EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

Enhanced recovery of low-grade iron ore by selective flocculation method

Beneficiation of low-grade iron ore was carried out by selective flocculation process using different flocculants, namely starch amylopectin (AP) and grafted copolymer of amylopectin (GAP). The iron ore used in the investigation contained 56.98% Fe, 5.45% Al₂O₃, and 4.22% SiO₂. Flocculant dosage, number of floc washing, and pH were considered as variable parameters to analyze their effect on the performance of grade and recovery of concentrate. A flocculant dosage of 0.4?mg/g was found to be the optimum condition for the sample and variable parameters under investigation. The investigation indicated that a grade of 64.77% Fe can be obtained with 96% recovery using AP; however, GAP showed the better result for Fe grade (67%) with a recovery of 97%.     

Determination of Trace Elements in Tea and Coffee by Neutron Activation Analysis

Thermal neutron activation analysis, a high-resolution Ge(Li) gamma-ray spectrometer, and an IBM 360/67 digital computer were used to determine the concentration of Na, K, Sc, Cr, Mn, Fe, Co, Cu, Zn, Se, Br, Rb, Sb, Cs, and Hg in ground coffee and tea. This nondestructive multielement technique requires neither pre- nor postirradiation chemistry and eliminates problems of reagent contamination. The method is simple, precise and sensitive to 15 elements. Interferences from fast neutron (n, p) and (n, α) reactions are small and, if necessary, corrections may be applied easily. This technique can be applied to percolated tea and coffee.     

Analytical Aspects of Photoelectron Spectroscopy

Photoelectron spectroscopy is a new technique for experimentally measuring the binding energies of electrons in molecules. The basic principles of the method are outlined and simple guidelines for the interpretation of u.v.-excited photoelectron spectra are laid down. The analytical potential and possible development of the method are briefly surveyed.     

Determination of lead (II) ion by highly selective and sensitive lead (II) membrane electrode based on 2-(((E)-2-((E)-1-(2-hydroxyphenyl) methyliden)hydrazono)metyl)phenol

A PVC (poly vinyl chloride) membrane electrode for lead ion based on 2-(((E)-2-((E)-1-(2-hydroxyphenyl)methyliden)hydrazono)metyl)phenol (HMHMP) as a membrane carrier was prepared. This electrode exhibited linear response with Nernstian slope of 29.2?±?0.2?mV per decade within the concentration range of 2.0?×?10^?7–1.0?×?10^?1?M lead ion. The limit of detection, as determined from the intersection of the extrapolated linear segments of the calibration plot, was 8.0?×?10^?8 M. The electrode exhibited high selectivity for Pb (II). The response time of the electrode was about 5–10?s for different concentrations. The electrode is suitable for use in aqueous solutions in a pH range of 5.0–7.5. It was used as an indicator electrode in a titration of Pb (II) with chromate at constant pH. This electrode was used for the determination of lead in ore samples, and the results were in agreement with those obtained with an atomic absorption spectroscopy (AAS) method. Also lead selective electrode was used for monitoring of lead in spiked samples of the Zayanderud River and waste water by the potentiometry technique.     

Determination of carbonate content in barite ore by headspace gas chromatography

This paper reports a method for determining the carbonate content in barite ore using headspace gas chromatography. Based on the acidification reaction, the carbonate in the barite ore was converted to CO₂ in a closed headspace vial. When the carbonate content was significant, the pressure caused changes in the CO₂ and O₂ signals and affected the measurement accuracy. It was found that carbonate content is proportional to the intensity ratio of the CO₂ to O₂ signals. Thus, the carbonate content in barite ore can be measured indirectly using a theoretical model. The results showed that the carbonate in 3 g of barite ore sample with a particle size of 74 μm could react completely with a hydrochloric acid solution (2 mol/L) at 65°C for 5 min. The method described herein had good precision (relative standard deviation < 4.14%) and accuracy (relative differences < 6.12%). Further, the limit of quantification was 0.07 mol/L. Owing to its simplicity and speed, this method can be used for the batch determination of carbonate content in barite ore.     

Si内标-X射线衍射法定量测定铁矿中Fe3O4、Fe2O3和SiO2

铁矿物相的准确定量对矿物价值评价及选冶工艺研究有重要作用,现有化学法流程复杂效率低,X射线衍射全谱拟合法可溯源性差,结果准确性难以评价和验证。本研究建立了以Si为内标,以Cu靶X射线为辐射光源,步进扫描方式获得衍射谱图,以待测相含量为横坐标,待测相与内标相峰面积比值为纵坐标建立校准曲线,以曲线对铁矿中Fe3O4、Fe2O3和SiO2物相进行定量的方法。试验对制样条件、扫描参数、内标物选择、积分方式、重叠峰校正等进行了优化选择,结果表明,试样全部通过45 μm标准筛,Si内标比例为10%,步进长度0.01°,步进时间30S,选择对Fe3O4（311）、Fe2O3（104）、SiO2（011）和Si（111）的衍射峰进行积分强度计算,可获得最优结果。在选定工作条件下,Fe3O4在1.07～100%范围内线性相关系数(R2)为0.9953,相对标准偏差(RSD)1.1%～13.2% (n=6),加标回收率99.7 %~114.8 %,检出限(LOD)4.29%;Fe2O3在1.51～100%范围内线性相关系数(R2)为0.9991,相对标准偏差(RSD)2.8%～10.6% (n=6),加标回收率87.1%~112.2%,检出限(LOD)2.56%;SiO2在0.79～29.72 %范围内线性相关系数(R2)为0.9957,相对标准偏差(RSD)3.2%～10.3% (n=6),加标回收率86.6%~98.9%,检出限(LOD)0.68%。方法易溯源、准确性易评价和验证,适合开展标准化检测和应用。