Deposition of goethite and ferrihydrite onto expanded vermiculite surface: chemical properties and potential application

Abstract

Current demand on adsorbent materials is in constant growth, hence scientific society is in ceaseless research subjecting cheap and optimal adsorbent. Abundant raw materials which may be utilized as adsorbent of cation species are mica minerals, and vermiculite as one of them is widely examined. Since wastewater may contain anion or/ and non-ionic pollutants it is needed to functionalize adsorbent so it may attract those species as well. Goethite and ferrihydrite are potential candidates for such modification since they: have large specific surface area (SSA), possess hydroxide group and they are not toxic to the environment. Goethite/ expanded vermiculite (Goe/EV) and ferrihydrite/ expanded vermiculite (Fer/EV) are successfully prepared and those composites have showed better adsorption related chemical properties than expanded vermiculite (EV) itself. Utilizing BET methodology, it is determined that Fer/EV possess five-time larger SSA than EV, while Goe/EV is two times larger. Measuring cation exchange capacity (CEC) it is determined that modified samples have only ~10% smaller values of CEC. Summary, both composites have shown higher affinity toward cationic dye, malachite green and also showed their adsorbent potential toward anionic dye, tartrazine. Thanks to facile preparation of such materials and its cost, it may be concluded that they are prospective choice as adsorbents, in first order of heavy metals and dyes.