ZnO-surfaced carboxymethyl cellulose-sodium alginate-guar gum composite hydrogel films for solar-responsive reactive textile dye degradation

Composite Hydrogel Films (CHFs) are multifunctional materials known for their excellent water absorption and retention capabilities, making them suitable for a wide range of environmental applications. In this study, CHFs were developed by integrating Carboxymethyl Cellulose (CMC), Sodium Alginate (SA), Guar Gum (GG), and zinc oxide (ZnO) nanoparticles. The synthesized CMC–SA–GG/ZnO CHFs were characterized using AFM, SEM, FT-IR, and XRD, confirming the successful incorporation of ZnO nanoparticles into the biopolymer matrix. The CHFs exhibited excellent water absorption capacity (∼1100% within 30 min), high biodegradability (∼98% within 6 days), and notable mechanical stability. Their efficacy was evaluated for the adsorption and solar-responsive degradation of a model reactive textile dye effluent containing Reactive Yellow, Reactive Red, and Reactive Blue dyes. Under focused solar irradiation (240 min), the CHFs achieved a high degradation efficiency ranging from 94% to 96%, facilitated by their strong adsorption capacity and photocatalytic activity. Additionally, a plausible photocatalytic degradation mechanism was proposed based on radical scavenging studies suggesting O 2 • - and •OH were the dominant reactive species for efficient degradation. HR-MS analysis revealed the breakdown of parent dye structures into lower molecular weight intermediates and end-products, indicating effective cleavage of azo and anthraquinone chromophores. Post-treatment analysis of the effluent indicated significant improvement in water quality parameters, particularly reduction in COD and BOD, suggesting its potential reuse for domestic applications. These results highlight the promise of CMC–SA–GG/ZnO CHFs in contributing towards Sustainable Development Goals (SDGs), specifically SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production). Schematic representation of the use of ZnO-surfaced CMC-SA-GG composite hydrogel films for solar-responsive textile dye degradation • Developed ZnO-surfaced CMC–SA–GG CHFs for solar-responsive dye degradation • Demonstrated 94–96 % degradation of reactive textile dyes within 240 min • Exhibited good reusability (∼90.6 % degradation efficiency over three cycles) and ∼98% biodegradation within 6 days). • Offers a sustainable and green approach for textile wastewater treatment