A novel method was developed for extracting alumina (Al2O3) from fly ash using an ammonium hydrogen sulfate (NH4HSO4) roasting process, and the thermodynamics and kinetics of this method were investigated. The the...A novel method was developed for extracting alumina (Al2O3) from fly ash using an ammonium hydrogen sulfate (NH4HSO4) roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1:8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-(2/3)α-(1-α)2/3=0.0374t exp[-16627/(RT)], whereαis the extraction rate and t is the roasting temperature.展开更多
The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were investigated.The chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy(XPS)techniq...The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were investigated.The chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy(XPS)techniques.It was found that interfacial passivation layers of chalcopyrite were formed from an iron oxide layer on top of a copper sulfide layer overlaying the bulk chalcopyrite,whereas CuFe1-xS2 or copper sulfides were formed via the preferential dissolution of Fe.The copper sulfide layer formed a new passivation layer,whereas the iron oxide layer peeled off spontaneously and partially from the chalcopyrite surface.The state of the copper sulfide layer was discussed after being deduced from the appearance of S2-,S22-,Sn2-,S0 and SO42-.A mechanism for the oxidation and passivation of chalcopyrite under different pH values and redox potentials was proposed.Accordingly,a model of the interfacial reaction on the chalcopyrite surface was constructed using a three-step reaction pathway,which demonstrated the formation and transformation of passivation layers under the present experimental conditions.展开更多
Extracting B2O3 from calcined boron mud(CBM) was studied. The effect of factors such as reaction temperature and NaO H-to-CBM mass ratio on B2O3 extraction efficiency was investigated. The results show that increasing...Extracting B2O3 from calcined boron mud(CBM) was studied. The effect of factors such as reaction temperature and NaO H-to-CBM mass ratio on B2O3 extraction efficiency was investigated. The results show that increasing reaction temperature and NaO H-to-CBM mass ratio increases B2O3 extraction efficiency. There are two stages for the B2O3 extracting process: 0–20 min is the first stage, which is rapid; 20–50 min is the second stage, which is slower than the first stage. The overall extracting process follows the shrinking core model, and the first and second stages are determined to obey the surface chemical reaction model and the diffusion through the products layer model,respectively. The activation energies of the first and second stages are calculated to be 41.74 and 15.43 kJ·mol-1,respectively. The B2O3 extracting kinetics equations of the first and second stages are also obtained.展开更多
Nickel leaching from low-grade nickel matte(LGNM) using aqueous ferric chloride solution was studied.The influence of factors such as leaching temperature and concentration of ferric chloride on the nickel leaching ra...Nickel leaching from low-grade nickel matte(LGNM) using aqueous ferric chloride solution was studied.The influence of factors such as leaching temperature and concentration of ferric chloride on the nickel leaching ratio was investigated.The results show that increasing leaching temperature and concentration of ferric chloride increases the nickel leaching ratio.The overall nickel leaching process follows the unreacted shrinking core model,and the surface chemical reaction is the rate-controlling step.The activation energy and the reaction order of the nickel leaching process,controlled by the surface chemical reaction,were calculated to be 52.96 kJ mol^(-1)and 0.5,respectively.Therefore,the kinetics equation for the nickel leaching was found to be 1-(1-α)^(1/3)=7.18×10~4C^(0.5)exp[-52,960/(RT)]t.展开更多
The effect of several parameters on the recovery of silicon dioxide from calcined boron mud(CBM)such as stirring speed, temperature, sodium silicate concentration, and carbonation time was studied. The recovery of s...The effect of several parameters on the recovery of silicon dioxide from calcined boron mud(CBM)such as stirring speed, temperature, sodium silicate concentration, and carbonation time was studied. The recovery of silicon dioxide is 88 % when the stirring speed is450 r min-1, temperature is 60 °C, sodium silicate concentration is 1 mol L-1, and the carbonation time is 6 h.The effect of carbonation time on the recovery of silicon dioxide is divided into three kinetic regimes, and the carbonation process of sodium silicate solution follows a second-order reaction based on the double-film theory model. The apparent rate constant of the three kinetic regimes is 0.064, 3.178, and 1.130 L h mol-1, respectively.The amorphous SiO_2 products obtained by carbonating the purified solution have 99.6 % purity and are spherical with diameters of about 100 nm.展开更多
基金financially supported by the National Basic Research Priorities Program of China(No.2007CB613603)the China Postdoctoral Science Foundation(No.2013M530934)
文摘A novel method was developed for extracting alumina (Al2O3) from fly ash using an ammonium hydrogen sulfate (NH4HSO4) roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1:8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-(2/3)α-(1-α)2/3=0.0374t exp[-16627/(RT)], whereαis the extraction rate and t is the roasting temperature.
基金Project(2014CB643405)supported by the National Basic Research Program of China
文摘The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were investigated.The chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy(XPS)techniques.It was found that interfacial passivation layers of chalcopyrite were formed from an iron oxide layer on top of a copper sulfide layer overlaying the bulk chalcopyrite,whereas CuFe1-xS2 or copper sulfides were formed via the preferential dissolution of Fe.The copper sulfide layer formed a new passivation layer,whereas the iron oxide layer peeled off spontaneously and partially from the chalcopyrite surface.The state of the copper sulfide layer was discussed after being deduced from the appearance of S2-,S22-,Sn2-,S0 and SO42-.A mechanism for the oxidation and passivation of chalcopyrite under different pH values and redox potentials was proposed.Accordingly,a model of the interfacial reaction on the chalcopyrite surface was constructed using a three-step reaction pathway,which demonstrated the formation and transformation of passivation layers under the present experimental conditions.
基金financially supported by the National Natural Science Foundation of China(No.51204037)
文摘Extracting B2O3 from calcined boron mud(CBM) was studied. The effect of factors such as reaction temperature and NaO H-to-CBM mass ratio on B2O3 extraction efficiency was investigated. The results show that increasing reaction temperature and NaO H-to-CBM mass ratio increases B2O3 extraction efficiency. There are two stages for the B2O3 extracting process: 0–20 min is the first stage, which is rapid; 20–50 min is the second stage, which is slower than the first stage. The overall extracting process follows the shrinking core model, and the first and second stages are determined to obey the surface chemical reaction model and the diffusion through the products layer model,respectively. The activation energies of the first and second stages are calculated to be 41.74 and 15.43 kJ·mol-1,respectively. The B2O3 extracting kinetics equations of the first and second stages are also obtained.
基金financially supported by the National Basic Research Program of China (No.2014CB6434085)
文摘Nickel leaching from low-grade nickel matte(LGNM) using aqueous ferric chloride solution was studied.The influence of factors such as leaching temperature and concentration of ferric chloride on the nickel leaching ratio was investigated.The results show that increasing leaching temperature and concentration of ferric chloride increases the nickel leaching ratio.The overall nickel leaching process follows the unreacted shrinking core model,and the surface chemical reaction is the rate-controlling step.The activation energy and the reaction order of the nickel leaching process,controlled by the surface chemical reaction,were calculated to be 52.96 kJ mol^(-1)and 0.5,respectively.Therefore,the kinetics equation for the nickel leaching was found to be 1-(1-α)^(1/3)=7.18×10~4C^(0.5)exp[-52,960/(RT)]t.
基金financially supported by the National Natural Science Foundation of China(No.51204037)the Fundamental Research Funds for the Central UniversitiesChina(No.N140204016)
文摘The effect of several parameters on the recovery of silicon dioxide from calcined boron mud(CBM)such as stirring speed, temperature, sodium silicate concentration, and carbonation time was studied. The recovery of silicon dioxide is 88 % when the stirring speed is450 r min-1, temperature is 60 °C, sodium silicate concentration is 1 mol L-1, and the carbonation time is 6 h.The effect of carbonation time on the recovery of silicon dioxide is divided into three kinetic regimes, and the carbonation process of sodium silicate solution follows a second-order reaction based on the double-film theory model. The apparent rate constant of the three kinetic regimes is 0.064, 3.178, and 1.130 L h mol-1, respectively.The amorphous SiO_2 products obtained by carbonating the purified solution have 99.6 % purity and are spherical with diameters of about 100 nm.