Dye‐containing wastewater treatment by photo‐assisted wet peroxidation using Au nanosized catalysts

Abstract

Background The aim of this study is to test different supports on which to deposit Au nanoparticles and to determine the most suitable for Orange II (OII) dye degradation by a photo‐assisted wet peroxidation (PWPO) process. The catalysts used (Au‐Fe2O3, Au‐TiO2, Au‐ZnO and Au‐Al2O3) were prepared by the deposition–precipitation method; a reference catalyst from the World Gold Council, hereafter denoted as Au‐Fe2O3*, was also used for comparison. The catalysts were characterized in terms of surface area (SBET), gold nanoparticles size, Au loading and Au oxidation state using several techniques (namely, nitrogen adsorption at −196°C, X‐ray photoelectron spectroscopy – XPS, and high resolution transmission electron microscopy – HR‐TEM). Several runs were carried out for each material, to evaluate its efficiency in OII dye degradation by the PWPO process. Results All catalysts reached OII dye removals of >96% and considerable total organic carbon (TOC) degradation – between 58.4% and 80.5%. The materials had negligible Au leaching, showing very good stability. For the catalyst with best performance (Au/Al2O3), a parametric study was carried out to assess the effect of different variables on dye and TOC removals. Under the best conditions, excellent efficiency of the advanced oxidation process was obtained. A simulated industrial acrylic dyeing effluent was also treated by PWPO and very good performance was reached, with removals up to 100%, 72.4% and 70.0% for color, TOC and COD, respectively, with only 2 h of reaction. Moreover, there was an improvement in biodegradability and a non‐toxic effluent was generated. Conclusions PWPO using nano‐sized gold‐based catalysts proved to be a promising technique for the degradation of pollutants in water. The used gold supports have an important role in the efficiency of the process. The best catalyst was obtained using large surface area Al2O3 as support, although no leaching of gold was found for any of the catalysts. The mineralization degree improved under radiation due the formation of hydroxyl radicals, being reached total dye removal and a decrease of the TOC values greater than 90%. © 2018 Society of Chemical Industry

Wastewater Treatment by Catalytic Wet Peroxidation Using Nano Gold-Based Catalysts: A Review

“…98% and 47%, respectively, consumption of H 2 O 2~9 6%, and higher hydroxyl radicals generation) and the highest TOF value for OII dye removal (75.5 × 10 −6 s −1 ).The best efficiency of CPWO for Au/Al 2 O 3 was associated to its higher adsorption capacity. The same was concluded for these same catalysts when light-assisted CWPO was used for OII dye degradation [110]. Au/Al 2 O 3 permitted total discoloration and TOC removal of about 80%, combining further formation of hydroxyl radicals [110].…”

“…The same was concluded for these same catalysts when light-assisted CWPO was used for OII dye degradation [110]. Au/Al 2 O 3 permitted total discoloration and TOC removal of about 80%, combining further formation of hydroxyl radicals [110]. In the same way, Drašinac et al [107] observed that the morphological properties of the catalysts and gold properties played an important role in methyl orange (MO) dye degradation.…”

“…This is due to the fact that the dye is degraded in the presence of UV/vis radiation alone. However, the authors observed a slight reduction in mineralization from 68.2 to 58.4% when the gold content increased, as well as in the production of hydroxyl radicals [110].…”

“…However, in a work using CWPO assisted with radiation to treat an OII dye solution with gold on iron oxide, the gold content had no effect on the colour removal [110]. This is due to the fact that the dye is degraded in the presence of UV/vis radiation alone.…”

“…In both studies mentioned above, the authors pointed out an explanation for the decay of the process performance with the increase of the gold content; if in excess, gold reacts with the hydroxyl radical (HO • + Fe 2 O 3 -Au 0 → Fe 2 O 3 -Au + + HO − ), being less available to oxidize the dye, and the reaction by-products [66,110].…”