Optimization of Continuous Flow Adsorption of Heavy Metal Ions by Peganum Harmala Seeds

Background & Aims of the Study: Heavy metals discharge to environment is a worldwideproblem growing in scale. When they accumulate in the environment and in food chains,they can profoundly disrupt biological processes. Peganum Harmala Seeds (PHS) was usedas a bio-sorbent, using a continuous system for removing Pb2+, Co2+, Ni2+ and Cu2+ ionsfrom aqueous solutions.Materials and Methods: PHS was used as adsorbent in adsorption of heavy metals fromaqueous solutions. A stock solution of Pb(II), Co(II), Cu (II) and Ni (II) was prepared andexperiments were down in a column as a reactor. The concentration was determined byatomic adsorption spectroscopy. The effect of various parameters such as pH, contact time,heavy metal concentration, ionic strength, particle size and adsorbent dosage on the processwas investigated. Langmuir, Frundlich and Temkin isotherms were studied to evaluate ofadsorption isotherms.Results: The adsorption efficiency was found to be pH dependent and enhanced byincreasing the solution pH. Maximum removal of ions were obtained at pH=4-8. Theequilibrium time was attained after 30 min and desorption studies were performed, usingdiluted HNO3, H2SO4 and HCl solution (1M) on adsorbed metal ions from PHS. Resultsillustrated that adsorbed metal ions could be recovered under acidic conditions.Investigation of the process kinetic was best fitted with pseudo second-order model.Langmuir, Freundlich and Temkin models were tested for describing the equilibrium data.The Langmuir isotherm illustrated the best description of the cobalt and copper adsorptionmechanism and Freundlich model describes lead and nickel ions adsorption on PHS.Conclusion: It was found that PHS would be a good adsorbent for removal of heavymetals.