Removal of anionic dyes from aqueous solution by leaching solutions of white mud

A leaching solution of white mud was prepared from this waste material of soda production, and used in the removal of the model anionic dyes reactive bright red K-2BP, reactive light yellow K-6G, acid orange II and direct yellow R. In alkaline conditions, the leaching solution of white mud generates hydroxide precipitates, which have relatively high specific surface area and excess surface energy, and readily adsorb the dyestuffs. In this study, the chemical composition of the white mud was determined by X-ray fluorescence and the hydroxide precipitates were characterized by dynamic light scattering, transmission electron microscopy and Fourier-transform infrared spectroscopy. The maximum adsorption capacity was observed at an adsorbent dosage of 2.0 g/L, pH 12.0 and 293 K, which for reactive bright red K-2BP, reactive light yellow K-6G, acid orange II and direct yellow R were 416.7, 454.5, 769.2 and 2186.4 mg/g, respectively. The adsorption was consistent with the Langmuir and Freundlich isotherms and was exothermic. Leaching data showed that the treated water was nontoxic. It is especially suitable for the treatment of alkaline dye effluents. The leaching solution also displayed significant removal of color and COD for the textile effluent from a printing and dyeing factory. (C) 2011 Elsevier B.V. All rights reserved.