Abstract
ZnO-ZnFe2O4 composite was applied for photocatalytic degradation of naphthalene in fresh and saline waters under visible light irradiation. The effects of initial concentration of naphthalene, ZnO-ZnFe2O4 dosage and salinity on photocatalytic degradation of naphthalene were investigated using the central composite design. Statistically significant model quadratic equation was developed for photocatalytic degradation of naphthalene using ZnO-ZnFe2O4 composite. The most significant parameter in the photocatalytic degradation is the ZnO-ZnFe2O4 dosage followed by the initial concentration of naphthalene and then salinity. The highest photocatalytic degradation of naphthalene was achieved at salinity of zero (that is in fresh water). The predicted optimum conditions for photocatalytic degradation of naphthalene using the ZnO-ZnFe2O4 composite are: initial naphthalene concentration of 16.8 mg/l, ZnO-ZnFe2O4 dosage of 0.50 g/l, and salinity of 0 ppt. The model quadratic equation was validated by performing experiments under the predicted optimum values. The experimental and the predicted values of naphthalene degradation under the predicted optimum values are 99.04 % and 98.8 %. Hence, the developed quadratic model is reliable for predicting photocatalytic degradation of naphthalene using ZnO-ZnFe2O4 composite.
Highlights
Polycyclic aromatic hydrocarbons are persistent organic pollutants that are often toxic, carcinogenic and mutagenic
Design of photocatalytic experiments The central composite design (CCD) of the response surface methodology as implemented in Design Expert 6.0.6 software package was applied to investigate the effect of initial concentration of naphthalene (A), ZnO-ZnFe2O4 dosage (B) and salinity (C) on the photocatalytic degradation of naphthalene using the ZnO-ZnFe2O4 composite
The developed quadratic model is reliable for predicting photocatalytic degradation of naphthalene
Summary
The trend in F values of the model terms suggests that ZnO-ZnFe2O4 dosage has the largest effect on the photocatalytic degradation process followed by the initial concentration of naphthalene and salinity. The results of the numerical optimization show that maximum percentage degradation of 98.8% can be achieved under the following predicted optimum conditions: initial naphthalene concentration of 16.8mg/l, ZnO-ZnFe2O4 dosage of 0.50 g/l, and salinity of 0 ppt. They developed a quadratic model that described the effect of the four independent parameters (agitation speed, air flow rate, photocatalyst dosage, and UV light intensity) on the degradation of naphthalene Their optimization results showed that maximum photocatalytic degradation of naphthalene of 66.3 % can be achieved at the following optimum conditions: agitation speed of 150 rpm, air flow rate of 5 L/h, TiO2 dosage of 2.17 g/l, and UV light power of 18.67 W [33]. The high photocatalytic activity of ZnO-ZnFe2O4 under visible light irradiation makes it a very promising photocatalyst for solar driven photocatalytic processes because 46% of the solar spectrum is visible light; UV constitutes less than 5% of the solar spectrum [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
