Adsorptive removal of methylene blue dye from aqueous streams using photocatalytic CuBTC/ZnO chitosan composites

In this study, the CuBTC/ZnO chitosan composite was synthesized for the adsorptive removal of methylene blue dye from aqueous streams. The characterization techniques, namely, scanning electron microscopy, Brunauer-Emmett-Teller, Fourier-transform infrared, X-ray diffraction, and thermogravimetric techniques, were used to characterize the CuBTC, ZnO, and CuBTC/ZnO chitosan composites. The scanning electron microscopy images revealed the rough and porous structures of the CuBTC/ZnO chitosan composite. The composites were tested for the adsorption capacity and the removal efficiency towards the methylene blue dye by varying adsorbent dosage, adsorbate concentration, pH and contact time. The pseudo-second-order and Langmuir model were the best fit for the adsorption of methylene blue on CuBTC/ZnO chitosan composite beads, indicating that the adsorption was chemical in nature. The equilibrium dose of the composites was 1.6 g L−1, and the contact time was 90 min with a removal efficiency of 98.75%. The maximum adsorption capacity was 50.07 mg g−1. The composites’ regeneration was performed to check the reusability of the synthesized CuBTC/ZnO chitosan composite beads. The active oxygenated species generated by the photocatalytic action of ZnO on the contaminated water was responsible for the degradation of methylene blue. The reported composite beads can be used for up to 5 cycles to remove methylene blue. HIGHLIGHTS Photocatalytic CuBTC/ZnO chitosan composite beads were synthesized for adsorptive removal of methylene blue dye. The adsorption efficiency of the composite for the removal of methylene blue was investigated by varying reaction parameters such as contact time, dosage, initial concentration, pH. The reported adsorbent could be used for up to 5 cycles to remove methylene blue without significant loss of removal efficiency.