Doping TiO2 with Fe from iron rusty waste for enhancing its activity under visible light in the Congo red dye photodegradation

Abstract

An afford to enhance TiO₂ activity under visible light as well as to utilize the iron rusty waste, has been conducted by doping Fe from the waste into TiO₂. The doping was performed by sol-gel method of titania tetra isopropoxide with Fe³⁺ ions dissolved from the iron rust waste. In the doping, the concentration of Fe³⁺ was varied giving various mole ratios of TiO₂:Fe. The doped TiO₂ photocatalysts were characterized using FTIR, XRD, SRUV, and SEM-EDX instruments. The photocatalytic activity of the doped TiO₂ was evaluated by photodegradation of Congo red under visible light. The effect of some parameters that govern the photodegradation process such as the amount of Fe dopant, reaction time, photocatalyst mass, solution pH, and initial concentration of dye was also studied. The characterization results reveal that Fe³⁺ ions from the rusty waste have been doped into TiO₂ which can remarkably narrow the band gap energy (Eg), shifting into the visible zone. In accordance, the activity of TiO₂ under visible light in the dye photodegradation is considerably enhanced. The Eg decreasing and actively improving the doped TiO₂ are controlled by the amount of Fe dopant, and the most effective Eg decreasing is shown by TiO₂–Fe (1:0.8), but the highest activity is observed for TiO₂–Fe (1:0.4). It is also found that the highest photodegradation of Congo red 5 mg/L in 50 mL of the solution over TiO₂–Fe (1:0.4) under visible light, that is about 99%, can be reached by applying 60 mg of the photocatalyst mass, in 60 min, and solution pH 5. It is implied that the rusty waste can be utilized to prepare the visible responsive photocatalyst that can be used for preventing dye pollution.