微细粒混合磁选精矿分级—分散浮选试验研究

针对东鞍山混合磁选精矿进行了预先分级—强化分散浮选试验研究，同时结合沉降试验、动电位测试、浊度测试等分析了分选效果改善的原因.在最优条件下分级—分散浮选闭路试验可获得精矿铁品位66.24%、铁回收率79.47%的浮选指标，与单一分散浮选的闭路试验相比，精矿铁回收率提高了4.47%.沉降试验和浊度测试表明，分散剂柠檬酸及粒度组成均会影响赤铁矿-石英混合矿的分散特性，柠檬酸主要吸附在赤铁矿表面从而增大矿粒间的静电斥力，优化粒度组成实现窄级别浮选则会进一步减弱矿粒间的非选择性团聚(罩盖)，为后续浮选分离创造有利条件，这也与DLVO理论及团聚动力学的分析结果基本一致.     

Solution chemistry of carbonate minerals and its effects on the flotation of hematite with sodium oleate

The effects of carbonate minerals (dolomite and siderite) on the flotation of hematite using sodium oleate as a collector were investigated through flotation tests, supplemented by dissolution measurements, solution chemistry calculations, zeta-potential measurements, Fourier transform infrared (FTIR) spectroscopic studies, and X-ray photoelectron spectroscopy (XPS) analyses. The results of flotation tests show that the presence of siderite or dolomite reduced the recovery of hematite and that the inhibiting effects of dolomite were stronger. Dissolution measurements, solution chemistry calculations, and flotation tests confirmed that both the cations (Ca2+ and Mg2+) and CO₃2- ions dissolved from dolomite depressed hematite flotation, whereas only the CO₃2- ions dissolved from siderite were responsible for hematite depression. The zeta-potential, FTIR spectroscopic, and XPS analyses indicated that Ca2+, Mg2+, and CO₃2- (HCO₃-) could adsorb onto the hematite surface, thereby hindering the adsorption of sodium oleate, which was the main reason for the inhibiting effects of carbonate minerals on hematite flotation.     

污泥化学链燃烧过程中氮迁移转化特性研究

在单流化床反应器上探究了污泥化学链燃烧过程中氮迁移转化特性。由于赤铁矿载氧体反应活性低,采用30%水泥对其改性。结果表明,水泥改性可提高污泥热解气化反应速率以及赤铁矿还原反应速率,进而提高污泥碳转化率,但是NO生成率也增加。随着反应温度的升高,污泥的碳转化率和NO生成率均增加。另外,随着水蒸气浓度的增加,碳转化率增加,同时可降低NO生成。在污泥化学链燃烧过程中,NO生成率为0.286%-0.768%,低于污泥空气焚烧氮氧化物排放量。     

寡养单胞属菌株USTB-2对赤铁矿的捕收效果及机理

对从司家营铁矿场土壤中筛选出来的非致病性寡养单胞属菌株USTB-2作为赤铁矿的捕收剂进行了研究.Zeta电位测试知该菌在较大pH范围内带负电.经菌体USTB-2作用后，赤铁矿接触角增加了3395°，表面疏水性得到了极大的提高.在pH为6，菌体添加量为60g/t时，赤铁矿浮选回收率可达到7631%.机理研究表明，菌体USTB-2表面具有的烃类物质、羧基、磷酸基团使其具有类似脂肪酸类捕收剂的特性，通过“桥联”作用促进赤铁矿颗粒之间形成絮团；这证实寡养单胞属细菌USTB-2可以充当赤铁矿捕收剂.     

Application of the Brownian dynamics method to a rod-like hematite particle dispersion

We have investigated various problems that arise in applying the Brownian dynamics method to a suspension composed of rod-like hematite particles, which have a magnetic moment normal to the particle axis direction. The accuracy and the deviation of simulation results from theoretical solutions have been discussed by comparison with the theoretical solutions that were obtained by solving the basic equations of the orientational distribution function. The characteristics of the negative viscosity are not observed to be dependent on a time interval unless a sufficiently short time interval is used. The present simulation results can satisfactorily reproduce the qualitative characteristics of the negative magneto-rheological effect that was predicted by the previous theoretical investigation. Good quantitative agreement is obtained in the range of small-applied magnetic fields, but agreement is not significantly good in the large magnetic field region. The deviation of the negative viscosity from the theoretical prediction cannot be improved by using a more accurate numerical algorithm such as moving from Euler to second-order or fourth-order Runge–Kutta. The results of the orientational distribution can well reproduce the characteristic features that the distribution has a gradual shape with low linear-like peak, which is in significant contrast to the sharp single-peak distribution of a ferromagnetic rod-like particle dispersion. The present orientational distributions are in significantly good agreement with those of the theoretical prediction in regard to the position and the height of a peak and the general shape of the overall profile. Good agreement of the present magnetisation curves with the theoretical prediction verifies that the spin rotational Brownian motion is activated at a physically reasonable level in the present simulations.     

Hematite/Polystyrene Raspberry-Like Microcomposites as Stable Support for Silver Nanoparticle Immobilization

Among the methods utilized for the preparation of raspberry-like microcomposites, due to its simplicity and universality, the electrostatically-driven deposition of nanoparticles at the surface of microparticles is especially attractive. This process, leading to the formation of a single nanoparticle monolayer, is widely reported. On the other hand, no data concerning the electrostatically-driven formation of nanoparticle bilayers at the surface of microparticles are reported. To fill this gap, the detailed investigation of the formation of silver/hematite nanoparticle bilayers at the surface of polystyrene microparticles is reported. First, the hematite/polystyrene raspberry-like microcomposites are obtained by immobilization of hematite nanoparticles under an electrostatically-driven process. The stability of hematite/polystyrene microcomposites at elevated temperatures up to 323 K is monitored using microelectrophoresis. No significant changes in the hematite nanoparticle layer coverage are observed after prolonged time of incubation. This proves the irreversible character of nanoparticle immobilization. Next, the hematite/polystyrene microcomposites are utilized as the interfaces for immobilization of negatively charged silver nanoparticles. This process is quantitatively described using electrokinetic measurements. The changes in the hydrodynamic diameter of microcomposites are also determined. Finally, the validity of the electrokinetic model used in this work for predicting the zeta potential of the silver/hematite/polystyrene microcomposites is confirmed.     

聚氧化乙烯絮凝微细粒高岭石强化赤铁矿反浮选脱硅机理研究

通过矿物浮选试验并结合激光粒度测试、扫描电镜(SEM)、矿物Zeta电位及XPS等检测方法对赤铁矿反浮选过程中聚氧化乙烯絮凝细粒高岭石的行为及机理进行了研究.矿物絮凝浮选试验表明：添加聚氧化乙烯可以提高高岭石的单矿物回收率和人工混合矿分离效率,促进赤铁矿和高岭石反浮选分离.激光粒度测试和扫描电镜检测结果表明：聚氧化乙烯不絮凝赤铁矿,但絮凝高岭石颗粒,使其表观粒径增大.Zeta电位测试和XPS分析表明：聚氧化乙烯在高岭石颗粒表面发生化学吸附,并使其Zeta电位正移.因此,开展聚氧化乙烯对硅酸盐矿物絮凝的研究对赤铁矿和高岭石反浮选分离具有意义.     

Surface areas of kaolin, α-Fe2O3 and hydroxy-Al montmorillonite

 Adsorption of eight organic molecules on kaolin, α-Fe₂O₃ and hydroxy-Al montmorillonite was studied to examine the effect of sorbate area on the values of the surface area of these materials. For each sorbent, the number of molecules at monolayer coverage per gram produced a single hyperbola when plotted as a function of the area occupied by an adsorbate. The equations of the hyperbolas are: NA=22.23 A ^0.098 for the kaolin, NA=53.70 A ^-0.399 for α-Fe₂O₃ and NA=161.81 A ^0.322 for the hydroxy-Al montmorillonite. These equations give accessible surface areas and not the true surface areas of the solids studied, which remain elusive. Received: 13 November 1997 Accepted: 24 January 1998     

Possibility of using strain F9（Serratia marcescens） as a bio-collector for hematite flotation

In this study, we characterized strain F9 and evaluated the interaction between strain F9 and hematite by scanning electron microscopy（SEM）, Fourier transform infrared spectrophotometry（FTIR）, zeta potential, flotation, and other methods. The results showed that strain F9 belongs to Serratia marcescens. This brevibacterium had CH2, CH3, and hydroxyl groups on its cell wall, which imparted a strong hydrophobic and negative charge. Adsorption of strain F9 reduced the zeta potential of the hematite surface and increased the hydrophobicity of the hematite surface, thereby generating hydrophobic hematite agglomerates. At least four groups on strain F9 interacted with the hematite surface, which contributed to chemical interactions of carboxylic groups and hydrophobic association among hydrophobic hematite particles. The possible use of strain F9 as a bio-collector for hematite flotation was proved.     

Mechanism of the formation of micropores in the thermal decomposition of goethite to hematite

The mechanisms of the formation of micropores in the thermal decomposition of goethite to hematite have been studied through the measurements of X‐ray diffraction, Brunauer–Emmett–Teller adsorption and scanning electronic microscopy, as well as the estimation of crystal cell parameters in this work. The results have shown that the thermal decomposition led to the crystal cells of goethite to be contracted along the [010] and [001] directions and to be elongated along the [100] direction, forming nano‐scale and rod‐like hematite. It was the contractions along the two directions that led to the formation of the micropores in the hematite particles. Copyright © 2015 John Wiley & Sons, Ltd.