• Beena Mathew

      Articles written in Journal of Chemical Sciences

    • Metal complexation of crosslinked polyacrylamide-supported dithiocarbamates: Effect of the molecular character and extent of crosslinking on complexation

      Beena Mathew V N Rajasekharan Pillai

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      Dithiocarbamate functions were incorporated into different polyacrylamide matrices crosslinked with a flexible and hydrophilic crosslinking agent, tetraethyleneglycol diacrylate (TEGDA), and their complexation behaviours were investigated. Crosslinked polyacrylamides with varying extents of the tetrafunctional TEGDA crosslinks were prepared by free radical solution polymerization at 60°C using potassium persulphate as initiator in ethanol. The dithiocarbamate functionality was incorporated into these polyacrylamides by a two-step polymer-analogous reaction involving (i)trans-amidation with ethylenediamine and (ii) dithiocarbamylation of the aminopolyacrylamide with carbon disulphide and alkali. The complexations of dithiocarbamate with Cu(II), Ni(II), Zn(II), Co(II) and Hg(II) ions were followed under different conditions. The metal ion intake varied with the extent of the crosslinking agent and the observed trend in complexation is Hg(II) > Cu(II)> Zn(II)> Co(II)> Ni (II). The time-course of complexation, the possibility of recycling, swelling characteristics, and spectral and thermal analyses were carried out. The thermal stability increases upon complexation with metal ions.

    • Metal ion complexation of hydrophilic polymeric amino ligands derived from tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polyacrylamides

      Beena Mathew V N Rajasekharan Pillai

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      Complexation behaviour of amino ligands supported on polyacrylamides with 2–20 mol% of tetraethyleneglycol diacrylate crosslinks was investigated towards Co(II), Ni(II), Cu(II), Zn(II) and Hg(II) ions. The metal ion intake was dependent on the extent of crosslinking and followed the order: Hg(II)>Cu(II)>Zn(II)>Ni(II)>Co(II). The aminopolyacrylamides and their metal complexes were characterised by IR and EPR techniques. The absorptions of the ligands were shifted by complexation with metal ions and the EPR spectrum suggested distorted tetragonal geometry for the Cu(II) complex. The thermogravimetric analysis of the metal complexes revealed a pattern of variation of thermal stability on incorporation of metal ions. The kinetics and adsorption parameters of complexation, swelling characteristics, recyclability and specificity of metal-desorbed systems are also described.

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