用EDTA标准溶液直接滴定石灰石中氧化镁

EDTA络合滴定法测定石灰石中氧化镁含量,一般分为差减法和直接滴定法。差减法往往由于钙的误差而引起镁更大的误差,准确度不高;直接滴定法由于溶液中钙会对镁造成干扰,从而影响准确性。下面就如何消除钙的干扰,用EDTA直接滴定镁这一方法作进一步探讨。1 原理在pH值约为6时,过量的草酸根能与钙离子形成溶解度极小的草酸钙沉淀,而与镁离子只有微量的络合。根据这一原理,向钙镁混合液中加入草酸沉淀钙,分离出沉淀后,直接滴定氧化镁。反应式如下:pH值为5～7时:Ca2 2COO-→CaC2O4↓pH值为10时:Mg2 KB→Mg - KB(纯蓝)(红色)Mg-KB …     

EDTA络合滴定法连续测定铁矿石中钙和镁

利用铁矿石的系统分析中重量法测定二氧化硅的滤液作为分析试液,EDTA络合滴定法测定其中钙和镁量,然后通过计算得到铁矿石中氧化钙和氧化镁含量。铁矿石中铁、铝、钛、铜、镍、锰等干扰元素不需要分离,可在酸性溶液中用酒石酸钾钠、盐酸羟胺、三乙醇胺和在氨性溶液中用铜试剂进行掩蔽消除干扰。在氨性溶液中,以酸性铬蓝K-萘酚绿B作指示剂,用EDTA标准溶液滴定钙镁合量。然后在滴定钙镁合量后的同一溶液中,加入KOH溶液,以钙试剂作指示剂,用钙标准溶液滴定EDTA-Mg络合物中释放出的EDTA,同时做EDTA/Ca的比对试验,求得比对系数。根据比对系数、滴定释放出EDTA时消耗钙标准溶液体积和样品量计算出氧化镁的含量,再用差减法计算氧化钙的含量。使用本方法对铁矿标准样品中氧化钙、氧化镁进行了多次平行测定,测定值与认定值相符,测定结果的相对标准偏差（RSD）在1.1%～４.０％（n=6）之间,回收率在98%～104％范围。     

水氯镁石和高钙菱镁石制备氢氧化镁

氢氧化镁是一种应用广泛的新型绿色环保材料,如何低成本制备高品质氢氧化镁引起广泛关注。以水氯镁石和高钙菱镁石为原料,采用湿法冶金工艺制取氢氧化镁,探讨反应时间、反应温度、水氯镁石浓度、煅烧后物料的粒度等对氢氧化镁纯度的影响。结果表明,在80℃恒温水浴、反应时间6 h、水氯镁石浓度5%、煅后菱镁石粒度-45μm条件下得到的氢氧化镁沉淀纯度可达94.89%,主要物相为Mg(OH)₂和CaO。     

烧结矿中MgO含量变化对EDTA滴定联测法的影响

2003年以前,烧结化验室化学分析烧结矿中的CaO、MgO时,常发生较大偏差,进而影响生产。而采用碱熔试样,EDTA滴定法联测Ca、Mg,通常表现为CaO偏低、MgO偏高。通过系列实验研究,发现烧结矿中MgO含量低于某个具体值时,导致上述现象发生;通过在实验中补加镁标液能有效解决分析误差。     

水氯镁石复盐法脱水工艺

用烧瓶蒸馏装置模拟固定床脱水设备,研究用苯胺盐酸盐作脱水剂的复盐法将水氯镁石(MgCl2.6H2O)脱水制备无水氯化镁(MgCl2)的过程,考察复盐配料比例、保护气含水浓度、热解温度、热解时间等因素对所制备无水氯化镁产品中氧化镁和水分含量的影响,优化用固定床脱水工艺条件。结果表明,完全脱水和脱苯胺盐酸盐的最佳温度和时间分别是300℃与25～30 min和320～350℃与10～20min。最佳配料摩尔比C6H5NH2.HCl∶MgCl2.6H2O为1.1∶1.0。在最佳条件下,可得到合格的无水氯化镁产品MgCl298%～98.6%,MgO 0.03%～0.38%,苯胺盐酸盐0.10%～0.12%,水分0.60%～0.81%。     

炉渣组分对CaO-MgO-Al2O3-Si2O-Cr2O3-FeO-TiO2渣系中铬尖晶石相析出影响的热力学

根据熔体的非平衡凝固理论,采用热力学数据库Factsage7.1模拟计算研究了不同碱度、MgO以及FeO的质量百分数对不锈钢渣微晶玻璃的基础玻璃成分CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃-FeO-TiO₂体系中尖晶石矿相开始析出温度、种类及其析出量的影响规律。计算结果表明,碱度为0.47时,析出矿物相主要包括透辉石、钙长石以及尖晶石等相,其中透辉石为主要物相。尖晶石相为高温析出相,主要由MgCr₂O₄和FeCr₂O₄组成。在不同碱度条件下,总尖晶石开始析晶温度随着MgO质量百分数的增加而增加。当w（C）/w（S）为0.47,氧化镁的质量百分数小于10.52%时,镁铬尖晶石和铁铬尖晶石的析出量随着氧化镁质量百分数的增加而增加。氧化镁的质量百分数大于10.52%时,随着氧化镁质量百分数的增加,镁铬尖晶石析出量增加,而铁铬尖晶石的析出则逐渐减少。FeO的质量百分数小于7.57%时,镁铬尖晶石和铁铬尖晶石的析出量随着氧化铁含量的增加而增加,FeO的质量百分数大于7.57%以后,随着氧化铁含量的增加,镁铬尖晶石析出量减少,铁铬尖晶石析出量增加。     

EDTA滴定法与电感耦合等离子体原子发射光谱法联合测定转炉大面修补料中氧化钙和氧化镁

采用转炉大面修补料对转炉的加料侧、炉底和出钢侧进行维护，可增加转炉炉衬寿命，减轻环境污染。其中MgO含量影响炉衬的使用寿命，而CaO含量影响MgO测定的准确性，因此，需要准确测定转炉大面修补料中的CaO和MgO。将试样在马弗炉中灼烧10 min,再以Na₂CO₃-H₃BO₃(质量比为2∶1)混合熔剂高温熔融处理，稀盐酸浸取酸化后定容，得到试液；移取一份试液，用5 mL三乙醇胺(1+1)掩蔽Cu²⁺、Ti(Ⅵ)、Al³⁺、Fe³⁺的干扰，以酸性铬蓝K-萘酚绿B为指示剂，在pH=10氨性缓冲溶液中，以EDTA标准滴定溶液滴定测得CaO和MgO合量；移取另一份试液，定容于100 mL容量瓶中，选择Ca 317.933 nm为分析谱线，用电感耦合等离子体原子发射光谱法(ICP-AES)测定CaO含量；将两者相减，所得差值即为MgO含量。据此，建立了EDTA滴定法与电感耦合等离子体原子发射光谱法联合测定转炉大面修补料中CaO和MgO的方法。按照...     

EDTA滴定法测定炉渣中氧化镁含量的不确定度评定

对EDTA溶液络合滴定法测定炉渣中氧化镁含量的不确定度的产生原因进行了分析,并对一个高炉渣中氧化镁含量测定结果的不确定度进行了评定.     

EDTA滴定法测定白云石中氧化钙和氧化镁含量方法的改进

以盐酸、氢氟酸和硝酸分解试样,盐酸冒烟除去残余的硝酸和氢氟酸。经过氨水沉淀分离铁、铝等干扰元素后,在pH=10的NH_3·H_2O-NH_4Cl缓冲体系中,以铬黑T为指示剂,EDTA滴定法测定氧化钙和氧化镁的合量;在pH≥12的氢氧化钾缓冲体系中,以钙试剂为指示剂,用EDTA滴定法测定氧化钙的含量。根据氧化钙和氧化镁的合量减去氧化钙的差值,得到氧化镁的含量。试验发现,采用盐酸、氢氟酸和硝酸溶解样品,代替国标方法用碳酸钠-硼酸混合熔剂熔融,稀盐酸浸取溶解样品,溶样省时,省力;两种方法溶样后,都需要加三乙醇胺掩蔽铁、铝等干扰元素,实验方法增加了氨水沉淀铁的步骤,进一步消除共存元素的干扰;EDTA滴定法测定氧化钙时,为了消除镁的干扰,实验方法加入甘露醇作辅助络合剂,代替国标方法中的设置预置滴定剂;在测定氧化钙和氧化镁的合量时,实验方法用铬黑T代替国标方法的酸性铬蓝K-萘酚绿B混合指示剂。精密度试验中,三个标准样品测定结果的相对标准偏差(RSD,n=6):氧化钙为0.25%~0.35%;氧化镁为0.35%~0.45%。采用国标方法和实验方法对不同的白云石样品进行测定,测定结果基本一致。     

电位滴定法测定石灰中氧化钙和氧化镁

石灰以其优越的造渣性能而备受钢铁冶金行业青睐,石灰的主要成分为氧化钙和氧化镁,高效、准确测定石灰中氧化钙和氧化镁至关重要。采用国家标准GB/T 3286.1—2012中EDTA络合滴定法测定石灰中氧化钙和氧化镁,过程繁琐流程长,滴定终点通过肉眼判断容易产生视觉误差,因此不能满足冶炼过程工艺动态控制生产需求。实验使用盐酸溶解样品,在待测样品中加入三乙醇胺,掩蔽Fe³⁺、Al³⁺;加入糊精,抑制样品溶液中生成大量的氢氧化镁沉淀对Ca²⁺的吸附;用EDTA标准溶液在强碱介质下,电位滴定法测定氧化钙、氧化镁含量。对使用盐酸溶解石灰后的不溶物进行回收和不回收两种处理方法,并对氧化钙和氧化镁的测定结果进行t检验,结果无显著差异。按照实验方法测定3个石灰样品中氧化钙、氧化镁,结果的相对标准偏差(RSD,n=11)均小于0.5%。选择一批石灰试样,分别按照实验方法和GB/T 3286.1—2012测定氧化钙和氧化镁含量,两种方法测得的氧化钙和氧化镁差值分别小于±0.20%和±0.10%。通过电位突变来判断滴定终点,减少了人员判定滴定终点的视觉误差,能够满足冶炼过程工艺动态控制的测定需求。     

Studies on Photocatalytic Performance of MgO Nanoparticles Prepared by Wet Chemical Method

In the present article, we explore a cost-effective and an environmentally benign route to prepare magnesium oxide (MgO) nanoparticles through thermal decomposition of magnesium hydroxide (Mg(OH)₂) nanoparticles. Mg(OH)₂ nanoparticles were prepared using different solvents namely ethylenediamine (EDA) and triethanolamine (TEA) by wet chemical method, and subsequently the as-synthesized Mg(OH)₂ nanoparticles were calcinated at 400°C for 2 h in air to obtain MgO nanoparticles. XRD pattern revealed that as-synthesized Mg(OH)₂ nanoparticles are polycrystalline in nature with hexagonal structure, and after annealing it transforms to MgO nanoparticles with cubic structure. FTIR spectrum of as-synthesized Mg(OH)₂ nanoparticles indicated the OH⁻ antisymmetric stretching vibration of the Mg(OH)₂ and after annealing the sharp peak at 3686 cm⁻¹ disappears, which confirms the complete transformation of hexagonal Mg(OH)₂ to cubic MgO. SEM analysis showed the formation of interfused Mg(OH)₂ nanoflakes and coral-like hierarchical MgO nanostructure made up of stacked nanoflakes. Optical band gap energy of Mg(OH)₂ and MgO nanoparticles prepared using different solvent were estimated using UV–Vis DRS. Degradation of methyl orange was performed to investigate the photocatalytic activity of coral-like hierarchical MgO nanostructure. Results demonstrate that coral-like hierarchical MgO nanostructure possessing large surface area and porous morphology exhibited good photocatalytic degradation of methyl orange.     

Removal of magnesium from nickel laterite leach liquors by chemical precipitation using calcium hydroxide and the potential use of the precipitate as a filler material

The chemical precipitation of magnesium from sulphate solution, resulting from heap leaching of nickeliferous laterites with sulphuric acid, was studied. Magnesium was removed as hydroxide using calcium hydroxide (Ca(OH)₂) and the precipitate produced was a mixture of magnesium hydroxide (Mg(OH)₂) and gypsum (CaSO₄·2H₂O). The variables studied were the temperature and the stoichiometric quantity of Ca(OH)₂. The responses measured were magnesium removal and the specific surface of the precipitate. Design of the experiments and statistical analysis of the data were used in order to determine the main effects and interactions of the factors. Scanning electron microscopy (SEM) was also used to investigate the effect of precipitation conditions on the morphological characteristics of the Mg(OH)₂–CaSO₄·2H₂O mixture. Kinetic analysis with the aid of Nielsen theory allowed the determination of the Mg(OH)₂ formation mechanism. The use of a magnesium hydroxide–gypsum mixture as a filler material was also examined. The suitability of the precipitate was evaluated by measuring a set of properties that can characterize a material as a filler and by measuring mechanical properties of polymers filled with the precipitate at various addition levels. The magnesium hydroxide–gypsum precipitate proved to be promising for this application, as it was found to have similar properties with other commercial products.     

EDTA络合滴定法联合测定硅钙钡镁合金中钙钡镁

建立了一种快速测定硅钙钡镁合金中钙、钡和镁含量的分析方法。以盐酸、硝酸和氢氟酸分解试样,高氯酸冒烟除去残余的盐酸、硝酸和氢氟酸,经过氨水沉淀分离铁、铝等干扰元素后,在pH 10的NH₃·H₂O-NH₄Cl缓冲体系中,以邻甲酚酞指示滴定终点, EDTA络合滴定法测定钙镁合量;在pH≥12的氢氧化钾缓冲体系中,分别以钙指示剂和钙黄绿素-茜素混合指示剂指示滴定终点, EDTA滴定法分别测定钙及钙钡合量。根据钙钡合量与钙含量的差值和钙镁合量与钙含量的差值,可分别得到钡和镁含量。经氨水沉淀后试液中残余的铁、铝和其他干扰离子用三乙醇胺掩蔽,钡对滴定钙和钙镁合量以及镁对滴定钙和钙钡合量的干扰分别通过生成硫酸钡和氢氧化镁沉淀的方法消除。建立的方法用于实际硅钙钡镁合金中钙、钡和镁测定,测定值与对照方法测定值相符,钙、钡和镁的相对标准偏差分别为0.38%、1.9%和1.9%。     

Electrochemical Properties of Intermetallic Compounds Mg2Ni,MgNi2, and the Hydride Mg2NiH4 in 30% KOH Solution

Using the potentiodynamic polarization curve method, x-ray phase analysis, and Auger electron spectroscopy, we have studied the mechanisms for cathodic and anodic processes occurring in a 30% KOH solution on the surface of the intermetallic compounds Mg₂Ni, MgNi₂ and the hydride Mg₂NiH₄. In contrast to MgNi₂, we observed hysteresis of the cathodic polarization curve for Mg₂Ni due to formation of a surface layer (a mixture of the hydride phases β‐Mg₂NiH₄ and Mg₂NiH_3.85) on the sample, as a result of reaction between Mg₂Ni and atomic hydrogen. We have shown that the surface of the samples is considerably enriched in magnesium and depleted of nickel, and their corrosion resistance in the indicated electrolyte is determined by active dissolution of nickel and formation of a surface layer (～25 nm) on the electrodes consisting of MgO and Mg(OH)₂ in the case of Mg₂Ni and Mg₂NiH₄, and also of MgO, Mg(OH)₂, and NiO in the case of MgNi₂. The intermetallic compound MgNi₂ was the most corrosion-resistant, probably because of the presence of a monolayer of the oxides MgO and NiO on the original surface.     

镁对X120管线钢夹杂物的作用

 运用热力学计算了X120管线钢中氧化镁及其复合夹杂物在钢液中的析出条件,以X120管线钢酸溶铝目标质量分数0.025%为例,0.00046% 0.0033%,钢中将有MgO生成。在X120管线钢的成分下,w(［Ti］)=0.016%时,w(［Mg］)=00008%就可以生成2MgO·Ti2O3复合夹杂。微镁处理的X120管线钢中的夹杂物全部是细小的含镁复合氧化物或是含镁氧化物与硫化物的复合夹杂。镁处理钢中的夹杂物小于2 μm的占85%,2~5 μm的占14.5%,5~10 μm的夹杂物仅有0.5%,看不到大于10 μm的夹杂物,大大优于钙处理钢。     

取向硅钢高温退火时内氧化层与MgO反应过程研究

对取向硅钢高温退火工艺进行实验室模拟,采用聚焦离子束显微镜（FIB）观察了氧化层中二氧化硅和氧化镁反应的微观形貌演变过程,采用能谱仪（EDS）分析了试样截面近表层Mg、Al、Si等元素的分布规律,最后采用透射电镜（TEM）分析了对成品试样硅酸镁底层的结构特征。结果表明：（1）Mg离子的扩散速度是影响硅酸镁底层反应的主要因素;（2）Mg离子最初沿着二氧化硅颗粒与铁基体之间的界面扩散,逐渐将二氧化硅颗粒包覆;随着温度的进一步升高,Mg离子开始向二氧化硅颗粒内部扩散,并与之反应;（3）随着温度的升高,特别是在AlN分解后,钢基中的Al会逐渐将钉扎部位的硅酸镁（Mg2SiO4）完全转化成为镁铝尖晶石（MgO·Al2O3）。     

离子选择性电极-逆格氏作图法测定镁合金微弧氧化衰变电解液中氟离子浓度

提出了一种将含氟的待测液加到氟离子标准溶液中以测定待测液中氟离子的方法--离子选择性电极 逆格氏作图法,并用此法测定了 AZ91D镁合金微弧氧化衰变电解液中氟离子浓度。待测试液中干扰离子和干扰的消除方法研究表明,从镁合金基体迁移到强碱性微弧氧化电 解液中的Zn²⁺、Cu²⁺、Ni²⁺和Fe³⁺离子均以沉淀形式被过滤除去, Mg²⁺、Al³⁺等离子的干扰以离子 强度剂TISAB消除,SiO₃^2-和多余的Al³⁺离子分别用C₄O₆H₂KNa 和EDTA掩蔽,溶液中的OH^-、Na⁺和K⁺均不干扰 氟的测定。用本法测定了老化的镁合金微弧氧化电解液中的氟离子浓度,加标回收率在99.7%～101.9%之间。用本法和离子选择性电极 标准曲线法对两种镁合金试样的微弧氧化电解液中的氟离子浓度分别进行测定并对测定结果的精密度和准确度进行分析,表明本法的精密度 比离子选择性电极-标准曲线法有所提高,而两种方法的正确度一致。本法可用于氟离子质量浓度高于1.9 g/L的复杂溶液体系中氟离子的 直接测定。     

高炉渣中硅、钙、镁的湿法分析

高炉渣试样用热的稀硝酸加氢氟酸分解完全后,取3份试液,其中1份试液用盐酸调节酸度后,在680nm波长处用硅钼蓝差示光度法测定二氧化硅含量,另外两份试液分别以钙指示剂和PAN指示剂指示滴定终点,用EDTA滴定法测定氧化钙及氧化钙和氧化镁合量,然后用差减法求得氧化镁的含量。用本法测定了高炉渣试样和标样中二氧化硅、氧化钙和氧化镁含量,并将本法的测定结果与X荧光光谱法的测定结果进行对照,结果表明两种方法的测定结果相符。本法测定结果的相对标准偏差≤2.7%（n=8）。     

Processing copper–vanadium precipitate formed from crude TiCl4 in titania and titanium sponge production

Copper wire is used to remove vanadium from crude TiCl₄ in titania and titanium sponge production which produces a copper–vanadium precipitate. The recovery of copper and vanadium from this precipitate was studied. Experiments found that the precipitate can be naturally oxidized by stacking for one month in air, converting > 90% metallic copper contained in the original precipitate into CuCl₂·2H₂O, Cu₂Cl(OH)₃ and Cu₂(OH)₃Cl. The copper oxy-chlorides were easily converted to Cu(OH)₂ by stirring in dilute NaOH at pH 11 and 80 °C under a liquid-to-solid ratio of 4:1. When the pH was lowered to about pH 2.5 by sulfuric acid, iron, titanium and vanadium oxides remained in the first acid leach residue and copper was selectively leached into solution. By evaporating and cooling the leach solution, a product of CuSO₄·5H₂O with 99.7% purity was obtained.To recover the vanadium, the filter cake was roasted with Na₂CO₃ at 700 °C for 3 h under the stoichiometric proportion of 2.5 for V. The calcine was then leached with water at 70 °C and NH₄VO₃ was precipitated by the addition of NH₄Cl. Calcination of NH₄VO₃ at 550 °C for 2 h produced V₂O₅ with a purity of 98.6%. After vanadium recovery, the residue was leached once again with sulfuric acid and the total recoveries of copper and vanadium were 98.6% and 95.7% respectively.