A Novel Process for Titanium Sand by Magnetic Separation and Gravity Concentration

With the continuous depletion of high-grade titanium ores and the increasing demand for titanium dioxide, the low-grade titanium sand has become an important source for the production of ilmenite concentrate; however, the large-scale utilization of the sand is disappointedly scarce, due to its leanness in valuable minerals and insufficient methods available to handle such low-grade sands. A typically low-grade titanium sand was first ground and then processed by low-intensity magnetic separation (LMS) and high gradient magnetic separation (HGMS) to recover titanomagnetite and ilmenite, respectively; as the TiO₂ grade of the sand is low, the primary treatment of the sand by magnetic separations is effective, with 78.45% by mass weight of the sand discarded as tailings. The primary titanomagnetite concentrate was further ground and liberated to obtain a high-grade titanomagnetite concentrate through LMS reconcentration; the primary ilmenite concentrate was separated with spirals to remove the sterile limonite and magnetic gangues, and its concentrate was ground and liberated to achieve a high-grade ilmenite concentrate through HGMS refining. This novel process achieved an effective processing of the sand and obtained a high-grade ilmenite concentrate assaying 46.30% TiO₂ with a high recovery of 57.88%, and a by-product of titanomagnetite concentrate assaying as high as 54.17% Fe.     

地质高背景区铅锌矿废弃地土壤重金属污染评价

调查研究了某废弃铅锌矿区周边农田土壤中重金属Hg、As、Cd、Cr、Pb、Cu、Zn的污染状况,并结合单因素指数法、地累积指数法、污染指数负荷法、灰色聚类法及聚类热图分析对重金属污染程度和空间分布状况进行评价,采用相关性分析和主成分分析识别污染途径。结果表明,研究区Cd、Zn、Hg、Pb、Cu和As含量均超过贵州省土壤背景值。Cd的外源污染最严重,Zn、Pb、Hg次之。重金属污染程度与河流以及距矿区距离呈正相关。主要污染因子为Cd,次要污染因子为Hg和Zn,各采样点均处于严重污染。研究区重金属来源可分为4类,Cu、Cd、Zn属工业源污染,主要为矿山开采;As、Hg污染与工业源和农业源有关;Cr、Pb含量受交通源与工业源以及自然源多方面影响。     

某矿区农田土壤重金属分布特征与生态风险评价

为探明贵州六盘水某矿区周边农田土壤重金属的分布特征及污染程度,以矿区周边农田为研究对象,采集表层土壤测定Cr、Ni、Cu、Pb、Zn和As含量,分析重金属空间分布特征,评价土壤重金属污染程度及潜在生态风险,并探究其来源。结果显示,6种重金属元素含量均高于贵州省土壤重金属背景值,超标倍数依次为Cu(5.82)>Ni(2.52)>Zn(2.46)>Pb(1.81)Cr(1.51)>As(1.18),重金属分布显示矿区煤矸石山和洗选厂周边的农田土壤重金属富集较为严重。单项污染指数均值显示Cu处于重度污染水平,Ni、Zn为轻度污染水平,Pb、Cr、As为轻微污染水平;综合污染处于重度污染级别。地质累积指数法评价结果显示:Cu、Ni、Zn、Pb处于轻度污染,Cr、As表现为尚未污染水平。研究区重金属的综合潜在生态风险指数为68.02,已经达到轻度危害程度,其中Cu、Ni对综合潜在生态风险(RI)的贡献最大。多元统计分析结果显示,Zn与Pb、Zn与As以及Cu与Pb的相关性较强,表明Zn、Pb、AS、Cu的来源较相似,为第一类来源,主要源于采矿活动产生的三废;Ni、Cr分别为第二、三类来源,第二类重金属来源与汽车尾气的排放、机械损耗有关;第三类重金属主要受土壤母质影响。4种评价结果基本一致,矿区周边农田土壤重金属处于重度污染,轻度危害程度,Cu、Ni是研究区土壤影响最显著的生态风险因子,重金属主要源于采矿活动产生的三废。     

选择性磷酸沉淀分离铬铁的新工艺

针对酸性水溶液中铬铁分离难题,基于Fe3+还原预处理,提出选择性磷酸沉淀铬分离铬铁的方法。研究沉淀剂Na₃PO₄用量、溶液初始pH值、反应温度及保温时间等对铬铁分离的影响,所得较优工艺条件为:溶液初始pH值为2.0,按PO₄3-/Cr3+摩尔比0.375的量加入Na₃PO₄,90 ℃保温60 min。在上述条件下,铬沉淀率可达98.53%,铁沉淀率仅1.42%,分离效果理想。实验还证明,该方法适用于较宽的铁浓度范围,而且Cu2+、Zn2+、Ni2+及Cl-等杂质离子对选择性沉铬无明显干扰。该方法为含铬物料的铬分离提取提供了一条新的可选途径。      

Fe20Cr9Ni铸造奥氏体不锈钢中σ相的析出动力学

采用EPMA、XRD、TEM等手段分析了压水堆核电站主管道用Fe20Cr9Ni铸造奥氏体不锈钢中σ相的成分和结构,通过等温时效处理、金相组织分析,研究了σ相析出动力学,获得了σ相析出的时间-温度-转变(TTT)曲线及JMA析出动力学方程.研究结果表明:Fe20Cr9Ni中σ相析出的温度范围为600～840℃,750℃时σ相析出动力学最快,600～750℃时σ相的析出量计算值与实验值符合得较好.σ相形成激活能为149kJ/mol,接近Cr在铁素体中的扩散激活能值,其过程主要受Cr扩散控制.Fe20Cr9Ni铸造奥氏体不锈钢中σ相析出特征主要由其特殊的合金成分和组织结构决定.     

北衙金矿金银铁矿石特性与选矿回收的关系

对北衙金矿矿石矿物组成、主要矿物嵌布关系、粒度特征、元素赋存状态和工艺特性等进行分析,研究不同磨矿细度下磁选对矿物分流的内在富集规律。结果表明:金、银粒度微细,磁赤铁矿、褐铁矿和铅硬锰矿是金、银、铁的主要载体矿物,其粒度和可磨度等工艺特性具有明显差异。为综合回收金、银、铁,围绕其载体矿物先进行磁选分流,再将各产品异性化地精细分选。在磨矿细度-0.074 mm占70%条件下磁选,可获得铁质量分数62.41%、铁回收率29.49%的磁铁精矿,金、银回收率分别为22.75%、24.99%的非磁产品,59.82%的金、67.49%的银和55.71%的铁富集至强磁产品,金、银、铁分流与富集效果明显,为后续分类提取金、银创造有利条件。     

Co-Al基三元系中B2相的溶解度间隙与稳定性

Information on phase equilibria in the Co-Al based systems which are related to some magnetic and heat resistance materials is important for their microstructural control. Recently, it was proposed with a theoretical calculation on electronic band structure that some Heusler-type alloys Co2 XAl (X: Cr and Mn) should be a new type of spinelectronic materials so-called half-metallic ferromagnet. In the case of the Co2CrAl, however, magnetic properties expected from the theoretical work can not been experimentally obtained and the reason has been still unknown. On the other hand, a tunne- ling magnetoresistance (TMR) effect due to the half-metallic properties was reported in Co2 (Cr0.6 Fe0.4 ) Al alloy, but not the Co2CrAl alloy. In the present paper, it is reported that this discrepancy with the theoretical work in the Co2CrAl alloy is bought about by phase separation between A2 and B2 phases, and that the substitution of Fe for Cr can suppress the precipitation of A2 phase in the B2 phase. Such a phase separation is originally due to the miscibility gap between CoAl and Cr formed in the Co-Al-Cr ternary system as well as that reported by Hao et al. in the Ni-Co-Al-Fe system.     

A Beneficiation Study on a Low Grade Iron Ore by Gravity and Magnetic Separation

In this paper, a sample from Tange-zagh iron mine was characterized by gravity and magnetic separation methods. The mineralogical studies showed that hematite and goethite are the main iron-bearing minerals with insignificant amounts of FeO. The results indicated that spiral separation yields higher separation efficiency than others. The combination of spiral and multi gravity methods showed that the grade and recovery could be obtained 58.7 and 55.6%, respectively. Scrubbing and de-sliming stages increased the recovery in the wet high intensity magnetic process. With a four-stage process of separation, the WHIMS by scrubbing and de-sliming was applied to achieve a final concentrate with grade of 62.6% Fe and recovery of 57.1% Fe.     

某铁矿尾矿回收利用选矿试验研究

针对某铁矿尾矿中赤、褐铁矿含量较高,矿物嵌布颗粒微细,试验探索不同解决方案,最终试验结果表明磁选尾矿再磨-溜槽重选流程,可获得铁精矿产率40.89%,品位TFe 52.65%的选别指标,而且回收率达50.9%,选别成本低、无环境污染。     

尾矿铁回收技术的研究与开发

以铁矿企业的尾矿为对象,以微磁学理论为基础,利用龙窑烧砖技术系统地模拟研究了高梯度磁选机回收含铁的强磁( Fe3O4)、弱磁(Fe2O3、FeCO3)矿物.结果表明:利用尾矿还原砖坯的传热性、龙窑内焙烧温度和时间控制、还原焙烧后的降温技术这三个关键环节,通过焙烧将弱磁性矿物转化为强磁性矿物,再经过磨矿磁选工艺,能够提取合格的铁精粉.     

湖南某难选黑白钨矿中的白钨浮选试验研究

为解决湖南某黑白钨矿中以萤石为主的脉石对白钨浮选干扰较大的问题,对该黑白钨矿通过浮选先回收钼、铋硫化矿,浮选尾矿经弱磁除铁,然后弱磁选尾矿经高梯度磁选机磁选得到的非磁产品作为白钨给矿(WO3 0.33%)进行浮选,采用调整剂TT+水玻璃和新型捕收剂TAB-3进行白钨矿粗选、NT+水玻璃进行白钨加温精选、白钨加温精矿经酸浸后取得品位为72.59%WO3,WO3回收率为70.64%的白钨精矿。     

基于多评估法的硫铁矿区土壤重金属污染特征及源分析

以川南某硫铁矿采选矿区及其尾矿渣场周边农用地为研究对象,采集并测定了51个表层土壤样品、4个背景点土壤样品和4个剖面土壤样品的Cd、Cr、Hg、Ni、Pb、As、Cu、Zn含量,分析其空间分布特征,应用内梅罗综合污染指数法剖析土壤重金属污染现状,并结合相关性分析和正定矩阵因子分析法对土壤重金属来源进行解析。结果表明：研究区土壤Cd、Cr、Hg、Ni、Pb、As、Cu、Zn含量均值分别为2.2、163.0、0.2、66.6、41.8、15.1、80.8、153.0 mg/kg,其中Cd、Cr、Ni、Cu存在不同程度的累积现象,且多个重金属元素之间存在显著相关性;Cd为主要污染元素,Cu具有较强的垂向迁移能力;土壤重金属主要来源为工矿活动源(39.5%)、自然源(37.6%)、大气沉降与交通混合源(22.9%)。川南某硫铁矿周边农用地存在多重金属元素复合污染,其中工矿活动起主导作用。     

合金碳化物M23 C6的磁性及磁致磁性

利用第一性原理研究了碳化物M23 C6 (M=Fe,Cr)的晶胞结构、磁矩和态密度,并结合魏氏分子场理论分析了磁场作用下一些碳化物的磁致磁性.结果 显示:Fe20 Cr3 C6碳化物中的Fe3和Fe4原子连接组成稳定的晶格框架,Cr1、Cr2和C原子位于框架中心;Fe20 Cr3 C6的磁性主要来源于Fe和Cr原子的3...     

Evaluation of Al3Mg2 Precipitates and Mn-Rich Phase in Aluminum-Magnesium Alloy Based on Scanning Transmission Electron Microscopy Imaging

Scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS) were used to observe intergranular and intragranular ??-phase (Al₃Mg₂) formation and growth in as-received sample and long-term (~1?year) thermally treated samples of 5083-H131 alloy. Rod-shaped and equiaxed particles rich in Mn, Fe, and Cr were present in the as-received and heat treated samples. The ??-phase precipitated along grain boundaries as well as around and between preexisting Mn-Fe-Cr rich particles. The measured thickness of ??-phase along grain boundaries was lower than Zener?CHillert diffusion model predicted value and the potential reasons were theoretically analyzed. Dislocation networks, grain boundaries, and different preexisting particles were observed to contribute to Mg diffusion and ??-phase precipitation.     

典型钒矿冶炼厂区域土壤重金属污染及陆生植物富集能力

植物修复是土壤重金属污染修复的重要手段。为了探明南水北调工程中线水源地土壤污染状况并对其进行修复,本研究以湖北省朝北河和典型钒矿冶炼厂为对象,按季节采集该区域土壤（样本量n = 14）和当地优势陆生植物（样本量n = 113）,使用微波消解?电感耦合等离子体质谱(ICP?MS)测定V、Cr、As和Cd重金属含量,根据内梅罗指数法综合评价了土壤污染程度,评估了各种植物对四种重金属的富集能力。结果表明,朝北河采样点中排污口与河水交汇处土壤中重金属Cd含量较高;钒矿冶炼厂原矿堆放区V超标近83倍,Cr、As和Cd重金属超标两倍以上,土壤受到严重污染;其他采样点均受到不同程度的重金属污染。植物重金属富集能力和耐受性评价结果表明,鼠麴草、密叶飞蓬、一年蓬对四种重金属耐受性极强,小蓬草、白茅、少花龙葵、野菊、白车轴草、稗是V、Cr和Cd的超富集植物,蜈蚣草、构树对As的富集能力极强,野艾蒿对Cr和Cd的富集能力较强,丁香蓼和日本毛连菜分别对Cr和V具有较强的耐受性和富集特异性,委陵菜和垂序商陆对Cd具有较强的富集能力和特异性。五种优势植物盆栽实验表明,苎麻在复合金属污染条件下耐受性最强,委陵菜富集能力最强。      

Recovery Improvement of Fine Magnetic Particles by Floc Magnetic Separation

The performance of floc magnetic separation (FMS) has been compared with wet high-intensity magnetic separator (WHIMS). This study was performed on low-grade iron ore slime contained 59.58% Fe with 4.57% silica and 3.78% alumina. Detailed characterization data indicated that a substantial amount of the slime was below 20 µm in size. Beneficiation studies indicated that the FMS process is effective to recover fine hematite and goethite particles, compared with the conventional magnetic separation. In conventional magnetic separation, the extent of the fluid drag force exceeds the magnetic force exerted on ultrafine particles. Thus, ultrafine magnetic particles were usually not recovered effectively by magnetic separators, resulting in the loss of valuable ultrafine slime particles. The FMS process significantly increases the magnetic force on the ultrafine iron ore in the form of hydrophobic flocs in a magnetic field, thus the ultrafine particles can be picked up effectively as magnetic concentrates. The FMS process improved the Fe recovery from 37.35% to 79.60%.     

Valuable Metals Recovery from Tailings of Patched Copper—Nickel Ores

Norilsk copper-nickel ores sulphide contain up to half its composition pyrrhotite of different magnetic values. Ferroplatinum features detectable magnetization also. On this basis, research on Norilsk products recovery by magnetic methods is beyond question.

With Norilsk patched ores tailings containing 0.14-0.17% nickel and 0.05-0.007 mm gain size, the magnetic product was produced by using usual separation in 1-3 kOe field with the following indices: outcrop 3-6%. nickel contents 0.67-0.89% and recovery 15-25%. High gradient magnetic separation (HGMS) in the field of I kOe gives outcrop 8.3% (ordinary 3%), nickel contents 0.35%, recovery 19.4%; in field of 2 kOe when equal nickel contents 0.4% outcrop—14.5%—three times as high as ordinary (4.2%) and accordingly recovery is larger, HGMS is able to raise an outcrop and nickel recovery out of the tailings by a factor of two or more but the quality is lost.

HGMS, in comparison with the usual one improves the separation indices by a factor of two on noble metals. The biggest sum is 8.11 g/t (“initial” content is 1.5 g/t), outcrop 18.7% and recovery 75.8%.

The magnetic fraction of the first separation contains approximately an equal quantity of pyrrhotite and magnetite. In the combined magnetic field (constant and variable) this product was partitioned into magnetic fraction mainly magnetite, and “non-magnetic” mainly pyrrhotite. There is 1.25% nickel in “non-magnetic” fraction, its outcrop 4% from the original mass of tailings.

The concentrate with nickel contents 1.25% and outcrop to 4% is separated out the tailings of patched ores by two-staged separation.     

钒冶炼厂周边陆生植物对重金属的富集特征

对某钒冶炼厂周边土壤和植被进行现场采样,共采集到高等植物20科29种,土壤样品7个,采用ICP-MS和ICPOES分析本土植物和土壤中重金属含量.结果表明,冶炼厂周边土壤普遍存在V、Cr和Cd污染现象,重金属V和Cr的污染问题突出.29种植物体内均检测到V、Cr、Cd和Pb,其中V含量相对较高.本土植物蜈蚣草体内重金属V含量最高,其地上部分V积累量为86.51 mg·kg-1,地下部分为814.25 mg·kg-1;野胡萝卜对Cd的富集和转运能力显著高于其他植物,地上部分和地下部分Cd含量分别为18.56 mg·kg-1和5.66 mg·kg-1.两种植物表现出对钒冶炼导致周边复合重金属污染极高的耐性,可作为钒冶炼厂周边土壤重金属污染植物修复的先锋物种.      

低铬和中铬含钛铁素体不锈钢高温氧化行为

通过对低铬（409L）和中铬（439）含钛铁素体不锈钢在900 ℃下空气中开展恒温氧化试验,获得了两种钢的氧化动力学曲线,并结合EPMA、SEM和XRD等方法对氧化皮的结构进行了分析。结果表明,409L和439氧化动力学曲线均遵从抛物线规律,但409L抛物线速度常数远高于439;409L氧化80 h后氧化层结构由外侧Fe2O3和内侧(Fe,Cr,Mn)3O4复合尖晶石组成;439氧化80 h后氧化层外侧则由Cr2O3和(Cr,Mn)3O4尖晶石组成,内侧为一层SiO2,基体内还伴有钛的内氧化;较高的铬含量能保证TiO2内氧化颗粒稳定存在,而TiO2内氧化颗粒阻止离子迁移,显著降低氧化速度。