Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching

The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.

Leaching kinetics of scheelite concentrate with sodium hydroxide in the presence of phosphate

The reaction kinetics for the leaching of low-grade scheelite concentrate was investigated in an autoclave with sodium hydroxide in the presence of phosphate. The effects of stirring speed (300-600 r/min), reaction temperature (353-383 K), sodium hydroxide concentration (1.69-6.76 mol/L) and phosphate concentration (0.68-1.69 mol/L) on the WO3 dissolution ratio were studied. The results showed that the WO3 dissolution ratio was practically independent of stirring speed, while it increased with increasing the reaction temperature, and the concentrations of sodium hydroxide and phosphate. The experimental data were consistent with the shrinking core model, with a surface chemical reaction as the leaching rate-determining step. The apparent activation energy was calculated as 49.56 kJ/mol, and the reaction orders with respect to the concentrations of sodium hydroxide and phosphate were determined as 0.27 and 0.67, respectively. The kinetics equation of the leaching process was established.

Kinetics and leaching behaviors of aluminum from pharmaceutical blisters in sodium hydroxide solution

A hydrometallurgical process was developed for recycling pharmaceutical blisters.Leaching aluminum from pharmaceutical blisters using sodium hydroxide(NaOH) solutions was investigated with respect to leaching behaviors and kinetics.AL9(34) orthogonal design of experiments suggests that the most significant factor is NaOH concentration followed by temperature and leaching time.Factorial experiments demonstrate that the leaching rate of aluminum increases with increasing of the factors.The optimum conditions are temperature of 70 °C,leaching time of 20 min,NaOH concentration of 1.25 mol/L,liquid-to-solid mass ratio of 15:1 and agitation speed of 400 r/min.Under optimum conditions,the leaching rate is up to 100%,implying that aluminum and polyvinyl chloride(PVC) plastic in pharmaceutical blisters are separated completely.Kinetics of leaching aluminum is best described by the product layer diffusion control model,and the activation energy is calculated to be 19.26 kJ/mol.

Influence of Sodium Carbonate Amount on Crystalline Phase and Structure Stability for Doping Nickel Hydroxide

Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni（OH）2 upon aging in a strong alkaline solution. In this study, the Al-Co, Al-Yb, Yb-Co and Al-Yb-Co multiple doping was used respectively. By controlling the amount of sodium carbonate, the α-Ni（OH）2 was prepared by ultrasonic-assisted precipitation. And the influence of sodium carbonate on the crystalline phase and structure stability for alpha nickel hydroxide was studied. The results demonstrate that, with increasing amount, the biphase nickel hydroxide transforms to pure alpha nickel hydroxide gradually, and the structure stability is also improved. When the amount of sodium carbonate is 2 g, the sample still keeps α-Ni（OH）2 after being aged for 30 days, for Al-Yb-Co-Ni（OH）2. And when the amount is less than 2 g, the phase transformations exist in the samples with different extents. These results demonstrated that the amount of sodium carbonate is a critical factor to maintain the structural stability of α-Ni（OH）2.

Leaching kinetics of low-grade copper ore containing calcium-magnesium carbonate in ammonia-ammonium sulfate solution with persulfate

The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentrations of ammonia, ammonium sulfate and sodium persulfate were determined. The results show that the leaching rate is nearly independent of agitation above 300 r/min and increases with the increase of temperature, concentrations of ammonia, ammonium sulfate and sodium persulfate. The EDS analysis and phase quantitative analysis of the residues indicate that bornite can be dissolved by persulfate oxidization. The leaching kinetics with activation energy of 22.91 kJ/mol was analyzed by using a new shrinking core model （SCM） in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. A semi-empirical rate equation was obtained to describe the leaching process and the empirical reaction orders with respect to the concentrations of ammonia, ammonium sulfate and sodium persulfate are 0.5, 1.2 and 0.5, respectively.

Separation and enrichment of elemental sulfur and mercury from hydrometallurgical zinc residue using sodium sulfide

The separation and enrichment of mercury and the recovery of elemental sulfur from flotation sulfur concentrate in zinc pressure leaching process were carried out by sodium sulfide leaching and carbon dioxide precipitating. The results show that the leaching rate of elemental sulfur is more than 98%, and 98.13% of mercury is enriched in the residue, under the optimized conditions of sodium sulfide concentration 1.5 mol/L, liquid/solid ratio 6：1 and leaching time 30 min at room temperature. In addition, the content of mercury is enriched 5.23 times that in the leaching residue. The elemental sulfur is precipitated from leaching solution under conditions of carbon dioxide flow rate 200 mL/min and blowing time 150 min, while solution is stirred adequately. The recovery efficiency of elemental sulfur reaches 97.67%, and the purity of elemental sulfur is 99.75%, meeting the requirements of industrial first-rate product standard according to the national standard of GB/T 2449-2006 （PRC）.

Secondary Crystallization of Na_2CO_3-Modified HZSM-5 Zeolites with Tetrapropylammonium Hydroxide and Their Catalytic Performance in Thiophene Alkylation Reaction

The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting samples were characterized by a complementary combination of X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, X-ray fluorescence spectroscopy, XPS, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, BET and temperature-programmed desorption techniques. The results showed that the secondary crystallization of the HZSM-5 zeolite could result in migration of non-framework species from the internal channels to the zeolite surface and their transformation into framework species. The catalytic activity of these modified samples for thiophene alkylation was evaluated. Both the activity and stability of the catalysts were improved after secondary crystallization.

A new sulfur-doped source and synergistic effect with nitrogen for carbon dots produced from glucose

The nitrogen and sulfur co-doped carbon dots(N, S-CDs) with increased luminescence were synthesized by a hydrothermal process in one green pot by using glucose, and a new sulfur-doping source of sodium sulfite was developed.The synergistic effect of the N and S groups was well discussed through the structure analysis of Fourier transform infrared spectra and x-ray photoelectron spectra. The surface states of N, S-CDs embody more complicated functional groups, and S element exists as –SSO3, –C–SO3, and SO-42groups due to the introduction of sodium sulfite. The sulfur-containing groups passivate the surface of the CDs, and the relatively high sulfur groups may reduce the non-radiation centers. The fluorescence is affected by the hydroxyl group of the solvent. The quenching of Fe3+ ion to fluorescence and the sensitivity of fluorescence to p H were also investigated.

Pressure leaching of bismuth sulfide concentrate containing molybdenum and tungsten in alkaline solution

The leaching results of bismuth sulfide concentrate containing molybdenum and tungsten in air-H2O2-NaOH system, pressure-O2-Na2CO3 system and pressure-O2-NaOH system were investigated. The results show that the extraction of molybdenum, tungsten and sulfur goes up with the increase of NaOH concentration, oxygen partial pressure and reaction time. The extraction of molybdenum and tungsten also rises up with temperature, but the leaching ratio of sulfur increases initially to a peak of 98% at 150℃ and then decreases with the increase of temperature. Under the optimal conditions, the extraction of molybdenum, tungsten and sulfur is more than 95.6%, 93.8% and 96.0%, respectively, and the main phases of residue are Bi2O3 and Fe2O3. Therefore, the method of pressure leaching in alkaline solution is provided as an effective separation of molybdenum, tungsten and sulfur from bismuth and a beneficial pretreatment for consequent process.

Kinetic process of oxidative leaching of chalcopyrite under low oxygen pressure and low temperature

Kinetic process of oxidative leaching of chalcopyrite in chloride acid hydroxide medium under oxygen pressure and low temperature was investigated. The effect on leaching rate of chalcopyrite caused by these factors such as ore granularity, vitriol concentration, sodium chloride concentration, oxygen pressure and temperature was discussed. The results show that the leaching rate of chalcopyrite increases with decreasing the ore granularity. At the early stage of oxidative reaction, the copper leaching rate increases with increasing the oxygen pressure and dosage of vitriol concentration, while oxygen pressure affects leaching less at the later stage. At low temperature, the earlier oxidative leaching process of chalcopyrite is controlled by chemical reactions while the later one by diffusion. The chalcopyrite oxidative leaching rate has close relation with ion concentration in the leaching solution. The higher ion concentration is propitious for chalcopyrite leaching.

Rare earth recovery from fluoride molten-salt electrolytic slag by sodium carbonate roasting-hydrochloric acid leaching

Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great importance to fully utilise this resource.In this study,the transformation mechanism of fluorinated rare earth molten-salt electrolytic slag roasted with sodium carbonate,and the regulation mechanism of rare earth leaching under different roasting conditions were investigated with the help of thermodynamic calculation of the reactions and kinetic analysis.The thermodynamic and differential thermal thermogravimetric(DTA-TG)analysis shows that the transformation of rare earth fluoride to rare earth oxide is promoted at elevated temperature.Furthermore,the leaching experimental results show that increasing the temperature,time,hydrochloric acid concentration,and liquid-solid ratio can effectively promote the recovery of rare earths.The optimum experimental conditions are a roasting temperature of 700℃,roasting time of 2 h,and sodium carbonate to molten salt electrolytic slag mass ratio of 0.6,followed by leaching at 80℃with a liquid-solid ratio of 10:1 by adding 3 moI/L hydrochlo ric acid with stirring for 2 h.Under these conditions,the rare earths in the molten salt electrolytic slag are biologically transformed at a lower temperature and the leaching efficiency of rare earths exceeds 98%.

Influence of sulfur doping on the molecular fluorophore and synergistic effect for citric acid carbon dots

In citric acid-based carbon dots,molecular fluorophore contributes greatly to the fluorescence emission.In this paper,the nitrogen and sulfur co-doped carbon dots(N,S-CDs)were prepared,and an independent sulfur source is selected to achieve the doping controllability.The influence of sulfur doping on the molecular fluorophore was systematically studied.The introduction of sulfur atoms may promote the formation of molecular fluorophore due to the increased nitrogen content in CDs.The addition surface states containing sulfur were produced,and S element exists as-SO_(3),and-SO_(4)groups.Appreciate ratio of nitrogen and sulfur sources can improve the fluorescence emission.The photoluminescence quantum yields(PLQY)is increased from 56.4%of the single N-doping CDs to 63.4%of double-doping CDs,which ascribes to the synergistic effect of molecular fluorophores and surface states.The sensitivity of fluorescence to pH response and various metal ions was also explored.

Process optimization of reaction of acid leaching residue of asbestos tailing and sodium hydroxide aqueous solution

Silica is the major component of the acid leaching residue of asbestos tailing. The waterglass solution can be prepared by the reaction of the residue with sodium hydroxide aqueous solution. Compared to the high temperature reaction method, this process is environmental friendly and low cost. In this paper, the reaction process of the residue and the sodium hydroxide aqueous solution is optimized. The optimum reaction process parameters are as follows: the usage of sodium hydroxide is 26.4 g/100 g acid leaching residue, the reaction temperature is 90℃, the reaction time is 1 h, and the ratio of the liquid/solid is 2.0. The significance sequence of the process parameters to the alkali leaching reaction effect is the usage of sodium hydroxide > the ratio of the liquid/solid > the reaction time > the reaction temperature. The significance sequence to the leaching ratio of SiO2 is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. The significance sequence to the modulus of the sodium silicate is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. Under the optimum conditions, the leaching ratio of the SiO2 is 77.5%, and the modulus of the sodium silicate is 3.15. The XRD analysis result indicates that the major components of the alkali leaching residue are serpentine, talc, quartz and some albite.

镓精矿氢氧化钠浸出过程镓的浸出行为

从湿法炼锌工艺中得到的镓精矿是制备金属镓重要的中间产品,氢氧化钠浸出镓精矿制备电积前液是制备高品质金属镓的生产关键环节。通过研究氢氧化钠浸出镓精矿过程中添加剂的种类、添加剂用量、氢氧化钠浓度、浸出液固比、反应温度和浸出时间等工艺参数,分析了各工艺参数在镓精矿浸出过程中对Ga、Al的浸出率及浸出滤液过滤性能的影响。结果表明,在添加剂CaO 15%、NaOH浓度3 mol/L、液固比L/S=10、反应温度80℃、浸出时间120 min的最优条件下,Ga的浸出率为98.15%,Al的浸出率为53.01%,浸出滤液过滤速度为108.88 mL/min,添加剂CaO在反应过程中生成的铝酸钙作为滤饼支撑骨架,有效改善了浸出滤液的过滤性能。

原位漫反射中红外光谱在氢氧化钠杂质分析的应用

对原位漫反射中红外光谱开展了氢氧化钠杂质研究。实验发现:氢氧化钠杂质主要包括:少量碳酸钠和水。碳酸钠分子主要的红外吸收模式包括:C=O基团伸缩振动模式(νC=O-Na_(2)CO_(3))和CO_(3)基团面内弯曲振动模式(βCO_(3)-Na_(2)CO_(3))的合频峰(νC=O-Na_(2)CO_(3)+βCO_(3)-Na_(2)CO_(3));C=O基团伸缩振动模式(νC=O-Na_(2)CO_(3));CO_(3)基团不对称伸缩振动模式(νasCO_(3)-Na_(2)CO_(3));CO_(3)基团对称伸缩振动模式(νsCO_(3)-Na_(2)CO_(3));CO_(3)基团面外弯曲振动模式(rCO_(3)-Na_(2)CO_(3))及CO_(3)基团面内弯曲振动模式(βCO_(3)-Na_(2)CO_(3));水分子主要的红外吸收模式包括:OH基团伸缩振动模式(νOH-H_(2)O)。原位漫反射中红外光谱在氢氧化钠杂质分析领域,具有重要的应用研究价值。

高砷铜精矿硫化钠-氢氧化钠碱浸除砷

云南某高砷铜精矿铜品位为13.46%,含砷质量分数为5.17%,主要矿物为黄铜矿、黄铁矿、毒砂、含砷黄锡矿、锡石和镁铝硅酸盐。在硫化钠-氢氧化钠碱性体系下浸出高砷铜精矿的砷,系统研究工艺参数条件如氢氧化钠浓度、硫化钠用量、浸出温度、转速、液固比、浸出时间等对砷脱除率的影响。结果表明,上述工艺参数条件均对砷的碱浸脱除率影响较大,最佳浸出工艺条件为:氢氧化钠浓度5 mol/L、硫化钠浓度为50 g/L、浸出温度90℃、转速为1000 r/min、液固比为10∶1、浸出时间为3 h,在此最佳条件下可最终获得砷去除率为60.55%的技术指标。采用EMPA-EDS对碱浸渣进一步分析发现,采用硫化钠-氢氧化钠碱性体系浸出可完全溶解高砷铜精矿中的毒砂,浸出渣中主要含砷矿物为含锌硫砷铜矿和砷黝铜矿;浸出过程形成的氢氧化铁以及脱水后生成的氧化铁覆盖在含砷矿物表面,阻碍了碱性浸出剂与矿物的充分接触,影响了浸出过程传质效果。

锌浸出液水热法制备纳米ZnO

纳米ZnO是一种新型的高功能精细纳米材料,用途广泛,采用水热法制备的纳米ZnO颗粒纯度高、晶形好且操作简便;含锌二次资源的锌浸出液中杂质元素较多,对后期产品纯素的影响较大,其中除铜、镉较为关键。本文以含锌二次资源的锌浸出液为原料,采用锌粉置换除铜、镉,然后以净化后的硫酸锌溶液为锌源,分别采用氨水、碳酸钠、氢氧化钠作为沉淀剂通过水热法制备纳米ZnO,并考察不同工艺参数对纳米ZnO物相和形貌的影响,结果表明:在合适条件下,锌粉置换后浸出液中铜、镉离子浓度分别为0.039 9 mg·L^(-1)、6.416 2 mg·L^(-1),可用于制备纳米ZnO;采用氨水和碳酸钠作为沉淀剂制得的产物均为ZnO和其他晶体的混合物,属于非纯相的不规则晶体;采用氢氧化钠作为沉淀剂可制得纯相纳米ZnO,最佳制备条件为锌碱摩尔比1∶2、反应时间1 h、反应温度120℃,制得的纳米ZnO呈现棱柱结构,粒径在50~100 nm之间,颗粒尺寸分布均匀。

碳化硼陶瓷材料试样分解方法探讨

碳化硼陶瓷材料被应用于航空航天、核工业和工程陶瓷等方面。鉴于化学成分检测结果的准确性与分解方法不可分割,有合理高效的分解方法才能得出真实的化学成分含量。本文对碳化硼陶瓷材料的分解方法进行对比,以碳酸钙为熔剂在高温下对碳化硼进行分解。结果表明,碳酸钙熔样方法测得的碳化硼结果更稳定,熔样方式更简单。

多流路在线分析仪在盐水精制中的应用

介绍了盐水精制过程中使用的卤水浓度在线分析仪、钙镁含量在线分析仪、硫酸根含量在线分析仪、游离氯含量在线分析仪和过碱量在线分析仪的测量原理及使用经验。

一次盐水精制工序在线监测仪的应用

介绍了一次盐水精制工序两碱含量在线监测仪、钙镁含量在线监测仪和氯化钠浓度在线监测仪的测量原理,对比分析了在线检测数据与人工检测数据,为稳定生产和降低成本奠定了基础。