The potential of a natural Ecuadorian mordenite-type zeolite for batch and column selenium removal

Abstract

ABSTRACT Selenium is found in natural waters of developing countries. The present study refers to Se (IV) adsorption onto an Ecuadorian natural zeolite, activated at 225°C. Its physicochemical characterization included particle size analysis, XRD, SEM-EDX, and FTIR. After selenium adsorption, the FTIR spectra denoted the presence of moved bands and new peaks, probably corresponding to new metal bond vibrations. Batch experiments were carried out at 26°C, for 2 h, at adsorbate doses within 0.01–50 mg L−1, bringing about a removal percentage in the range of 57−90%. Eventually, Se (IV) adsorption was performed at a pH of 7.5, resembling realistic well-water matrix conditions. Zeolite accomplished a maximum Se adsorption capacity of 53 mg g−1 zeolite, corresponding to roughly 90% of Se removal. The results obtained upon constant flow mode were analyzed with various kinetic models, appearing Thomas and BDST models to fit better. The highest Se removal percentage on typical well waters leaves a Se value lower than the permissible levels. Thus, natural zeolites offer an economic and competitive alternative for Se (IV) removal, especially from groundwater and industrial wastewater in developing countries.