Functionalized polymer sheet sorbent for selective preconcentration and determination of mercury in natural waters

Abstract

Mercury is considered as a highly toxic and widespread heavy-metal pollutant. In the present work, two flat-sheet polymer sorbents have been synthesized for the selective preconcentration of mercury from natural waters. These are a silver nanoparticle (AgNP)-embedded poly(acrylamide)-grafted poly(propylene) sheet (Ag-PAM-PP) and a 1,8-octanedithiol-functionalized gold-coated poly(propylene) sheet (HS-octyl-S-Au-PP). The functional groups acrylamide and thiol provide the binding sites for Hg²⁺ ions; whereas silver nanoparticles reduce Hg²⁺ to Hg⁰ and it is held on the sheet by amalgam formation. Various factors that influence the preconcentration of Hg²⁺ from aqueous solution were investigated. Based on the comparison of the experimental results, it was observed that Ag-PAM-PP had superior performance for uptake of Hg²⁺ from natural water samples in terms of sorption capacity, sorption kinetics and working pH range. The uptake of Hg²⁺was found to be pH dependent with a maximum of 95% at pH 7.5. The preconcentration of Hg²⁺ from a large volume of aqueous solution was used to extend the lower limit of the concentration range that can be quantified by EDXRF and CV-AAS. The sorbed Hg(II) from aqueous samples was quantitatively detected within 1 min using EDXRF. The LOD (3σ) for CV-AAS (RSD = 2%) and EDXRF (RSD = 5%) were 6 and 30 μg L⁻¹, respectively. The method was applied for the determination of Hg²⁺ in groundwater and seawater samples in the presence of a high concentration of interfering ions.