Fenton-like oxidation of Orange II solutions using heterogeneous catalysts based on saponite clay

Abstract

Fe-clay catalysts have been prepared and tested for Orange II oxidation with H2O2 in aqueous solution. The reaction is carried out in a batch reactor, using different hydrogen peroxide concentrations, and in a wide range of temperature and pH values. Twelve samples were prepared, with three different iron loads (7.5, 13.0 and 17.0 %, w/w), and using four iron salts as precursors, namely Fe(II) acetate, Fe(II) oxalate, Fe(II) acetylacetonate and Fe(III) acetylacetonate. The samples were characterized using X-ray diffraction, thermal analysis, infrared spectroscopy and adsorption of nitrogen at 77K. The catalytic results show that these solids present good catalytic properties for the degradation and mineralization of Orange II solutions, allowing to reach, in the best conditions and after 4h of oxidation, 99% of dye degradation with 91% of TOC (Total Organic Carbon) reduction (at 70ºC), using only ca. 90 mg of clay catalyst per litre of solution. Nevertheless, 96% of dye removal with 82% of mineralization were also reached at 30ºC. Besides, the amount of iron released into the final solution is lower than 1 ppm, in the worst of the cases, and 0.09 ppm in the best case.

Heterogeneous Fenton-like degradation of Rhodamine 6G in water using CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis

“…The increase of TOC elimination and the decrease of naphthalene ring removal with hydrogen peroxide concentration indicate that benzene ring removal is enhanced by the increase of H 2 O 2 concentration. The effect of H 2 O 2 on degradation and TOC removal being similar to those reported by Ramirez et al [4] in the Fenton-like oxidation of Orange II solutions over heterogeneous catalysts based on saponite clay, by Dutta et al [26] in the chemical oxidation of methylene blue using a Fenton-like reaction, by Guedes et al [27] in the Fenton oxidation of cork cooking waste water and by Stolyarova et al [3] in oxidative degradation of Rhodamine 6G over FeZSM-5 zeolites. …”

“…The absorption spectra of Rhodamine 6G is characterized by three main bands, one in the visible region ( max = 523 nm) which is responsible for the chromophoric components (for the color of dye arising from aromatic rings connected by azo groups) and the others in the UV region ( max = 246 nm and max = 275 nm) which represent the absorption of benzene-like and naphthalene-like structures in the molecule, respectively [4]. Rhodamine 6G is also called as R6G, Rh6G, C.I.…”

“…After stabilization of the temperature at 323 K, pH of the solution was again measured and the solution was analyzed in order to determine whether the dye is adsorbed by the catalyst. 4 into the dye solution. The samples taken periodically at every 15 min were diluted in 1:10 ratio.…”

“…These drawbacks can be overcome by using heterogeneous Fenton-type catalysts, in particular, zeolites, whose recovery from water is not difficult. Iron and copper containing zeolites show redox properties because these metals can change their oxidation states [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Recently, high catalytic activity of iron containing zeolites for phenol oxidation [15,16] and for degradation of dyes [2,3] has been reported.…”

“…Recently, high catalytic activity of iron containing zeolites for phenol oxidation [15,16] and for degradation of dyes [2,3] has been reported. Supported Fe-saponite clay catalysts revealed to be quite active in the Fenton-like oxidation of Orange II [4]. FeZSM-5 prepared by ion-exchange was tested in wet oxidation with hydrogen peroxide of diluted formic, acetic and propionic acid [17].…”