脂肪酸类白钨矿捕收剂的结构性能关系研究

主要研究了不同结构的脂肪酸捕收剂浮选白钨矿的性能关系,并且从脂肪酸烃基中的双键数目、碳链的长短、加入羟基、碳链异构这4个方面研究了脂肪酸类捕收剂对白钨矿捕收性能的影响,并通过测量白钨矿的吸附量和热力学△G-pH计算来说明存在这种差异的可能性。实验结果表明：不同结构的脂肪酸类捕收剂对白钨矿的捕收能力存在差别。不饱和脂肪酸不饱和程度越大,浮选效果越好;脂肪酸碳链碳原子数目在一定范围内时,其浮选白钨矿的效果随着碳原子数目的增加而加强;碳链异构的烃链不饱和脂肪酸比正构烃链的不饱和脂肪酸,浮选白钨矿的效果要好些;当脂肪酸分子引入羟基时,浮选效果反而不如没有羟基的脂肪酸。     

煤泥选择性絮凝浮选中聚丙烯酰胺的作用机制

测试了阴离子型低相对分子质量聚丙烯酰胺PAM A401作用对煤及高岭石絮体表观粒径分布、样品红外光谱以及表面润湿性的影响,并通过浮选速度实验验证PAM A401的作用效果.研究表明,12 mg·L-1PAM A401且循环搅拌11 min时,煤絮体累积粒度分布达到10%、50%和90%时对应的粒径分别是高岭石絮体的6.86、2.22和2.45倍,呈较好的絮凝选择性.吸附PAM A401后,煤的亲水性官能团特征峰增强,疏水性降低;高岭石的亲、疏水性官能团均有增加,疏水性略高.与常规浮选相比,选择性絮凝浮选实验的浮选速率较大,捕收剂用量降低30%.浮选3 min时,选择性絮凝浮选实验的可燃体回收率为81.57%,较常规浮选实验高3.64%,精煤灰分相当.PAM A401虽使煤颗粒的表面润湿性降低,但微细粒煤颗粒表观粒径增大的效应促进微细粒煤泥的分选.      

硫酸铝作为活化剂的浮选试验及其活化机理探讨

某钨钼和萤石共生矿石的浮选试验中,考察了硫酸铝、硝酸铅和氟化氢铵对白钨矿、钨钼钙矿、钼钙矿和萤石的活化作用。结果表明:硫酸铝的活化作用显著优于其他2种。通过对硫酸铝活化机理探讨,可知其活化作用在于铝离子可沉淀于矿物表面,并与捕收剂分子反应生成难溶盐,形成疏水性膜,从而使矿物颗粒粘附在气泡上并随其上浮。     

甲基取代基对阳离子捕收剂浮选性能的影响

浮选药剂的结构对其性能具有重要影响,向现有药剂中引入适宜的取代基,基于取代基效应实现药剂浮选性能的改变,已成为高性能浮选药剂开发的重要手段。为明确甲基对阳离子捕收剂浮选性能的影响,以十二胺（DDA）、N—十二烷基甲胺（MDA）、N,N—十二烷基二甲基叔胺（DMDA）、十二烷基三甲基氯化铵（DTAC）为样本,通过浮选试验考察了甲基取代基引入对药剂捕收能力和浮选选择性的影响规律,并基于药剂静电势图和极性基范德华体积的计算,明确了甲基对阳离子捕收剂浮选性能的影响机制。浮选试验结果表明,随着阳离子捕收剂中心原子中甲基的引入,石英和赤铁矿单矿物的浮选回收率逐渐降低,但人工混合矿的分离指数升高。给电子基团甲基的引入,改变了阳离子捕收剂的电荷分布密度,促使中心原子上的电荷数增加,削弱了药剂与矿物表面的静电吸附强度,从而导致浮选回收率下降。同时,甲基引入后,阳离子捕收剂中极性基尺寸变大,从而增加了药剂与矿物表面作用的空间位阻,增强了阳离子捕收剂的浮选选择性。      

酚醛树脂基铝电解用炭素材料的静态浸润过程

选取电煅煤和沥青焦为骨料,研究工艺参数和原料特性对酚醛树脂与炭素骨料静态浸润性能的影响,并通过FT-IR、XPS分析炭素骨料与酚醛树脂的表面官能团和元素赋存形态。结果表明,酚醛树脂对电煅煤/沥青焦的静态浸润性随着骨料粒度、加热温度、加热时间的增加而逐渐增大,随着振动次数的增加呈现先增加后减小的变化趋势。酚醛树脂对电煅煤/无烟煤的浸润性能受到原料化学组成、晶体结构及流变性能的共同影响,酚醛树脂在炭素骨料表面的铺展和扩散取决于表面官能团的相互作用（氢键、静电键及酸碱中和反应）。     

强搅拌调浆在金川硫化铜镍矿浮选中的作用机制研究

通过浮选试验、粒度分析测试和扫描电镜(SEM)分析,研究强搅拌调浆在金川硫化铜镍矿浮选中的作用,并考察其作用机制。浮选试验结果表明:强搅拌调浆能够提高金川硫化铜镍矿的浮选指标,强搅拌的时间越长,强度越强,金川硫化铜镍矿的浮选指标越好。固定调浆时间为20 min,当调浆强度从1950增加到2800 r·min-1时,镍的浮选回收率从81%增加到87%。金川硫化铜镍矿中的蛇纹石矿泥与硫化矿物颗粒表面电性相反,容易通过静电吸引作用吸附在硫化矿物表面形成矿泥罩盖层,细颗粒矿泥的罩盖阻碍了硫化矿物颗粒和气泡的粘附,降低了硫化矿物的浮选回收率。粒度测试和扫描电镜分析结果证实了金川硫化铜镍矿中的粗颗粒硫化矿物表面罩盖有细颗粒矿泥,矿泥的主要成分为蛇纹石等含镁硅酸盐矿物。对矿浆进行强搅拌调浆能够脱附硫化矿物表面罩盖的蛇纹石矿泥,蛇纹石矿泥粒度越粗,越容易从硫化矿物表面脱附,而粒度极细的蛇纹石矿泥较难脱附。强搅拌的强度越强,时间越长,硫化矿物表面罩盖的蛇纹石矿泥数目越少,越容易与浮选气泡粘附,浮选回收率越高。     

精炼塔尔油在磷酸盐浮选中的应用及QCM-D吸附研究

对Georgia-Pacific公司新开发的精炼塔尔油捕收剂GP193G75在佛罗里达CF Industries公司的磷酸盐浮选中应用效果进行了研究.采用具有测定能量耗散功能的石英晶体微天平(QCM-D)研究了GP193G75在羟基磷灰石(HAP)表面的吸附过程,并与油酸钠和CF Industries公司目前所用的药剂粗塔尔油脂肪酸PR1进行了比较.考察了捕收剂用量、pH值、柴油用量和浮选时间等参数对GP193G75浮选效果的影响.结果表明,当pH值为10,捕收剂用量为0.45kg.t-1,且与柴油用量的比例为9∶8时,GP193G75的正浮选P2O5回收率最高可达到91.7%.QCM-D测定结果显示,GP193G75与油酸钠有相似的吸附过程,但GP193G75比油酸钠更易于且更快在羟基磷灰石表面吸附.在相同条件下,与PR1相比,GP193G75形成的吸附层密度更大,而且吸附更牢固,因此可以使羟基磷灰石表面的疏水性更强,从而得到较高的浮选效果.     

浮选过程中颗粒--气泡黏附作用机理及研究进展

系统分析总结了浮选过程中颗粒与气泡的黏附概率模型、EDLVO理论、颗粒-气泡集合体的受力分析、影响因素分析和颗粒-气泡黏附的研究进展.基于接触时间、感应时间的方法和能量势垒的方法,分别从动力学和热力学的角度分析总结了黏附概率模型,并从动力学和热力学的角度解释了颗粒大小、气泡大小、颗粒疏水性、颗粒表面粗糙度和溶液pH对黏附概率的影响,对静态环境和湍流环境中颗粒-气泡集合体进行了受力分析,颗粒和气泡的黏附力有毛细作用力、液体静压力和浮力,静态环境中的脱附力只有重力,但是湍流环境中的脱附力还包括振荡力和离心力.很多研究学者利用先进的仪器和检测手段对颗粒-气泡的黏附做了大量的研究,取得了大量研究成果.颗粒-气泡黏附作用过程相当复杂,试验研究时简化了作用条件,目前理论不能满意解释黏附过程,需要结合实际进行更深层次、更全面的研究.      

HNO_3氧化改性对国产PAN基炭纤维表面成分和组织结构的影响

采用HNO3对国产PAN基炭纤维进行表面改性处理。采用氧氮氢联测仪、XPS、FTIR、Raman、SEM检测改性后炭纤维表面活性基团和微观结构的变化。结果表明:经55℃氧化处理后,纤维质量减小;而经80℃和100℃处理后,纤维质量增加。氧化处理后,纤维整体和表面的氧含量都增加,整体的氧含量明显低于表面,而增幅却高于表面。在氧化过程中,—OH、C—O、C=O、COOR及吡啶型氮、四价氮、—NO2的生成与转变同时发生,形成了低活性基团向高活性基团转变的动态过程,且随氧化温度升高或时间延长,纤维表面无序度降低。     

工业化制备分散性良好的纳米银粉

采用丙三醇作为还原剂,加入有机高分子分散剂0.5%~1.0%,在碱性环境介质下,将AgNO3还原制备纳米银粉。在银粉脱水干燥以前,对纳米银粉进行表面改性,通过油酸不饱和基、脂肪羧酸基团或多元醇羟基基团有机官能团取代颗粒表面的所有非架桥羟基及薄层水膜,可有效防止粉末在过滤、干燥过程中发生聚结。该种纳米银粉制备工艺简单、方便、批量大、团聚小、易分散,已在电子工业得到大量应用。     

Physico-Chemical Factors Affecting the Separation of Cassiterite and Fluorite by Froth Flotation

Abstract

Cassiterite flotation is achieved industrially with some anionic collectors. However, the presence of fluorite in primary tin ores usually poses a problem in relation to the selectivity between the two minerals. In this work, a comparative study was undertaken involving adsorption, electrophoretic mobility and suspension stability measurements of both cassiterite and fluorite as a function of oleic acid concentration. These properties are discussed with reference to the calculated free energy of adsorption equation pending of oleic acid on the two minerals. Hallimond tube flotation tests conducted with the two minerals showed a distinctly higher floatability of fluorite at low oleic acid concentration. Micro-flotation studies using Procol CA-540. a sulphosuccinamate collector, presented similar results, indicating that fluorite can be floated selectively from cassiterite at low collector concentration and neutral pH.     

Sensitivity of Staphylococcus aureus to unsaturated fatty acids

Some unsaturated fatty acids were found to inhibit the growth of Staphylococcus aureus. Their effectiveness was related both to the degree of unsaturation and to the configuration of the molecule about the double bonds. Both linoleic acid and linolenic acid increased the proportion of plasmid-negative bacteria in a growing culture of bacteria containing a penicillinase plasmid. This was not due to a 'curing' effect of the fatty acids but was the result of greater sensitivity of the growth of bacteria containing penicillinase plasmid to inhibition by the unsaturated fatty acids. The presence of a plasmid conferring resistance to tetracycline, however, did not make the bacterium more sensitive to inhibition by linoleic or linolenic acids.     

Flotation of diaspore and aluminosilicate minerals applying novel carboxyl hydroxamic acids as collector

Three novel carboxyl hydroxamic acids including ortho-carboxyl tetrachlorobenzohydroxamic acid (OCB), ortho-carboxyl hexahydrobenzohydroxamic acid (OHB) and ortho-carboxyl tetrahydrobenzohydroxamic acid (OTB), were synthesized and tested as collectors for flotation of diaspore, kaolinite and illite contained in diasporic bauxite from China. Subsequently, their flotation mechanism to diaspore and aluminosilicate minerals was investigated by zeta potential measurements and FT-IR spectrum checking. The results of flotation experiments show that by using carboxyl hydroxamic acid as collectors, the pulp pH value has significant influence on their collecting performance as the floatability of either diaspore or aluminosilicates varies sharply with their change, and the appropriate pH value for the flotation of diaspore gets close to neutral condition where diaspore presents good floatability while kaolinite and illite exhibits poor performances. Additionally, the floatability of diaspore and aluminosilicates is in the descending order of diaspore, kaolinite, and illite in the presence of three collectors, and their collecting capacity to three minerals is in the ascending order of OTB, OHB and OCB. Of three synthesized carboxyl hydroxamic acids, OCB has the strongest collecting capability to diaspore while relatively weak to aluminoscilicate minerals, whose good selectivity for the flotation between diaspore and aluminosilicates is possibly suited for direct flotation desilication of diasporic bauxite. Moreover, the optimum pH value for diaspore flotation associated with FT-IR spectrum and zeta potentials indicate that the adsorption interaction between the synthesized collectors and diaspore is dominantly a kind of chemical bonding one in the form of three cycle chelate rings due to the coordination of carboxyl and hydroxamate to the metal aluminum atoms, where the oxygen atoms contained in carboxyl and hydroxamate of the polar group have the stereo conditions to form five to seven membered rings. By contrast, the adsorption interactions of the carboxyl hydroxamic acid on the surfaces of aluminosilicate minerals are mainly dominated by means of hydrogen bonds.     

Flotation Mechanism of Wolframite with Varied Components Fe/Mn

Wolframite is a series of minerals belonging to the isomorphic (Fe, Mn)WO₄ with varied Fe/Mn ratios, for which the floatability changes with its composition. In this work, the effects of composition on floatability were studied using micro flotation, collector adsorption tests, infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that with an increasing Fe/Mn ratio, the flotation recovery of wolframite increased when using benzohydroxamic acid (BHA) as collector, but decreased when sodium oleate (NaOl) was applied. The chemisorption differences of these collectors were observed on the surface of wolframite, i.e., adsorption of BHA is greater at the surface of high-Fe wolframite, while NaOl is more easily adsorbed on high-Mn wolframite. Moreover, XPS analysis indicates that a new ferric product was generated on the surface of wolframite in the presence of BHA. In contrast, a new manganese product was formed after the addition of NaOl. These results demonstrate that Fe is the adsorption site for BHA, while Mn is the site for NaOl.     

Elaboration of the messenger transport organizer pathway for localization of RNA to the vegetal cortex of Xenopus oocytes

1. Two experiments were designed to study the influence of free fatty acid content and degree of saturation of free fatty acids and neutral fat on digestibility of added fats and fatty acids. Sunflower oil and tallow were used as neutral fats, and palmitic, stearic, oleic and linoleic acids as free fatty acids. Fat inclusion was 80 g/kg and mixtures of each fat and each free fatty acid were prepared in the proportions 100:0, 70:30 and 40:60. 2. Experimental diets were evaluated for fat and fatty acid digestibilities with broiler chickens at 21 d of age. The metabolisable energy of fat was calculated from the product of digestibility and gross energy. Increasing concentrations of saturated free fatty acids decreased the ME of added fat, whereas unsaturated free fatty acids did not significantly affect the ME value of added fat. 3. Digestibilities of individual fatty acids were analysed by linear regression with rate of inclusion of free fatty acid in the fat blend: palmitic and stearic acids gave a negative slope, whereas oleic and linoleic acids gave a slope not statistically different from zero. Because slopes for saturated fatty acids did not differ between the sunflower oil and tallow treatments, synergism between unsaturated and saturated fatty acids was not detected.     

Collector Chemistry for Bastnaesite Flotation – Recent Developments

ABSTRACT

One of the most important aspects in any flotation separation is the choice of the flotation collector. For this reason, based on both our recent research developments and the results from other researchers, this detailed review focuses on fundamental surface chemistry features of fatty acid, hydroxamate, phosphonate, and phosphate as collectors for the flotation recovery of the rare earth (RE) mineral, bastnaesite, including selectivity considerations with respect to separation from calcite, barite, and quartz.     

Improved Flotation Separation of Apatite from Calcite with Benzohydroxamic Acid Collector

ABSTRACT

Apatite (Ca₁₀(PO₄)₆F₂) is the most important phosphate mineral, and flotation is the main beneficiation method to separate apatite from its major gangue mineral calcite (CaCO₃). Till date, fatty acids and their salts have been widely used as collectors in the apatite/calcite flotation separation due to their low cost and strong collecting ability, but their selectivity is limited. Therefore, screening or designing a selective collector becomes the key to the efficient separation. In this work, an attempt was made to utilize benzohydroxamic acid (BHA) as the collector for the selective separation of apatite from calcite without any depressant. The single and mixed binary mineral flotation experimental results prove the excellent selectivity of BHA in the apatite/calcite flotation separation. Zeta potential measurement results indicate a greater affinity of BHA on the apatite surface than calcite, which is also confirmed by the higher adsorption energy of BHA on the apatite surface based on the first-principle density functional theory calculations. The X-ray photoelectron spectroscopy analysis shows that the selective chemisorption of BHA on apatite over calcite is due to the stronger reactivity and the higher density of Ca²⁺ ion on the apatite surface than calcite. This work shows that surfactants of hydroxamic acid type can be an ideal collector for phosphate mineral flotation.     

The occurrence of furan fatty acids in Isochrysis sp. and Phaeodactylum tricornutum

Two algae species with a fundamentally different fatty acid composition were investigated for their furan fatty acid (F-acid) content. Isochrysis sp. contains different F-acids with a pentyl side chain in alpha'-position of the furan ring. In consideration of its fatty acid composition which is predominated by compounds with a C-18 chain, this result supports the assumption that pentyl-F-acids derive from linoleic acid. In contrast, only F-acids with propyl side chain were found in Phaeodactylum tricornutum. The low content of C-18 fatty acids in this diatomae contradicts the previous hypothesis that linolenic acid is the precursor of propyl-F-acids. But the presence of (n - 4) unsaturated fatty acids with 16 carbon atoms in Phaeodactylum tricornutum suggests that propyl-F-acids are synthesized from 9,12-hexadecadienoic acid in a very similar biogenetic pathway than pentyl-F-acids.     

Unsaturated fatty acids induce inhibition of the A1-adenosine receptor in rat brain membranes

We examined the effect of fatty acids (FA) and some other bioactive lipids on A1-adenosine receptor (A1-AR) binding in rat brain membranes using the selective agonist (3H)-N6-cyclohexyladenosine [(3H)CHA]. A significant reduction in ligand binding was observed at micromolar concentrations of unsaturated fatty acid with the following potency: oleic < arachidonic < decosaenoic < linoleic < linolenic acid. The other tested compounds: lysophospholipids, platelet-activating factor (PAF) and GM1-ganglioside were without effect on A1-AR expression. The inhibition with unsaturated FA was non-competitive and partially reversed by albumin. The A1-AR agonist binding inhibition evoked by unsaturated FA in many respects is similar to that observed previously following ischaemia and may be contributory to the increased excitability of post-ischaemic brain.     

微细粒辉钼矿疏水聚团浮选研究

研究了微细粒辉钼矿疏水聚团浮选的影响因素,即:非极性油、矿浆pH值以及动能输入.浮选试验结果表明:非极性油的添加和适当的动能输入能在很大程度上强化辉钼矿颗粒疏水聚团的效果.同时,微细辉钼矿颗粒发生疏水聚团的最佳浮选环境为弱酸性条件,而在碱性条件下,会恶化微细颗粒的聚团效果,从而降低微细粒辉钼矿的可浮性.