The presented study was focused on the simple, eco-friendly synthesis of composite hydrogels of crosslinked carboxymethyl cellulose (CMC)/alginate (SA) with encapsulated g-C₃N₄ nanoparticles. The structural, textural, morphological, optical, and mechanical properties were determined using different methods. The encapsulation of g-C₃N₄ into CMC/SA copolymer resulted in the formation of composite hydrogels with a coherent structure, enhanced porosity, excellent photostability, and good adhesion. The ability of composite hydrogels to eliminate structurally different dyes with the same or opposite charge properties (cationic Methylene Blue and anionic Orange G and Remazol Brilliant Blue R) in both single- and binary-dye systems was examined through adsorption and photocatalytic reactions. The interactions between the dyes and g-C₃N₄ and the negatively charged CMC/SA copolymers had a notable influence on both the adsorption capacity and photodegradation efficiency of the prepared composites. Scavenger studies and leaching tests were conducted to gain insights into the primary reactive species and to assess the stability and long-term performance of the g-C₃N₄/CMC/SA beads. The commendable photocatalytic activity and excellent recyclability, coupled with the elimination of costly catalyst separation requirements, render the g-C₃N₄/CMC/SA composite hydrogels cost-effective and environmentally friendly materials, and strongly support their selection for tackling environmental pollution issues.

Due to its potential to provide sustainable solutions to pollution and contamination, photocatalysis is a promising area of research in the fields of environmental protection and water remediation. The main objective of this work was to prepare an environmentally friendly, durable, easily-separable, and reusable nanocomposite hydrogel with g-C3N4 encapsulated into a carboxymethylcellulose (CMC) and sodium alginate (SA) polymer matrix for wastewater remediation. The physicochemical properties of the prepared hydrogel were characterized by FE-SEM and ATR-FTIR spectroscopy. The g-C3N4/CMC/SA hydrogel photocatalytic efficiency was investigated using an anionic Orange G (OG) dye as a model pollutant.