IN SITU LEACHING OF URANIUM USING DILUTE SULFURIC ACID AND MOLECULAR OXYGEN

The technical feasibility of in situ uranium leaching using dilute sulfuric acid and molecular oxygen has been assessed and the important process parameters examined by use of laboratory high pressure leaching columns.

The dilute H₂SO₄/O₂ lixiviant was effective in leaching uranium from the ore samples tested. The leaching process was chemical reaction rate limited and can be represented using pseudo first-order kinetics. The leaching rate constant is proportional to the proton concentration of the lixiviant.

Much of the uranium was leached from the ore before decomposition of carbonate minerals by the acid was complete. Acid consumption per pound of U₃O₈ increased sharply as the uranium recovery level exceeded 70%. There appears to be a minimum oxygen pressure for effective uranium leaching. A pressure of 2758 KPa was adequate for the ore samples tested     

锌灰制备活性氧化锌新工艺

以炼锌厂废锌灰为原料，经硫酸浸取制备活性氧化锌，考察了工艺条件对锌浸出率的影响。实验结果表明：锌灰在50℃浸取，酸用量40g／L，可使锌的溶出率达92．8％。碱式碳酸锌最佳水解温度为40℃，水解时间为2h，pH为7．5时，溶液中锌质量浓度为10g／L，得到96％以上的水解率。采用该工艺制得的氧化锌符合HG／T2572-1994。     

Transformations and losses of fertilizer nitrogen on no-till and conventional till soils

A field study was conducted in 1982 to measure the effect of no-till (NT) and conventional till (CT) systems on N transformation after surface and subsurface applications of N fertilizers. Urea, urea-ammonium nitrate (UAN) solution, (NH₄)₂SO₄ (AS), and CA(NO₃)₂ were applied to NT and CT plots (5.95 m²) at a rate of 448 kg N ha^–1. A comparison of fertilizer N recovered in soils receiving incorporated or surface applied N was used to estimate NH₃ volatilization while denitrification was estimated from fertilizer N recovered in the presence and absence of nitrapyrin with incorporated N. Immobilization was assessed in microplots (0.37 m²) after surface application of (¹⁵NH₄)₂SO₄ to NT and CT systems at a rate of 220 kg N ha^–1.The results indicate little difference between NT and CT systems on urea hydrolysis rates and immobilization of surface applied fertilizer N. Approximately 50% and 10% of the surface applied N was recovered in the inorganic and organic fractions, respectively, on both tillage systems. The N not recovered was likely lost from plot areas through soil runoff. Incorporation of UAN, urea and AS resulted in 20 to 40% greater inorganic N recovery than from surface application. Nitrification rates were greater under the NT than the CT system. The similarities in concentration in the various N pools observed between the two tillage systems may be partially due to the short length of time that NT was imposed in this field study (<1 year) since other researchers using established tillage systems (>5 y) indicate that NT tends to promote decreased efficiency of fertilizer N.     

Seawater-soluble pigments and their potential use in self-polishing antifouling paints: simulation-based screening tool

This work concerns the on-going development of efficient and environmentally friendly antifouling paints for biofouling control on large ocean-going ships. It is illustrated how a detailed mathematical model for a self-polishing antifouling paint exposed to seawater can be used as a product engineering tool to obtain a quick estimate of the paint behaviour that a given seawater-soluble pigment will provide. In the present context, “pigment” refers to relevant particulate solids of organic-, inorganic-, or biological nature. Simulations performed at 15 and 30 °C suggest that pigment solubility and seawater diffusivity of dissolved pigment species have a significant influence on the polishing and leaching behaviour of a typical self-polishing paint system. The pigment size distribution, on the other hand, only has a minor influence on the paint–seawater interaction. Simulations also indicate that only compounds which are effective against biofouling at very low seawater concentrations are useful as active antifouling paint ingredients. The need for model verification and exploration of practical issues, subsequent a given pigment has been found of interest, is discussed. The model approach is of relevance in the search for novel antifouling paints and for the development of accelerated test methods.     

Electric-oxidation extraction of molybdenite concentrate in alkaline NaCl electrolyte

The dissolution of molybdenite concentrate in NaCl electrolyte was investigated. The results show that the dissolution rate increases with the increase in liquid-to-solid ratio, stirring speed, NaCl concentration and temperature. When the liquid-to-solid ratio is 30:1, stirring speed is 400 r/min, concentration of NaCl is 4 mol/L at pH=9 and room temperature, the leaching efficiency of molybdenite concentrate will reach 99.5% in 240 min. Molybdenite concentrate cannot be electro-oxidized directly on the anode. The kinetic studies show that the dissolution of molybdenite concentrate is represented by shrinking core model with diffusion through a porous product layer of element sulfur, and the apparent activation energy for the dissolution reaction is 8.56 kJ/mol.     

A new process of extracting vanadium from stone coal

A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V2O5 in the residue can be between 0.22%-0.25% in the process of ore fine grinding→oxidation roasting→mixing and ripen-ing→aqueous leaching→P2O4 solvent extraction→sulfiuie acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V2O5 produced by this process can meet the requirements of GB3283-87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.     

赤泥中氧化铝和氧化铁的浸出

为回收赤泥中的铝和铁,解决赤泥污染和占地问题,研究了用盐酸溶出废赤泥中的氧化铝和氧化铁的工艺,考察了赤泥的焙烧、盐酸与赤泥的液固比、盐酸的浓度、酸浸时间、酸浸温度及酸浸方式对赤泥中氧化铝、氧化铁浸出率的影响.结果表明：赤泥不需要焙烧,盐酸与赤泥的液固比4∶1,盐酸的浓度为6mol/L,酸浸温度在109℃左右,酸浸时间为60 min,酸浸方式为二次浸出,氧化铝和氧化铁的浸出率分别为89.00%和98.39%.     

活性染料湿摩擦牢度提升剂的性能研究

介绍自制改性水性PU活性染料湿摩擦牢度提升剂的应用及性能。提升剂使用于活性染料染色的纯棉和及其混纺织物,其湿摩擦色牢度提高1级以上,可达到3级以上。分析了影响湿摩擦牢度提升剂WPU效果的各种因素,确定了最佳处理工艺条件,采用浸轧工艺,烘干温度为80℃,焙烘温度为110-120℃,处理液pH值5—6．5。     

Kinetics of nickel leaching from roasting-dissolving residue of spent catalyst with sulfuric acid

Sulfuric acid leaching process was applied to extract nickel from roasting-dissolving residue of a spent catalyst, the effect of different parameters on nickel extraction was investigated by leaching experiments, and the leaching kinetics of nickel was analyzed. The experimental results indicate that the effects of particle size and sulfuric acid concentration on the nickel extraction are remarkable; the effect of reaction temperature is mild; while the effect of stirring speed in the range of 400–1 200 r/min is negligible. Decreasing particle size or increasing sulfuric acid concentration and reaction temperature, the nickel extraction efficiency is improved. 93.5% of nickel in residue is extracted under suitable leaching conditions, including particle size (0.074–0.100) mm, sulfuric acid concentration 30% (mass fraction), temperature 80 °C, reaction time 180 min, mass ratio of liquid to solid 10 and stirring speed 800 r/min. The leaching kinetics analyses shows that the reaction rate of leaching process is controlled by diffusion through the product layer, and the calculated activation energy of 15.8 kJ/mol is characteristic for a diffusion controlled process. Foundation item: Project (50574101) supported by the National Natural Science Foundation of China; Project (2003UDBEA00C020) supported by the Collaborative Project of School and Province of Yunnan Province, China     

高砷铜精矿浸出液制备砷酸铜及热力学研究

高砷铜精矿浸出液中因含砷较高存在砷害问题,砷回收利用具有重要的意义。研究针对某高砷硫化铜精矿除杂后的浸出液,探讨了以砷酸铜形式综合利用砷的热力学及工艺参数。绘制了Cu-As-H2O系电位-pH图,进行了砷酸铜制备工艺过程的热力学分析,对净化后的某高砷硫化铜精矿浸出液,以氨水为中和剂,当pH=5.0~8.0,温度80~90℃时,制得了CuAs2O4、C4H6As6Cu4O16、Cu5As2O10.5H2O、Cu5As4O15.9H2O、Cu2AsO4OH.3H2O及Cu2AsO4OH 6种不同结构的砷酸铜,沉砷后溶液中砷含量为9.11~35.82 mg/L。