Adsorption&Separation Properties For New Pyridine-type Chelating Resins Toward Nickel From Cobalt And The Preparation And Purification For High Purity Cobalt

High purity cobalt,as one of the crucial raw materials and key resources for socioeconomic development and national defense construction,shows high strategic and economic values.Meanwhile,the concentrations of metal ions such as cobalt and nickel are also key indicators of environmental pollution due to non-biodegradability,persistence and high toxicity.Thus,separation and purification of heavy metal ions are of great practical significance considering the scarcity of metal resources.However,traditional techniques such as extraction and precipitation always give rise to secondary pollution,so it is necessary to develop a novel technology for producing high purity cobalt in which the content of nickel should be minimized.How to remove trace nickel from high-concentration cobalt predominantly controls the quality improvement of high purity cobalt,which shows promises for the development of nonferrous industry as well as remarkable economic and environmental values.According to HSAB theory,the binding affinity between nitrogen atom from pyridine and transition metals is strong,so pyridine-type chelating resin is typified by high selectivity,adsorption rate and acid resistance.In this thesis,great efforts were devoted to the synthesis of a new pyridine chelating resin through"chloromethylation-amination",and the adsorption behaviors and separation laws of Ni(?)and Co(?)in both single and binary systems were investigated.A new method that separated and concentrated the solution was proposed,providing a theoretical basis for practical nickel removal from high-concentration cobalt solution.In this thesis,the resin matrix was prepared through suspension polymerization and chloromethylation,into which dimethylpyridine amine was introduced.Response surface methodology(RSM)was used to optimize the key parameters of synthesis condition,based on which the resin with the best adsorption performances was selected.The resin was characterized by elemental analysis(EA),Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS),all revealing that the pyridine compound was successfully attached to the matrix.In single component adsorption,the optimum pH value was around 3 and the Langmuir model could describe the isotherm well.The capacities of adsorption for nickel and cobalt were calculated as 1.240 mmol/g and 0.793 mmol/g,respectively.The adsorption processes,as revealed by the thermodynamics,were endothermic and spontaneous.The Lagergren-second-order model could describe the kinetic data well.The capacities of equilibrium followed the descending order of Ni(?)>Co(?),being positively correlated with polarization force,ionic potential and electronegativity.The calculated initial rate constants followed the order of Ni(?)>Co(?).The FTIR and XPS spectra of the resin after adsorption demonstrated nitrogen was chelated through coordination.Moreover,the configuration of chelation was optimized by using density functional theory,in which N atoms on PSPA434 resin formed a tridentate ligand that complexed with metal ions as two five-membered rings.In binary component adsorption,the lower adsorption capacities and initial rate constants of Ni(?)and Co(?)proved an antagonism between them with direct competitive effects on the active sites of solid phase.The results of competition experiment indicated the pyridine resin selectively removed Ni(?),particularly in highly concentrated solution of Co(?).The fixed bed breakthrough curves for simultaneous adsorption indicated cobalt ions were displaced by the subsequently adsorbed nickel ions on PSPA434 resin.The purities of cobalt in the effluents of 155 BV and 235 BV were augmented by more than an order of magnitude to 100%and 99.999%,respectively.According to the theoretical study mentioned above,a new preparation and recycling process for high purity cobalt was proposed with PSPA434 resin.It managed to selectively separate and to recycle nickel from high-concentration cobalt solutions,yielding cobalt with the purity of more than 99.999%(5N).The direct operating cost was only 6.17 yuan/t and it could benefit more than 300 thousand yuan in one processing cycle,so this process was of considerable economic benefit.In summary,this thesis provides a novel process for the preparation of high purity cobalt in our country.