采用(NH_(4))_(2)SO_(4)焙烧-水浸工艺提高菱镁矿的利用效率

研究采用硫酸铵焙烧—水浸工艺提高菱镁矿的利用效率,结合XRD和TG-DTA分析以及对比硫酸铵焙烧MgO的物相变化得到焙烧过程中矿相的转化过程。实验结果表明,在菱镁矿粒度为~74μm、硫酸铵与菱镁矿物料摩尔比为1.6:1、焙烧温度为475℃和焙烧时间为2 h的条件下,镁的提取率达到98.7%。反应中物相转化过程可以概括如下:MgCO_(3)先转变为(NH_(4))_(2)Mg_(2)(SO_(4))_(3),再分解得到MgSO_(4)。反应遵循化学反应和扩散混合控制机理,其表观活化能为33.02 k J/mol。

硫酸氢铵焙烧-水浸工艺综合利用氧化锌矿

采用硫酸氢铵焙烧-水浸工艺综合利用氧化锌矿,将氧化锌矿与硫酸氢铵混匀,经焙烧、水浸分离得到溶出液和滤渣,溶出液净化除杂后制备碱式碳酸锌/氢氧化锌和硫酸铵,碱式碳酸锌/氢氧化锌煅烧制备氧化锌,硫酸铵溶液蒸浓结晶后制取硫酸氢铵返回焙烧氧化锌矿;滤渣转化浸取法提铅、锶后碱浸提硅,分离得到硅酸钠溶液和尾渣,净化硅酸钠溶液与氢氧化钙乳液反应制得硬硅钙石和氢氧化钠溶液,氢氧化钠溶液蒸浓循环利用;尾渣回收铁。整个工艺过程实现了氧化锌矿中有价组元的综合提取利用和化工原料的循环利用。

废抛光粉中综合回收Ce、La研究

以湖南某企业废抛光粉为研究对象,采用硫酸焙烧-水浸-草酸沉淀-煅烧工艺从废铈抛光粉中回收铈镧,并制备成低级抛光粉。结果表明,在硫酸焙烧温度300℃、浓硫酸用量(mL/g)3∶5、焙烧时间2 h;水浸温度25℃、水浸液固比(mL/g)20∶1、水浸时间2 h;草酸沉淀温度25℃、草酸用量为理论值1倍、沉淀时间1 h;焙烧温度850℃、焙烧时间2 h的条件下,可获得Ce、La品位分别为65.56%和24.12%的稀土氧化物,达到低级Ce稀土抛光粉标准。

复杂烟尘高效浸出铟的工艺研究

以某公司复杂含铟烟尘为原料,分别研究了氧化酸浸和硫酸化焙烧-水浸两种浸出铟工艺。氧化酸浸工艺主要考察了初始硫酸酸度、液固比、浸出温度、反应时间、氧化剂添加量等因素对铟浸出效果的影响;硫酸化焙烧-水浸工艺主要考察了硫酸用量、焙烧温度、焙烧时间等因素对铟浸出效果的影响。实验结果表明,在初始硫酸浓度6.0 mol/L,液固比6∶1,浸出温度90℃,浸出时间3 h,氧化剂H2O2添加量为12%条件下进行氧化酸浸,铟浸出率由常规酸浸的46.5%提高到70%;在硫酸用量1.0 m L/g,焙烧温度300℃,焙烧时间2 h条件下进行硫酸化焙烧-水浸,铟浸出率达到92%,实现了铟的高效浸出。

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting(SCS)dust using a sulfating roasting−water leaching process were investigated.The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl.Under the sulfating roasting conditions of the roasting temperature of 250℃ and the sulfuric acid excess coefficient of 1.8,over 74 wt.%of F and 98 wt.%of Cl were volatilized into flue gas.Approximately 98.6 wt.%of Zn and 96.5 wt.%of Cu in the roasting product were dissolved into the leaching solution after the water leaching process,while the leaching efficiencies of Pb and Sn were only 0.12%and 0.22%,respectively.The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

Extraction of molybdenum and nickel from roasted Ni-Mo ore by hydrochloric acid leaching, sulphation roasting and water leaching

To extract molybdenum and nickel from the roasted Ni-Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leaching rate of Mo and Ni. Under the optimum conditions of hydrochloric acid leaching （roasted Ni-Mo ore leached with 0.219 mL/g hydrochloric acid addition at 65 ℃ for 30 min with a L/S ratio of 3 mL/g）, sulphation roasting （51.9% sulfiaric acid addition, roasting temperature 240 ℃ for 1 h）, followed by leaching with the first stage hydrochloric acid leaching solution at 95 ℃ for 2 h, the leaching rates of Mo and Ni reached 95.8% and 91.3%, respectively.

Recovery of valuable metals from zinc leaching residue by sulfate roasting and water leaching

Zinc leaching residue(ZLR),produced from traditional zinc hydrometallurgy process,is not only a hazardous waste but also a potential valuable solid.The combination of sulfate roasting and water leaching was employed to recover the valuable metals from ZLR.The ZLR was initially roasted with ferric sulfate at640°C for1h with ferric sulfate/zinc ferrite mole ratio of1.2.In this process,the valuable metals were efficiently transformed into water soluble sulfate,while iron remains as ferric oxide.Thereafter,water leaching was conducted to extract the valuable metals sulfate for recovery.The recovery rates of zinc,manganese,copper,cadmium and iron were92.4%,93.3%,99.3%,91.4%and1.1%,respectively.A leaching toxicity test for ZLR was performed after water leaching.The results indicated that the final residue was effectively detoxified and all of the heavy metal leaching concentrations were under the allowable limit.

An environmentally benign and sustainable process for carbon recovery and efficient defluorination of spent carbon cathode

A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.