南方稀土矿抑铝浸出研究

南方稀土矿浸出过程中,铝是影响产品质量的主要杂质。本研究在浸矿剂中加入抑制铝浸出的添加剂,抑制浸矿过程中铝的浸出。经优化试验,结果表明:对于南方某稀土矿,在浸矿剂中加入0.05%的抑铝剂HZA,控制浸矿剂溶液pH值为5.5时,所得浸出液中铝的含量减少56.85%,而稀土浸出率几乎不损失。

离子型稀土矿抑杂浸出中抑铝剂的研究

研究了在抑杂浸出过程中添加抑铝剂对稀土浸出的影响，筛选出了适宜的抑铝剂．所筛选出的抑铝剂能适应于我国南方不同类型离子型稀土矿，抑铝剂的添加几乎不影响稀土的浸出率．通过抑杂浸出得到的浸出液中铝离子含量小于2mg／L，去除率达到98％以上，铁离子含量小于0．3mg／L，该浸出液无需净化直接用碳酸氢铵沉淀得到的碳酸沉淀稀土符合生产质量要求．稀土产品质量达到国内现行标准，有效地简化了生产流程，并能减少5％-15％的稀土损失．

羧酸铵盐浸取剂对风化壳淋积型稀土矿助浸过程研究

目前,稀土矿浸出研究仅针对稀土浸出过程中抑杂浸出或抑制黏土矿物膨胀的某一方面。为综合考虑稀土浸出过程中高效抑铝和抑制黏土矿物膨胀的协同作用,采用氯化铵分别与不同浓度的乙酸铵、酒石酸铵、柠檬酸铵3种羧酸铵盐助浸剂组成复配溶液,通过柱浸方法回收风化壳淋积型稀土矿,从而实现在保证稀土浸出率的情况下,达到有效降低浸出液中杂质铝含量的目的,同时得到黏土矿物的最佳抑膨条件。选用0.2 mol/L氯化铵分别与3种羧酸铵盐助浸剂复配,探讨了助浸剂浓度、浸出温度及浸出液pH对风化壳淋积型稀土矿浸出过程以及对黏土矿物膨胀性能的影响。结果表明,3种羧酸铵盐助浸剂的最佳添加浓度为:0.04 mol/L乙酸铵、0.07 mol/L酒石酸铵、0.005 mol/L柠檬酸铵,在最佳添加剂浓度下抑铝能力为:乙酸铵>柠檬酸铵>酒石酸铵,黏土矿物的膨胀率大小为:δ乙酸铵<δ酒石酸铵<δ柠檬酸铵。在常温下,0.2 mol/L氯化铵与0.04 mol/L乙酸铵复配溶液作为浸取剂时抑铝和防膨效果最佳,在pH=4时,稀土浸出率为90.08%,铝浸出率为26.37%,黏土矿物膨胀率为2.705%。

Leaching behaviors of iron and aluminum elements of ion-absorbed-rare-earth ore with a new impurity depressant

Ion-absorbed rare-earth ore is an important mineral resource which is widely extracted by in-situ leaching process. And such process generates a significant amount of impurities such as aluminum and iron ions in leaching solution simultaneously. The surface characteristics and interactions by infrared spectroscopy and X-ray diffraction were studied to optimize the leaching conditions. It is found that the environment-friendly depressant LG-01 can react with the impurity ions through the formation of a new complex on the surface of leaching residues. Thus, it reduces significantly the concentration of impurity ions in leaching solution and improves the leaching rate of rare-earth ore. Moreover, a leaching rate of 95.6% and an impurity removal rate of 92% have been achieved under the optimized conditions.

Effect of degree of substitution of carboxymethyl starch on diaspore depression in reverse flotation

Carboxymethyl starchs（CMS） with low and high degrees of substitution（CMSL and CMSH in short,respectively） were employed as depressants of diaspore in cationic reverse flotation using dodecylamine（DDA） as collector.The effect of degree of substitution of CMS on its depression performance was examined and the interaction mode and behavior were investigated in a comparative manner.Micro-flotation test showed that CMSL exhibited better performance in depressing diaspore than CMSH in a broad pH range.The adsorption of CMS on diaspore was studied by adsorption test,zeta potential measurement,and atomic force microscopy.It was found that CMSH corresponds to lower adsorption amount,thinner adsorption layer,and more negative charge than CMSL,resulting from the more chelating sites brought by the high degree of substitution.The surface tension measurement and DDA adsorption test further revealed that CMSL/DDA system gives a better depressing performance benefiting from the trapping effect by enveloping some DDA molecules inside the loop chains,while CMSH/DDA system is likely considered a quasi-surfactant.

Formation of precipitates and recrystallization resistance in Al-Sc-Zr alloys

Al-x%Sc-0.11%Zr alloys （x=0, 0.02, 0.05, 0.08, 0.11, 0.15） were produced by a chill cast procedure. The effect of Sc content on the precipitation of Al3（Sc,Zr） during heat treatment at 475 °C for 12 h was studied. Nucleation, precipitation and distribution of Al3（Sc,Zr） precipitates were found to be strongly related to the Sc content. With increasing the Sc content, the average radius of the precipitates decreases, while the number density of the precipitates increases, as investigated by transmission electron microscopy （TEM）. The distribution of the precipitates becomes more and more homogeneous when the Sc content is increased. The recrystallization resistance of samples that was 90% cold rolled and isothermal annealed for half an hour in the temperature range of 200-600 °C was investigated. The results show that the recrystallization temperature varies from 250 °C for the alloy without Sc to about 600 °C for the alloy containing 0.15% Sc because of the high density of Al3（Sc,Zr） precipitates.

Effect of minor Sc and Zr addition on microstructure and properties of ultra-high strength aluminum alloy

The Al-9Zn-2.8Mg-2.5Cu-xZr-ySc alloys （x=0, 0.15%, 0.15%; y=0, 0.05%, 0.15%）, produced by low-frequent electromagnetic casting technology, were subjected to homogenization treatment, hot extrusion, solution and aging treatment. The effects of minor Sc and Zr addition on microstructure, recrystallization and properties of alloys were studied by optical microscopy （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that Sc and Zr addition can refine grains of the as-cast alloy by precipitation of primary Al3（Sc,Zr） particles formed during solidification as heterogeneous nuclei. Secondary Al3（Sc,Zr） precipitates formed during homogenization treatment strongly pin the movement of dislocation and subgrain boundaries, which can effectively inhibit the alloys recrystallization. Compared with the alloy without Sc and Zr addition, the Al-Zn-Mg-Cu-Zr alloy with 0.05%Sc and 0.15%Zr shows the increase in tensile strength and yield strength by 172 MPa and 218 MPa, respectively. Strengthening comes from the contributions of precipitation, substructure and grain refining.

Effect of aqueous extract of leaves of Morinda tinctoria on corrosion inhibition of aluminium surface in HCl medium

The effect of Morinda tinctoria(MT) leaves extract on the corrosion inhibition of Al in acid medium was studied. The inhibition studies were carried out on Al in 0.5 mol/L HCl with the extract of leaves of MT using mass loss and electrochemical techniques. Parameters, such as concentration of the inhibitor, concentration of the acid, temperature and concentration of halide ions, were varied and optimized. Increase of the temperature and concentration of acid can decrease the performance of the inhibitor. Thermodynamic parameters show that the physisorption of the inhibitor molecules on Al surface obeys Langmuir isotherm.

Flotation techniques for separation of diaspore from bauxite using Gemini collector and starch depressant

The floatability of diaspore and three kinds of silicate minerals,including kaolinite,illite and pyrophyllite,by a cationic Gemini surfactant as collector and starch as depressant was investigated as function of reagents concentration and pulp pH.Further studies of artificially mixed minerals and bauxite ore were also detailedly conducted.At last,the pre-desliming reverse flotation separation process was adopted.It can be concluded that the combinational use of a Gemini cationic collector and the starch depressant is effective.The concentrates with Al2O3 to SiO2 mass ratio of 9.66 and the recovery of Al2O3 of 71.73% are obtained from natural bauxite ore(A/S=5.70) at pH value of around 10.