电镍钴渣还原溶出钴的试验研究

以电镍钴渣为原料,探讨了影响钴渣还原酸溶过程钴溶出率的因素。试验结果表明,在SO2的量为8 L/h、浸出时间为120 min、浸出温度为85℃及液固比为4∶1的条件下,沉钴渣中钴溶出率可达到96.83%,具有较好的溶出效果。

铅在铂电极上的还原电位溶出分析法

研究了以亚铁氰化钾为还原剂铅在铂电极上的还原电位溶出法；讨论了电极的预处理、阳极富集和随后的还原电位溶出及铅测定的干扰。

Conversion of ferric oxide to magnetite by hydrothermal reduction in Bayer digestion process

Digesting aluminum-bearing minerals and converting ferric oxide to magnetite simultaneously in Bayer digestion process is crucially important to deal with high-iron diasporic bauxite economically for alumina production.The reaction behaviors of hydrothermal reduction of ferric oxide in alkali solution were studied by both thermodynamic calculation and experimental investigation.The thermodynamic calculation indicates that Fe3O4 can be formed by the conversion of Fe2O3 at proper redox potentials in alkaline solution.The experimental results show that the formation ratio of Fe3O4 either through the reaction of Fe and Fe2O3 or through the reaction of Fe and H2O in alkaline aqueous solution increases remarkably with raising the temperature and alkali concentration,suggesting that Fe（OH）3- and Fe（OH）4- form by dissolving Fe and Fe2O3,respectively,in alkaline aqueous solution and further react to form Fe3O4.Moreover,aluminate ions have little influence on the hydrothermal reduction of Fe2O3 in alkaline aqueous solution,and converting iron minerals to magnetite can be realized in the Bayer digestion process of diasporic bauxite.

Transformation of hematite in diasporic bauxite during reductive Bayer digestion and recovery of iron

The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based on the differences of their surface properties.The results show that the differences of surface properties between magnetite and DSP in zeta potential,wettability and solvation trend facilitate magnetite to agglomerate,grow up and thus to dissociate from DSP.The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of98.91%.Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate60%and recovery of about86%through magnetic separation,resulting in reduction of red mud emission higher than70%.The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.

Stepwise dissolution of chalcopyrite bioleaching by thermophile A.manzaensis and mesophile L. ferriphilum

Chalcopyrite dissolution was evaluated by bioleaching and electrochemical experiments with thermophile A. manzaensis（Acidianus manzaensis） and mesophile L. ferriphilum（Leptospirillum ferriphium） cultures at 65 ℃ and 40 ℃, respectively. It was investigated that the bioleaching of chalcopyrite was stepwise. It was reduced to Cu2 S at a lower redox potential locating in the whole bioleaching process by A. manzaensis at high temperature while only at initial days of bioleaching by L. ferriphilum at a relative low temperature. No reduced product was detected when the redox potential was beyond a high level（e.g., 550 m V（vs SCE）） bioleached by L. ferriphilum. Chalcopyrite bioleaching efficiency was substantially improved bioleached by A. manaensis compared to that by L. ferriphilum, which was mainly attributed to the reduction reaction occurring during bioleaching. The reductive intermediate Cu2 S was more amenable to oxidation than chalcopyrite, causing enhanced copper extraction.

碱性过氧化氢预处理条件对木薯渣酶解作用效果的研究

为了探究不同碱性过氧化氢预处理条件对酶解的作用效果,对于不同预处理条件的木薯渣测定了木素去除率并且进行X-射线双晶衍射。采用Design-Expert.V.8.0.6.1分析软件对碱性过氧化氢预处理过程中的反应温度、反应时间、过氧化氢用量3个因素及各自的3个水平,以酶水解液中还原糖提取率为评价指标,进行实验设计及分析。结果表明:最佳预处理条件为:固液比1:20、反应pH 11.5、反应温度42℃、反应时间274 min、过氧化氢用量5.4%。在此条件下预处理的木薯渣进行酶解,酶解条件为:液比1:30,p H 4.5,纤维素酶用量400 U·g^(-1)(对绝干原料),多糖水解酶用量120 FXUs·g^(-1)(对绝干原料),摇床转速150 r·min^(-1),50℃恒温,酶解时间36 h。酶水解液中还原糖的溶出率最高,为85.93%。木薯渣的结晶指数:最佳预处理条件下,降低了46.51%,双酶解后降低了67.87%。