| With the development of modern industry and high-tech, the demand of nickel, especially high-purity nickel, increased year by year, which has become one of the important strategic reserve metals. Nickel is an important raw material to manufacture steel, non-ferrous alloys and stainless steel, has a wide range of applications in chemical industry, electronics manufacturing, machinery, military, aerospace etc. But the nickel reserves of our country is lack, together with a large number of mining in recent years, lead to more and more low-grade nickel ore left. The reports of the use of ion-exchange method for the recovery of trace or little nickel in solution has been appeared many. And the waste water was discharged during the manufacture of nickel products or nickel plating, or in the low-grade laterite ore leaching solutions, Ni2+ content is generally 1～10g/L, which is the low concentration nickel sulfate solution. Whatever the study about the nickel enrichment of this concentration range is less reported. The topic is for the 2.5g/L nickel sulfate solution, the macroporous styrenic iminodiacetic acid chelating resin which has excellent selecting performance was selected to study the adsorption and desorption properties of above solution, its aim is to provide a theoretical basis for industrial production. Generally, including the following contents:Firstly, the D402 resin with high recovery of nickel is screened through the static adsorption and desorption experiments. Then the effect of the initial pH, initial concentration, adsorption exchanging time, the resin amount and the oscillation frequency on the static adsorption effect and selective adsorption properties of D402 resin are investigated. The results showed:when the resin amount is 1.0g, pH is 5, the adsorption time is 3.5h, the maximum adsorption amount is reached. The adsorption amount is increasing with the initial concentration and the oscillation frequency increases. When the pH value is 5.0, D402 selective adsorption order for cobalt and nickel follows:Ni2+> Co2+. BET adsorption, infrared spectroscopy, SEM and XPS spectra are used to characterize the before and after adsorption resin, discussed its adsorption mechanism, found that D402 resin has large specific surface area and good adsorption properties. The ligand ratio of resin functional groups and Ni2+ is 2:1.On the basis of the static adsorption experiments, the adsorption kinetics curves, adsorption isotherms, adsorption kinetics, controlling mechanism and adsorption thermodynamics about the Ni2+ adsorption on D402 resin were studied. The results showed that: Langmuir equation is more accurate to describe the adsorption exchange process; Lagrange pseudo-first-order and pseudo-second-order reaction kinetic equations all fit the experimental data better; during the membrane diffusion model, the particle diffusion model and chemical reaction-diffusion model, the main control step of the adsorption process is particle diffusion controlling; the relevant thermodynamic parameters:Ea=10.282kJ/mol, AG=-1.8909kJ/mol, AH= 6.4660kJ/mol, △S= 28.0431J/(mol·K), the result showed the adsorption process is entropy-driving spontaneous endothermic process.Straight column dynamic adsorption process is used to investigate the effect of initial concentration, temperature, flow rate and column height on dynamic adsorption result. The results from the analysis shows that: the higher the initial concentration, the shorter the breakthrough time; higher temperature is favorable for adsorption; the greater the flow rate, the shorter the breakthrough time, the smaller the amount of adsorption and breakthrough equilibrium adsorption capacity; the higher the resin column, the longer breakthrough time, the equilibrium adsorption capacity and the breakthrough adsorption amount increases simultaneously.The absorbent sulfuric acid is selected via static desorption experiments. The straight column dynamic desorption process is used to study absorbent concentration, the absorbent flow rate and temperature on the desorption effect. From the results obtained: the bigger the absorbent concentration, the better desorption impact; the greater the absorbent flow rate, the shorter the time required for desorption, but it should not be too large, lead to a waste of absorbent; the higher the temperature of the desorption system, the shorter the completing time required, the actual production of industrial operations is carried out at room temperature generally. Realistic basis is provided from above research and data about nickel ion recovery from low concentration sulfate solution using D402 resin with some reference value. |
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