The role of pH in metal ion removal using coir dust and its modified extract resins

Abstract

The role of pH on metal ion adsorption by unmodified coir dust and its modified extract forms (namely carboxylated and sulphonated coir extract resins) was studied in a batch system. The zero point charge pH (pH pzc) of the adsorbents was determined and the results demonstrated that the amount of metal ions adsorbed by the adsorbents was dependent on pH(pzc). The adsorption of these metal ions by the adsorbent increased with increasing pH. The unmodified coir dust, being a lignocellulosic material, removed more metal ions than the modified coir extract resins derived from a tannin-polyhydroxy compound. Hydroxyl, carboxylic and sulphonic functional groups are responsible for the metal ion binding in these adsorbents, as revealed by infra-red spectroscopic analysis. Coir dust, carboxylated coir extract (CTR) and sulphonated coir extract resin (STR) are effective adsorbents for removal of metal ions from aqueous solution and industrial effluents/wastewater. © 2012 Taylor & Francis.