Removal of Mn2+ ions from drinking water by using Clinoptilolite and a Clinoptilolite-Fe oxide system

Clinoptilolite, a natural zeolite, was used for the synthesis of a high surface area Clinoptilolite-Iron oxide system, in order to be used for the removal of Mn2+ ions from drinking water samples. The new system was obtained by adding natural clinoptilolite in an iron nitrate solution under strongly basic conditions. The Clin-Fe system has specific surface area equal to 151.0 m2/g and is fully iron exchanged (Fe/Al = 1.23). Batch adsorption experiments were carried out to determine the effectiveness of the Clin and the Clin-Fe system in removal of manganese from drinking water. Adsorption experiments were conducted by mixing 1.00 g of each of the substrates with certain volume of water samples contaminated with 10 different Mn concentrations (from 3.64 x 10(-6) to 1.82 x 10(-2) M or from 0.2 to 1000 ppm). For the present experimental conditions, the Mn adsorption capacity of Clin was 7.69 mg/g, whereas, of Clin-Fe system was 27.12 mg/g. The main factors that contribute to difference adsorption capacity of the two solids are due to new surface species and negative charge of Clin-Fe system. In addition, the release of counterbalanced ions (i.e., Ca2+, Mg2+, Na+ and K+) was examined as well as the dissolution of framework Si and Al. It was found that for the most of the samples the Clin-Fe system releases lower concentrations of Ca, Mg and Na and higher concentrations of K than Clin, while the dissolution of Si/Al was limited. Changes in the composition of water samples as well as in their pH and conductivities values were reported and explained.