Study On Synergistic Solvent Extraction And Mechanism Of Copper,Nickel,Cobalt,Zinc And Cadmium In Complex Solution With Organic Acids And Hydroxyoximes

With rapid development of metallurgical industry,a large quantity of heavy metal wastewater,containing copper,nickel,cobalt,zinc etc.,is produced,which results in the environment problems and serious resource wastes.Seeking methods to separate and recycle heavy metals from the wastewater can alleviate the environment pollution and realize resource comprehensive utilization.However,separation and recycling of the heavy metals from the wastewater is suffering from the complicated composition,low concentration and similar chemical properties of the metals.The paper achieves the separation and recovery of copper,nickel,zinc and cadmium from magnesium and calcium in heavy metal wastewater by synergistic solvent extraction and solved the serious problem of separation and recycling heavy metals from complicated sulfuric solution.The solvent extraction mechanism of nickel and cobalt with the mixtures of organic acids and ?-hydroxyoxime were studied and extraction microscopic mechanism of nickel and cobalt was discussed.The poisoning of cobalt to ?-hydroxyoxime with the mixtures of organic acids and ?-hydroxyoxime was studied.The poisoning mechanism and the inhibition mechanism of the poisoning with the addition of organic acids were inferred.This paper will provide the theoretical foundations for extraction and separation of nickel and cobalt from the complicated sulfate solution.First,the impregnated resin containing P204 was prepared.The influences of pH and temperature on separation of iron from copper,nickel,zinc,cadmium,magnesium and calcium in complicated sulfate solution by static adsorption with CL-P204 impregnated resin was investigated.The process parameters were obtained and further optimized by column operations for adsorption and separation of Fe(?)by CL-P204.The separation of Fe(?)from the other metals in the complicated sulfate solution is achieved.The extraction and separation performance of copper,nickel,zinc and cadmium from magnesium and calcium in the deironing sulfate solution with typical phosphate acids/?-hydroxyoxime and carboxylic acids/?-hydroxyoxime were evaluated and the mixture containing Cyanex 272 and Mextral 84H was selected to be most optimal for separation and recycling of the heavy metals.The effects of reagents concentrations,equilibrium pH,temperature and contact time of two phases on extraction and separation of copper,nickel,zinc and cadmium were tested and the extraction parameters were obtained.The solvent extraction flowsheet that all of the heavy metals are extracted simultaneously and stripped in stepwise ways by sulfuric acid in different concentrations is designed.Continuous tests on solvent extraction of copper,nickel,zinc and cadmium with Cyanex 272 and Mextral 84H are conducted and the continuous extraction parameters were further optimized.The rich solutions of each metal were obtained by the continuous tests.The recovery of copper,nickel,zinc and cadmium are 99.8%,99.8%,98.2%and 98.3%,respectively.Second,the nickel and cobalt extraction mechanism with P204/Mextral 84H and Versatic 10/Mextral 84H were studied comparatively.The synergistic effect of nickel and cobalt with typical phosphate acids/p-hydroxyoxime and carboxylic acids/?-hydroxyoxime were studied by equimolar method and the nickel and cobalt synergistic coefficients were calculated.The results show significant synergistic effects for nickel and cobalt with P204/Mextral 84H while negligible synergistic effects with Versatic 10/Mextral 84H.The compositions and space structures of nickel and cobalt extracted complexes with P204/Mextral 84H and Versatic 10/Mextral 84H were determined by slope method,infrared spectrums and ultraviolet-visible spectrums.The results show that the molecular formula is MA2B2 and the coordination number is probably 6 for nickel and cobalt extracted complexes with P204/Mextral 84H.The oxygen atom of P=O in P204 and the oxygen atom of C-OH and the nitrogen atom of N-OH in Mextral 84H are coordinated together to nickel and cobalt with P204/Mextral 84H.The molecular formula is NiB2 for nickel extracted complex and CoB2·2H2O for cobalt extracted complex and the probable coordination numbers are 4 and 6 respectively for nickel and cobalt extracted complexes with Versatic 10/Mextral 84H.The oxygen atom of C-OH and the nitrogen atom of N-OH in Mextral 84H are coordinated to nickel and cobalt with Versatic 10/Mextral 84H.No atom in Versatic 10 is coordinated to nickel and cobalt.Finally,the poisoning of cobalt to ?-hydroxyoxime and the inhibition mechanism of the poisoning with the addition of organic acids were studied.The effects of typical phosphate and carboxylic acids in different acidity and concentrations on cobalt poisoning to Mextral 84H were studied and the change rules of the poisoning were concluded.The composition of cobalt extracted complexes and oxidation potential of cobalt with different mixtures of organic acids and Mextral 84H were analyzed by element analyses,visible region absorption and cyclic voltammetry.The mechanism of cobalt poisoning to Mextral 84H and the inhabitation mechanisms of cobalt poisoning to Mextral 84H with addition of the organic acids were analyzed based on hybrid orbital theory.The results show that the hybridization forms of cobalt and Mextral 84H is inner-orbital d2sp3 configuration,resulting in easy cobaltous oxidation and worsening a more stable extracted complex.The trivalent cobalt ion in organic solution cannot be stripped even using strong acid,which yields the poisoning finally.The hybridization form of cobalt and Mextral 84H probably changes with addition of organic phosphate acid and the oxidation potential of cobalt in extracted complex rises,which inhibit the cobalt poisoning to Mextral 84H.