Optimization of a novel visible-light-driven Ag/C-TiO2 nanophotocatalyst for treatment of recombinant DNA in biopharmaceutical wastewater

The aim of this research was to optimize and model the synthesis and application of a novel visible-light-driven Ag/C-TiO2 nanophotocatalyst for degradation of recombinant DNA in Hepatitis B surface antigen production plant wastewater. The synthesized nanoparticles were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectra, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The effects of the dopant content of silver and carbon, calcination temperature, heating rate, initial recombinant DNA copy number, pH value, and contact time were evaluated experimentally and optimized separately as the synthesis and operational parameters. Application of response surface methodology showed the optimum values of Ag content, C content, calcination temperature, and the heating rate as 2.2 wt%, 0.06 wt%, 444 °C, and 12 °C/min, respectively. Synthesized nanoparticles resulted in 60% recombinant DNA degradation at the optimized operation conditions experimentally (i.e., pH of 5.5, contact time of 24 h, and the maximum initial recombinant DNA concentration of 2.12E13 copy number in 200 mL wastewater). The synthesis and operating quadratic models adequately predicted the experimental data. The statistical analysis showed that the square of carbon dopant content, calcination temperature, initial recombinant DNA concentration, and contact time had the greatest effects on the recombinant DNA degradation.