Removal of mercury(II) from wastewater using poly(vinyl pyrrolidinone)

Abstract

In this study a water soluble polymer, poly(vinyl pyrrolidinone) (PVP), was used for separation and preconcentration of Hg(II) prior to their analysis by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Poly(vinyl pyrrolidinone) polymers containing a pendant lactam ring which is part of a monomeric repeat unit structure can form complexes with target metal ions via oxygen and nitrogen. The Hg(II) and polymer solution were mixed and Hg(II)-bound polymer was precipitated upon addition of acetone. Adding saturated KNO3 solution to the sample, by the salting out effect, causes the precipitation to be completed faster with less amount of acetone. The precipitate was separated from the solution and dissolved directly with ultra deionised water. In this way, analyte elements were again transferred into the liquid phase and analysed by ICP-AES. The effects of pH, amount of the polymer, molecular weight of the polymer, Hg(II) ion concentration and centrifuging time on the recovery of the target metal ion have been investigated. The equilibrium experimental data were fitted to Langmuir and Freundlich isotherms models. The maximum Hg(II) adsorption capacity from aqueous solutions obtained was 30.4 mg/g at pH of about pH 6.0. Adsorption of heavy metal ions from artificial waste water was also studied. The adsorption capacities were 26.5 mg/g for Hg(II), 20.2 mg/g for Cd(II) and 15.3 mg/g for Pb(II) with recoveries greater than 97% and relative standard deviations of lower than 3% n=5.