Synthesis and characterization of hybrid iod exchange resins embedded with hydrous ferric oxide nanoparticles for the removal of metal ions from acid mine drainage

Abstract

Acid mine drainage (AMD) is a serious water pollutant that contaminates freshwater sources such as rivers, lakes, ground water and even sediments with heavy metals which include Cr(VI), Cd(II) and Pb(II). In this study a novel remediation strategy for the remediation of Cr(VI), Cd(II) and Pb(II) was developed. Hybrid anionic and cationic exchange resins embedded with hydrous ferric oxide nanoparticles were synthesized and then subjected to batch adsorption tests to determine the factors influencing the adsorption of Cr(VI), Pb(II) and Cd(II). Lastly, the hybrid cationic resin, HCIX-HFO was used to determine the adsorption of metal ions from a real AMD water sample. The hybrid anion exchanger (HAIX-HFO) was used for the remediation of Cr(VI). The optimum pH for the removal of Cr(VI) was found to be pH 4. The adsorption of Cr(VI) with and without sulphate was a better fit to the pseudo-second order kinetic model, with an equilibration time of 360 minutes. In the absence of co-competing sulphate the experimentally determined adsorption capacity for Cr(VI) was 4.9 mg.g-1. In the presence of 3000 mg/L sulphate the adsorption capacity for Cr(VI) decreased to 2.2 mg.g-1 while percentage of Cr (VI) adsorbed was 50.8 % in the presence of sulphate. The isotherm studies for Cr(VI) in the absence of sulphate was found to be a better fit to the Langmuir isotherm model, and with the Temkin isotherm model in the presence of sulphate. The hybrid cationic ion exchange resin (HCIX-HFO) was used to adsorb both Cd(II) and Pb(II). The pH for the optimum adsorption both the two metallic species (Cd(II) and Pb(II)) was found to be pH 4. Like in the case for Cr (VI), the kinetic studies for Cd(II) and Pb(II) in the presence of sulphate followed the pseudo-second order kinetic model and equilibrium was achieved in 360 minutes. The experimentally determined adsorption capacities for Cd(II) and Pb(II) were 1.45 mg.g-1 and 2.27` mg.g-1 respectively. The isotherm adsorption data for both Cd(II) and Pb(II) were a good fit to the Freundlich model. In a competitive study with both Cd(II) and Pb(II) the adsorption of Pb(II) was favoured. HCIX-HFO was effectively regenerated by NaCl with 99.9% of Cd(II) and 98.8% of Pb(II) recovered. On contacting HCIX-HFO with real AMD containing ten different metal ions, high percentage removals were found for Ni(II) (92.6%), Cu(II) (92.5%) and Pb(II) (46.8%). HCIX-HFO has been shown to adsorb cationic metal species in the presence of sulphate and HAIX-HFO has been shown to effectively adsorb Cr(IV) in the presence of sulphate.