Photocatalytic mineralization and degradation kinetics of ampicillin and oxytetracycline antibiotics using graphene sand composite and chitosan supported BiOCl

• BiOCl nanoplates were supported over graphene sand composite(GSC) and chitosan(CT).
• Photocatalytic activity of BiOCl/GSC and BiOCl/CT was tested for antibiotic removal.
• Simultaneous adsorption and photocatalysis had synergistic effect on process.
• Complete photo-mineralization of antibiotics was attainted under solar light.
• Power law model validated the complex kinetics of long term degradation process.

In precedent work, nano-sized BiOCl was immobilized onto graphene sand composite (GSC) and chitosan (CT) to report efficient photocatalytic system for wastewater treatment. GSC was prepared by graphitization of sugar over river sand. The supported BiOCl was prepared by modified hydrolysis method to report BiOCl/GSC and BiOCl/CT photocatalysts. The citric acid directed nucleation and growth process resulted in well dispersed BiOCl nanoplates over GSC and CT. The supported catalysts were characterized by FESEM, TEM, HRTEM, FTIR, XRD, EDX, BET, Raman, photoluminescence and UV–vis diffuse reflectance spectral analysis. The optical band gap of BiOCl/GSC and BiOCl/CT was given by 3.31 and 3.33 eV, respectively. The size of BiOCl/GSC and BiOCl/CT was found to be 50 and 70 nm respectively. The catalytic efficiency of BiOCl/GSC and BiOCl/CT was tested for ampicillin (AMP) and oxytetracycline (OTC) removal. The adsorption of AMP and OTC followed pseudo second order kinetics. Both BiOCl/GSC and BiOCl/CT exhibited significant photocatalytic activity for the mineralization of ampicillin (AMP) and oxytetracycline (OTC) antibiotics under solar light. Simultaneous adsorption and degradation process (A+P) process showed higher antibiotic degradation rate. The applicability of power law model showed the complex nature of mineralization process. During A+P process, both antibiotics were mineralized to CO2, H2O and NO3− ions. BiOCl/GSC and BiOCl/CT exhibited significant recycle efficiency for 10 catalytic cycles in comparison to native BiOCl.

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