The effect of the reagent suite on froth stability in laboratory scale batch flotation tests

In batch flotation tests conducted on ores from the Merensky reef, changes in froth stability invariably occur with variations in the reagent suite. The main reagents are collectors (primary and secondary), activators, depressants and frothers. Since the particles entering and leaving the froth in a batch flotation system are continuously changing, the stability of the froth can vary. Under these conditions the simplest measure of froth stability is the measure of water recovery at a fixed froth height. The batch flotation system developed at UCT allows for the separation of gangue which is entrained relative to gangue which is floated. It has been found that the presence of naturally floatable gangue (NFG) leads to froth stabilisation, whereas the presence of hydrophobic sulfide minerals may lead to destabilisation of the froth depending on the hydrophobicity (contact angle) of the sulfide minerals. This can vary with ore type since particle shape and amount of particles present can influence the extent of destabilisation. At low depressant dosages sodium isobutyl xanthate (SIBX) always results in lower froth stability than sodium ethyl xanthate (SEX). The frothing nature of dithiophosphate leads to increased froth stability and the addition of copper sulfate results in destabilised froths. Increasing depressant dosage reduces the stabilising influence of NFG and the depressant type (guar gum or CMC) also affects froth stability. Frother can be used in an attempt to overcome the destabilising effects of high depressant dosage. This work examines the effect of variations in the reagent suite and uses water recovered at a fixed froth height as an indication of froth stability in order to analyse these effects on the recovery of sulfide minerals, floatable gangue and entrained gangue.     

The response of sulphide and gangue minerals in selected Merensky ores to increased depressant dosages

Depressants are added to flotation circuits to reduce naturally floatable gangue (NFG) present in ores, but under certain conditions have been shown to affect sulphide mineral recovery, particularly guar reducing the recovery of pyrrhotite. Copper sulphate is added to increase sulphide mineral recovery, but may also activate gangue particularly in the presence of dithiophosphate. This has also been shown to vary with ore type. Previous work has shown the usefulness of analysing reagents holistically, decoupling pulp and froth effects and assessing material recovered by true flotation and that recovered by entrainment separately. This work assesses the effect of copper activation on different ores and the ability of two classes of depressants, guar gum (guar) and carboxymethylcellulose (CMC) to reduce this effect and shows that by a depressant dosage of 300 g/t almost all the NFG had been removed from the concentrate. It also evaluates the effect of depressants on the sulphide minerals and shows that pyrrhotite was most affected.     

The effect of frother blends on the flotation performance of selected PGM bearing ores

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers provides more independent control of bubble size and froth stability. This study demonstrates through the use of batch flotation tests how blending low molecular weight alcohols with commercially available frothers impacts the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.     

The effect of a new polysaccharide on the depression of talc and the flotation of a nickel–copper sulfide ore

The effect of the depressant galactomannan (KGM) on the depression of talc and the flotation of a nickel–copper sulfide ore have been investigated through microflotation, batch flotation and industrial flotation tests, zeta potential and infrared spectrum measurements. The flotation results indicated that KGM had a straining influence on the depression of talc while had little effect on nickel minerals flotation. Compared with the depressant carboxymethyl cellulose (CMC) and guar gum, the KGM increased the nickel recovery dramatically, it not only negated the need for a talc removal process, but also achieved a significant decrease in the depressant consumption by half. Zeta-potential and infrared spectrum measurements illustrated that chemical adsorption was seen between KGM and talc, and a possible weak physical adsorption was seen between KGM and pentlandite. This was the reason why KGM had high depression selectivity for talc and little depression effect on nickel minerals.     

非极性表面矿物滑石与辉钼矿浮选分离中的多糖抑制

多糖作为非极性矿物表面抑制剂应用非常普遍,但关于其抑制机理和影响其抑制的因素研究还未完善。将国内外有关采用糊精、羧甲基纤维素（CMC）、木质素磺酸盐及古尔胶抑制滑石和辉钼矿的研究进行了总结,介绍了多糖抑制剂抑制非极性表面的研究进展,并从浮选分离滑石和辉钼矿的角度分析了这4种有机抑制剂对这2种矿物抑制的影响因素和抑制效果。研究表明,多糖的抑制效果不仅与矿浆的pH值、离子强度和离子种类有关,还与多糖分子的特性有关;在2种矿物的浮选分离方面,除了木质素磺酸盐能够高效率地分离滑石和辉钼矿外,十二烷在辉钼矿表面的吸附可有效阻止木质素磺酸盐的吸附,使木质素磺酸盐也可能成为滑石和辉钼矿有效分离的抑制剂;多糖对2种矿物的抑制不能仅从吸附量方面阐释,更重要的是多糖吸附层的特性;关于多糖的吸附机理则存在争议,主要有疏水力论、静电力论、化学力论、氢键和羟基作用论,或它们的综合作用论。     

The effect of increased frother dosage on froth stability at high depressant dosages

High energy costs required to smelt low grade concentrates could be alleviated by the production of high grade concentrates. Obtaining maximum PGM recovery by the use of high dosages of polysaccharide depressants may be problematic in that a significant decrease in the stability of the froth, particularly with CMC, results. These highly unstable froths may result in restricted mass pulls and decreased valuable mineral recovery. There are a number of ways of counteracting unstable froths, such as increasing airflow rate, reducing froth height or increasing frother dosage. Although necessary to maximise PGM recovery, all of these are likely to lead to increased water recovery and dilution of the concentrate by entrained material. This work examines the effect of increasing frother dosage on the recovery of sulphide minerals and floatable gangue from a Merensky ore at varying dosages of guar gum and CMC, as well as on the recovery of entrained gangue and its dependence on the physical nature of the flotation pulp.     

Adsorption of guar gum and CMC on pyrite

The depression of pyrite in sulfide flotation by two types of polysaccharides, CMC and guar, was investigated using micro-flotation tests, zeta potential measurements and adsorption tests. Environmentally and from an occupational safety standpoint – this would be a better processing option than cyanide. The range of variables tested included molecular weight of guar, degree of substitution of CMC, pH and the concentration of calcium ions in the flotation process water. The guar gums depressed pyrite considerably even at low dosages. An optimum dosage of 10 ppm was recommended. The CMC’s were not as effective as the guar gums, and required much higher dosages to achieve pyrite depression. Within the range of CMC’s tested, lower degree of substitution was more effective than high degree of substitution. This was presumably due to lower electrostatic repulsion between the negatively charged CMC and pyrite. When calcium ions were introduced with CMC’s, the adsorption of the CMC was considerably enhanced. No such effect was observed for guar gums. Both CMC and guar gums demonstrated Langmuirian behavior in their adsorption isotherms. Two different adsorption mechanisms were displayed. The guar gum adsorption was attributed to hydrogen bonding and Bronsted acid–base interaction. The CMC was considered to occur through electrostatic interaction in the presence of calcium ions, and Bronsted acid–base interaction depending on pH.     

Use of organic polymers in the flotation of polymetallic ores: A review

Organic polymers are used in flotation for a wide range of oxides, silicates and industrial minerals as dispersants, depressants and as flocculants. Most of the investigations with polymers were conducted in this area and theories were advanced to explain the mode of adsorption on non-metallic mineral surfaces.In the area of sulphide flotation, polymers have found only limited application, although there is a great potential for the application of polymers in the selective separation of sulphide minerals. The use of polymers in sulphide flotation was not studied extensively and consequently, there are few reliable data available to explain the adsorption mechanism of polymers on sulphides.Published data on the use of polymers in flotation of sulphide minerals is reviewed in the following sections.     

改性淀粉抑制赤铁矿反浮选石英的作用机理研究

通过矿物浮选试验、动电位测定以及吸附量测试,考察了4种淀粉抑制剂对赤铁矿和石英浮选性能的影响,并探讨了其作用机理。在碱性条件下,改性淀粉抑制剂对赤铁矿抑制效果明显,且以改性玉米淀粉效果最佳,改性磷酸酯淀粉、改性羧甲基淀粉的抑制效果次之,而普通淀粉抑制作用一般。同时4种淀粉抑制剂对主要脉石矿物石英的抑制效果均不明显。pH=10~12.5条件下,改性玉米淀粉因其羟基氧和裸露在赤铁矿表面的铁元素发生了化学键合,因而选择性抑制能力最佳。分子动力学模拟表明,改性玉米淀粉片段与赤铁矿作用更为紧密,验证了改性淀粉能更好地抑制赤铁矿。     

The use of ToF-SIMS and microflotation to assess the reversibility of binding of CMC onto talc

Carboxymethyl cellulose (CMC) is commonly used as a depressant for talcaceous minerals. To assess whether CMC depressants are strongly, or weakly and reversibly bound to the surface of talc, desorption experiments were conducted on New York talc. The floatability was monitored through microflotation experiments, combined with the determination of the CMC coverage on talc by ToF-SIMS. CMC adsorption and desorption were carried out in distilled water and in electrolyte containing Ca²⁺ ions. CMC adsorption levels were higher using Ca²⁺ electrolyte, in line with the depression behavior in the microflotation tests. Washing did not affect the flotation behavior. ToF-SIMS showed that CMC coverage of the talc particles was good and the distribution homogeneous. Adsorption and subsequent desorption in distilled water however, showed a partially restored floatability after desorption, which could be related to an inhomogeneous CMC distribution on the talc surface as shown by ToF-SIMS. By additional exposure to Ca²⁺ ions CMC redistribution occurs causing depression.     

Investigation into the flotation response of a sulphide ore to depressant mixtures

The Merensky reef in the Bushveld Complex is well-known to contain a number of platinum group elements (PGEs). These PGEs are strongly associated with the sulphide minerals found in the Merensky reef. In order to recover the PGEs from the Merensky reef, a combination of reagents is used to optimise the flotation process by various operations across the Bushveld Complex. These reagents usually include; collectors, activators and depressants. The most common collectors are the xanthates, while the activator copper sulphate (CuSO₄) is most often used. The depressants, either carboxymethylcellulose (CMC) or modified guar gum (guar) are typical.This study examines the effect of blending depressants on the flotation response of a typical Merensky ore. The effect of each depressant, being guar and CMC, was examined in turn by changing the concentrations used in initial flotation tests; this was followed by blending guar and CMC in equal ratios by various procedures to determine the effects thereof. The depressants were blended in two ways: (1) premixed followed by a single conditioning stage and (2) stage wise; as primary and secondary depressants, each conditioned in turn.     

高效组合抑制剂D1对钨矿物和含钙矿物抑制性能研究

为实现钨矿物和含钙矿物浮选分离,采用一种高效的组合抑制剂,强化对萤石、方解石等含钙脉石矿物的抑制。单矿物和人工混合矿试验结果表明,组合抑制剂D1能有效地抑制萤石和方解石,而对于白钨矿和黑钨矿可浮性未产生较大影响。实际矿石试验结果表明,经一次粗选可得到WO3品位为4.56%、回收率为82.34%的钨粗精矿。并通过考察组合抑制剂D1在白钨矿、黑钨矿、萤石和方解石四种矿物表面ζ-电位的变化和M2+吸附量,初步探讨了抑制的机理。     

Reagents used in the flotation of phosphate ores: a critical review

Phosphate rock needs processing to reduce the content of gangue minerals such as silicates, carbonates, and clays to meet the requirements of the phosphate industry. Froth flotation method has been an important part of the concentration process since the 1920s and today, more than half of the world’s marketable phosphate is produced by froth flotation. The literature on the processing of phosphate rocks by flotation is critically reviewed. Commonly used collectors, depressants, auxiliary reagents, and their mixtures in the flotation of the phosphate ores were tabulated. The advantages and disadvantages of the reagent type and structure (e.g., ionic and nonionic) on flotation were criticized. Based on the literature it was concluded that using surfactant mixtures has certain advantages over single surfactant as synergistic effect between surfactant mixtures were observed at different experiments such as surface tension, contact angle, adsorption, and flotation.     

The mechanism of pyrite depression at acidic pH by lignosulfonate-based biopolymers with different molecular compositions

Electrochemical studies, adsorption isotherms and contact angle measurements were conducted to compare the effect of three lignosulfonate-based biopolymers (DP-1775, DP-1777 and DP-1778) as pyrite depressants in flotation at acidic pH. The adsorption isotherms showed that DP-1775 and DP-1778 had a higher adsorption capacity than DP-1777. The contact angle of pyrite particles was reduced by the three biopolymers in the order of DP-1778 > DP-1777 > DP-1775 at a similar adsorbed amount. These results are in accordance with biopolymers’ ability to inhibit collector adsorption in electrochemical studies. The depressing effect of these biopolymers was related to the biopolymer composition. It was found that the biopolymer molecular weight determined its adsorption capability and surface coverage. The content of functional groups was responsible for the change in contact angle. While a higher molecular weight led to greater pyrite depression, calcium ion as a counterion in the biopolymer structure also played a role.     

Depressing effect of flocculants on molybdenite flotation

The quality of recycled process water is an important issue in the flotation of Cu–Mo ores. Processing of Cu–Mo ores includes two steps: a bulk flotation where molybdenite is recovered together with Cu sulfides, and a subsequent selective flotation step where molybdenite is separated from depressed copper sulfides. Flocculants are usually employed in the middling thickeners in the copper plant, and in the Cu–Mo bulk concentrate ahead of the molybdenite plant. However, the floatability of molybdenite, similarly to other naturally hydrophobic minerals, is highly sensitive to the presence of both natural and synthetic polymers. In this work flotation tests demonstrate that conventional flocculants, high-molecular weight anionic polyacrylamides (PAM), are strong molybdenite depressants. Low-molecular weight shear degraded polyacrylamides in spite of losing flocculation efficiency maintain depressing ability for molybdenite. Also a non-ionic flocculant, polyethylene oxide (PEO), has been studied in this project. Our results indicate that PEO is an efficient flocculant for molybdenite suspensions in a wide pH range. However, similarly to polyacrylamides, the PEO flocculant also depresses molybdenite flotation.     

钛铁矿和辉石浮选分离试验研究及抑制剂作用机理

以MOH为捕收剂,水玻璃、草酸、LD-C(一种有机高分子抑制剂)为抑制剂,对钛铁矿和辉石进行单矿物浮选试验研究,并通过浮选溶液化学分析、Zeta电位测试和红外光谱测试,研究了LD-C与钛铁矿和辉石的作用机理.试验结果表明:LD-C对辉石的选择性抑制效果明显优于水玻璃和草酸,在弱酸性环境(pH=5～6)、捕收剂MOH用量...     

Investigation on alternative depressants for iron ore flotation

Iron ore concentration through flotation represents an important application of reagents in mineral processing. Nowadays all Brazilian iron ore concentrators use starch as iron oxides depressant. This study evaluated the application of other depressants, which are commonly used in other flotation systems. Six carboxymethylcelluloses, three lignosulphonates, one guar gum, and four humic acids samples were investigated in the reverse cationic flotation. Laboratory flotation tests showed that only two polymers (one carboxymethylcellulose and guar gum) reached the same performance as starch. The superior performance of these reagents was due to the presence of the glucopyranose ring. The use of polymers blends led to promising results.     

植物胶型抑制剂选矿试验探索研究

羧甲基瓜尔胶属于强抑制力、高选择性的绿色天然多糖类有机大分子抑制剂。通过对智利某铜矿矿石采用羧甲基瓜尔胶抑制剂的选矿试验研究分析了药剂的性能。试验结果表明,羧甲基瓜尔胶是滑石的有效抑制剂,药剂用量120 g/t原矿条件下,羧甲基取代度为0.12、分子量为174万的瓜尔胶表现出的选择性抑制作用最明显,其抑制作用强于羧甲基纤维素钠。     

方铅矿抑制剂在铜铅分离中的研究进展

在复杂铜铅锌多金属硫化矿浮选分离中，由于铜铅硫化矿嵌布粒度关系复杂，可浮性相近，铜铅分离历来是一个难题，而解决其分离的关键则在于高效选择性抑制剂的应用。本文从无机抑制剂和有机抑制剂两个方面详细介绍了铜铅分离常用的方铅矿抑制剂及其作用机理。无机抑制剂主要为重铬酸盐、亚硫酸类及组合抑制剂，因重铬酸盐毒性大，正逐渐被少铬和无铬工艺取代；有机抑制剂种类多、来源广、对环境污染小，小分子有机抑制剂虽选择性较好，但抑制能力欠缺；大分子有机抑制剂虽抑制能力较强，通常与无机抑制剂组合使用，但选择性不高。总体来讲，这两类方铅矿抑制剂的作用机理主要是通过物理或化学吸附作用，在方铅矿表面形成一层亲水性薄膜从而达到抑制作用。随着可持续发展和环境保护越来越被重视，绿色高效的方铅矿抑制剂将成为矿物加工领域研究的重要方向之一。      

硫化铜铅矿物分离过程铅抑制剂的研究现状与进展

硫化铜铅矿物的天然可浮性接近且在浮选时部分含铜矿物溶解的铜离子会对方铅矿产生活化,因而硫化铜铅矿物的分离是矿物加工工程领域的难点。随着社会对铜铅等有色金属的需求量增大,方铅矿抑制剂的研究工作也越来越受到重视。从无机抑制剂、有机抑制剂2方面介绍了铜铅分离浮选常用的铅抑制剂。无机抑制剂主要为亚硫酸盐（二氧化硫及亚硫酸）、重铬酸盐,重铬酸盐因有毒性和污染环境,正逐渐被少铬和无铬工艺替代。有机抑制剂主要通过络合矿浆中的活化离子、吸附于方铅矿表面使得矿物表面亲水、与捕收剂发生竞争吸附以减少捕收剂在矿物表面的吸附等方式抑制方铅矿,有机抑制剂由于低毒、高效、对环境污染小,得到推广应用。指出今后应加强抑制剂抑制机理的研究,减少重铬酸盐的使用,研发和推广新型、高效、绿色抑制剂。