溶液电位及堆结构影响次生硫化铜矿生物堆浸的动力学

基于堆中溶液Fe3+与Fe2+的浓度比、颗粒空隙度、颗粒半径与各化学反应组分对次生硫化铜矿生物堆浸的影响,建立堆浸过程硫化矿细菌氧化反应速率动力学模型。计算与实验结果表明:模型仿真结果与实际结果较符合;堆浸过程次生硫化铜矿(辉铜矿)的氧化分为2个阶段,其中,辉铜矿反应步骤Ⅰ受溶液Fe3+浓度控制,随着Fe3+浓度增加,反应速率加快;反应步骤Ⅱ较反应步骤Ⅰ慢,为浸出反应的限制性步骤,Fe3+与Fe2+的浓度比是影响该反应步骤的关键因素。由于受扩散的限制,反应物颗粒粒径的增大导致浸出速率下降,但粒径过小时浸出率提高不明显。当喷淋强度由3.47/(m2.h)增加到69.00/(m2.h)时,浸出率逐渐下降,说明喷淋强度过大时,造成空隙间流体与颗粒孔道流体间界面剪切力过大,不利于物质传输与交换;当堆过高时,堆中离子的传输受阻,不利于次生硫化铜矿的浸出。

氧化还原电位标准溶液电位值不确定度的评定

对硫酸亚铁铵-硫酸高铁铵溶液和氢醌溶液分别进行了从溶液配制、仪器测量和结果重复性3方面不确定度来源分析,确立了数学模型,综合评定了2者的合成标准不确定度和扩展不确定度.结果表明,氢醌溶液中,邻苯二甲酸氢钾缓冲溶液和磷酸盐缓冲溶液的合成标准不确定度分别为4.20mV和2.76mV,扩展不确定度分别为8.40mV和5.52mV(近似95%置信概率),都小于硫酸亚铁铵-硫酸高铁铵溶液的合成标准不确定度6.49mV和扩展不确定度12.98mV(近似95%置信概率).说明氢醌溶液电位值的测量结果更可信,精确度更高,应广泛作为测定氧化还原电位仪器的标准溶液来使用.

分步加药调控溶液氧化还原电位强化硫代硫酸盐浸金

绿色环保型硫代硫酸盐提金技术因浸出过程药剂消耗量过大,导致其无法大规模工业应用,而硫代硫酸盐在浸金过程中的消耗与溶液氧化还原电位密切相关。因此,开展硫代硫酸盐浸金过程的溶液氧化还原电位基础研究,对提高硫代硫酸盐稳定性,强化硫代硫酸盐浸金行为,推动硫代硫酸盐提金产业化具有重要意义。通过浸出试验,详细探究了在铜-乙二胺-硫代硫酸盐体系中金浸出行为与溶液氧化还原电位之间的关系,试验结果表明,当溶液氧化还原电位在187 mV左右时,硫代硫酸盐相对稳定,且此条件下的浸金速率也相对较快。基于这一发现,提出了通过分步加药和引入铁离子来调控溶液氧化还原电位的方法,以达到降低硫代硫酸盐消耗量和提高金溶解量的双重效果。经过试验发现,分步加药可以有效地提高溶液氧化还原电位,金的溶解速率提高了3.2倍,硫代硫酸盐消耗速度降低了56.71%。铁离子的引入可提高初始时的溶液氧化还原电位,使其较快地稳定在187 mV附近,从而使硫代硫酸盐消耗量降低了54.87%,金溶解量提高了1.25%。相关研究结果将促进环保型硫代硫酸盐提金技术的进一步发展,同时也为黄金行业绿色可持续发展提供了有力支持。

氧化还原电位标准溶液均匀性和稳定性检验

按照《中华人民共和国行业标准—氧化还原电位的测定(电位测定法)》,制备了分别以蒸馏水和实际海水作为溶剂的氧化还原电位标准溶液.采用电位测定法测量了标准溶液的氧化还原电位值,对制备的标准溶液采用F检验法和t检验法分别进行了均匀性和稳定性的评价.实验结果表明,标准溶液的均匀性良好,并且以海水为溶剂的标准溶液均匀性更好;标准溶液在低温和常温保存条件下稳定性较好,并且硫酸亚铁铵-硫酸高铁铵溶液的稳定性要强于氢醌溶液,低温保存的标准溶液稳定性要好于常温保存条件的.

电位滴定-水溶液银量法测定盐酸林可霉素注射液中氯化钠的含量

目的 建立测定盐酸林可霉素注射液中氯化钠含量的方法。方法 电位滴定 -水溶液银量法结合HPLC外标法。在水溶液中 ,以Mettler复合银电极指示 ,用 0 .1mol·L- 1 硝酸银液滴定至电位发生突跃 ;测得结果扣除注射液中林可霉素盐酸盐对硝酸银滴定液的本底消耗 ,即得注射液中氯化钠的纯含量。结果 林可霉素A、B组分总含量在 6 .0～ 1 2 0 .2mg·ml- 1 范围内 ,溶液中林可霉素总浓度与硝酸银滴定液的消耗体积有良好的线性关系 ,r=0 .9999;方法重复性好 (RSD =0 .1 % ,n =5) ;准确度高 ,回收率为 99.2 % (RSD =0 .5 % ,n =6) ,加样回收率为1 0 0 .2 % (RSD =0 .4 % ,n =6)。结论 方法准确、便捷、适用 。

关于电位缓冲溶液的理论初探

首次讨论了“电位缓冲溶液”的问题,并推导了Pe,Pe^0与E,E^0和C_(ox)/C_(Red)间的关系,给出了缓冲指数β及定义式:,求得,验证了当α_(ox):α_(Red)(C_(ox):C_(Red)=1:1时,β有极大值,由此得电位缓冲溶液最佳缓冲范围为。

浓硫酸中羟基乙酸的游离态含量及其总含量的测定

针对水溶液电位滴定法无法将硫酸与羟基乙酸的滴定曲线突跃点分开,无法测定浓硫酸中羟基乙酸的问题,采用非水溶液电位滴定法,使用丙酮作为溶剂,对含有浓硫酸的羟基乙酸样品中的游离态羟基乙酸及其总含量进行了测定。以丙酮为溶剂,可以很好地将2种酸的滴定曲线突跃点区分开来,并能对游离的羟基乙酸做定量分析。此外,羟基乙酸自身容易失水生成二乙交酯和多交酯,通过碱水解,再采用上述方法,可以测定出羟基乙酸盐的含量,即得到羟基乙酸的总含量。试验表明:该方法准确性高、重现性较好、操作简便;但无法有效区分羟基乙酸和其他有机强酸。

Mechanism of different particle sizes of quartz activated by metallic ion in butyl xanthate solution

To investigate effect of metallic ion activation on different particle sizes of quartz in butyl xanthate solution,six common ions(Pb^(2+),Cu^(2+),Fe^(3+),Fe^(2+),Mg^(2+) and Ca^(2+)) were introduced as activators.The approaches of micro-flotation,adsorption test and zeta potential measurement were adopted to reveal the mechanism of ion activation.The results show that Pb^(2+),Cu^(2+) and Fe^(3+) are effective activators for the flotation of quartz in butyl xanthate solution because of their absorption on activated quartz surface.Average recoveries of fine particles(<37 μm) are greater than those of coarser particles(37-74 μm),suggesting that the former is easier to be activated and more likely to be floated and thus entrained in sulphide concentrate.From another perspective,addition of metallic ions(Pb^(2+),Cu^(2+) and Fe^(3+)) renders zeta potentials move positively,and addition of the same metallic ions and butyl xanthate makes zeta potential drop apparently,which support a mechanism where they adsorb onto quartz surface,resulting in an expected increase in butyl xanthate collector adsorption with a concomitant increase in the flotation recoveries.

Thermodynamic analysis of Li-Ni-Co-Mn-H2O system and synthesis of LiNi0.5Co0.2Mn0.3O2 composite oxide via aqueous process

The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activity range of 0.01-1.00.A predominant co-region of LiNiO2,LiCoO2 and LiMnO2 oxides(Li-Ni-Co-Mncomposite oxide)is found in the Li-Ni-Co-Mn-H2O potential-pH diagrams,in which the co-precipitation region expands towards lower pH with rising temperature,indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution.The experimental results prove that it is feasible to prepare the LiNi0.5Co0.2Mn0.3O2 cathode materials(NCM523)by an aqueous routine.The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonalα-NaFeO2 structure with good crystallinity.It is reasonable to conclude that the aqueous routine for preparing NCM cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.

Role and maintenance of redox potential on chalcopyrite biohydrometallurgy:An overview

Chalcopyrite is one of the most important copper minerals;however,the extracted efficiency of chalcopyrite is still not satisfactory in hydrometallurgy owing to its high lattice energy which leads to its low dissolution kinetics.To overcome the difficulties,many advanced technologies have been developed,including the selection of high effectively bacteria,the inhibition of the passivation film adhered onto the minerals surface,and the maintenance of solution redox potential under an optimum range.Up to date,considerable researches on the first two terms have been summarized,while the overview of the last term has been rarely reported.Based on corresponding works in recent years,key trends and roles of solution redox potential in copper hydrometallurgy,including its definition,effect and maintenance,have been introduced in this review.

Characterization of polysulfone hollow-fiber ultrafiltration membrane and its cleaning efficiency by streaming potential and flux method

Polysulfone(PS)hollow-fiber ultrafiltration membrane was characterized combined with flux and streaming potential in single electrolyte solutions.The effects of trans-membrane pressure,electrolyte concentration,ion valence and pH value of electrolyte solution on the streaming potential(SP)of the membrane were investigated.The zeta potential and surface charge density of the membrane were calculated on the basis of Helmholtz-Smoluchowski equation and Gouy-Chapmann theory.The results indicate that the valence and concentration of cation have a greater influence on the SP and surface charge density of PS membrane than those of anion,and the pH value of electrolyte solution has great effects on the SP and zeta potential of the membrane surface. Both the absolute value of the streaming potential and water flux of the adsorbed membrane decrease,compared with those of the clean membrane.The streaming potential and flux of the cleaned membrane can be completely recovered by cleaning with the mass fraction of 0.8%EDTA at pH=10.

Membrane Potentials Across Hybrid Charged Mosaic Membrane in Organic Solutions

Membrane potentials across hybrid charged mosaic membrane in organic solutions were measured. Equilibrium swelling degree （SD） and fixed charge density in both organic solutions and water were also determined. Ethylene glycol, ethanol, n-propanol and glycerol were used as organic solutes; meanwhile 0.001mol-dm^-3 aqueous KCl solution was utilized as a strong electrolyte to measure the electrical difference. Equilibrium swelling degree indicated that it could be affected by the density of organic solutes; while it enhanced with the increasing density of these solutes. The measurement of fixed charge density showed that the membrane had the maximal absolute value in water among these solvents whether for cationic or anionic groups; the difference of dielectric constant between the water and the organic solutes might be responsible for these change trends. It was confirmed that membrane potentials increased with both the increasing concentration of the organic solutions and the elevated pH values. These results demonstrated that the characteristics of the hybrid charged mosaic membrane could be highly impacted by the properties of the organic solutes. A theoretical modal for charged membranes in ternary ion systems of weak electrolyte can be used to explain the above-mentioned phenomena.

Calculating models of mass action concentrations for structural units or ion couples in RbCl-H_2O binary system and RbCl-RbNO_3-H_2O ternary system

Thermodynamic models of calculating mass action concentrations for structural units or ion couples in RbCl-H2O binary and RbCl-RbNO3-H2O ternary strong electrolyte aqueous solutions were developed based on the ion and molecule coexistence theory at 298.15 K.A transformation coefficient is needed to compare the calculated mass action concentration and the reported activity because they are obtained at different standard states and concentration units.The results show that the transformation coefficients between the calculated mass action concentrations and the reported activities of the same structural units or ion couples in RbCl-H2O binary and RbCl-RbNO3-H2O ternary strong electrolyte aqueous solutions change in a very narrow range.The transformed mass action concentrations of structural units or ion couples in RbCl-H2O binary system are in good agreement with the reported activities. The transformed mass action concentrations of RbCl and RbNO3 in RbCl-RbNO3-H2O ternary solution are also in good agreement with the reported activities,aRbCl and 3RbNOa,with different total ionic strengths as 0.01,0.05,0.1,0.5,1.0,1.5,2.0,3.0 and 3.5 mol/kg,respectively.All those results mean the developed thermodynamic model of strong electrolyte aqueous solutions can reflect structural characteristics of RbCl-H2O binary and RbCl-RbNO3-H2O ternary strong electrolyte aqueous solutions and the mass action concentration also strictly follows the mass action law.

两种方法测定比沙可啶纯度及不确定度评定

目的:采用两种不同原理的测定方法对比沙可啶纯度进行联合定值,并建立其不确定度评定方法。方法:采用高效液相色谱法(HPLC)与非水溶液电位滴定法测定比沙可啶纯度,并依据相关规范要求,对两种方法测定过程的不确定度进行了系统分析。结果:比沙可啶HPLC法、非水溶液电位滴定法纯度测定值分别为(99.81±0.29)%、(99.82±0.51)%,两种方法联合测定比沙可啶纯度的标准值及其不确定度分别为99.82%、(±)0.59%(k=2,P=0.95)。结论:采用HPLC与非水溶液电位滴定法联合测定比沙可啶纯度及不确定度评定结果准确可靠,避免了采用一种技术带来的分析方法缺陷,有利于提高比沙可啶的质量评价与控制水平,同时为比沙可啶纯度标准物质的研制提供了科学依据。

Synthesis of ultrathin Co2AlO4 nanosheets with oxygen vacancies for enhanced electrocatalytic oxygen evolution

In this work, we reported the synthesis of twodimensional spinel structure of ultrathin Co2AlO4 nanosheets via dealloying and subsequent annealing processes. Oxygen vacancy defects were further introduced into Co2AlO4 nanosheets by a mild solvothermal reduction method, resulting in large electrochemical surface area and high active site densities, making the related Co atoms get electrons, and producing more empty orbitals. The positive charge of Co and Al atoms adjacent to the O vacancies in VO-rich Co2AlO4 reduced significantly, that is, more electrons are concentrated on the Co and Al atoms. Those electrons closed to the Fermi level have a promoting effect during the H2O activation. As a result, the obtained ultrathin Co2AlO4 nanosheets with oxygen vacancies show a low overpotential of 280 m V at the current density of 10 mA cm^-2 and a small Tafel slope of70.98 m V dec^-1. Moreover, it also displays a remarkable stability in alkaline solution, which is superior to most of the reported Co3O4 electrocatalysts. The present work paves a new way to achieve efficient new energetic materials for sustainable community.

A Finite Genus Solution of the Veselov's Discrete Neumann System

The Veselov's discrete Neumann system is derived through nonlinearization of a discrete spectral problem.Based on the commutative relation between the Lax matrix and the Darboux matrix with finite genus potentials,a special solution is calculated with the help of the Baker-Akhiezer-Kriechever function.

A new strategy to improve the sensitivity and selectivity of dopamine detection

We applied the combination of in situ electrochemical liquid-phase microextraction and square-wave voltammetric stripping analysis for the first time as a highly sensitive and selective approach for the detection of dopamine. A mixed gel of graphene sheets and an ionic liquid of 1-octyl-3-methylimidazolium hexaflurophosphate(OMim PF6) was used as a micro liquid-phase to pre-concentrate dopamine by controlled potential electrolysis from an aqueous solution(as a donor phase), followed by square-wave voltammetric stripping detection. Under optimized conditions, a linear calibration curve was obtained in the range of 0.05 to 1.0 ?mol/L in the presence of excess ascorbic acid and uric acid. The detection limit has been found to be 8.0 nmol/L(S/N=3).