Regenerable chitosan-bismuth cobalt selenide hybrid microspheres for mitigation of organic pollutants in an aqueous environment.

Degradation of hazardous organic pollutants like dyes by semiconducting materials has been considered as one of the dynamic solutions for wastewater treatment. Herein, novel bismuth cobalt selenide (BCSN) tri-composite nanoparticles were prepared with a crystalline structure and narrow bandgap of (2.48 eV). The prepared nanoparticles were embedded in chitosan microspheres to avoid leaching and ensure the easy recovery of the composite. FTIR studies confirmed the synthesis of nanoparticles and chitosan‑bismuth cobalt selenide hybrid microspheres (BCSN-CM). SEM images showed the smooth face morphology having an average nanoparticles size of 30 nm and an average microspheres size of 734 μm. The crystallite size of the nanoparticles was also verified using the XRD technique and found to be 21.3 nm by applying Scherer's equation. EDX result demonstrated the presence of bismuth, cobalt, and selenium in the prepared sample. Congo red dye (CR) was degraded using the prepared BCSN-CM in sunlight irradiation, and operational parameters were evaluated to optimize the conditions responsible for maximum dye degradation. It was found that degradation of dye depends on factors like catalyst amount, irradiation time, dye concentration, and pH of dye solution. The degradation efficiency of prepared microspheres was found to be 85% of the 90-ppm solution under optimized conditions in sunlight irradiation for 100 min. The first-order kinetics was well fitted to degradation of CR having a rate constant of 1.50 × 10 min. Moreover, the prepared sample gave an excellent result after regeneration and reused up to five cycles. The newly fabricated chitosan-bismuth cobalt selenide hybrid microspheres might display a high potential for the removal of organic pollutants from the dye and textile industries wastewater.