Abstract
Refined natural Fe-chromite was characterized by XRD, FT-IR, reflected polarized microscope, XRF and UV spectrophotometer. Photocatalytic degradation and photo-Fenton oxidation of Congo red dye by Fe-chromite was investigated using 1 mL H2O2. The degradation of dye was studied as a function of illumination time, chromite mass, initial dye concentration, and pH. Fe-chromite acts as binary oxide system from chromium oxide and ferrous oxide. Thus, it exhibits photocatalytic properties under UV illumination and photo-Fenton oxidation after addition of H2O2. The degradation in the presence of H2O2 reached the equilibrium stage after 8 h (59.4%) but in the absence of H2O2 continued to 12 h (54.6%). Photocatalytic degradation results fitted well with zero, first order and second order kinetic model but it represented by second order rather than by the other models. While the photo-Fenton oxidation show medium fitting with the second order kinetic model only. The values of kinetic rate constants for the photo-Fenton oxidation were greater than those for the photocatalytic degradation. Thus, degradation of Congo red dye using chromite as catalyst is more efficient by photo-Fenton oxidation. Based on the response surface analysis, the predicted optimal conditions for maximum removal of Congo red dye by photocatalytic degradation (100%) were 12 mg/l, 0.14 g, 3, and 11 h for dye concentration, chromite mass, pH, and illumination time, respectively. Moreover, the optimum condition for photo-Fenton oxidation of dye (100%) is 13.5 mg/l, 0.10 g, 4, and 10 h, respectively.
Highlights
Rapid urbanization, industrialization and economic development in recent years lead to a continuous influx of toxic materials such as heavy metals, dyes, and pesticides into a water body which frequently causes water pollution (Shaban et al 2017a)
Degradation of Congo red dye using chromite as catalyst is more efficient by photo-Fenton oxidation
To study the influence of pH on degradation process, 0.04 gm from chromite was stirred with 100 mL of Congo red dye solutions (25 mg/l) of different pH values for 2 h either in the absence of H2O2 or after adding 1 mL from it
Summary
Industrialization and economic development in recent years lead to a continuous influx of toxic materials such as heavy metals, dyes, and pesticides into a water body which frequently causes water pollution (Shaban et al 2017a). Low cost and environmental heterogeneous photocatalysts were preferred in the degradation of dyes and water remediation applications (Sivakumar et al 2004). The main advantage of dye degradation using heterogeneous photocatalysts is the ability to profiteer the sunlight in the production of hydroxyl radicals (Shaban et al 2017d; Sivakumar et al 2010). Several natural minerals such as anatase, rutile, magnetite and ilmenite possess band gap energies which qualify them for photochemical reactions (Bubacz et al 2010) Such minerals are and widely available, cheap, efficient, and present in very high reserves around the world. We have studied the photocatalytic and photo-Fenton oxidation characterization of natural chromite for low-cost degradation of Congo red dye in water. We used response surface methodology (RSM) and statistical central composite rotatable design (CCRD) to evaluate the interactive effect of the selected parameters and the ideal optimum conditions for maximum removal of Congo red dye by chromite
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