The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravi...The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 m L ceramic crucible(11 mm in internal diameter and 14 mm in height).The effect of particle size was also analyzed.The experimental results of mass loss data,X-ray diffraction(XRD)analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb_(4)O_(6)(g)without the formation of any intermediary compound in the entire temperature range.At roasting temperatures,the volatilization kinetics of Sb_(2)O_(3) was analyzed using the model X=kappt.The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 k J/mol was obtained in this temperature range.Based on the volatilization kinetics at the melting temperatures,for linear behaviour in nitrogen gas,kinetic constants were determined,and an activation energy of 73.9 k J/mol was calculated for the volatilization reaction with a surface area of 8.171×10^(-5)m^(2).展开更多
The dissolution kinetics of synthetic molybdite(MoO3)in a potassium hydroxide(KOH)medium was studied by varying the system temperature,KOH concentration,and particle size.Additionally,the effects of the stirring rate ...The dissolution kinetics of synthetic molybdite(MoO3)in a potassium hydroxide(KOH)medium was studied by varying the system temperature,KOH concentration,and particle size.Additionally,the effects of the stirring rate and different reagents such as barium hydroxide(Ba(OH)2),calcium hydroxide(Ca(OH)2),and sodium hydroxide(NaOH)were also evaluated.The experiments were performed in a reactor with controlled temperature and agitation.The results indicated that the dissolution reaction mechanism of molybdite generates potassium molybdate(K2MoO4)without intermediate compounds.Temperature(6-80°C),KOH concentration(0.0005-0.025mol/L),and particle size(5-40μm)positively affected the dissolution of molybdite.The maximum Mo recovery was67.5%in0.25h for80°C and0.01mol/L KOH.At the lowest temperature(6°C),which is near the freezing point of water(0°C),a substantial amount of Mo was recovered(17.8%in45min).The kinetics equation describing the molybdite dissolution in a KOH environment indicated that diffusion occurs through the porous layer.The activation energy was calculated to be47.81kJ/mol.A reaction order of1.0with respect to KOH concentration was obtained and was found to be inversely proportional to the squared particle size.The kinetics equation was obtained.The dissolution of molybdite resulting from the oxidation of a molybdenite concentrate(MoS2)led to a low molybdenum recovery,which was primarily caused by the consumption of KOH by impurities such as CaCO3and Cr(MO4)3.展开更多
Cuprite is a difficult oxide to leach under acidic conditions(for the maximum extraction of50%).In this research,the feasibility of leaching cuprite in an ammoniacal medium was studied.The working conditions addressed...Cuprite is a difficult oxide to leach under acidic conditions(for the maximum extraction of50%).In this research,the feasibility of leaching cuprite in an ammoniacal medium was studied.The working conditions addressed here were the liquid/solid ratio(120:1-400:1mL/g),stirring speed(0-950r/min),temperature(10-45℃)and NH4OH concentration(0.05-0.15mol/L).In addition,different ammoniacal reagents(NH4F and(NH4)2SO4)were analyzed.The experiments were performed in a2L reactor with a heating mantle and a condenser.The most important results were that the maximum leaching rate was obtained at pH10.5,0.10mol/L NH4OH,45℃,4h,850r/min and a liquid/solid ratio of400:1,reaching a copper extraction rate of82%.This result was related to the non-precipitation of copper in solution by the formation of copper tetra-amine (Cu(NH2)4^2+).The liquid/solid ratio and stirring speed were essential for increasing the cuprite leaching.The maximum leaching rate was achieved at higher temperatures;however,significant copper leaching rate occurred at temperatures near the freezing point of water(17.9%over4h).Increasing NH4OH concentration and decreasing particle size increased the cuprite leaching rate.The two ammoniacal reagents(NH4F and(NH4)2SO4)had low extraction rate of copper compared with NH4OH.The kinetic model representing cuprite leaching was a chemical reaction on the surface.The order of the reaction with respect to the NH4OH concentration was1.8,and it was inversely proportional to the radius of the ore particles.The calculated activation energy was44.36kJ/mol in the temperature range of10-45℃.展开更多
文摘The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 m L ceramic crucible(11 mm in internal diameter and 14 mm in height).The effect of particle size was also analyzed.The experimental results of mass loss data,X-ray diffraction(XRD)analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb_(4)O_(6)(g)without the formation of any intermediary compound in the entire temperature range.At roasting temperatures,the volatilization kinetics of Sb_(2)O_(3) was analyzed using the model X=kappt.The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 k J/mol was obtained in this temperature range.Based on the volatilization kinetics at the melting temperatures,for linear behaviour in nitrogen gas,kinetic constants were determined,and an activation energy of 73.9 k J/mol was calculated for the volatilization reaction with a surface area of 8.171×10^(-5)m^(2).
文摘The dissolution kinetics of synthetic molybdite(MoO3)in a potassium hydroxide(KOH)medium was studied by varying the system temperature,KOH concentration,and particle size.Additionally,the effects of the stirring rate and different reagents such as barium hydroxide(Ba(OH)2),calcium hydroxide(Ca(OH)2),and sodium hydroxide(NaOH)were also evaluated.The experiments were performed in a reactor with controlled temperature and agitation.The results indicated that the dissolution reaction mechanism of molybdite generates potassium molybdate(K2MoO4)without intermediate compounds.Temperature(6-80°C),KOH concentration(0.0005-0.025mol/L),and particle size(5-40μm)positively affected the dissolution of molybdite.The maximum Mo recovery was67.5%in0.25h for80°C and0.01mol/L KOH.At the lowest temperature(6°C),which is near the freezing point of water(0°C),a substantial amount of Mo was recovered(17.8%in45min).The kinetics equation describing the molybdite dissolution in a KOH environment indicated that diffusion occurs through the porous layer.The activation energy was calculated to be47.81kJ/mol.A reaction order of1.0with respect to KOH concentration was obtained and was found to be inversely proportional to the squared particle size.The kinetics equation was obtained.The dissolution of molybdite resulting from the oxidation of a molybdenite concentrate(MoS2)led to a low molybdenum recovery,which was primarily caused by the consumption of KOH by impurities such as CaCO3and Cr(MO4)3.
文摘Cuprite is a difficult oxide to leach under acidic conditions(for the maximum extraction of50%).In this research,the feasibility of leaching cuprite in an ammoniacal medium was studied.The working conditions addressed here were the liquid/solid ratio(120:1-400:1mL/g),stirring speed(0-950r/min),temperature(10-45℃)and NH4OH concentration(0.05-0.15mol/L).In addition,different ammoniacal reagents(NH4F and(NH4)2SO4)were analyzed.The experiments were performed in a2L reactor with a heating mantle and a condenser.The most important results were that the maximum leaching rate was obtained at pH10.5,0.10mol/L NH4OH,45℃,4h,850r/min and a liquid/solid ratio of400:1,reaching a copper extraction rate of82%.This result was related to the non-precipitation of copper in solution by the formation of copper tetra-amine (Cu(NH2)4^2+).The liquid/solid ratio and stirring speed were essential for increasing the cuprite leaching.The maximum leaching rate was achieved at higher temperatures;however,significant copper leaching rate occurred at temperatures near the freezing point of water(17.9%over4h).Increasing NH4OH concentration and decreasing particle size increased the cuprite leaching rate.The two ammoniacal reagents(NH4F and(NH4)2SO4)had low extraction rate of copper compared with NH4OH.The kinetic model representing cuprite leaching was a chemical reaction on the surface.The order of the reaction with respect to the NH4OH concentration was1.8,and it was inversely proportional to the radius of the ore particles.The calculated activation energy was44.36kJ/mol in the temperature range of10-45℃.
