The removal of molybdenum from a copper ore concentrate by sodium hypochlorite leaching was investigated. The results show that leaching time,liquid to solid ratio,leaching temperature,agitation speed,and sodium hypoc...The removal of molybdenum from a copper ore concentrate by sodium hypochlorite leaching was investigated. The results show that leaching time,liquid to solid ratio,leaching temperature,agitation speed,and sodium hypochlorite and sodium hydroxide concentrations all have a significant effect on the removal of molybdenum.The optimum process operating parameters were found to be:time,4 h;sodium hydroxide concentration,10%;sodium hypochlorite concentration,8%;liquid to solid ratio,10:1;temperature,50℃;and, agitation speed,500 r/min.Under these conditions the extraction of molybdenum is greater than 99,9%and the extraction of copper is less than 0.01%.A shrinking particle model could be used to describe the leaching process.The apparent activation energy of the dissolution reaction was found to be approximately 8.8 kJ/mol.展开更多
In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores....In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores.The thermodynamic model was constructed and the solubility of malachite Cu2(OH)2CO3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance.It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine.The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia.The conditions of malachite Cu2(OH)2CO3 converting to atacamite Cu(OH)1.5Cl0.5 were also studied.A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.It is found that the thermodynamic model is reliable and it can guide the leaching process.展开更多
A numerical model was established to predict and optimise the chemical cleaning process of Polyvinylidene Fluo- ride (PVDF) Ultrafiltration (UF) membranes with the results from the experiment that applied the Resp...A numerical model was established to predict and optimise the chemical cleaning process of Polyvinylidene Fluo- ride (PVDF) Ultrafiltration (UF) membranes with the results from the experiment that applied the Response Sur- face Method (RSM) and Central Composite Design (CCD). The factors considered in the experimental design were sodium hydroxide (NaOH) concentration, sodium bypochlorite concentration (NaCIO), citric acid concentration and cleaning duration, The interactions between the factors were investigated with the numerical model. Humic acid (20 mg· L-1) was used as the model foulant, and chemical enhanced backflush (CEB) was employed to sim- ulate the chemical cleaning process. The concentrations of sodium hydroxide, sodium hypochlorite, citric acid and cleaning duration tested during the experiments were in the range of 0.1%-0.3% 100-300 mg· L-1 1%-3% and 0.5-1.5 h, respectively. Among the variables, the sodium hypochlorite concentration and the cleaning dura- tion showed a positive relationship involving the increased efficiency of the chemical cleaning. The chemical cleaning efficiency was hardly improved with increasing concentrations of sodium hydroxide. However, the data was sharply decreased when at a low level of sodium hydroxide concentration. In total, 54 sets of cleaning schemes with 80% to 100K cleaning efficiency were observed with the R&M model after calibration.展开更多
The bacterial pre-oxidation process of arsenic-containing gold concentrates and the bacterial activity under different chloride ion concentrations were studied by using a mixture of thermophilic strains TCJ domesticat...The bacterial pre-oxidation process of arsenic-containing gold concentrates and the bacterial activity under different chloride ion concentrations were studied by using a mixture of thermophilic strains TCJ domesticated in production.The experimental result shows that with different samples and leaching systems,the adaptability and Cl- tolerance of bacteria are different,and that appropriate chloride ion concentration is conductive to bacterial oxidation,while higher chloride ion concentration will inhibit the bacterial activity and affect the pre-oxidation performance.Under the present production conditions,TCJ can adapt to the changes of water quality in the source of water and its critical chloride ion tolerance value is 2.7 g/L.展开更多
Our analysis of published results of experiments in the Polar Regions substantiates and further develops our new approach to the photochemical processes in the polar stratosphere involving the charged particles. The d...Our analysis of published results of experiments in the Polar Regions substantiates and further develops our new approach to the photochemical processes in the polar stratosphere involving the charged particles. The dipole interaction of molecules with charged particles, primarily with ions, leads to the adhesion and disintegration of a number of molecules including ozone. Molecules acquire additional energy on the surface of the charged particles, enabling reactions that are not possible in space. Galactic cosmic rays are the main source of ions in the polar stratosphere, their equilibrium concentration at altitudes of 15 to 25 km can reach up ~ (1-5) ~ 103 ions/cm3. Estimations show that if the ozone destruction in the regime of"collision" with ions then the lifetime of ozone will vary from 10 days to 2 months. We suppose that alongside with the chlorine mechanism of ozone destruction there is a mechanism of ozone decay on a charged particle which can act also at those latitudes and altitudes where chlorine oxide CIO is absent, as well as in the night conditions. Here, we demonstrated the close connection of photochemical processes with the dynamic, electrical and condensational phenomena in the stratosphere, in particular, with the accumulation of unipolar charged particles on the upper and lower boundaries of the polar stratospheric clouds and aerosol layers as a result of the activity of the global electric circuit.展开更多
It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting ...It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model systems,and the equilibrium concentration(theoretical limiting concentration,TLC)for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values(4.0–5.0)in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.展开更多
基金the 11th Five-Year Plan of the National Scientific and Technological Program of China(No. 2007BAB22B01)the National Natural Science Foundation of China(No.50704036).
文摘The removal of molybdenum from a copper ore concentrate by sodium hypochlorite leaching was investigated. The results show that leaching time,liquid to solid ratio,leaching temperature,agitation speed,and sodium hypochlorite and sodium hydroxide concentrations all have a significant effect on the removal of molybdenum.The optimum process operating parameters were found to be:time,4 h;sodium hydroxide concentration,10%;sodium hypochlorite concentration,8%;liquid to solid ratio,10:1;temperature,50℃;and, agitation speed,500 r/min.Under these conditions the extraction of molybdenum is greater than 99,9%and the extraction of copper is less than 0.01%.A shrinking particle model could be used to describe the leaching process.The apparent activation energy of the dissolution reaction was found to be approximately 8.8 kJ/mol.
基金Project(2007CB613604)supported by the National Basic Research Program of ChinaProject(50674104)supported by the National Natural Science Foundation of China
文摘In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores.The thermodynamic model was constructed and the solubility of malachite Cu2(OH)2CO3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance.It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine.The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia.The conditions of malachite Cu2(OH)2CO3 converting to atacamite Cu(OH)1.5Cl0.5 were also studied.A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.It is found that the thermodynamic model is reliable and it can guide the leaching process.
基金Supported by State Key Laboratory of Urban Water Resource and Environment(2016DX01)the Fundamental Research Funds for the Central University(NSRIF.2014096)Science and Technology Planning Project of Chancheng District(2013A1044)
文摘A numerical model was established to predict and optimise the chemical cleaning process of Polyvinylidene Fluo- ride (PVDF) Ultrafiltration (UF) membranes with the results from the experiment that applied the Response Sur- face Method (RSM) and Central Composite Design (CCD). The factors considered in the experimental design were sodium hydroxide (NaOH) concentration, sodium bypochlorite concentration (NaCIO), citric acid concentration and cleaning duration, The interactions between the factors were investigated with the numerical model. Humic acid (20 mg· L-1) was used as the model foulant, and chemical enhanced backflush (CEB) was employed to sim- ulate the chemical cleaning process. The concentrations of sodium hydroxide, sodium hypochlorite, citric acid and cleaning duration tested during the experiments were in the range of 0.1%-0.3% 100-300 mg· L-1 1%-3% and 0.5-1.5 h, respectively. Among the variables, the sodium hypochlorite concentration and the cleaning dura- tion showed a positive relationship involving the increased efficiency of the chemical cleaning. The chemical cleaning efficiency was hardly improved with increasing concentrations of sodium hydroxide. However, the data was sharply decreased when at a low level of sodium hydroxide concentration. In total, 54 sets of cleaning schemes with 80% to 100K cleaning efficiency were observed with the R&M model after calibration.
基金Project(2007AA060902) supported by the National High Technology Research and Development Program of ChinaProject(2010CB630905) supported by the National Basic Research Program of China
文摘The bacterial pre-oxidation process of arsenic-containing gold concentrates and the bacterial activity under different chloride ion concentrations were studied by using a mixture of thermophilic strains TCJ domesticated in production.The experimental result shows that with different samples and leaching systems,the adaptability and Cl- tolerance of bacteria are different,and that appropriate chloride ion concentration is conductive to bacterial oxidation,while higher chloride ion concentration will inhibit the bacterial activity and affect the pre-oxidation performance.Under the present production conditions,TCJ can adapt to the changes of water quality in the source of water and its critical chloride ion tolerance value is 2.7 g/L.
文摘Our analysis of published results of experiments in the Polar Regions substantiates and further develops our new approach to the photochemical processes in the polar stratosphere involving the charged particles. The dipole interaction of molecules with charged particles, primarily with ions, leads to the adhesion and disintegration of a number of molecules including ozone. Molecules acquire additional energy on the surface of the charged particles, enabling reactions that are not possible in space. Galactic cosmic rays are the main source of ions in the polar stratosphere, their equilibrium concentration at altitudes of 15 to 25 km can reach up ~ (1-5) ~ 103 ions/cm3. Estimations show that if the ozone destruction in the regime of"collision" with ions then the lifetime of ozone will vary from 10 days to 2 months. We suppose that alongside with the chlorine mechanism of ozone destruction there is a mechanism of ozone decay on a charged particle which can act also at those latitudes and altitudes where chlorine oxide CIO is absent, as well as in the night conditions. Here, we demonstrated the close connection of photochemical processes with the dynamic, electrical and condensational phenomena in the stratosphere, in particular, with the accumulation of unipolar charged particles on the upper and lower boundaries of the polar stratospheric clouds and aerosol layers as a result of the activity of the global electric circuit.
基金supported by the Chinese National Key Technology Research and Development Program(2006AA03Z455)NSFC-RGC(20731160614)+2 种基金Program for Changjiang Scholars and Innovative Research Team in Univer-sity(IRT0732)National Basic Research Program of China(2009CB226103)the National Natural Science Foundation of China(20976080)
文摘It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model systems,and the equilibrium concentration(theoretical limiting concentration,TLC)for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values(4.0–5.0)in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.