Ag0, Re0, and Ag@Re heterogeneous persulfate activators for reactive radical based oxidation of water contaminant

Abstract

Silver-rhenium bi-metallic nanoparticles (Ag-Re) were prepared by the combination of colloidal sols of silver and rhenium at room temperature. The silver and rhenium sols were synthesized by using the chemical reduction of silver nitrate and ammonium perrhenate with sodium borohydride in presence of cetyltrimethylammonium bromide (CTAB). The morphology (shape, size, elemental composition, oxidation states, and crystalline nature) and textural properties (pore size, pore volume, and surface area) of Ag0-Re0 were determined with EDX, SEM, TEM, XPS, XRD, and nitrogen adsorption-desorption isotherm. The Ag0-Re0 was used as heterogeneous persulfate (S2O82−) activator to generate reactive radical species (SO4−• and HO•) for the degradation of xylenol orange (XO) at 434 nm. The Ag-Re exhibits higher XO degradation efficiency than that of mono-metallic Ag0 and Re0 nanoparticles, respectively. The degradation efficiency strongly depends on the concentrations of S2O82−, XO, pH, temperature, and amount of Ag0-Re0. The role of SO4−• and HO• were established by using ethanol, and tertiary butanol as radical scavengers. The activation energy was found to be 85.2, 63.5, and 32.6 kJ/mol, respectively, to the degradation of XO by activated S2O82− with Re0, Ag0, and Ag0-Re0.