Cationic Surfactant-Modified Cellulose Nanocrystal/Alginate Hydrogel Beads for Enhanced Adsorptive Removal of 4-Chlorophenol from Wastewater

4-Chlorophenol being a phenolic endocrine-disrupting chemical is one of the most commonly detected pollutants in water resources, which is well known for its high toxicity and carcinogenicity. The present study aimed to develop cost-effective and efficient hydrogel beads in treating wastewater contaminated with 4-chlorophenol. Herein, cetyltrimethylammonium chloride-modified cellulose nanocrystals were grafted onto the backbone of alginate to fabricate porous eco-friendly hydrogel beads (CTAC-CNC/ALG@HB) to utilize as an adsorbent. Porous CTAC-CNC/ALG@HB were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, surface area/porosity measurement, and zeta potential analysis. Characterization results revealed that cetyltrimethylammonium chloride modification and the disintegration of calcium phosphate within the hydrogel beads enhanced the pore network and its structural stability. The adsorptive removal of 4-CP was optimized by altering various experimental conditions. The pseudo-second-order rate equation and the Langmuir adsorption isotherm best described the adsorption of 4-chlorophenol onto CTAC-CNC/ALG@HB. The maximum adsorption capacity was 64.935 mg g−1, which could be reused up to five repeated cycles. The thermodynamic study indicated that the adsorption process was exothermic, spontaneous, and reversible within the analyzed temperature range. The Weber–Morris model revealed that intraparticle diffusion was not the singular rate-controlling step in the adsorption process. The results revealed that CTAC-CNC/ALG@HB could be employed as a sustainable and effective adsorbent for 4-chlorophenol remediation.