Copper and chromium removal from synthetic textile wastewater using clay minerals and zeolite through the effect of pH

The textile industries release a substantial amount of effluents into water resources every year. The vast majority of these effluents are composed of heavy metals that bind the textile fibres with dyes. This work proposes to use an adsorption system composed of clay-minerals (kaolinite and montmorillonite) and molecular sieve (zeolite) for separating the Cu2+ and Cr6+ ions, considering the pH changes of aqueous solutions. The adsorbent materials were characterized using the following state of the art techniques such as X-ray fluorescence, X-ray diffraction, Raman spectroscopy and Cation exchange capacity. During the adsorption tests, the contact time of the adsorbates (Cu2+ and Cr6+ ions in concentrations of 100, 50, 10 and 5 mg/L) with the adsorbents vary from 1 to 4 h in acidic and alkaline conditions (pH 3.5 and 7.5). The results indicate maximum adsorption of Cu2+ (at pH 3.5) and Cr6+ (at pH 7.5) ions on application of the zeolitic material. The clay minerals conclusively proved to be less efficient when compared to zeolite. It can be concluded that the adsorption system has achieved the desired efficiency, with substantial removal of Cu2+ and Cr6+ ions for zeolites in synthetic wastewater solutions of the textile industry.