A potential remediation of chromium (VI) containing aqueous media onto surface-treated clinoptilolite vs. brief evaluation of other natural materials

Abstract

A broad range of various natural and commercial adsorption materials and waste products was examined in order to verify the removal of commonly occurring cationic, anionic and some organic pollutants and briefly to compare each other. The inland natural zeolites of clinoptilolite type and its surface-treated modifications were used too. Actually, untreated clinoptilolite can compete with other natural materials or even waste products, occurring in the markets of many countries at very low prices. Industrial adsorbents are usually characterized with a high surface area, mechanical stability and uniformly accessible and interlinked pores. Abundantly occurring clinoptilolite tuffs, the Slovak one used in this research, possess the necessary interparticle mesoporosity. Moreover it is a natural cost-effective resource. The most extensive uptake of the studied chromate oxyanions at laboratory measure was observed by montmorillonite (142.86 mg/g), probably based on the large interplanar dimensions of this microcrystallite. The octadecyl ammonium hydrophobized i.e. ODA-clinoptilolite approached the second highest adsorption capacity to chromate (64.93 mg/g), while the MnOx-zeolite (clinoptilolite) proved the lowest adsorption ability (12.99 mg/g). Almost for all the systems studied, the Langmuir isotherm fitted better for mathematical description of the above adsorption process. From the breakthrough curves recorded, the Pb – and ODA – clinoptilolite packed column quantitatively removed chromate anion from the solution, apparently more efficiently using the lower flow rate.