Optimization of solar degradation efficiency of bio-composting leachate using Nd: ZnO nanoparticles

Composting leachate is one of the highly polluted liquids generated at landfills and compost plant. Therefore, the aim of this research work was to photodegrade leachate generated from a biocomposting plant from Iran by neodymium-doped ZnO hybrid nanoparticles (Nd:ZnO NPs). The photocatalytic degradation of leachate was optimized based on surface response methodology. For the experimental design and process optimization, the central composite design was applied. The parameters studied were the dosage of Nd:ZnO NPs, solution pH, contact time, H₂O₂ concentration, and leachate concentration. Using “ Design Expert software (Trial Version 7.0)” totally 33 runs were considered for photodegradation studies. Mineralization of the leachate was confirmed by COD analysis. The response was assessed for different models and the high regression coefficient (R² = 0.9782, R_adj = 0.9909) between the variables and the response confirmed excellent estimation of experimental data by quadratic model. The optimum conditions (COD removal efficiency of 82.19%) were found to be at pH 6.74, Nd-doped ZnO dosage of 1920 mg/l, leachate concentration of 2000 mg/l, contact time of 114.62 min, the H₂O₂ concentration of 12.56 Mmole, and dopant percentage of 0.75.