Highly efficient green synthesized nitrogen-doped zinc oxide nanoparticles incorporated into guar gum-agar agar polymeric matrix for sunlight-induced photocatalytic removal of water pollutants.

The study focuses on a green-synthesized nanocomposite for effective sunlight-driven degradation of dyes and phenols. Herein, nitrogen-doped zinc oxide (N-ZnO) nanoparticles were incorporated in guar gum-agar agar (GGAA) polymeric matrix via in situ method to form GGAA@N-ZnO nanocomposite for efficient removal of 4-chlorophenol (4-CP) and yellow dye (YD). The synthesized nanocomposite was characterized by powder X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy, while the band gaps were determined through Tauc plots. The Scherrer equation revealed the average crystallite sizes for ZnO and N-ZnO to be 19.68 nm and 10.17 nm, respectively. The optimized GGAA@N-ZnO (20 mg and pH 7) composite showed superior photocatalytic efficiency compared to pure ZnO, i.e., 94% for 4-chlorophenol (4-CP) degradation and 92% for YD in 150 min. Kinetic and adsorption studies indicated that the degradation followed a first-order kinetic model and Langmuir isotherm. GGAA@N-ZnO exhibited the minimum half-life and maximum rate, indicating the swiftest elimination of pollutants related to the native materials. LC-MS analysis identified degradation pathways, revealing safer byproducts. The nanocomposite demonstrated recyclability over six cycles while maintaining high activity. Radical trapping tests confirmed that ·OH was the key driver of photocatalytic degradation. This research offers an affordable, simple, and highly efficient approach to develop novel hydrogel supports that exhibit strong stability and effective photocatalytic capabilities.