Synthesis and Characterization of Chitosan-Based Hydrogels Grafted Polyimidazolium as Nitrate Ion Adsorbent from Water and Investigating Biological Properties

Abstract

In this study, a chitosan-based polymer composite hydrogel grafted with polyimidazolium was synthesized and evaluated as an adsorbent for nitrate removal from water. The synthesis began with the preparation of a dinitro compound, followed by the synthesis of a diamine monomer, which was then conjugated with chitosan in the presence of glyoxal and formaldehyde to form the final composite. The chemical structure of the synthetic monomers and the composite was characterized using FT-IR, ¹H-NMR, FE-SEM, EDX, and TGA analyses. The concentration of nitrate ions in aqueous solutions was quantified using a spectrophotometer at wavelengths of 220 nm and 275 nm. Various operational parameters, including pH, contact time, initial nitrate ion concentration, and adsorbent dosage, were optimized to maximize nitrate removal efficiency. At an initial nitrate concentration of 70 mg/L, a pH of 7, an adsorbent dosage of 40 mg, and a contact time of 40 min, the synthesized composite exhibited a maximum removal efficiency of 97.75% and an adsorption capacity of 85.53 mg/g. The selectivity of the composite for nitrate ions in the presence of competing ions such as sulfate, bicarbonate, chloride, and phosphate was also evaluated. The presence of competing ions reduced nitrate removal, with bicarbonate having the most significant inhibitory effect and phosphate the least. The adsorption kinetics was best described by a Pseudo-second-order model, while the equilibrium data conformed to the Langmuir isotherm model. The PCH reusability was checked by an adsorption/desorption experiment, and the results showed acceptable constant loading efficiency after five reuse cycles. In addition to the adsorption studies, the composite’s anti-cancer properties were assessed. Cytotoxicity tests were conducted in vitro against three cancer cell lines: A431 (skin carcinoma), HT29 (colorectal cancer), and MCF7 (breast cancer), using cisplatin as a reference standard. The results demonstrated a potent anti-cancer effect against the MCF7 cell line, with an IC50 value of 4.80 µM. Furthermore, the composite included a collapse in the mitochondrial membrane potential (MMP) in MCF7 cells, highlighting its potential as a therapeutic agent.

Graphical abstract