalongkorn University’s pond, canal water (untreated water), and tap water with satisfactory results. Therefore, the chitosan-modified waste tire crumb rubber adsorbent was the novel adsorbent which has the potential to be an economical and effective adsorbent for the removal of anti-inflammatory drugs.