Use of clinoptilolite and an Fe-overexchanged clinoptilolite in Zn~(2+) and Mn~(2+) removal from drinking water

摘要

Clinoptilolite, a natural zeolite, was used for the synthesis of a high surface area clinoptilolite-iron oxide system (Clin-Fe system) to be used for the removal of Mn~(2+) and Zn~(2+) ions from drinking water samples. The new system was obtained by adding natural clinoptilolite to an iron nitrate solution in the presence of KOH solution. The Clin-Fe system had a specific surface area equal to 151 m~2/g and was fully iron exchanged (Fe/Al = 1.23). Batch adsorption experiments were carried out to determine the effectiveness of the Clin and of the Clin-Fe system in the removal of zinc and manganese from drinking water. For our experimental conditions, the maximum adsorbed Mn amount for Clin was 7.69 mg/g, whereas that for the Clin-Fe system was 27.1 mg/g. The respective values for the adsorption of Zn were 71.3 mg/g and 94.8 mg/g. In addition, the release of counterbalanced ions (i.e. Ca~(2+), Mg~(2+), Na~+ and K~+) was examined, as well as the dissolution of framework Si and Al. Desorption experiments were also carried out to determine which of the substrates is more effective in holding the adsorbed metals on its surface sites.