Removal of Heavy Metals in Drinking Water by Iron-based Sorption Materials

Abstract

Adsorption on a suitable adsorption material is the most frequently used methods in water treatment. In terms of plant operation, filtration (sorption) process represents a simple, effective and economical friendly method of heavy metals removal namely for the possibility of using a large scale of substances with a sorption ability - sorbents. Oxides, oxyhydroxides and hydroxide containing iron are among the most frequently used sorbents of the heavy metal removal. The quality of the treated water (pH, silica, phosphorus, fluorides, sulphates, total mineralization, iron and manganese, organic matter, etc.), redox conditions, the valency of metal and filtration conditions has the impacts on heavy metal removing efficiency. The objective of this work was to verify the sorption properties of granular iron-based sorption materials (CFH12, CFH18, Bayoxide E33, GEH) in removal of arsenic, antimony and nickel from drinking water. Under the given operational conditions (average concentration of arsenic in raw water 52,96 μg/L, average velocity 5.6 m/h, concentration As 10 μg/L at the outlet of media) adsorption capacity of filtration material CFH12 and Bayoxide E33 for arsenic was 1.203 mg/g and 1.463 mg/g, respectively. The limit of 10 μg/L of as was exceeded after 24048 BV and 28623 BV (Bed volume), respectively. According to the model tests (concentration of nickel in raw water of about 50 μg/L, filtration rate 5.8 m/h, concentration Ni 20 μg/L at the outlet of media, pH 7.0) the adsorption capacity of nickel for Bayoxide E33 was set to 198 μg/g, for CFH18 107.5 μg/g, GEH 97.5 μg/g and CFH12 38.1 μg/g. The limit of 20 μg/L of Ni was exceeded after 4808 BV for Bayoxide E33, 1409 BV for CFH12, 3007 BV for CFH18 and 3218 BV for GEH. For the average antimony concentration of 58.35 μg/L in raw water and filtration rate between 4.27-4.51 m/h, the limit concentration of 5 μg/l at the outlet of the sorption column was reached at the bed volume 3470 for GEH, 2225 for CFH 12 and 1274 for Bayoxide E33. The adsorption capacities were as follows: 167.8 μg/g for GEH, 105.7 μg/g for CFH12 and 90.9 μg/g for Bayoxide E33. The experiments proved that iron-based sorption materials GEH, CFH12, CFH18 and Bayoxide E33 can help reduce the concentration of heavy metals in water below the limit of the Slovak Republic Decree No. 247/2017 on Drinking Water.