Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaC12 aqueous solution, liquid-to-solid （L/S） ratio, leaching temperature, and leaching time, were inves- tigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaC12 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7：1, a leaching tempera- ture of 80℃, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

Effect of Different Kinds of Zinc (Ⅱ) on Early Hydration of Calcium Aluminate Cement

The early hydration of calcium aluminate cement (CAC) with different kinds of zinc (II),such as ZnSO4g7H2O,ZnO,Zn(NO3)2·6H2O and ZnCl2,was analyzed.Changes in consistency,setting time,hydration heat flow,hydration heat amount,ion concentration in solution,and hydration products were found upon the addition of different Zn^2+.The water consumption of standard consistency of CAC is decreased with different Zn^2+.Zn^2+ can delay the initial hydration of CAC.The induction period of cement with Zn^2+ is longer than that of CAC,especially the reaction time of the acceleration period is extended.Zn^2+ can promote hydration hydrate of CAC at 24 h.The characteristic diffraction peaks of CA and CA2 in CAC with different Zn^2+ are significantly reduced.It can inhibit the formation of CAH10 and promote the formation C3AH6 and AH3 in hydration products at 24 h.

Effect of dephytinization on bioavailability of iron,calcium and zinc from infant cereals assessed in the Caco-2 cell model

AIM:To test the effect of the dephytinization of three different commercial infant cereals on iron, calcium, and zinc bioavailability by estimating the uptake, retention, and transport by Caco-2 cells.METHODS:Both dephytinized (by adding an exogenous phytase) and non-dephytinized infant cereals were digested using an in vitro digestion protocol adapted to the gastrointestinal conditions of infants younger than 6 mo. Mineral cell retention, transport, and uptake from infant cereals were measured using the soluble fraction of the simulated digestion and the Caco-2 cells. RESULTS: Dephytinization of infant cereals significantly increased (P<0.05) the cell uptake efficiency (from 0.66%-6.05% to 3.93%-13%), retention (from 6.04%-16.68% to 14.75%-20.14%) and transport efficiency (from 0.14%-2.21% to 1.47%-6.02%), of iron, and the uptake efficiency (from 5.0%-35.4% to 7.3%-41.6%) and retention (from 4.05%-20.53% to 14.45%-61.3%) of zinc, whereas calcium only cell uptake showed a significant increase (P<0.05) after removing phytate from most of the samples analyzed. A positive relationship (P<0.05) between mineral solubility and the cell uptake and transport efficiencies was observed.CONCLUSION: Removing phytate from infant cereals had a beneficial effect on iron and zinc bioavailability when infant cereals were reconstituted with water. Since in developing countries cereal-based complementary foods for infants are usually consumed mixed with water, exogenous phytase additions could improve the nutritional value of this weaning food.

THE STUDY ON THE CHANGES OF ZINC, COPPER, CALCIUM AND MAGNESIUM IN PLASMA AND ERYTHROCYTES DURING CARDIOPULMONARY BYPASS

Objective To study the changes and their influence factors involved of zinc, copper, calcium and magnesium in plasma and erythrocytes during cardiopulmonary bypass(CPB). Methods Zinc, copper, calcium and magnesium values in plasma and erythrocytes were measured by atomic absorption spectrophotometer during CPB. Results Zinc and copper levels in plasma were significantly elevated above preinduction level before perfusion, but calcium and magnesium levels did not change significantly; zinc, copper and calcium levels in plasma were significantly below preoperation level during CPB, but magnesium level in plasma was significantly increased above preoperation; zinc level in plasma was increased to preoperation level after CPB and began to decrease again at 8 hours after CPB, copper level in plasma was increased to preoperation level at 20 hours after CPB, calcium in plasma was increased significantly from beginning to 8 hours after CPB, magnesium level in plasma was decreased to preoperation level at 8 hours afterCPB. Concentration of zinc , copper, calcium and magnesium in erythrocytes did not change significantly. Conclusion During CPB, the changes of zinc, copper, calcium and magnesium had relation to hemodilution, operative wound, carrier protein, stress and component of priming solution and cardioplegic solution, but no relation to transfer from plasma erythrocytes. The results indicate that it is beneficial to patient's recovery to supplement zinc, copper, calcium and magnesium properly by different ways during cardiac perioperation.

Effects of Copper-Zinc Alloy Doped with Rare Earth Elements on Crystal of Calcium Carbonate

A copper-zinc alloy doped with rare earth elements was prepared and the mechanism was demonstrated in a simulating boiler and circulating cooling water with rigidity 1 mmol·L-1. The polar curve and scale inhibiting ability of the alloy was tested by a corrosion measurement system and a scale inhibition evaluation system, respectively. Scale samples were characterized with SEM and XRD. It is found that the transfer of cations could be promoted by doping with proper rare earth elements, and the corrosion potentials descend by 25～126 mV. The results indicated that the copper-zinc alloy doped with rare earth elements has higher scale inhibiting ability of CaCO3. The growth of calcite was affected by zinc ions dissolved because of primary battery reaction, and the transition of calcium carbonate from aragonite to calcite was hampered resulting in the proportion of aragonite to calcite is changed from 1.7∶1 to 2.7∶1.

Effect of "Jia Wei Fo Shou San" on Erythrocyte Membrane Calcium,Zinc Concentration in Pregnant Rats with Asymmetrical Intrauterine Growth Retardation Induced by Passive Smoking

Using experimental model of pregnant rats with asymmetrical intrauterine fetal growth retardation induced by passive smoking, the effects of natural herb 'Jia Wei Fo Shou San' on erythrocyte membrane calcium, zinc concentration were observed by atomic absorption spectrophotometry. The results showed that the mean fetal birth weight, zinc concentration of erythrocyte membrane were found to be decreased in the model group as compared with the control group (P＜0. 01, P＜0. 01). On the other hand, the element of calcium onto erythrocyte membrane were higher in model group than that in control group(P＜0. 05). These changes were significantly mild in the treated group and were similar to those of the control group (P＜0.05). Furthermore,our findings indicated that the zinc concentration of erythrocyte membrane seems to be positively correlated with the birth weight(P＜0. 01). Calcium composition of red cell membrane showed a significant negative relation to the birth weight (P＜0.05). Our results provided an experimental evidence that normal concentrations of calcium and zinc onto erythrocyte play an important part in fetal growth. One of the mechanisms of 'Jia Wei Fo Shou San' in improving fetal growth may have something to do with modulation of erythrocyte calcium,zinc element,thereby protecting bio-functions of erythrocyte and promoting blood circulation.

Phase Transformation of Amorphous Calcium Carbonate to Single-Crystalline Aragonite with Macroscopic Layered Structure in the Presence of Egg White Protein and Zinc Ion

Highly oriented calcium carbonate lamellas are exquisite structure produced by biomineralization. Strategies mimicking nature have been developed to synthesize inorganic materials with excellent structures and optimal properties. In our strategy, egg white protein and zinc ion were employed in the solution to induce the crystallization of calcium carbonate, resulting in the macroscopic aragonite laminate with an average length of 1.5 mm, which was comprised of single-crystalline tablets. During the crystallization at initial stage, it was found that the particles displayed the characteristics of amorphous calcium carbonate, which was then transformed into the sophisticated structured aragonite through a multistage assembly process. The rebuilt nacre structure in vitro was achieved owing to the synergistic effects of egg white protein and zinc ion.

THE EFFECT OF STATUS OF ZINC, CALCIUM ON GROWTH OF CHILDREN AGED 3～6 YEARS IN XI'AN AND ANALYSIS OF EFFECTIVENESS OF ZINC SUPPLEMEINT

In this study the correlation of heights and weights of 456 healthy children in xi'an aged 3 to 6 years with concentrations of serum zinc, calcium was investigated. The results showed that the concentrations of serum zinc and calcium in the three groups with heights (weights) <x, <x - sand < x - 2s were significantly lower than those in the group with heights (weights) ≥x (P <0. 01). Heights- weights and level of serum calcium of 156 zinc deficient children were lower than those of the children with normal zinc. After zinc supplement, heights and weights of children rapidly increased (P < 0. 01) and calcium level significantly rose (P < 0. 01), with the increase in serum zinc- It is suggested that the deficiency of Zn in children in Xi'an is considerably common and the preschool children with poor growth should be supplemented by zinc

Spectral Properties and Sensitization of Ce^(3+) and Eu^(2+) Codoped Calcium Zinc Chlorosilicate

The Ce^3+ and Eu^2+ ions codoped calcium zinc chlorosilicate Ca_8Zn(SiO_4)_4Cl_2 phosphors have been synthesized for the first time. The diffuse reflection, excitation and emission spectra of Ca_8Zn(SiO_4)_4Cl_2∶Ce^3+, Eu^2+ have been measured at room temperature. The luminescence sensitizaiton of Eu^2+ by Ce^3+ inCa_8Zn(SiO_4)_4Cl_2∶Ce^3+, Eu^2+ has been expounded under the excitation of ultraviolet light and the efficient nonradiative energy transfer from Ce^3+ to Eu^2+ in this system is confirmed.

Structural characterization of calcium glycinate,magnesium glycinate and zinc glycinate

Metal glycinate chelates are formed by glycine and metal compounds through chemical reactions.Calcium glycinate,magnesium glycinate and zinc glycinate are kinds of new-type and ideal nutrient supplements,which have satisfactory physico-chemical properties and bioactivities.They are important for prophylaxis and treat metal deficiency.The structural characterization shows that the metal ion is bonded to the amino and carboxyl group to form two five-membered rings.This paper mainly studies the structure characterization of the metal chelated glycinates by their solubility,infrared spectrum,thermal analysis,mass spectrometry,polycrystal difrac-tion,the metal contents and glycine contents of calcium glycinate,magnesium glycinate and zinc glycinate.

Effects of pH value of reaction solution on structure and electrochemical performance of calcium-containing active material of secondary zinc electrodes

The calcium-containing active material of secondary alkaline zinc electrodes was prepared by a chemical coprecipitation method and characterized by scanning electron microscopy(SEM) and X-ray diffractometry(XRD). Their electrochemical performance was tested by the Galvanstatic charge-discharge method. The experimental results show that the sample synthesized at pH=11.15 has a typical calcium zincate crystal. The zinc electrode using this sample as active material shows higher discharge capacity, more negative discharge plateau potential and longer cycle lifetime.

薏米多肽-钙、锌螯合物制备及结构表征

目的:制备1种薏米多肽-钙、锌螯合物并研究其结构。方法:利用枯草芽孢杆菌和嗜热链球菌混合发酵薏米,采用葡聚糖凝胶Sephadex G-15、反相高效液相色谱(RP-HPLC)分离纯化薏米发酵液得到薏米多肽(CSP),Tricine-十二烷基硫酸钠-聚丙烯酰胺凝胶(Tricine-SDS-PAGE)电泳检测其分子质量。以锌螯合率和钙螯合率为指标,在单因素实验的基础上,采用响应面试验优化薏米多肽-钙、锌螯合物(CSP-Ca-Zn)的制备工艺,采用紫外光谱、红外光谱和荧光光谱表征其结构。结果:薏米发酵液经Sephadex G-15分离得到4个峰,其中A3的钙、锌螯合率最高。RP-HPLC分离A3得到的CSP纯度达93.91%,其分子质量约7.8 ku。CSP与Ca-Zn螯合的最佳制备工艺为:CSP与钙、锌质量比4.4∶1,钙、锌质量比1∶1,pH 3.7,在此条件下,锌螯合率、钙螯合率分别达到52.63%和63.79%。CSP与钙、锌螯合的主要位点是氨基氮、羧酸基,其空间结构也发生改变。结论:所确定的螯合工艺条件使CSP同时螯合钙、锌两种金属,为薏米多肽新产品的开发提供了技术参考,为制作食源性有机钙、锌补充剂提供了新思路。

白云石可控碳化联产氢氧化镁和碳酸钙及其改性

综合利用白云石开发出高端产品及其技术成为当前研究者关注的焦点。本文通过可控碳化法进行白云石联产制备了高附加值的氢氧化镁和碳酸钙并对其进行改性研究。分别考察了碳化终点pH、温度、二氧化碳流速对产物晶型、粒径、形貌的影响以及硬脂酸锌的添加量、搅拌转速、改性时间、改性温度对产物改性效果的影响。结果表明,当碳化反应终点pH控制为10.5时,生成产物为碳酸钙和氢氧化镁混合物,且得率最高;最优的碳化反应条件为温度20℃、二氧化碳流速1L/min,生成的氢氧化镁和碳酸钙平均粒径为190.4nm;得到的产物氢氧化镁和碳酸钙最优的改性条件为硬脂酸锌添加量1.0%、搅拌转速600r/min、改性时间60min、改性温度50℃,得到改性的氢氧化镁及碳酸钙的活化度为95.8%,吸油值为41.2g/100g。

乙酰丙酮锌催化扩链增容PBAT类玻璃体

与传统塑料相比,现有的聚对苯二甲酸-己二酸丁二酯(PBAT)仍存在力学性能低、热稳定性和耐久性差的缺点。因此,为了增强PBAT的综合性能,利用乙酰丙酮锌催化环氧扩链剂ADR扩链增容PBAT类玻璃体,研究了催化剂含量对PBAT类玻璃体化学结构、分子量、热性能、力学性能和水解降解性能的影响。结果表明,PBAT的端羧基和端羟基与ADR的环氧基之间存在相互作用。乙酰丙酮锌的催化介入可以有效促进ADR上的环氧基团开环,导致生成大量交联支链结构和大量β-羟基,与PBAT上丰富的酯基之间发生酯交换反应,从而形成了更致密的交联网络结构。乙酰丙酮锌可在一定程度上提高PBAT类玻璃体的分子量,但降低了PBAT类玻璃体结晶温度和熔点。适量乙酰丙酮锌的加入可明显提升PBAT类玻璃体的力学性能,当乙酰丙酮锌质量分数为0.1%时,PBAT类玻璃体拥有最好的耐久性和水解降解性,在4次拉伸循环后仍能保持较高的断裂伸长率(684%)和拉伸强度(18.94 MPa)。

利用含锌工业固废制备高纯氧化锌的工艺研究

针对氧化锌尾矿和废弃水渣等工业固废中有价锌难以回收的问题,以当地工业含锌固废为原料,利用碳热还原氧化法,制备了高纯氧化锌微粉。通过HSC Chemistry进行热力学计算和试验研究结合的方式,分析了含锌废渣中硅酸锌与碳还原反应的热力学过程。讨论了配碳量、焙烧温度、焙烧时间以及CaF_(2)对硅酸锌还原过程锌产率的影响。结果表明,在以CaF_(2)为催化剂时,1000~1100℃催化效果最显著。得出最佳工艺条件:在温度为1100℃、保温时间40 min、碳含量20 wt%、CaF_(2)添加5 wt%的条件下锌产率(氧化锌回收率)为97.44%。对挥发产物进行结构和成分分析,其物相为六方纤锌矿结构的氧化锌晶体,粒度大小2~4μm,纯度达到了99.47%。

血清25-羟基维生素D、钙、锌水平与儿童生长发育的关系

目的观察儿童血清25-羟基维生素D钙、锌水平,并探析3项指标与儿童生长发育的关系。方法将2021年1月至2022年12月于自贡市妇幼保健院接受治疗的98例生长发育迟缓患儿纳入生长发育迟缓组,另取同期于该院体检的80例生长发育正常的儿童为生长发育正常组,对比2组血清25-羟基维生素D钙、锌水平及其他临床资料,分析血清25-羟基维生素D钙、锌水平与生长发育的关系。结果生长发育迟缓组身长/身高、体重、钙、锌、25-羟基维生素D水平低于生长发育正常组(P<0.05);经点二列相关性分析结果显示,钙、锌、25-羟基维生素D水平与儿童生长发育迟缓呈负相关(r<0,P<0.05);建立Logistic回归模型,结果显示,身长/身高(95%CI:0.673~0.824)、体重(95%CI:0.477~0.717)、钙(95%CI:0.127~0.467)、锌(95%CI:0.140~0.571)、25-羟基维生素D(95%CI:0.130~0.461)水平是儿童生长发育的保护因素(OR<1,P<0.05);绘制ROC曲线,结果显示,钙、锌、25-羟基维生素D水平对儿童生长发育具有一定预测价值(AUC=0.601、0.627、0.667),3项指标并联预测价值更高(AUC=0.808)。结论儿童生长发育状况与血清25-羟基维生素D钙、锌水平密切相关,临床应动态监测血清25-羟基维生素D钙、锌水平变化,有助于早期预测儿童生长发育状况。

环保钙/锌PVC热稳定剂的发展现状及应用

热稳定剂是聚氯乙烯(PVC)加工过程中重要的塑料助剂,可以抑制聚氯乙烯在高温下发生热降解,改善PVC热稳定性能。PVC是全球五大通用塑料之一,国内外对PVC的需求量逐渐增大,热稳定剂的消耗量随之增长,因此,低毒、无污染且高效环保的钙/锌热稳定剂成为研究热点。介绍了近年来国内外聚氯乙烯热稳定剂的发展现状,由于铅、镉盐类热稳定剂有毒,已被欧盟禁用,有机锡类热稳定剂价格昂贵,而环保钙/锌热稳定剂市场需求急剧增加。综述了钙/锌热稳定剂的研究现状,分析了环保热稳定剂对PVC的作用机理,提出了钙/锌热稳定剂市场应用前景和未来的发展重点及方向。

湿法炼锌污酸处理中石膏渣减量化工艺探索

针对目前湿法炼锌中采用石灰中和法处理污酸产生的石膏渣量较大的问题,本文提出采用锌焙砂-碳酸钙两段中和法处理硫化后液的工艺并进行试验。该工艺通过锌焙砂中和部分酸,再采用碳酸钙进行中和,将氟除去的同时减少污酸石膏渣产量。实验结果表明,采用锌焙砂中和时,控制pH值为2.0~2.5,在温度35℃条件下中和1 h,沉降过滤后采用碳酸钙进行二段中和,控制终点pH为5.0~5.5,反应1 h,沉氟后液含氟量小于20 mg/L,沉氟率超过98%,产出石膏渣仅为传统石灰中和法所产石膏渣量的24.94%,溶液经过除氯后可返回湿法系统中。

某铅锌尾矿综合回收重晶石

铅锌尾矿矿样中主要有价矿物为黄铁矿和重晶石,含少量闪锌矿、方铅矿、灰硫砷铅矿、维硫锑铅矿、针硫锑铅矿等金属硫化物;脉石矿物主要为白云石,少量石英、云母、长石等。主要矿物组成:重晶石约占15%、白云石66%、黄铁矿16%、闪锌矿0.4%、方铅矿0.1%。矿样中BaSO_(4)含量为13.84%,CaCO_(3)、MgCO_(3)含量较高,分别为31.16%、23.69%,白云石可浮性与重晶石相似,因此该矿样为低品位难选重晶石矿。针对该矿石,采用浮选方案进行了实验室小型闭路试验和半工业试验,针对BaSO_(4)品位为16.65%的铅锌尾矿矿样,小型闭路试验获得了产率为10.73%、BaSO_(4)品位为91.27%、作业回收率为70.25%的重晶石精矿;针对含BaSO_(4)16.89%的矿样,半工业试验获得了产率为8.72%、BaSO_(4)品位为95.31%、作业回收率为49.20%的重晶石精矿1和产率为3.59%、BaSO_(4)品位为84.22%、作业回收率为17.90%重晶石精矿2,重晶石总精矿产率为12.31%,BaSO_(4)品位为92.08%、作业回收率为67.10%。半工业试验技术指标和小型试验指标基本吻合,半工业试验结果很好地验证了小型试验结果的可靠性和稳定性,为下一步工业试验及生产打下了基础。

用于可见光降解甲基橙的ZnIn_(2)S_(4)/CaIn_(2)S_(4)光催化剂性能

采用一步水热法构建了ZnIn_(2)S_(4)/CaIn_(2)S_(4)(ZIS/CIS)异质结光催化剂。通过XRD、SEM、DRS、电化学测试等表征研究此异质结光催化剂的晶体结构、形貌、光学性质及光生载流子的分离效率,在模拟可见光下考察其对甲基橙的降解效率。实验结果表明,ZIS/CIS异质结材料对甲基橙的降解效果明显优于CIS和ZIS。ZIS摩尔分数为30%的复合样品具有最佳的甲基橙降解效率,60 min内达到95.54%,并且具有良好的稳定性。