Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ ca...Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ calculation,X-ray photoelectron spectroscopy(XPS)analysis,time of flight secondary ion mass spectrometry(ToF-SIMS)analysis,and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate((NH_(4))_(2)SO_(4))on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation.The results showed that(NH_(4))_(2)SO_(4)exhibited a positive influence on hemimorphite sulfidation flotation.It was ascribed to the number of zinc components in the form of Zn^(2+)and[Zn(NH_(3))_(i)]^(2+)(i=1–4)increased in the flotation system after hemimorphite treatment with(NH_(4))_(2)SO_(4),which was beneficial to its interaction with sulfur species in solution,resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface.[Zn(NH_(3))_(i)]^(2+)participated in the sulfidation reaction of hemimorphite as a transition state.In addition the sulfidation reaction of hemimorphite was accelerated by(NH_(4))_(2)SO_(4).Thus,(NH_(4))_(2)SO_(4)presents a vital role in promoting the sulfidation of hemimorphite.展开更多
In this work,the effect of ammonium sulfate on the adsorption characteristics of low-concentration Pb(Ⅱ)ions on the sulfidized hemimorphite surface was comprehensively investigated.The results showed that ammonium su...In this work,the effect of ammonium sulfate on the adsorption characteristics of low-concentration Pb(Ⅱ)ions on the sulfidized hemimorphite surface was comprehensively investigated.The results showed that ammonium sulfate could increase the maximum recovery of hemimorphite from 69.42%to 88.24%under a low concentration of Pb(Ⅱ)ions.On the hemimorphite surface pretreated with ammonium sulfate,the adsorption of Pb(Ⅱ)ions was enhanced and the main species of Pb adsorbed was changed from Pb―O/OH to PbS.This was due to the larger amount of ZnS providing more effective adsorption sites for Pb components to generate Pb S.Meanwhile,the intensity of ZnS decreased with the formation of PbS,demonstrating that ZnS was covered by PbS which formed later on the mineral surface.It was beneficial for the adsorption of butyl xanthate on the hemimorphite surface to form more hydrophobic substances.As a result,ammonium sulfate played a crucial role in realizing the efficient recovery of hemimorphite.展开更多
Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by (NH4)2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the z...Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by (NH4)2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and (NH4)2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows: 1 - (1 - α)1/3 = 30.85 exp(-45.57/RT)·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.展开更多
Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with wat...Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with water. During the process the effects of the amotmt of ammonium sulfate, roasting temperature, and roasting time on the leaching recovery of metal elements were analyzed. The optimum technological parameters were determined as follows: ammonium sulfate/ore ratio, 0.8 g/g; roasting temperature, 400℃; and roasting time, 2 h. Under the optimum condition the leaching recoveries ofNi, Cu, Fe, and Mg were 83.48%, 76.24%, 56.43%, and 62.15%, respectively. Furthermore, the dissolution kinetics of Ni and Mg from the nickel ore was studied. The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ.mo1-1, which were consistent with the values of diffusion control reactions. Therefore, the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.展开更多
When EDTA was added alone in the Pb\|contaminated sand, the plant biomass and the total Pb amount in plant decreased in both species, Brassica pekinensis and B. juncea var. multiceps, though the shoot Pb a...When EDTA was added alone in the Pb\|contaminated sand, the plant biomass and the total Pb amount in plant decreased in both species, Brassica pekinensis and B. juncea var. multiceps, though the shoot Pb amount increased. In contrast, when (NH 4) 2SO 4 was added alone in the Pb\|contaminated sand, little effect was observed on the shoot Pb amount, though the root Pb amount was significantly increased in B. juncea var. multiceps. When amending EDTA and (NH 4) 2SO 4 in combination, however, the shoot Pb amount in both species substantially increased, being, on an average, 2 times and 9 times higher than that in EDTA alone or (NH 4) 2SO 4 alone amended treatment, respectively. The two amendments showed antagonism for plant growth, but synergism for Pb bioaccumulation. B. pekinensis showed its highest level of shoot and total Pb amount in the treatment amended with EDTA and (NH 4) 2SO 4 only a half as much as in the other treatments. It is inferred that the mechanisms responsible for the joint\|enhanced Pb accumulation might be concerned with the acidification of the growth medium, cation exchange reaction and relieving EDTA induced toxicity as results by amending ammonium sulfate.展开更多
In this study,the role of(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)prior to sulfurization decreased...In this study,the role of(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)prior to sulfurization decreased the formation of colloid in flotation pulp,and the floatability of the suppressed azurite caused by excess sodium sulfide was restored.After adding(NH_(4))_(2)SO_(4)prior to sulfurization,the formation of Cu(NH_(3))_(n) ^(2+)intermediate products changed the path of the sulfurization reaction,which slowed the direct impact of HSon the azurite surface.The nucleation rate was reduced,and the growth of copper sulfide crystal was improved.Covellite(syn,CuS)with larger crystal grains was formed on the azurite surface,thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface.Therefore,the generated copper sulfide colloid significantly reduced,ultimately promoting the effective adsorption of xanthate on the azurite surface.展开更多
A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surfac...A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).展开更多
hhen ammonium sulfate-iron oxide is treated below 573 K, ammonium sulfate can spontaneously desperse on the surface of iron oxide. Simultaneously ammonium sulfate decomposes to some extent. During or after the dispers...hhen ammonium sulfate-iron oxide is treated below 573 K, ammonium sulfate can spontaneously desperse on the surface of iron oxide. Simultaneously ammonium sulfate decomposes to some extent. During or after the dispersion, sulfate ion can interact with Fe atom on the surface of iron oxide to form a sort of surface sulfato complex of Fe and thus is transformed from the isolated into the bidentately bound form. Above 573 K the sulfato complex of Fe will gradually decompose with a further increase in temperature.展开更多
The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative meth...The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative method using the non-isothermal thermogravi- metric analysis data. The products and intermediates were synchronously characterized by X-ray diffraction and mass spectrometry. The obtained results indicate that the decomposition process of ammonium sulfate catalyzed by ferric oxide can be divided into four stages of which the activation energies are 123.64, 126.58, 178.77 and 216.99 kJ. mol^-1 respectively. The decomposition mechanisms at the first and the fourth stage both belong to Mample power theorem, the second stage belongs to Avrami-Erofeev equation and the third belongs to contracting sphere (volume) equation. The corresponding pre-exponential factors (A) are calculated simultaneously.展开更多
Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active l...Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active lime (CaO) was recovered via thermal decomposition. We used a purpose-built device to decom- pose the residue in a semi-suspension state. We found that CaO had the highest activity when residue was decomposed at 850-900 ~C. Our experiments indicated that ammonium sulfate residue should be decom- posed in a suspension state to produce active CaO. Based on our laboratory test findings, an industrial-scale production line with a high solid/gas ratio in a suspension state was devised. The optimal operating con- ditions for the decomposition of the ammonium sulfate residue to produce high quality CaO were also investigated.We found that the CaCO3 decomposition rate was high and the CaO product was highly active, averaging 170 s by the citric acid method. Morphology measurements showed that the CaO product had a porous structure and a large specific surface ensuring high activity.展开更多
The effect of ammonium sulfate ((NH4)2SO4) and urea (CO(NH2)2) on polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) formation from active carbon was investigated in this study. Both additives could ...The effect of ammonium sulfate ((NH4)2SO4) and urea (CO(NH2)2) on polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) formation from active carbon was investigated in this study. Both additives could significantly inhibit PCDD/F formation, and PCDD/F (TEQ) generation was reduced to 98.5% (98%) or 64.5% (77.2%) after 5% (NH4)2S04 or CO(NH2)2 was added into model ash, respectively. The inhibition efficiency of PCDDs was higher than the value of PCDFs, however, the reduction of PCDD/F yield was mainly from PCDFs decreasing. In addition, the solid-phase products were reduced more than the gas-phase compounds by inhibitors. By the measurement of chlorine emission in the phase of ion (Cl[Cl^-]) and molecule gas (Cl[Cl2]), it was observed that both Cl[Cl^-] and Cl[Cl2] were reduced after inhibitors were added into ash. Cl[Cl2] was reduced to 51.0% by urea addition, which was supposed as one possible mechanism of PCDD/F inhibition.展开更多
We investigated the effect of small amounts of ammonium sulfate (NH4)2SO4 on compound fertilizer granulation. We examined the following raw materials: humic acid, ammonium chloride, urea, potassium chloride, and mo...We investigated the effect of small amounts of ammonium sulfate (NH4)2SO4 on compound fertilizer granulation. We examined the following raw materials: humic acid, ammonium chloride, urea, potassium chloride, and monoammonium phosphate. The mass ratio of organic matter, nitrogen, phosphorus, and potassium was typically 22:17:7:2. In the absence of (NH4)2SO4, the granulation rate of the compound fertilizer was low, and increased significantly following the addition of 1–2% (NH4)2SO4. We suggested the following physical and chemical processes as potential mechanisms: (NH4)2SO4 promoted the conversion of yellow flue gas desulfurization gypsum into gypsum whiskers; (NH4)2SO4 interacted with humic acid and urea to generate a new complex; urea sulfate was formed under acidic conditions. The combined effect of the above physical and chemical processes was an increase both in the rate of interactions between the materials and in system viscosity, which has the end result of increasing the granulation rate.展开更多
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
In this study,a route for simultaneous mineralization of CO2 and production of titanium dioxide and ammonium alum,and microporous silicon dioxide from titanium-bearing blast furnace slag(TBBF slag)was proposed,which i...In this study,a route for simultaneous mineralization of CO2 and production of titanium dioxide and ammonium alum,and microporous silicon dioxide from titanium-bearing blast furnace slag(TBBF slag)was proposed,which is comprised of(NH4)2 S04 roasting,acid leaching,ammonium alum crystallization,silicic acid flocculation and Ti hydrolysis.The effects of relevant process parameters were systematically investigated.The re sults showed that under the optimal roasting and leaching conditions about 85%of titanium and 84.6%of aluminum could be extracted while only 30%of silicon entered the leachate.84%of Al^3+was crystallized from the leachate in the form of ammonium aluminum sulfate dodecahydrate with a purity up to 99.5 wt%.About 85%of the soluble silicic acid was flocculated with the aid of secondary alcohol polyoxyethylene ether 9(AEO-9)to yield a microporous SiO2 material(97.4 wt%)from the crystallized mother liquor.The Al-and Si-depleted solution was then hydrolyzed to generate a titanium dioxide(99.1 wt%)with uniform particle size distribution.It was figured out that approximately 146 kg TiO2 could be produced from 1000 kg of TBBF slag.Therefore,the improved process is a promising method for industrial application.展开更多
This paper reports the results of the visual observations and micro-analysis of concrete core samples after 6 and 12 months of their exposure to sodium, ammonium and magnesium sulfate solutions with the same concentra...This paper reports the results of the visual observations and micro-analysis of concrete core samples after 6 and 12 months of their exposure to sodium, ammonium and magnesium sulfate solutions with the same concentration of sulfate ions. XRD, SEM and EDS were used for micro-analysis of the mi-crostructure and the composition of the interface zone in the samples. The results indicate that the deterioration of concrete by different sulfate solutions could proceed differently with regard to the mechanism and the mode of damage caused. The damage of concrete exposed to sodium sulfate solution is mainly caused by the gypsum crystals formed in the interface zone, which lead to expansion and cracking. In the case of concrete immersed in magnesium sulfate solutions, a layer of brucite (magnesium hydroxide) and gypsum was produced in the interface zone, which reduces the cohesiveness of the interface zone in concrete. For the concrete immersed in ammonium sulfate solutions, the conversation of mortar to some mush mass by ammonium ions and the formation of a large of gypsum occurred in the interface zone, consequently, serious softening of hydrated cement pastes and expansion and cracking of concrete are the characteristics of the attack by ammonium sulfate solutions. Also, it is considered that using drilled concrete core as samples to evaluate the sulfate resistance of concrete is a good and accelerated method.展开更多
Camptotheac acuminata Decne is a unique tree species in China with an important secondary metabolite,camptothecin(CPT),used in the treatment of cancer.Nitrogen(N)is an important element that affects plant growth and t...Camptotheac acuminata Decne is a unique tree species in China with an important secondary metabolite,camptothecin(CPT),used in the treatment of cancer.Nitrogen(N)is an important element that affects plant growth and the accumulation of CPT.Reports on the effect of N on CPT synthesis from a genetic perspective are scarce.To explore the effects of different N sources and levels on CPT synthesis in C.acuminata,two-year-old seedlings were fertilized with different concentrations of pure ammonium sulphate,source of ammonium N(NH4+-N),and potassium nitrate for nitrate N(NO3--N).Concentrations of 2.5,5,7.5,and10 g pot-1 NH4+-N and NO3--N were used.The results showed that 7.5 g NH4+-N and NO3--N treatments were best for growth and fresh weight of leaves.Compared with the other treatments,the CPT content,tryptophan synthase and tryptophan decarboxylase activities,and expression of the CaTSB and CaTDCl genes under the 2.5 g NH4+-N and NO3--N treatments peaked significantly at 30 days.However,the expression of CaTDC2 surpassed that of the other two genes at 60 days.Therefore,compared with NH4+-N source,the NO3--N source was more beneficial for growth,and NO3--N was better for CPT yield.Consequently,leaves of C.acuminata treated with 2.5 g NO3--N could be harvested after 30 days to obtain maximum CPT content.CaTDC1 is more closely linked to CPT synthesis.The results of this study improved the production of CPT in C.acuminata via fertilization.展开更多
An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,r...An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,roasting temperature,and holding time on zinc extraction.The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol^−1.The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry–differential thermal analysis curves.The water leaching conditions,including the leaching temperature,leaching time,stirring velocity,and liquid-to-solid ratio,were discussed,and the leaching kinetics was studied.The reaction rate was obtained under outer diffusion without product layer control;the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol^−1.The maximum zinc extraction ratio reached 96%while the efficiency of iron extraction was approximately 32%under appropriate conditions.This work offers an effective method for the comprehensive use of zinc oxidized ores.展开更多
Leaching studies of low-grade pyrolusite, containing 11.84﹪ Mn with high silicon, were carried out using sodium sulfite as a reductant in ammonium sulfate medium. Various process parameters including temperature, lea...Leaching studies of low-grade pyrolusite, containing 11.84﹪ Mn with high silicon, were carried out using sodium sulfite as a reductant in ammonium sulfate medium. Various process parameters including temperature, leaching time, solid-liquid ratio, quantity of ammonium sulfate, as well as the amount of reducing agent were studied in detail. The manganese extraction yield was the response of the process. Temperature and reagent concentration exerted the most important positive effect on the manganese extraction. The optimized conditions showed that when the amount of reducing agent was a stoichonmetric amount, over 90﹪ manganese extraction and the lowest impurities were achieved, the amount of heavy metal impurities in the manganese leaching liquid was less than 5 mg/L, and almost no iron and aluminum were extracted in 3 mol/L ammonium sulfate concentration at 100 ℃ in 45 min.展开更多
The ambient concentrations of PM-related anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Ca2+, Mg2+), total and contained in the PM fractions, were investigated in a typical urban area within the Silesian Agglom...The ambient concentrations of PM-related anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Ca2+, Mg2+), total and contained in the PM fractions, were investigated in a typical urban area within the Silesian Agglomeration. A DEKATI low pressure impactor (DLPI) was used to sample PM and separate it into 13 fractions. The PM concentrations were determined gravimetrically, the ion content of the PM water extracts—by means of ion chromatography (Herisau Metrohm AG ion chromatograph). In general, sulfate, nitrate, and ammonia had the greatest ambient concentrations. PM1 contained over 60% of the PM-related sulfate and nitrate mass and 90% of the ammonia mass. Also the majority of Na+ and Cl- were bound onto fine particles. Instead, more of the PM-related K+, Ca2+ and Mg2+ mass were in PM2.5-10 than in PM2.5. In the fine particles (sub-fractions of PM1.6) sulfate, nitrate and ammonia occur mainly as (NH4)2SO4 and NH4NO3. In the sub-fractions of PM1.6-10 sulfate and nitrate might also occur as K2SO4, CaSO4, Ca(NO3)2 or NaNO3.展开更多
Drop freezing experiments with ammonium sulfate water solutions have shown the existence of the temperature maxima that are a function of the salt concentration.The maxima were:-12℃ for 10-4 M solution on filter,-9℃...Drop freezing experiments with ammonium sulfate water solutions have shown the existence of the temperature maxima that are a function of the salt concentration.The maxima were:-12℃ for 10-4 M solution on filter,-9℃ for 10^(-4) to 10^(-3)M solution in contact with particles of continental origin,and -4℃ for 10^(-4) M solution in contact with particles of marine origin. It was speculated that the presence of ice-forming nuclei active at high temperature (-4℃) should extend the for- mation of ice in clouds toward lower latitudes,increase their albedos,and provide additional cooling during daytime for the earth.The microphysics of clouds must be included in studying climate.展开更多
基金Fundamental Research Funds for the Central Universities(No.2023YQTD03,2022JCCX HH09,2022YJSHH01)the Yueqi Outstanding Scholaraward of China University of Mining&Technology(Beijing)+3 种基金the National Natural Science Foundation of China(No.52274283)the National Key R&D Program of China(No.SQ2022YFC2900065)the Ordos Science&Technology Plan(No.202204&2023XM06)the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF 2107)。
文摘Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ calculation,X-ray photoelectron spectroscopy(XPS)analysis,time of flight secondary ion mass spectrometry(ToF-SIMS)analysis,and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate((NH_(4))_(2)SO_(4))on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation.The results showed that(NH_(4))_(2)SO_(4)exhibited a positive influence on hemimorphite sulfidation flotation.It was ascribed to the number of zinc components in the form of Zn^(2+)and[Zn(NH_(3))_(i)]^(2+)(i=1–4)increased in the flotation system after hemimorphite treatment with(NH_(4))_(2)SO_(4),which was beneficial to its interaction with sulfur species in solution,resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface.[Zn(NH_(3))_(i)]^(2+)participated in the sulfidation reaction of hemimorphite as a transition state.In addition the sulfidation reaction of hemimorphite was accelerated by(NH_(4))_(2)SO_(4).Thus,(NH_(4))_(2)SO_(4)presents a vital role in promoting the sulfidation of hemimorphite.
基金the Fundamental Research Funds for the Central Universities(Nos.2022JCCXHH09 and 2022YJSHH01)the Yueqi Outstanding Scholar award of CUMTB+3 种基金the National Key R&D Program of China(No.SQ2022YFC2900065)the Ordos Science&Technology Plan(No.202204)the National Natural Science Foundation of China(No.52274283)the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF2107)。
文摘In this work,the effect of ammonium sulfate on the adsorption characteristics of low-concentration Pb(Ⅱ)ions on the sulfidized hemimorphite surface was comprehensively investigated.The results showed that ammonium sulfate could increase the maximum recovery of hemimorphite from 69.42%to 88.24%under a low concentration of Pb(Ⅱ)ions.On the hemimorphite surface pretreated with ammonium sulfate,the adsorption of Pb(Ⅱ)ions was enhanced and the main species of Pb adsorbed was changed from Pb―O/OH to PbS.This was due to the larger amount of ZnS providing more effective adsorption sites for Pb components to generate Pb S.Meanwhile,the intensity of ZnS decreased with the formation of PbS,demonstrating that ZnS was covered by PbS which formed later on the mineral surface.It was beneficial for the adsorption of butyl xanthate on the hemimorphite surface to form more hydrophobic substances.As a result,ammonium sulfate played a crucial role in realizing the efficient recovery of hemimorphite.
基金financially supported by a Project Supported by the National Natural Science Foundation of China (No. 51204054)the Fundamental Research Funds for the Central Universities of China (N110402012)the National Basic Research Program of China (No. 2007CB613603)
文摘Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by (NH4)2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and (NH4)2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows: 1 - (1 - α)1/3 = 30.85 exp(-45.57/RT)·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.
基金supported by the National Natural Science Foundation of China (Nos.20876160 and 21176026)
文摘Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with water. During the process the effects of the amotmt of ammonium sulfate, roasting temperature, and roasting time on the leaching recovery of metal elements were analyzed. The optimum technological parameters were determined as follows: ammonium sulfate/ore ratio, 0.8 g/g; roasting temperature, 400℃; and roasting time, 2 h. Under the optimum condition the leaching recoveries ofNi, Cu, Fe, and Mg were 83.48%, 76.24%, 56.43%, and 62.15%, respectively. Furthermore, the dissolution kinetics of Ni and Mg from the nickel ore was studied. The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ.mo1-1, which were consistent with the values of diffusion control reactions. Therefore, the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.
基金TheNationalNaturalScienceFoundationofChina (No .2 98770 2 1) FoundationforUniversityKeyTeacherbytheEducationMinistryofChina theNaturalScienceFoundationofHubeiProvince
文摘When EDTA was added alone in the Pb\|contaminated sand, the plant biomass and the total Pb amount in plant decreased in both species, Brassica pekinensis and B. juncea var. multiceps, though the shoot Pb amount increased. In contrast, when (NH 4) 2SO 4 was added alone in the Pb\|contaminated sand, little effect was observed on the shoot Pb amount, though the root Pb amount was significantly increased in B. juncea var. multiceps. When amending EDTA and (NH 4) 2SO 4 in combination, however, the shoot Pb amount in both species substantially increased, being, on an average, 2 times and 9 times higher than that in EDTA alone or (NH 4) 2SO 4 alone amended treatment, respectively. The two amendments showed antagonism for plant growth, but synergism for Pb bioaccumulation. B. pekinensis showed its highest level of shoot and total Pb amount in the treatment amended with EDTA and (NH 4) 2SO 4 only a half as much as in the other treatments. It is inferred that the mechanisms responsible for the joint\|enhanced Pb accumulation might be concerned with the acidification of the growth medium, cation exchange reaction and relieving EDTA induced toxicity as results by amending ammonium sulfate.
基金This research project was supported by the National Natural Science Foundation of China(No.52074138)Basic research project of Yunnan Province(No.202001AS070030)Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2020-03).
文摘In this study,the role of(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)prior to sulfurization decreased the formation of colloid in flotation pulp,and the floatability of the suppressed azurite caused by excess sodium sulfide was restored.After adding(NH_(4))_(2)SO_(4)prior to sulfurization,the formation of Cu(NH_(3))_(n) ^(2+)intermediate products changed the path of the sulfurization reaction,which slowed the direct impact of HSon the azurite surface.The nucleation rate was reduced,and the growth of copper sulfide crystal was improved.Covellite(syn,CuS)with larger crystal grains was formed on the azurite surface,thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface.Therefore,the generated copper sulfide colloid significantly reduced,ultimately promoting the effective adsorption of xanthate on the azurite surface.
文摘A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).
文摘hhen ammonium sulfate-iron oxide is treated below 573 K, ammonium sulfate can spontaneously desperse on the surface of iron oxide. Simultaneously ammonium sulfate decomposes to some extent. During or after the dispersion, sulfate ion can interact with Fe atom on the surface of iron oxide to form a sort of surface sulfato complex of Fe and thus is transformed from the isolated into the bidentately bound form. Above 573 K the sulfato complex of Fe will gradually decompose with a further increase in temperature.
文摘The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative method using the non-isothermal thermogravi- metric analysis data. The products and intermediates were synchronously characterized by X-ray diffraction and mass spectrometry. The obtained results indicate that the decomposition process of ammonium sulfate catalyzed by ferric oxide can be divided into four stages of which the activation energies are 123.64, 126.58, 178.77 and 216.99 kJ. mol^-1 respectively. The decomposition mechanisms at the first and the fourth stage both belong to Mample power theorem, the second stage belongs to Avrami-Erofeev equation and the third belongs to contracting sphere (volume) equation. The corresponding pre-exponential factors (A) are calculated simultaneously.
基金Wengfu Phosphate Fertilizer Plant(WPFP),WengFu(Group) Co.,Ltd,Guizhou,China for financial supportgrants from National Science and Technology Support Program(No.2012BAA08B00)Science and Technology Integrated Innovation Project of Shaanxi Province(No.2012KTZB03-04)
文摘Ammonium sulfate residue is a particulate solid and is produced during the manufacture of ammonium sulfate fertilizer. The residue used in this study contained a large portion of calcium carbonate, from which active lime (CaO) was recovered via thermal decomposition. We used a purpose-built device to decom- pose the residue in a semi-suspension state. We found that CaO had the highest activity when residue was decomposed at 850-900 ~C. Our experiments indicated that ammonium sulfate residue should be decom- posed in a suspension state to produce active CaO. Based on our laboratory test findings, an industrial-scale production line with a high solid/gas ratio in a suspension state was devised. The optimal operating con- ditions for the decomposition of the ammonium sulfate residue to produce high quality CaO were also investigated.We found that the CaCO3 decomposition rate was high and the CaO product was highly active, averaging 170 s by the citric acid method. Morphology measurements showed that the CaO product had a porous structure and a large specific surface ensuring high activity.
基金supported by the Major State Basic Research Development Program of China (973 Program) (No. 2011CB201500)the National High Technology Research and Development Program of China (No. 2012AA062803)
文摘The effect of ammonium sulfate ((NH4)2SO4) and urea (CO(NH2)2) on polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) formation from active carbon was investigated in this study. Both additives could significantly inhibit PCDD/F formation, and PCDD/F (TEQ) generation was reduced to 98.5% (98%) or 64.5% (77.2%) after 5% (NH4)2S04 or CO(NH2)2 was added into model ash, respectively. The inhibition efficiency of PCDDs was higher than the value of PCDFs, however, the reduction of PCDD/F yield was mainly from PCDFs decreasing. In addition, the solid-phase products were reduced more than the gas-phase compounds by inhibitors. By the measurement of chlorine emission in the phase of ion (Cl[Cl^-]) and molecule gas (Cl[Cl2]), it was observed that both Cl[Cl^-] and Cl[Cl2] were reduced after inhibitors were added into ash. Cl[Cl2] was reduced to 51.0% by urea addition, which was supposed as one possible mechanism of PCDD/F inhibition.
基金This work was supported by The Natural Science Foundation of Shanxi Province (Grant No. 2012011009-3).
文摘We investigated the effect of small amounts of ammonium sulfate (NH4)2SO4 on compound fertilizer granulation. We examined the following raw materials: humic acid, ammonium chloride, urea, potassium chloride, and monoammonium phosphate. The mass ratio of organic matter, nitrogen, phosphorus, and potassium was typically 22:17:7:2. In the absence of (NH4)2SO4, the granulation rate of the compound fertilizer was low, and increased significantly following the addition of 1–2% (NH4)2SO4. We suggested the following physical and chemical processes as potential mechanisms: (NH4)2SO4 promoted the conversion of yellow flue gas desulfurization gypsum into gypsum whiskers; (NH4)2SO4 interacted with humic acid and urea to generate a new complex; urea sulfate was formed under acidic conditions. The combined effect of the above physical and chemical processes was an increase both in the rate of interactions between the materials and in system viscosity, which has the end result of increasing the granulation rate.
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financial support of the National Key Projects for Fundamental Research and Development of China(2016YFB0600904)Sichuan University Postdoctoral Research and Development Fund(2017SCU12017)+1 种基金Project of State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization(18H0083)Sichuan Science and Technology Department Project(2019YJ0111)。
文摘In this study,a route for simultaneous mineralization of CO2 and production of titanium dioxide and ammonium alum,and microporous silicon dioxide from titanium-bearing blast furnace slag(TBBF slag)was proposed,which is comprised of(NH4)2 S04 roasting,acid leaching,ammonium alum crystallization,silicic acid flocculation and Ti hydrolysis.The effects of relevant process parameters were systematically investigated.The re sults showed that under the optimal roasting and leaching conditions about 85%of titanium and 84.6%of aluminum could be extracted while only 30%of silicon entered the leachate.84%of Al^3+was crystallized from the leachate in the form of ammonium aluminum sulfate dodecahydrate with a purity up to 99.5 wt%.About 85%of the soluble silicic acid was flocculated with the aid of secondary alcohol polyoxyethylene ether 9(AEO-9)to yield a microporous SiO2 material(97.4 wt%)from the crystallized mother liquor.The Al-and Si-depleted solution was then hydrolyzed to generate a titanium dioxide(99.1 wt%)with uniform particle size distribution.It was figured out that approximately 146 kg TiO2 could be produced from 1000 kg of TBBF slag.Therefore,the improved process is a promising method for industrial application.
基金Funded by the Natural Science Foundation of China (No. 50378092)
文摘This paper reports the results of the visual observations and micro-analysis of concrete core samples after 6 and 12 months of their exposure to sodium, ammonium and magnesium sulfate solutions with the same concentration of sulfate ions. XRD, SEM and EDS were used for micro-analysis of the mi-crostructure and the composition of the interface zone in the samples. The results indicate that the deterioration of concrete by different sulfate solutions could proceed differently with regard to the mechanism and the mode of damage caused. The damage of concrete exposed to sodium sulfate solution is mainly caused by the gypsum crystals formed in the interface zone, which lead to expansion and cracking. In the case of concrete immersed in magnesium sulfate solutions, a layer of brucite (magnesium hydroxide) and gypsum was produced in the interface zone, which reduces the cohesiveness of the interface zone in concrete. For the concrete immersed in ammonium sulfate solutions, the conversation of mortar to some mush mass by ammonium ions and the formation of a large of gypsum occurred in the interface zone, consequently, serious softening of hydrated cement pastes and expansion and cracking of concrete are the characteristics of the attack by ammonium sulfate solutions. Also, it is considered that using drilled concrete core as samples to evaluate the sulfate resistance of concrete is a good and accelerated method.
基金This research was sponsored by the 13th Five-Year-Plan National Projects for Camptotheca acuminata Decne Effi cient Cultivation Technology Research of China(2017YFD0600706).
文摘Camptotheac acuminata Decne is a unique tree species in China with an important secondary metabolite,camptothecin(CPT),used in the treatment of cancer.Nitrogen(N)is an important element that affects plant growth and the accumulation of CPT.Reports on the effect of N on CPT synthesis from a genetic perspective are scarce.To explore the effects of different N sources and levels on CPT synthesis in C.acuminata,two-year-old seedlings were fertilized with different concentrations of pure ammonium sulphate,source of ammonium N(NH4+-N),and potassium nitrate for nitrate N(NO3--N).Concentrations of 2.5,5,7.5,and10 g pot-1 NH4+-N and NO3--N were used.The results showed that 7.5 g NH4+-N and NO3--N treatments were best for growth and fresh weight of leaves.Compared with the other treatments,the CPT content,tryptophan synthase and tryptophan decarboxylase activities,and expression of the CaTSB and CaTDCl genes under the 2.5 g NH4+-N and NO3--N treatments peaked significantly at 30 days.However,the expression of CaTDC2 surpassed that of the other two genes at 60 days.Therefore,compared with NH4+-N source,the NO3--N source was more beneficial for growth,and NO3--N was better for CPT yield.Consequently,leaves of C.acuminata treated with 2.5 g NO3--N could be harvested after 30 days to obtain maximum CPT content.CaTDC1 is more closely linked to CPT synthesis.The results of this study improved the production of CPT in C.acuminata via fertilization.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51774070,52004165,and 51574084)and the National Key Research and Development Program of China(No.2017YFB 0305401).
文摘An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,roasting temperature,and holding time on zinc extraction.The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol^−1.The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry–differential thermal analysis curves.The water leaching conditions,including the leaching temperature,leaching time,stirring velocity,and liquid-to-solid ratio,were discussed,and the leaching kinetics was studied.The reaction rate was obtained under outer diffusion without product layer control;the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol^−1.The maximum zinc extraction ratio reached 96%while the efficiency of iron extraction was approximately 32%under appropriate conditions.This work offers an effective method for the comprehensive use of zinc oxidized ores.
基金This paper is financially supported by the Department of Science and Technology of Wuhan (No. 20065004116-22).
文摘Leaching studies of low-grade pyrolusite, containing 11.84﹪ Mn with high silicon, were carried out using sodium sulfite as a reductant in ammonium sulfate medium. Various process parameters including temperature, leaching time, solid-liquid ratio, quantity of ammonium sulfate, as well as the amount of reducing agent were studied in detail. The manganese extraction yield was the response of the process. Temperature and reagent concentration exerted the most important positive effect on the manganese extraction. The optimized conditions showed that when the amount of reducing agent was a stoichonmetric amount, over 90﹪ manganese extraction and the lowest impurities were achieved, the amount of heavy metal impurities in the manganese leaching liquid was less than 5 mg/L, and almost no iron and aluminum were extracted in 3 mol/L ammonium sulfate concentration at 100 ℃ in 45 min.
基金partially supported by grant No.N N523 564038 from the Polish Ministry of Science and Higher Education.
文摘The ambient concentrations of PM-related anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Ca2+, Mg2+), total and contained in the PM fractions, were investigated in a typical urban area within the Silesian Agglomeration. A DEKATI low pressure impactor (DLPI) was used to sample PM and separate it into 13 fractions. The PM concentrations were determined gravimetrically, the ion content of the PM water extracts—by means of ion chromatography (Herisau Metrohm AG ion chromatograph). In general, sulfate, nitrate, and ammonia had the greatest ambient concentrations. PM1 contained over 60% of the PM-related sulfate and nitrate mass and 90% of the ammonia mass. Also the majority of Na+ and Cl- were bound onto fine particles. Instead, more of the PM-related K+, Ca2+ and Mg2+ mass were in PM2.5-10 than in PM2.5. In the fine particles (sub-fractions of PM1.6) sulfate, nitrate and ammonia occur mainly as (NH4)2SO4 and NH4NO3. In the sub-fractions of PM1.6-10 sulfate and nitrate might also occur as K2SO4, CaSO4, Ca(NO3)2 or NaNO3.
文摘Drop freezing experiments with ammonium sulfate water solutions have shown the existence of the temperature maxima that are a function of the salt concentration.The maxima were:-12℃ for 10-4 M solution on filter,-9℃ for 10^(-4) to 10^(-3)M solution in contact with particles of continental origin,and -4℃ for 10^(-4) M solution in contact with particles of marine origin. It was speculated that the presence of ice-forming nuclei active at high temperature (-4℃) should extend the for- mation of ice in clouds toward lower latitudes,increase their albedos,and provide additional cooling during daytime for the earth.The microphysics of clouds must be included in studying climate.