Applied Fundamental Research On The Synchronous Separation And The Resource Utilization Of Aluminum And Vanadium Of The Cleaner Chromate Production Process

Chrome salt,as an important inorganic chemical material,is widely used in metallurgy,electroplating,tanning,dye,wood corrosion and other fields.In the chromate production process,the Cr(?),Al(?)and V(?)from chromite are separated in the form of water soluble sodium salt to form Na2CrO4-NaAlO2-NaVO3-H2O multiple complex solutions.In order to obtained Na2CrO4 solutions to prepare sodium dichromate products,the acid and calcium compounds are added to separate Al(?)and V(?),respectively,taking advantage of the low solubilities of Al(OH)3 and Ca(VO3)2.The separation method produces Cr(VI)containing Al(OH)3 residue and CaCrO4 containing Ca(VO3)2 residue.It is difficult to dispose due to the high moisture and the low content of vanadium and chromium distributed in slag.It not only does harm to the ecological environment,but also causes the waste of aluminum and vanadium resources,which seriously restricts the sustainable development of chrome salt industry.At present,they have been classified as hazardous solid waste.Therefore,there is an urgent demand for developing a novel method to eliminate the aluminum and vanadium residues and realize the utilization of resources in the multiple complex solutions.The thesis mainly focused on the synthesis of mesoporous y-AlOOH with high BET surface area,and the selectively separation of V(V)from highly concentrated Cr(?)multiplex complex solutions and in situ synthesis-synchronous adsorption.The idea of synchronous separation and the resource utilization of aluminum and vanadium were proposed,avoiding the chromium containing calcium vanadate slag from the source.The new method for comprehensive utilization of aluminum mud was established.The main innovative achievements were summarized as follows:(1)The new synthesis method of mesoporous ?-AlOOH was established by reacting NaAlO2 with H2SO4.The selective adsorption of V(?)from highly concentrated Cr(?)multiplex complex solutions.was investigated.The maximum adsorption capacity of V(?)on the mesoporous y-AlOOH could achieve at 3.61 mmol/g in single vanadium solution.While the adsorption ratio of V(?)to Cr(?)reached more than 500 in the solution with highly concentrated Cr(?)and low concentrated V(?).The adsorption mechanism was expressed that the adsorption of Cr(?)changed from chemical adsorption to physical adsorption,while the adsorption of V(?)remained chemical adsorption.(2)The method of in situ synthesis-synchronous adsorption was proposed in term of chromium salt multiple complex solution system,achieving the synchronous separation of aluminum and vanadium from highly concentrated Cr(?)multiplex complex solutions.The equilibrium adsorption time of V(?)and Cr(?)was achieved instantaneously.The in situ synthesis and synchronous adsorption ratio of V(?)to Cr(?)reached more than 2000.The mechanism of transient pH and nano scale mass transfer was also revealed.(3)The pilot plant test of the synchronous separation of aluminum and vanadium in chromium salt production was completed.In the process of batch operation,the mesoporous y-AlOOH with large specific surface area was obtained The residual contents of V(?)and Al(?),Si(?),Fe(?)after adsorption decreased to 0.08 g/L,0.001 g/L,0.001 g/L and 0.001 g/L,respectively.In the process of the continuous operation,the adsorption ratio of V(V)to Cr(?)reached more than 50000.The results showed that the content of V(?)decreased from approximately 700 mg/L-2 mg/L.Additionally,the residual concentration of A(?)in solutions are less than 2 mg/L.(4)The idea for the preparation of Cr(VI)removal adsorbent by surface regulation of y-AlOOH was proposed in term of aluminum mud.The new method of comprehensive utilization of ?-AlOOH hazardous wastes and textile wastewaters was established.By crosslinking between ?-AlOOH and chitosan to prepare adsorbents,Cr(VI)could be adsorbed from the Cr(VI)-containing solutions by the adsorbents with the maximum adsorption capacity of 120.2 mg/g.After adsorption,the adsorbents were dissolved H2SO4 solution.The insoluble chitosan was recycled in a closed loop,and the chromium-aluminum tanning agent was prepared as product.