Oxidized Pectin-Cross-Linked O- Carboxymethyl Chitosan/EDTriAA Intercalated LDH: An Antibiotic Adsorbent Hydrogel

This study focuses on benzylpenicillin (BP) antibiotic removal from water using conventional O-carboxymethyl chitosan (O-CMC) /pectin hydrogel (HGEL). In addition, the effect of the incorporation of layered double hydroxides (LDH) and Ethylenediaminetriacetic Acid (EDTriAA) intercalated LDH on the adsorption process was studied. After incorporating nanomaterials, different tests were conducted to observe chemical and physical changes in hydrogels. FTIR and XRD results confirmed the successful placement of nanomaterials. In the TGA test, the first step of weight loss in LDH-containing hydrogels was 2.5 folds more than in HGEL, approving the higher hydrophilicity of these hydrogels. SEM analysis showed more uniform pores in the presence of EDTriAA, claiming uniform access of BP molecules to the pores. Nanocomposite hydrogel containing EDTriAA intercalated LDH had the highest swelling ratio. Furthermore, adsorption studies resulted in the optimum adsorption parameters. The lowest dosage of all hydrogels (1 g/L), the initial concentration of BP at 250 mg/L, pH of 7, and temperature at 25 °C were optimized parameters. Besides, the existence of LDH enhanced the adsorption capacity of hydrogels. Moreover, fitting the experimental data to different kinetic models revealed that the BP adsorption process for all hydrogels was governed by the pseudo-second-order kinetic. Finally, adsorption data of the conventional hydrogel and LDH-containing hydrogels were well-fitted to the Langmuir and R–P isotherm models, respectively. According to these isotherms, the adsorption process of the antibiotic on the LDH-less hydrogel was monolayer, homogeneous and chemical, while, for LDH-containing hydrogels was between a homogeneous and heterogeneous process.