Microwave-promoted M-PFR resin: kinetics, isotherms and sequestration of Cr(III) and Pb(II) from environmental samples

Abstract

Microwave-promoted phthalic acid–formaldehyde–resorcinol (M-PFR) based chelating resin was synthesized in DMF media at 2.45 GHz and its performance was compared with conventional phthalic acid–formaldehyde–resorcinol (C-PFR) chelating resin, synthesized earlier in our laboratory. M-PFR resin was characterized by FTIR and elemental analysis. Thermal stability and structural morphology of the synthesized resin were evaluated by TGA, SEM, and BET analysis. The energy of activation (Ea) was estimated by thermal analysis data using Broido and Horowitz–Metzger methods. The physico-chemical properties of M-PFR resin have also been determined. The adsorption capacities of M-PFR resin for Cr(III) and Pb(II) have been studied by batch equilibrium method, and were found maximum 0.43 and 3.12 mmol/g at pH 6.0, respectively. Operational variables such as pH, metal concentration and equilibrium rate were optimized. The sorption equilibrium data follow Langmuir and Freundlich adsorption models. A pseudo-second order kinetic model has been proposed to correlate the data. Sequestration of Cr(III) and Pb(II) from estuarine sediment extract was carried out at optimized Kd values in tartaric acid media by column method. The regeneration of M-PFR resin was successfully carried out by 2 M HCl and reused several times.