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

Abstract

ABSTRACTSelenium 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.KEYWORDS: Adsorption bed columnsadsorption isotherm modelsadsorption selenium removalbreakthrough curvesnatural zeolites Highlights Batch experiments with doses resembling groundwater and industrial waters brought about 57% 90% Se removal.Se (IV) adsorption could be successfully attained at pH 7.5, thus avoiding chemicals usage.Natural mordenite-type zeolite accomplished a maximum Se adsorption capacity of 53 µg L–1 zeolite.Kinetic studies from Se adsorption on column fit well Thomas and BDST models.The highest Se removal percentage at groundwater levels leaves a Se value lower than permissible levels.Disclosure statementNo potential conflict of interest was reported by the author(s).Data availability statementThe data that support the findings of this study are available on request from the corresponding author.Statement of noveltyThe present study deals with the treatment of water contaminated with selenium, a typical nonmetal in groundwaters generated from industrial activities. The metal has been proposed to be removed using the adsorption principle onto a natural mordenite-type zeolite, on which scarce studies are reported for selenium removal, unlike artificial ones. In a particular way, the study is outstanding because it also compares Se adsorption on natural and artificial mordenite and intentionally declines the most suitable adsorption conditions to favor others which still results in practical, i.e., pH adjustment avoidance, consequently avoiding chemical usage. Upon these conditions, batch and column trials were performed. Finally, the strategy brings economic and environmental benefits such as reducing costs, especially for developing countries, where inexpensive adsorption technologies are not common.Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/01496395.2023.2250549