Kinetic and equilibrium studies on bioadsorption of copper and lead by water hyacinth (Eichhornia crassipes) plant powder

Abstract

Common water hyacinth plant (Eichhornia crassipes) found in various water bodies in Assam, India, was used as bioadsorbent for removal of toxic metals (Cu and Pb) from synthetic medium. The functional groups present in the bioadsorbent, water hyacinth plant powder (WPP) were determined by using Fourier transform infra red spectroscopy (FTIR) and surface topography by scanning electron microscopy (SEM) technique. The specific surface area of WPP was also determined. The optimum adsorption properties of WPP was determined by considering pH, agitation time, metal concentration, temperature and the amount of adsorbent. The adsorbent showed good adsorption of toxic metal, Cu and Pb from synthetic medium. Water hyacinth plant was used to treat ten synthetic mediums containing 40, 50, 60 70 and 80 mgL⁻¹ of the two heavy metals, Cu and Pb. From the batch study, it was observed that the adsorption mechanism for the studied metals follow the 2ⁿᵈ order kinetics and the isotherm study showed that Langmuir model is suitable for explaining the adsorption equilibrium data for bioadsorption of Cu²⁺ and Pb²⁺ ions on WPP. For Cu(II) adsorption on WPP, the maximum adsorption was observed at pH 7 while for Pb(II), the maximum adsorption was observed at pH 5.