Polypyrrole-coated gum ghatti-grafted poly(acrylamide) composite for the selective removal of hexavalent chromium from waste water.

The aim of this study was to synthesize a gum ghatti-g-poly(acrylamide)/polypyrrole composite using a multi-step aqueous polymerization method, in which the pyrrole monomer was absorbed into the network of the gum ghatti-acrylamide graft copolymer followed by the polymerization of the pyrrole monomers, and use it for the removal of Cr(VI) from water. The prepared was characterized using FT-IR, SEM, BET, XPS and XRD. The effects of the pH, adsorbent dose, contact time, concentration of Cr(VI), and temperature on the adsorption performance of the composite were investigated systematically. The adsorption of Cr(VI) on the composite depended strongly on the pH, and a Cr(VI) removal of 99.6% was attained at pH 2.0, initial concentration of Cr(VI) of 100 mg/L, and adsorbent dosage of 0.035 g. The kinetics of the adsorption followed a pseudo-second order model and the adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity of the adsorbent at 298, 308, and 318 K was determined to be 321.5, 357, and 416 mg/g, respectively. The presence of coexisting ions in the solution did not affect the adsorption of Cr(VI) significantly. Adsorption-desorption experiments revealed that the synthesized polymer composite could be used for up to four consecutive cycles.

Removal of Congo red from aqueous solution by adsorption using gum ghatti and acrylamide graft copolymer coated with zero valent iron.

Gum ghatti (Gg) and acrylamide (AAm) grafted copolymer [poly (Gg-AAm)] coated by zero valent iron (ZVI) was developed to remove toxic Congo red (CR) from waste water. Prepared composite, [poly (Gg-AAm)/ZVI] was characterized by FESEM, TEM, BET, FTIR and XRD. CR adsorption from water using [poly (Gg-AAm)/ZVI] was investigated and several parameters discussed, such as solution pH, contact time, dosage and temperature to find out removal efficiency of polymer composite. The kinetic data for the adsorption of CR followed the pseudo-second-order model and the Langmuir maximum adsorption capacity for CR at pH 7.0 were found to be 153.8, 200 and 250 mg/g at 25, 35 and 45 °C correspondingly. Desorption studies revealed that prepared composite can be used up to three cycles efficiently and thermodynamic parameters such as Gibbs free energy (ΔG0), enthalpy (ΔH0) and entropy (ΔS0) changes showed the adsorption of CR onto [poly (Gg-AAm)/ZVI] was feasible, spontaneous and endothermic.