Production Of Metallic Arsenic From Thermally Reduced Titanium-Arsenic Slag And Realization Of Titanium Cycle

At present,the harm of arsenic in the arsenic titanium slag produced by the removal of arsenic by high-priced titanium-based sulfate and the recovery of titanium resources needs to be solved urgently.Therefore,this article proposes a new process of short-process reduction roasting-sulfuric acid maturation transition for arsenic titanium slag.Objective While obtaining metallic arsenic with certain commercial value,the high-valent titanium-based sulfate is regenerated through concentrated sulfuric acid treatment residue,so as to realize recycling utilization of arsenic titanium slag to produce metallic arsenic and titanium.The research content includes thermal reduction of arsenic titanium slag to produce metal arsenic and the thermodynamic analysis of the regeneration of high-valent titanium-based sulfate,the pyrolysis behavior of arsenic titanium slag in a reducing atmosphere,the direct pyrolysis behavior of arsenic titanium slag,and the preparation of hot carbon layers Research on the feasibility of metallic arsenic,concentrated sulfuric acid cooking residue process,and the experiment of removing arsenic by regenerating high-valent titanium-based sulfate.The major discoveries are as showing below:Based on the available thermodynamic data and applying HSC Chemistry 6.0Calculations,temperature-Gibbs free energy diagrams and temperature equilibrium molar mass diagrams were plotted.Provide theoretical support for studying the critical reaction temperature and phase transition process of the analysis system.In this paper,three experiments are carried out for thermodynamic research on the three experiments of reducing arsenic titanium slag by carbon monoxide to produce metallic arsenic,reducing arsenic titanium slag to produce metallic arsenic by inert pyrolysis carbon layer,and the mature transformation of concentrated sulfuric acid.The thermodynamic analysis results show that the pyrolysis temperature of arsenic titanium slag reduced by carbon monoxide is at 648℃,arsenic leaves the slag phase with As₂O₃gas,and is decreased to As₄by carbon monoxide in the gas phase.The inert pyrolysis temperature of arsenic titanium slag is 840℃,which is much higher than reduction pyrolysis.Arsenic leaves the slag phase with As₄O₆gas and is reduced to As₄by the hot carbon layer.Thermodynamic analysis of concentrated sulfuric acid and titanium dioxide confirmed the feasibility of regenerating high-valent titanium-based sulfate from the residue,and the temperature of the system should not exceed the pyrolysis temperature of concentrated sulfuric acid（375℃）.The optimal process and kinetics of preparing metallic arsenic from arsenic titanium slag by carbon monoxide reduction was studied.The results show that the arsenic volatilization rate of arsenic titanium slag can reach 94%at 700℃,60 min,CO roasting.Arsenic products are metal flake arsenic and white particles of arsenic trioxide,and residues are black loose anatase titanium dioxide and rutile titanium dioxide.The thermo-gravimetric analysis indicated that there are three stages of weight loss in the carbon monoxide reduction of arsenic titanium slag.First,the dehydration stage,the temperature is between 35℃and 110℃;the second,the pyrolysis stage of excess high-valent titanium-based sulfate,the temperature is between 590℃and 650℃;third,the arsenic is separated from the slag phase,and the temperature is between 640℃and 720℃.The kinetic model fitting of the third stage shows that the process of arsenic leaving the slag phase conforms to the phase boundary reaction（one-dimensional）model.At a heating rate of 5℃·min^-1,the apparent activation energy is 145.57 k J·min^-1.The optimal process and kinetics of arsenic titanium slag inert pyrolysis carbon layer reduction to produce metallic arsenic was studied.The results show that the arsenic volatilization rate of arsenic titanium slag can reach 97%at 900℃,60 min,Ar roasting.Arsenic products are metallic flake arsenic and particulate metallic arsenic,and the residue is yellow hard rutile titanium dioxide.The thermogravimetric analysis shows that there are three weight loss stages in the inert pyrolysis of arsenic titanium slag.First,the dehydration stage,the temperature is between 55℃and130℃;the second,the excess high-valent titanium sulfate pyrolysis stage is 600℃to 640℃;third,the arsenic is separated from the slag phase,and the temperature is between 780℃and 900℃.The kinetic model fitting of the third stage shows that the process of arsenic leaving the slag phase conforms to the solid phase decomposition reaction model.At a heating rate of 5℃·min^-1,the apparent activation energy is370.02 k J·min^-1.The transformation process and kinetics of research concentrated sulfuric acid matured residue was carried out.The results show that low-temperature residues are more likely to react with concentrated sulfuric acid to form high-valent titanium sulfates than high-temperature residues.The isothermal thermal analysis method shows that the transformation of concentrated sulfuric acid matured residue conforms to the nuclear shrinkage model.The kinetic rate equation of the reaction between CO residue and concentrated sulfuric acid at 700℃for 60 min is0.6[1-（1-α）^1/3]+0.4[1-2α/3-（1-α）^2/3]=0.0016t-0.0057.The kinetic rate equation of900℃,60min,Ar residue and concentrated sulfuric acid is0.15[1-（1-α）^1/3]+0.85[1-2α/3-（1-α）^2/3]=0.0007t-0.0171.