| China is a major antimony smelting country,and antimony is listed as one of the four strategic metals in China,according to reports,the current antimony smelting produces harmful arsenic-alkali residue is accumulating at a rate of 0.5-10 thousand tons per year.The water leaching disposal process of arsenic-alkali residue is still the mainstream,and the removal of arsenic from the leaching solution is the focus of research,due to the disadvantages of the arsenic-containing phase instability,long process and high reagent consumption in the arsenic removal process,it is a difficult problem to completely solve the harmlessness of arsenic in the leaching solution.Using the characteristic that arsenic is harmless and can be used as the raw material of gallium arsenide,this study proposes a method for the preparation of arsenic monomers by water leaching of arsenic-alkali residue,crystallization of leaching solution and fire reduction of crystallization products to realize the harmless treatment of arsenic and resource recovery of antimony.To provide a reference for the harmless treatment of arsenic in arsenical slag of antimony smelting and the development of new processes,the main research results are as follows.The process mineralogy study of arsenic-alkali residue was carried out,and the results showed that the antimony-containing phase in the arsenic-alkali residue was dominated by insoluble sodium antimonate,sodium subantimonate and metallic antimony,and part of the antimony-containing phase was wrapped by sodium arsenate;the arsenic-containing phase was dominated by soluble sodium arsenate,and the output form of sodium arsenate was relatively simple,in the form of fibrous and granular aggregates,and part of the arsenic-containing phase existed with the antimony-containing phase wrapped and embedded in each other,therefore,the water leaching process intensified the leaching of sodium arsenate by enhanced agitation.The leaching effect and process of arsenic and antimony in the water leaching process of arsenic-alkali residue were studied.The results showed that the leaching rate of arsenic was greatly influenced by the liquid-solid ratio and stirring speed when no oxidant was added;the leaching rate of antimony was greatly influenced by the temperature and leaching time.The leaching can be enhanced by appropriately increasing the liquid-solid ratio and strengthening the stirring to enhance the leaching of arsenic.The optimal experimental conditions were: water leaching temperature of90 ?,leaching time of 2 h,liquid-solid ratio of 3:1,stirring speed of 300 r/min,the leaching of arsenic reached 90.59%,and the leaching rate of antimony was only1.06%.When hydrogen peroxide was added,the leaching rate of arsenic increased insignificantly compared to that without the addition of oxidant,while the leaching rate of antimony decreased,while the excessive amount of hydrogen peroxide would inhibit the hydrolysis of antimony salts,making the leaching rate of antimony increase.Therefore,leaching can be reduced by adding the appropriate amount of hydrogen peroxide to reduce the leaching of antimony.The optimal experimental conditions were: leaching time of 2 h,water immersion temperature of 90 ?,the amount of hydrogen peroxide added was 5% of the solution volume,liquid-solid ratio of 2:1,stirring speed of 300 r/min,the leaching rate of arsenic reached 91.79%,and the leaching rate of antimony was only 0.62%,and the addition of hydrogen peroxide reduced the leaching rate of antimony to half of the original.The main physical phases of the crystallization products are sodium arsenate and alkali,which can be used as raw materials for the preparation of monolithic arsenic by reduction and the thermodynamics and process of carbon thermal reduction of crystalline products and carbon monoxide reduction were carried out.The thermodynamics of the fire reduction of sodium arsenate as a crystalline product shows that under experimental conditions below 1000 ?,sodium arsenate does not decompose by itself during the fire reduction of sodium arsenate,but goes through two stages,the first stage is the reduction of sodium arsenate by C or CO to produce sodium arsenite and arsenic oxide,and the second stage is the continued reaction of sodium arsenite with C or CO to produce gaseous monolithic arsenic.The optimal experimental conditions for the carbon thermal reduction are: reduction time of 1 h,reduction temperature of 800 ?,and 1.2 times of the theoretical amount of C,and the reduction volatility of arsenic can reach 98.3%;the optimal experimental conditions for the reduction of crystalline by carbon monoxide reduction are:reduction time of 1 h,reduction temperature of 900 ?,and the reduction volatility of arsenic can reach 99.65%.The main phase of the reduction slag is alkali,which can be returned to the arsenic removal process of crude antimony refining as an arsenic removal agent,and the product monomeric arsenic can be used as a raw material for the production of gallium arsenide.The kinetics of the thermal analysis of the crystalline product reduction process was investigated.The results show that there are two main stages of the crystalline product reduction process,stage ? is the reduction of sodium arsenate by C to produce sodium arsenite and arsenic oxide,and stage ? is the continued reduction of sodium arsenite by C to produce gaseous arsenic monomers,and the average activation energies of stages ? and ? are 349.92 k J/mol and 802.33 k J/mol respectively;stage ? belongs to the random nucleation and subsequent growth,and the stage ? belongs to the control model of three-dimensional diffusion.The validation of the mechanism functions of stages ? and ? showed that the obtained mechanism functions were very reliable. |
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