Some aspects of the electrochemistry of the flotation of pyrrhotite

The iron sulfide mineral, pyrrhotite (Fe_(1–x)S), has long been known to be more difficult to recover by flotation from alkaline slurries than many other base metal sulfide minerals. This paper summarizes the results of an electrochemical study of the surface reactions that occur during the flotation of nickeliferous pyrrhotite in the recovery of nickel and the platinum group metals. Mixed potential measurements conducted with natural pyrrhotite electrodes in various stages of an operating flotation plant showed that the mineral potential is positive to the equilibrium potential of the xanthate/dixanthogen couple. Similar results were obtained during batch flotation experiments and in synthetic solutions in the laboratory. Cyclic voltammetric and potentiostatic current/time transient experiments were used to investigate the oxidation of pyrrhotite under various conditions. In addition, the reduction of oxygen, the reaction of copper ions and the oxidation of xanthate ions at the mineral surface were investigated. The formation of dixanthogen on pyrrhotite surfaces is thermodynamically favourable in plant flotation slurries. However the interaction with xanthate at pH values above 7 is inhibited by a surface species formed during the conditioning prior to xanthate addition. In acidic solutions copper ions react readily with pyrrhotite to form a species, possibly CuS that can be oxidized at potentials above 0.4 V. At pH 9 this species does not form and there is no electrochemical reaction between pyrrhotite and copper ions. The beneficial effects of copper ions to flotation performance appear to be related to an enhancement of the oxidation of xanthate.     

黄原酸钾含量的示波滴定

报道了用示波滴定法测定黄原酸钾含量 ,在 p H5～ 6的 HAc- Na Ac缓冲底液中 ,加入四苯硼钠 ( Na- TPB)沉淀 K+ ,过量的 Na- TPB用氯化四乙基铵标准溶液滴定 ,滴至 Na- TPB示波图切口消失为终点 ,终点直观敏锐 ,方法快速简便 ,准确度、精密度均高。标准加入回收率在 99.8%～1 0 0 .2 % ,RSD<0 .2 %     

Electrodeposition of dixanthogen（TETD） on pyrite surface

The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements.Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion,and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface.The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09×10- 6cm2/s.Using the galvanostatic technique,the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as Ja=200μA/cm2 ,β=0.203 and J0=27.1μA/cm2.     

Relationship of structure and enhanced photocatalytic activity of S-scheme BiOCl/g-C3N4 heterojunction for xanthate removal under visible light

Constructing heterojunctions is an excellent way to enhance the photocatalytic property of semiconductors. Herein, a range of S-scheme BiOCl/g-C₃N₄ heterojunctions with varying mass ratios were designed using a facile hydrothermal route, and their photocatalytic ability was assessed by degrading the ethyl xanthate (EX) under visible light (λ > 400 nm). The results showed that the degradation efficiency of BiOCl/g-C₃N₄-0.1 heterojunction for EX was up to 91.2 % within 180 min, and its apparent rate constants (K_app) were 4.3 and 11 times greater than those of BiOCl and g-C₃N₄, respectively. The experimental and characterization results revealed that the excellent photocatalytic property was ascribed to the construction of S-scheme heterojunctions. Such structure not only enhanced the visible light response but also facilitated the efficient separation of photoinduced carriers with the S-scheme transfer route, retaining strong redox-capable holes and electrons to participate in surface reactions. Furthermore, the cycling experiments indicated that the fabricated photocatalysts have great recyclability and stability. Based on the results of active substance capture, the S-scheme charge transfer model was proposed and the photodegradation mechanism of EX was reasonably elucidated. Overall, this work offers some theoretical direction for the design and construction of S-scheme heterojunctions with superior visible-light-driven photocatalytic performance.     

甲壳素黄原酸酯/聚丙烯腈复合纳滤膜的研究

甲壳素黄原酸酯溶液浇铸在聚丙烯腈超滤膜上,并与戊二醛交联制得一种新型的荷负电复合纳滤膜,研究了复合膜的制备影响因素及操作条件对膜性能的影响.0.4MPa下制备的纳滤膜对1000mg/LNa3PO4、K2SO4、Na2SO4、MgSO4、KCl、NaCl和MgCl2的截盐率分别为90.25%、89.01%、85.15%、36.42%、32.60%、28.90%和15.81%.利用复合膜对PO34-、SO24-有较高的截留率,此膜可用于脱除PO34-、SO24-等阴离子及水的净化.     

丁基黄原酸甲酸乙酯的合成及对黄铜矿浮选研究

考察了不同条件对丁基黄药合成丁基黄原酸甲酸乙酯(BXEF)的影响。研究结果表明,合成BXEF反应的最佳工艺参数为：反应温度25℃,反应时间200 min,n(丁基黄药)：n(氯甲酸乙酯)=1．04：1。在此条件下,BXEF的产率可以达到94．5%。对江西永平铜矿硫化物矿石的浮选试验结果表明,与丁基黄药相比,BXEF对硫化铜矿有更高的浮选回收率,而且铜精矿中铜的品位更高。对丁基黄药和BXEF的量子化学计算结果表明,BXEF比丁基黄药有更低的能量,稳定性更强。     

新疆某银矿选矿试验研究

针对该赋存于氧化矿中的自然银矿石，采用浮选方法进行回收。闭路试验采用-0.074mm占60%的磨矿细度，以异戊基黄药为捕收剂。通过一粗三精四扫的工艺流程，成功获得了品位为5427g/t，回收率81.91%的银精矿。该流程药剂种类少，便于简单，且满足了现场选矿指标的要求。     

Application of three xanthates collectors on the recovery of nickel and pentlandite in a low-grade nickel sulfide ore using optimum flotation parameters

One of the challenges encountered when processing nickel ore is the presence of other minerals like chalcopyrite, pyrrhotite, pyrite and amphiboles in mineral dressing. Hence, there is need to investigate the selectivity of some collectors at optimum flotation parameters (particle size, milling time, pH and flotation cell) to maximize nickel and pendlandite recovery. Three xanthate collectors, namely potassium amyl xanthate (PAX), sodium isobutyl xanthate (SIBX) and sodium ethyl xanthate (SEX), were investigated in this study. In order to achieve this aim, the physical treatment of nickel sulfide ore and percentage chemical composition of nickel sulfide ore were investigated. The analyses of the concentrates were done using x-ray diffraction (XRD) and x-ray fluorescence spectroscopy (XRF). The optimum nickel and pentlandite recovery was achieved at particle size of 64.73 µm milled for 1.5 h, pH of 9.65 and using a new flotation cell. Also, SEX collector recovered more nickel and pentlandite contents compared to PAX and SIBX collectors when optimum parameters of particle size, milling time, pH and flotation cell were considered. In conclusion, the results showed that the selectivity of SEX is the strongest and will recover more pentlandite in a complex and low-grade nickel sulfide ore.     

和谐选矿低碱度条件选锌生产实践

1990-2002 年,七宝山铅锌矿的锌浮选采用石灰 +CuSO4+ 黄药方法。该方法的特点是石灰用量很大,锌粗选 pH 值为 9.5~10.0,锌精选 pH 值为 11.5~12.0,拉锌压硫的平衡度,在操作上较难把控。自 2007 年开始,选厂自行探索选锌的新方法,通过把丁铵黑药和黄药混用,降低了石灰用量,改善了锌与硫的分离效果,在低碱度条件下,浮选出锌精矿,保证了锌回收率。经过长期的生产实践表明,低碱度条件下选锌,锌回收率提高了 3%。     

Efficient one-pot preparation of bisalkyl xanthogen disulfides from alcohols

An efficient one-pot synthetic procedure for the preparation of bisalkyl xanthogen disulfides is achieved via oxidation of the in situ generated xanthate salt in an aqueous condition using half an equivalent of molecular iodine in one pot.