Removal of Ni (II), Mn (II) and Zn (II) from crude yellow cake aqueous solution by cross-linked chitosan and polyvinyl alcohol

The removal of Ni (II), Mn (II) and Zn (II) from crude yellow cake onto chitosan cross-linked by Epichlorohydrin (CS-ECH) and polyvinyl alcohol (PVA) were investigated in nitrate solutions. The influence of contact time, pH, temperature and initial metal concentrations on the adsorption processes were investigated using batch modes. Langmuir and Fruindlish models were used for investigation of adsorption isotherm. The results showed that the equilibrium adsorption behavior of metal ions onto CS-ECH and PVA could be fitted to Langmuir model. The total maximum adsorption capacity of CS-ECH and PVA were calculated, and the results indicate the higher values of CS-ECH than PVA, due to the properties of chemical structure of CS-ECH. The adsorption kinetics parameters were also tested using pseudo-first-order, pseudo-second-order models, and interparticle diffusion models. The results indicate the adsorption processes of metal ions on both CS-ECH and PVA followed the pseudo-first-order and the pseudo-second-order models which meaning the mixed adsorption, except the adsorption of Mn (II) on PVA is only described by the pseudo-second-order equation. The results indicate the adsorption processes of metal ions followed the pseudo-second-order models for both CS-ECH and PVA. Otherwise, the values of thermodynamic parameters (ΔH^o_ads, ΔS^o_ads, and ΔG^o_ads) of metal ions removal by CS-ECH and PVA exhibit the spontaneity, and exothermicity of adsorption processes.