Preparation of double functional carbon-based ZnO derived from rape straw for dye wastewater treatment

Rape straw is used as feedstock to prepare the double functional carbon-based ZnO (RS/ZnO) using ZnCl2 as activation agent by one-pot method for dye wastewater removal. RS/ZnO has well-developed pore structure and ZnO, which can be used as the adsorbent and photocatalyst for rhodamine B (RB) and evans blue (EB) waste-water removal. RB and EB adsorption process are investigated by adsorption isotherms, kinetics and thermo-dynamic studies. The possible adsorption mechanism includes hydrogen bonding, pi-pi interactions, electrostatic attraction, pore filling and surface complexation. The adsorption amount of EB is larger compared to RB, which is further explained by density functional theory calculation. RB and EB photocatalytic degradation removal are close to 100 % under UV irradiation. The center dot OH and center dot O2(-) generated by RS/ZnO are responsible for RB and EB photocatalytic degradation based on electron paramagnetic resonance spectrometer analysis. Besides, the adsorption performance of RS/ZnO contributes to RB and EB photocatalytic degradation. This work indicates that rape straw waste is converted into RS/ZnO for dye wastewater purification.

Automated summary

Rape straw waste was converted into double functional carbon-based ZnO (RS/ZnO) by activation with ZnCl2, and it showed excellent adsorption and photocatalytic properties for the removal of rhodamine B (RB) and evans blue (EB) in wastewater. The adsorption mechanism involves hydrogen bonding, pi-pi interactions, electrostatic attraction, pore filling, and surface complexation. The adsorption amount of EB is higher than RB, which is supported by density functional theory calculations. The photocatalytic degradation of RB and EB reached close to 100% under UV irradiation, and the generated ·OH and ·O2(-) were responsible for the degradation process, as confirmed by electron paramagnetic resonance spectrometer analysis. This work demonstrates the potential of utilizing rape straw waste for dye wastewater purification.