为了优化菱镁矿尾矿酸浸提镁工艺,提高酸浸效率,对某菱镁矿尾矿中的镁进行了酸浸行为研究,考察了不同反应因素对菱镁矿尾矿中镁浸出率的影响,从动力学角度分析了菱镁矿尾矿中镁的浸出行为。研究结果表明:提高菱镁矿尾矿的细度、硫酸的浓度和浸出温度均有利于镁浸出率的提高,液固比变化对镁浸出率的影响不大。当试样的粒度为0.074~0 mm,硫酸的浓度为1.5 mol/L,浸出液固比为3 m L/g,浸出温度为80℃,浸出时间为2 h时,镁浸出率可达84%。镁的硫酸浸出过程符合液-固相非催化反应的缩芯模型,浸出过程受扩散和化学反应共同控制,浸出反应的表观活化能为21.02 k J/mol。
To investigate the effect of nitrogen on the photoluminescence properties of carbon quantum dots (CO Ds), N-doped carbon quantum dots (N-CQDs)were synthesized by one-step hydrothermal treatment using biomass tar as the carbon precursor.As an inevitable organic pollutant,the unsaturated bonds in biomass tar,such as carboxylic acids,aldehydes,and aromatics,are favorable for formation of the graphitic carbon lattice.The obtained N-CQDs are spherical with an average particle size of 2.64nm and the crystal lattice spacing is 0.25nm,corresponding to the (100)facet of graphitic carbon.The N-CQDs emit bright blue photoluminescence under 365nm ultraviolet light,and they have excellent water solubility and stability with a high quantum yield of 26.1%.Coordination between the functional groups on the N-CQD surface and Fe^3+ ions is promoted because of the improved electronic properties and surface chemical reactivity caused by N atoms,leading to a significant fluorescence quenching effect of the N-CQDs in the presence of Fe^3+ions with high selectivity and sensitivity.There is a linear relationship between In (Fo/F)and the Fe^3+ concentration in the N-CQD concentration range 0.06-1400μmol/L with a detection limit of 60nmol/L, showing that the N-CQ.Ds have great potential as a fluorescent probe for Fe^3+detection.
Xiangyi DengYali FengHaoran LiZhuwei DuQing TengHongjun Wang
Cornstalk is usually directly used as a reductant in reduetive leaching manganese. However, low utilization of cornstalk makes low manganese dissolution ratio, In the research, pretreatment for cornstalk was proposed to improve manganese dissolution ratio. Cornstalk was preprocessed by a heated sulfuric acid solution （1.2 M of sulfuric acid concentration） for 10 min at 80℃. Thereafter, both the pretreated solution and the residue were used as a reductant for manganese leaching. This method not only exhibited superior activity for hydrolyzing cornstalk but also enhanced manganese dissolution. These effects were attributed to an increase in the amount of reductive sugars resulting from lignin hydrolysis. Through acid pretreatment for cornstalk, the manganese dissolution ratio was improved from 50.14% to 83.46%. The present work demonstrates for the first time the effective acid pretreatment of cornstalk to provide a cost-effective reductant for manganese leaching.
Ai-fei YiMeng-ni WuPeng-wei LiuYa-li FengHao-ran Li
The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe^3+/Fe^2+couple and material exchange.The passivation of iron settling correlates with ferrous ion content in bio-leaching solution.In medium containing A.ferrooxidans and Fe(Ⅲ),the increment in Fe(Ⅱ)concentration leads to the formation of jarosite,generating a decline in vanadium extraction efficiency.Analysis of cyclic voltammetry shows that Fe(Ⅱ)ion is apt to be oxidized and translated into precipitate by A.ferrooxidans,which strongly adsorbed to the surface of the residue.Fe(Ⅲ)ion promotes the vanadium extraction due to its oxidizing activity.Admixing A.ferrooxidans to Fe(Ⅲ)medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution.This motivates 3.8%and 21.8%increments in recovery ratio and leaching rate of vanadium compared to the Fe(Ⅲ)exclusive use,respectively.Moreover,Fe(Ⅱ)ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.
Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with water. During the process the effects of the amotmt of ammonium sulfate, roasting temperature, and roasting time on the leaching recovery of metal elements were analyzed. The optimum technological parameters were determined as follows： ammonium sulfate/ore ratio, 0.8 g/g; roasting temperature, 400℃; and roasting time, 2 h. Under the optimum condition the leaching recoveries ofNi, Cu, Fe, and Mg were 83.48%, 76.24%, 56.43%, and 62.15%, respectively. Furthermore, the dissolution kinetics of Ni and Mg from the nickel ore was studied. The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ.mo1-1, which were consistent with the values of diffusion control reactions. Therefore, the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.
Xin-wei L iuYa-li FengHao-ran L iZhi-chao YangZhen-lei Cai
Bacillus mucilaginosus was used in pretreatment ofpyrolusite to facilitate the flotation removal of quartz from pyrolusite minerals. Quartz was activated by B. mucilaginosus, whereas pyrolusite was unaffected at pH 7 with laurylamine as collector. Flotation recovery of pyrolusite with B. mucilaginosus pretreatment is 73.62%, slightly lower than that of the process without biopretreament, namely 74.70%. The grade of concentrate of recovered pyrolusite is 19.44%, 2.18% higher than that of the recovered pyrolusite without B. mucilaginosus pretreatment （17.26%）. The results of FTIR and SEM showed that no bacteria were adsorbed on the surface of quartz or pyrolusite, indicating that the better selectivity and collectability of flotation resulted from bacterial byproducts. And interaction of bacterial byproducts such as extracellular bacterial polysaccharide, extracellular bacterial protein and acetic acid, on minerals were studied by FTIR and adsorption.
