Water pollution caused by copper (Cu²⁺) ions is an environmental problem because these ions are toxic and can accumulate in organisms. One method that can be used to remove heavy metal ions from water is adsorption. This study aims to synthesize and evaluate biopolymer-based hydrogel composites of CMCS/sodium alginate and CMC/CMCS/sodium alginate as Cu²⁺ adsorbents. Chitosan is poorly sol…