Simultaneous adsorption of Cd2+ , Ni2+ and Pb2+ on peat

Abstract

The aim of the present work was to investigate iflocally available untreated peat could beused as filter material for the removal of heavy metals from leachate. The aqueoussolutions containing Cd2+, Ni2+ and Pb2+ ions in single-metal and multi-metal solutionswere used to study the adsorption of metals on peat. The peat was obtained fromSouthern Estonia. The decomposition rate of the peat was H6-H7 on the von Post scale.In order to assess the adsorption mechanism, the amounts of Ca2+ and Mg2+ ions desorbedfrom untreated peat were measured and compared to the adsorption efficiency of Cd2+,Ni2+ and Pb2+ ions from solution on the peat. The desorption of other cations, such asAl3+, K+, Na+, Fe3+, Zn2+ etc. were negligible during all experiments. Adsorption batchisotherm studies were carried out by using IO experimental series with the initialconcentration of 10 - 300 mg/I. The samples were analyzed by using the axial ICP-AES.Results of the single- as well as multi-metal adsorptions show that peat can be effectivelyused. Adsorption of metals on molar basis was found in the indicated order: Pb2+ > Cd2+> Ni2+. The removal of single metal ions from ternary-metal solution was less than itsremoval from single-metal solution. However, the total adsorption capacity of metalsfrom multi-metal solution to peat increased. The Langmuir isotherm equation constantswere calculated and isotherms were drawn by using the program of calculating hyperbolefunctions. Correlations for Ni2+ and Cd2+ with the Langmuir isotherm equation was foundto be good, whereas for Pb2+ the plot (amount absorbed vs. the equilibrium aqueousconcentration) was linear.