Preparation of an adsorbent by graft polymerization of acrylamide onto coconut husk for mercury(II) removal from aqueous solution and chloralkali industry wastewater

Abstract

Graft copolymerization of acrylamide onto coconut husk (CH), initiated by the ferrous ammonium sulfate/H2O2 redox initiator system, was studied. To determine the optimum conditions of grafting, the effect of the concentrations of ferrous ammonium sulfate, the monomer, and H2O2 and the time and temperature on percentage of the graft yield was studied. A new adsorbent media having a carboxylate functional group was synthesized by the surface modification of polymer‐grafted coconut husk (PGCHCOOH). The mechanism of graft polymerization and surface functionalization is proposed. The material exhibits a very high adsorption potential for Hg(II). The sorption of Hg(II) was found to be dependent on the contact time, concentration, pH, and temperature. Maximum removal of 99.4% with 2 g/L of the sorbent was observed at 125 μmol L−1 Hg(II) concentration at pH 6.0. The slow step which determines the rate of exchange of Hg(II) ions is diffusion through the adsorbent particles. The diffusion coefficients, energy of activation, and entropy of activation were calculated and used to determine the theoretical behavior of the sorption process. The applicability of the Langmuir isotherm established the endothermic character of the adsorption. Acid regeneration was tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state. The adsorbent efficiency toward Hg(II) removal was tested using synthetic and chloralkali industry wastewaters. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1261–1269, 2000

Preparation of ion‐exchange membranes by the hydrolysis of radiation‐grafted polyethylene‐g‐polyacrylamide films: Properties and metal‐ion separation

“…This was the reason that grafted chains were expanded at this pH, and it facilitated the accessibility of the mercury ions. A similar pH dependence of metal ions in graft copolymers was reported by Saliba et al,5 El‐Rehim et al,15 Sreedhar and Anirudhan,28 and Hegazy et al29…”

Ability of iron(III)‐loaded carboxylated polyacrylamide‐grafted sawdust to remove phosphate ions from aqueous solution and fertilizer industry wastewater: Adsorption kinetics and isotherm studies

“…Materials such as iron(III) oxide, silica gel, chitosan, and biomass have been used as polymer supports for the preparation of adsorbent material having different functional groups. 8, 9 Adsorbents, such as polyacrylamide‐grafted sawdust10 and coconut husk11 having carboxylate groups and polymerized coconut coir12 with the amine functionality, have been reported to be useful for the removal of heavy metals from wastewaters. Yoshida et al13 reported that, of the iron(III)‐loaded weakly acidic carboxylate‐type cation‐exchange resin, Amberlite IRC–50 was the most advantageous adsorbent for phosphate with regard to its adsorption capacity, thermal stability, iron‐binding property, and recycling performance.…”

Effect of chloride and nitrate salts on Hg(II) sorption by raw and pyrolyzed malt spent rootlets

“…More specifically, Mohan et al ., Babic et al ., and Hassan et al . reported higher Hg(II) removal at pH 2, whereas, Sreedhar and Anirudhan and Zhang et al . argued that the Hg(II) removal increased with increasing pH.…”

“…using activated carbon, reported that the adsorption of Hg(NO 3 ) 2 in HNO 3 /NaOH aqueous solutions was favored by a decrease in pH (up to 2). Conversely, Sreedhar and Anirudhan and Zhang et al . also using activated carbon, found an increase in sorption capacity when pH was raised from acid level up to 6.…”