Water Science and Engineering (Dec 2020)
Green synthesis of bentonite-supported iron nanoparticles as a heterogeneous Fenton-like catalyst: Kinetics of decolorization of reactive blue 238 dye
Abstract
This study aimed to synthesize green tea nano zero-valent iron (GT-NZVI) and bentonite-supported green tea nano zero-valent iron (B-GT-NZVI) nanoparticles using green tea extracts in an environmentally sustainable way. Bentonite was used as a support material because it disperses and stabilizes GT-NZVI, and it helps to reduce the cost, increase the adsorption capacity of GT-NZVI, and decrease the optimum amount of GT-NZVI used in Fenton-like oxidation. A scanning electron microscope, an atomic force microscope, and a Fourier transform infrared spectroscope were used to characterize GT-NZVI and B-GT-NZVI, while the zeta potential was measured to evaluate the stability of iron nanoparticles. The decolorization kinetics of reactive blue 238 (RB 238) dye in the aqueous phase in the Fenton-like oxidation process were investigated as well. The effects of various experimental conditions such as reaction time, dosages of catalysts, concentration of H2O2, temperature, addition of inorganic salts, and other parameters were investigated. The results show that the oxidative degradation efficiencies of RB 238 dye catalyzed by GT-NZVI and B-GT-NZVI were 93.5% and 96.2%, respectively, at the optimum reaction conditions as follows: c(H2O2) = 5 mmol/L, ρ(GT-NZVI) = 0.5 g/L or ρ(B-GT-NZVI) = 0.5 g/L, c(RB 238 dye) = 0.05 mmol/L, and pH = 2.5 at 180 min. The best catalytic performance was exhibited when B-GT-NZVI was used. Three kinetic models were employed, and the second-order model was found to be the best model representing the experimental kinetic data of RB 238 dye. The value of activation energy decreased from 38.22 kJ/mol for GT-NZVI to 14.13 kJ/mol for B-GT-NZVI. This indicates that the effect of B-GT-NZVI in decreasing the energy barrier is more pronounced than that of the GT-NZVI catalyst, leading to improved Fenton-like oxidation processes.
