Development of hybrid membrane process with surfactant modified powdered activated carbon(SM-PAC) to remove anionic pollutant

Abstract

Hybrid membrane process with surfactant modified-powdered activated carbon(SM-PAC) is investigated to remove ionic pollutant from water. At first, adsorbent that has affinity to anionic pollutant is prepared by modifying surface property of activated carbon. Ceptylpyridinium chloride (CPC) is used to modify activated carbon. SM-PAC indicates positive charge due to adsorbed cationic surfactant. And it can adsorb anionic pollutant from water by electrostatic attraction. Mixture of SM-PAC and anionic pollutant can be separated by filtration with MF/UF membrane. Arsenate ($H_2AsO_4^-$), chromate ($CrO_4^{2-}$) and ferricyanide ($Fe(CN)_6^{3-}$) are used as ionic contaminant. Adsorption affinity of SM-PAC to anionic contaminants is tested at different conditions. The adsorption isotherm of each contaminant is well fitted with Langmuir type. Chromate shows the highest adsorption capacity (0.234 mmol/g). Maximum adsorbed amount arsenate and ferricyanide are similar to each other ($\approx$ 0.09 mmol/g). In case of mixed contaminant system, the contaminant adsorption affinity changed. In mixed contaminant system, contaminants compete with each other to occupy binding site. Higher valence anion holds the binding site due to strong electrostatic force. As a result adsorption affinity changes as ferricyanide > chromate > arsenate. With 2 g/L of SM-PAC, it is possible to treat 0.001mM of arsenate, 0.5 mM of chromate and 0.2 mM of ferricyanide completely. Also SM-PAC can remove organic and ionic pollutant simultaneously. Humic acid (HA) and ferricyanide are removed by SM-PAC. There is synergistic effect when HA and ferricyanide present together. In the presence of ferricyanide, removal of HA is raised to > 90%. The removal of ferricyanide is also increased by HA. In ultrafiltration system, hybrid membrane process with SM-PAC is applied to remove anionic contaminant. 4 g/L of SM-PAC can completely remove 0.3 mM of chromate and ferricyanide but arsenate removal is inhibit...