BIOSORPTION OF Pb(II) AND Cu(II) IONS FROM AQUEOUS SOLUTION USING COFFEE SENNA (Senna occidentalis) LEAVES AS BIOMASS

Abstract

Conventional reagents for the remediation of heavy metals from wastewaters are expensive. Plant materials are being investigated to serve as alternative. The potential of Senna occidentalis leaves in removing Pb (II) and Cu (II) ions from aqueous solution was investigated using Batch adsorption method. The process was subjected to different experimental conditions such as initial metal concentration, solution pH, contact time, biosorbent dose, temperature and shaking speed. Atomic absorption spectroscopy (AAS) was employed in the determination of metal ion concentrations in solution after agitation, and characterization of plant biomass was done using infrared (IR) and scanning electron microscopy (SEM) analytical techniques. The adsorption process vary with the pH of the reaction medium. The optimum adsorption of Pb (II) and Cu (II) ions was achieved at pH 6 and 4 with percent uptake recorded at 97.70% and 82.32% respectively. At optimum temperatures of 40oC & 60oC for Pb (II) and Cu (II) ions, reaction equilibrium was attained after 120 min and 90 min of contact with 20 mg and 40 mg doses of the biomass respectively. The adsorption data for Pb (II) ion fitted well to Langmuir, Freundlich, Temkin and Dubbinin-Radushkevich isotherms. However, Cu (II) ion adsorption mechanism showed exception to Langmuir adsorption isotherm. The plant material was found to be effective in removing Pb (II) and Cu (II) ions and thus, can serve as a substitute for costly adsorbents in the remediation of Pb (II) and Cu (II) ions from wastewaters.