EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

EDTA络合滴定法测定选铁尾矿中CaF2含量

采用EDTA络合滴定法测定选铁尾矿中的氟化钙含量。选用稀乙酸浸取试样中的碳酸钙,分离过滤氟化钙,用锆-二甲酚橙褪色分光光度法测定浸取液中的氟含量,折算为在稀乙酸中微溶的氟化钙的量;同时沉淀部分用氯化铝溶液在沸水浴中溶解浸取氟化钙,以三乙醇胺掩蔽干扰离子,在KOH介质中,以钙指示剂为指示剂,用EDTA标准滴定溶液测定沉淀中氟化钙的量,两者之和为试样中氟化钙的含量。用此法对试样进行11次平行测定,相对标准偏差（RSD）小于1.0%。在选铁尾矿试样中加入萤石标准物质进行加标回收实验,加标回收率在99%-102%。方法流程短,操作简单。精密度和加标回收率均能满足要求。     

X-ray absorption and diffraction analysis for determination of the amount of calcium carbonate and porosity in paper sheets

Papers are mostly made with lignocellulose and additives among which calcium carbonate has a primarily importance. Calcium carbonate as a filler provides specific properties to the paper like brightness, porosity, etc. Because of low retention, calcium carbonate remains in large quantities in the waste water when at the final stage, the paper is couched and pressed. It is therefore interesting to develop some methods to analyze in a nondestructive way the content of calcium carbonate that remains in the paper. We report in this article an X-ray study of paper sheets with the aim to determine not only the content of calcium carbonate in a nondestructive way but also the porosity of the paper sheets. The analysis is carried out in a quantitative way by refining the wide angle X-ray diffraction patterns using the Rietveld method and by modeling the absorption of the direct beam through paper sheets.     

Fillers in polypropylene. II

Part I showed that significant differences exist between calcium carbonate and silicate minerals when incorporated into polypropylene (three grades). It showed further that an ultrafine calcium carbonate, when coated with stearic acid, gives significantly better impact properties to the composite than a coated ground whiting but with no significant effect on its tensile properties. This article examines the effect of particle size and surface coating of chalk-based calcium carbonate on the physical properties of GWE 21 Propathene homopolymer. The effect of variation in filler level was also investigated.     

Use of calcium carbonate – fumed silica mixtures as filler in polyurethane adhesives

Natural ultramicronized calcium carbonate and mixtures of fumed silica‐natural ultramicronized calcium carbonate are proposed as fillers of solvent based polyurethane (PU) adhesives. PU adhesive containing only calcium carbonate shows similar rheological, thermal, mechanical, surface and adhesion properties than the PU adhesive without filler. Addition of 90 wt% fumed silica +10 wt% calcium carbonate mixture to PU adhesive produced a similar performance than the PU adhesive containing only famed silica. The increase in the amount of natural calcium carbonate in respect to fumed silica in the filler mixture produced detrimental effect on the rheological and mechanical properties of the PU adhesives (in respect to those provided by the PU adhesive only containing fumed silica), although the surface and adhesion properties were not noticeably modified.     

全自动电位滴定法测定镍钴锰酸锂中残余的碳酸锂含量

采用自动电位滴定法测定镍钴锰酸锂中残余的碳酸锂含量。试样经搅拌水浸出其中的残余碳酸锂,用盐酸进行滴定。对试样进行11次平行测定,相对标准偏差(RSD)小于3.2%。在镍钴锰酸锂试样中加入基准物质无水碳酸钠进行碳酸根的加标回收实验,碳酸根的加标回收率在97.7%~103%。方法测定结果准确、可靠。     

碱熔-蒸馏-滴定法测定萤石中的氟化钙含量

采用碱熔-蒸馏-滴定法测萤石中氟含量,计算得到氟化钙含量.萤石试样首先用碳酸钠碱熔消解,然后经硫酸-水蒸气蒸馏分离氟,以茜素磺酸钠作指示剂,用硝酸钍溶液滴定测出其中氟含量,并计算得到氟化钙含量.利用X射线衍射光谱(X RD)法验证了萤石中氟的存在形式,并通过实验确定了碳酸钠使用量、硫酸溶液加入量、蒸馏温度和蒸馏时间等的...     

Aspects on the interaction between sodium carboxymethylcellulose and calcium carbonate and the relationship to specific site adsorption

The mechanisms of adsorption and association for sodium carboxymethylcellulose (NaCMC) in calcium carbonate suspensions have been determined from isothermal calorimetry and adsorption measurements. The equilibrium adsorption isotherms were determined by two different methods of separation; a depletion method and a serum exchange method. The enthalpy of dilution for NaCMC was determined on supernatants obtained from the calcium carbonate suspensions in order to investigate the interaction between NaCMC and dissolved species from the mineral. For comparison, NaCMC was injected into CaCl(2) solutions in order to determine the role of calcium ions in the adsorption process. The initial part of the adsorption isotherm showed a quasi-infinite slope indicating a high affinity for the NaCMC to the calcium carbonate surface, which was significantly reduced when anionic sodium polyacrylate was preadsorbed onto the calcium carbonate implying competitive adsorption. An endothermic enthalpy change was observed between the NaCMC and the calcium carbonate surface, suggesting attachment of the carboxylic acid groups onto the hydrated calcium sites. A similar endothermic enthalpy was observed when NaCMC was injected into CaCl(2) solutions or supernatants obtained from the calcium carbonate suspensions, indicating a complexation of carboxylic acid groups and hydrated calcium ions. It was concluded that the mechanisms of interaction of NaCMC in calcium carbonate suspensions are primarily an association between NaCMC and Lewis acid sites on the calcium carbonate surface and the formation of NaCMC-Ca(2+) complexes in the bulk solution, both of which will be affected by the amount of anionic sodium polyacrylate present.     

The influence of flow-induced crystallization on the impact toughness of high-density polyethylene

The relation between the impact toughness and flow-induced crystalline orientation of high-density polyethylene (HDPE) was investigated. Flow-induced crystalline orientation was created in the samples via injection moulding and the amount of orientation was controlled through variation of processing conditions (injection temperature) and sample thickness. The impact toughness behaviour was found to be strongly dependent on the amount of crystalline orientation, whereas the loading direction also had a strong influence, e.g. giving highest impact properties in flow direction. Subsequently, injection moulded samples of HDPE modified with calcium carbonate filler particles were tested. In this case a similar relation between crystalline orientation and loading direction was found, whereas the total amount of flow-induced crystallization was observed to be strongly influenced by the presence of the filler particles.     

X射线荧光光谱法测定萤石中氟化钙

采用X射线荧光光谱仪可以快速准确测定萤石中总钙的含量.但测定其中氟化钙含量时,一方面,由于样品中碳酸钙计入钙量,从而造成氟化钙测定结果准确性较差.另一方面,铜、锌等金属元素在熔融制样时对铂金坩埚腐蚀较大,因此需要进行酸处理除去碳酸钙及铜、锌等金属元素.然而,样品经过酸处理后,质量会发生变化,造成熔剂与样品的比例不一致,从而影响测定结果.对样品前处理条件、XRF分析中熔片和仪器工作条件等进行了优化,建立了熔融制样、X射线荧光光谱法（XRF）准确测定萤石中氟化钙含量的方法.方法干扰少,具有良好的准确度和精密度,操作简单,提高了分析效率.     

全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对两个不同品位试样分别进行了11次平行测定,相对标准偏差(RSD)均小于1％.在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的...     

Aerobic biodegradation of calcium carbonate filled polyethylene film containing pro-oxidant additives

Two low density polyethylene films, which contained pro-oxidant additives, where investigated, one of them containing micro-milled calcium carbonate filler. Both materials were subjected to controlled thermal oxidation, the oxidation was obviously retarded in the filler-containing sample. Following this, the biodegradability of samples pre-oxidized for 40 and 80 days was investigated. The levels of carbon mineralization reached 13% and 16% for the 40 and 80 days pre-oxidized polyethylene containing filler, respectively, after approximately 16 months in a soil environment at 25 °C, and both types of sample were mineralized to about 19% in compost environment at 58 °C during the same period. The sample not containing filler was mineralized to about 7% in soil after 13 months, and about 23%, after 8 months in compost. Scanning electron microscopy revealed dense colonization of the sample surfaces in both soil and compost. The data presented here provide clear quantitative evidence that part of the polyethylene material was biodegraded.     

A low-cost method for determination of calcium carbonate in cement by membraneless vaporization with capacitively coupled contactless conductivity detection

This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO₂ gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO₂ gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C⁴D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on ‘membraneless vaporization’ (MBL-VP).The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33-99% (w/w) CaCO₃). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision.     

Styrene epoxidation with hydrogen peroxide over calcium oxide catalysts prepared from various precursors

A series of CaO samples were prepared by calcination of commercially available and synthesis of calcium salt precursors such as calcium acetate,carbonate,hydroxide and oxalate etc.CaO samples were found to be effective for the epoxidation of styrene using hydrogen peroxide as an oxidant in the presence of acetonitrile.To determine the influence of the physicochemical properties and surface basicity on the catalytic activity,the prepared CaO samples were characterized using thermogravimetry(TG),X-ray diffraction(XRD),scanning electron microscopy(SEM),N2-adsorption and temperature-programmed desorption of CO2(CO2-TPD).The results indicate that the amounts of very strong basic sites and high basicity strength on CaO sample are key factors for its excellent catalytic performance.In contrast,the surface area,porosity and the surface structure of CaO sample have a relatively minor effect on the catalytic activity.CaO sample,obtained by the decomposition of Ca(OH)2,prepared by precipitating calcium nitrate with sodium hydroxide in ethylene glycol solution,exhibits the highest amount of very strong basic sites and stronger strength of basic sites,and therefore it catalyses the epoxidation of styrene with the highest rate among the tested CaO samples.Under the selected reaction conditions,the selectivity of 97.5% to styrene oxide at a conversion in excess of 99% could be obtained.     

高频燃烧红外吸收光谱法测定碳酸钴中的硫

采用高频燃烧红外吸收光谱法测定碳酸钴中的硫,在测定过程中先将样品进行灼烧处理,并选用纯铁和钨助熔剂熔样,解决了水分干扰和样品熔解不完全的问题。方法可以准确测定碳酸钴中质量分数为0.001%~0.01%的硫,加标回收率为98.4%~101.4%,相对标准偏差RSD为2.8%~6.3%。     

红外吸收测定铝质耐火材料中碳

试验以锡粒、纯铁、钨粒为助熔剂,用红外吸收测定铝质耐火材料中碳。通过加入碳酸钙进行回收率试验,回收率在９５％～１０５％内,ＲＳＤ在１％以下。在没有标样情况下,用合成标样或标准加入法计算样品结果与化学分析法基本一致。     

改性硝酸铵爆轰安全性研究 Ⅰ.CaCO3和MgSO4对硝酸铵爆轰安全性的影响

将碳酸钙和硫酸镁改性的硝酸铵按照工业炸药配方配制成铵油(ANFO)炸药，以8号雷管起爆，对硝酸铵的爆轰安全性进行了评价。采用恒温热分解和示差扫描量热法，研究了改性硝酸铵及铵油炸药的热分解行为。测定了改性硝酸铵的比表面积以解释爆轰结果。得出如下结论：硝酸铵含40％的碳酸钙，或25％碳酸钙和5％硫酸镁的混合物，所配制的铵油炸药不能被8号雷管起爆。碳酸钙同硝酸铵发生复分解反应放出NH3、H2O和CO2气体，反应程度与碳酸钙的含量、温度和时间成正比。虽然硝酸铵中加入碳酸钙后提高了ANFO炸药的热稳定性，但由于上述气体的逸出增加了改性硝酸铵的比表面积。因此，在硝酸铵中加入少量的碳酸钙不能达到爆轰安全性的要求。硫酸镁与硝酸铵形成复盐，可减缓硝酸铵和碳酸钙之间复分解反应的速度．有利于降低硝酸铵的起爆感度。     

Enhanced thermal conductivity of epoxy–matrix composites with hybrid fillers

The results of thermal conductivity study of epoxy–matrix composites filled with different type of powders are reported. Boron nitride and aluminum nitride micro‐powders with different size distribution and surface modification were used. A representative set of samples has been prepared with different contents of the fillers. The microstructure was investigated by SEM observations. Thermal conductivity measurements have been performed at room temperature and for selected samples it was also measured as a function of temperature from 300 K down to liquid helium temperatures. The most spectacular enhancement of the thermal conductivity was obtained for composites filled with hybrid fillers of boron nitride–silica and aluminum nitride–silica. In the case of sample with 31 vol.% of boron nitride–silica hybrid filler it amounts to 114% and for the sample with 45 vol.% of hybrid filler by 65% as compared with the reference composite with silica filler. However, in the case of small aluminum nitride grains application, large interfacial areas were introduced, promoting creation of thermal resistance barriers and causing phonon scattering more effective. As a result, no thermal conductivity improvement was obtained. Different characters of temperature dependencies are observed for hybrid filler composites which allowed identifying the component filler of the dominant contribution to the thermal conductivity in each case. The data show a good agreement with predictions of Agari‐Uno model, indicating the importance of conductive paths forming effect already at low filler contents. Copyright © 2014 John Wiley & Sons, Ltd.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定气井产出液中金属元素

气井产出液中金属元素组成和含量的测定,对于集输系统缓蚀剂的配伍性研究和应用,以及判定下游天然气净化厂脱硫装置发泡、堵塞、腐蚀产生的原因均具有指导意义,因此建立了电感耦合等离子体原子发射光谱(ICP-AES)法测定气井产出液中钾、钠、钙、镁、铁、钡元素的含量。实验确定了最佳分析谱线、样品前处理步骤和酸度等分析条件。利用膜过滤、有机溶剂萃取分离油脂和酸处理3个步骤对工业样品进行前处理,实现了6种元素同时检测。各元素在1~100μg/mL内呈良好线性关系,检出限不高于0.08μg/L,加标回收率达到97.1%~105%,重现性相对标准偏差(RSD)<3.5%;和国家标准溶液比对,方法的相对误差<4%。方法重现性和准确度均满足分析要求。方法成功地检测了气田水、酸化返排液中钾、钠、钙、镁、铁、钡组分含量,具有良好的可靠性和实用性。