Dual cation cross-linked alginate-kaolin hydrogel beads: a sustainable and powerful toolkit for enhancing wastewater remediation

Abstract

The research focuses on the removal of chlortetracycline hydrochloride (CTC) from water using a sustainable functional material designed as a toolkit, consisting of dual cation cross-linked alginate beads that incorporate kaolin (Fe/Ca-Alg@K). Key findings include: (1) the beads incorporate 3 g of K (Fe/Ca-Alg@K3), effectively adsorbed CTC; (2) an optimal dosage of 200 mg of beads achieved a notable removal rate of 95.12% at an initial concentration of 50 mg/L; (3) the pH level of the solution slightly affected the adsorption process; (4) the kinetic data aligned well with both pseudo-first-order and pseudo-second-order models, with physisorption being the dominant mechanism; (5) isotherm studies indicated that the adsorbent followed the Langmuir model, achieving a high correlation (R² = 0.94) and a maximum uptake of 156.46 mg/g at 318 K; (6) the inclusion of K in the Alg matrix notably enhanced the adsorbent’s reusability; (7) the presence of high concentration of various ions slightly reduce the removal of CTC; (8) XPS analysis revealed that the adsorption mechanism of CTC involved several interactions involving both the functional groups of beads and the silicon component of K; (9) these beads have the potential to reduce chemical oxygen demand to acceptable levels in pharmaceutical and surface wastewaters.