Kinetic and equilibrium studies of the heavy metal remediation potential of Helix pomentia

Abstract

Heavy metals are one of the major pollutants in water and are very toxic. However, chitosan – a waste biomass of agricultural products possess the ability to chelate heavy metals in water. In this study, the application of snail (Helix pomatia) shell based chitosan for remediating heavy metals contaminated Osun River (OSR), Odo-ebu stream (OBS) and Aso well water (AWW), all in Osogbo community, Nigeria;  and the binding efficiency of chitosan for heavy metals in these water sources were evaluated. The result shows the prevalence of Iron (Fe), Cadmium (Cd), Zinc (Zn), Copper (Cu), Chromium (Cr), and Lead (Pb) ions in the three water samples with OBS and OSR having higher metal concentrations in the order: Pb > Cd > Fe > Zn > Cr > Cu compared with AWW which follows the order: Fe > Zn > Pb > Cr > Cd > Cu.  The concentration range of heavy metals in OBS and OSR were (0.0011 -2.831) mg/L and (0.0012 -1.687) mg/L respectively, while for AWW it was (0.0004-0.0237) mg/L and below the Standard Organization of Nigeria (SON) 2007  and World Health Organization (WHO) 2004; maximum permissible level of metal ions in drinking water. The prepared chitosan  is a selective candidate for remediating four heavy metals ions from these water samples, with the  maximum sorption capacities for the metal ions in the sequence: Pb > Cd > Fe > Cr. The  sorption behaviour followed a pseudo-second-order model, while the equilibrium data correlated well with the  Langmuir isotherm models with the RL values in the range 0 < RL < 1. Key words: Heavy metals, Helix pomatia, chitosan, dumpsite, equilibrium studies.