Red water treatment by photodegradation process in presence of modified TiO2 nanoparticles and validation of treatment efficiency by MLR technique

An active photocatalyst under sunlight irradiation was proposed for treatment of red water of TNT production process. The nanoparticles of TiO₂/S_0.05,Zn_0.05 were prepared by the sol–gel method and were verified by XRD pattern, TEM image, EDXS analysis, BET analysis and DRS spectra. The proposed photocatalyst showed the surface area of 146 m² g^?1, anatase and rutile phases and band-gap energy of 2.92 eV. The prepared nanoparticles were used as photocatalyst in treatment of red water under UV lamp and sun irradiations. The photodegradation process was optimized in conditions of 5 g L^?1 of photocatalyst, irradiation time of 4 h and dilution times of 1000 of real samples. The treatment efficiency of 76 and 69 % and rate constants of 0.368 and 0.319 h^?1 were obtained under UV and sun irradiations, respectively. The multiple linear regression as a statistic technique was used for study of validation and verification of four factors of mole fraction of S dopant, the irradiation intensity of UV lamp, the dose of photocatalyst and dilution times on samples as predictor’s on the treatment efficiency of red water as the response variable. The output of MLR showed the obtained P values <0.05 in confidence level of 95 % for all of the variables. Thus, the null hypothesis is rejected, and a meaningful addition is observed in the model because changes in the predictor’s value are related to changes in the response variable.