Dispersion—flocculation studies on a Goethite-clay system

Dispersion–flocculation studies on a Goethite–clay system using flocculants were carried out as a function of flocculant concentrations, pH of slurry, time of agitation and dispersant dosage. Also, the effects of pH and polymer concentrations on the adsorption behaviour of the system were investigated. Results show that well flocculated goethite was preferentially obtained from 4% goethite/kaolinite clay suspensions, with 50 ppm causticised starch in the slurry at pH values of 3–11·5 and with 50 ppm polyacrylamide at pH values of 3–8. Good flocs were also obtained on flocculation of the goethite suspension with 50 ppm polyacrylamide at pH values of 5–7, while the kaolinite suspension did not respond to the same dosage of causticised starch in the same pH range. Results further reveal that for the goethite/kaolinite suspension, the best results was obtained with 50 ppm polyacrylamide at pH values of 7–10. Based on the data generated in the study, it was concluded that causticised starch is a better flocculant than polyacrylamide for goethite suspensions although polyacrylamide is an excellent flocculant for kaolinite suspensions.     

Preparation of Nanosized Hematite Particles by Mechanical Activation of Goethite Samples

Nanosized single crystals of hematite with a very narrow particle size distribution were prepared by mechanical activation of two different goethite samples. Both goethite samples transformed completely into hematite after 70 h grinding time. Transmission electron microscopy showed that the final particles were spherical in shape and of ∼17 nm average particle size. This particle size was coincident with that estimated from specific surface measurements, indicating that the hematite samples consisted of nonporous and nonaggregated particles. The crystallite size, calculated from the broadening of the XRD peaks, in the hematite samples indicated that particles consisted of single crystals. No influence of the precursor was observed in the products, so both goethite samples yielded identical rounded single crystals with a narrow particle size distribution.     

含锰溶液中Fe、Pb杂质的脱除工艺研究

对浮选方铅矿精矿和软锰矿两矿法共同浸出含锰溶液中Fe、Pb杂质的净化工艺条件进行了研究。得出了在pH为4时,采用针铁矿法除铁,其除铁效果已达到要求。在温度为4513、pH为4、硫化剂／方铅矿为1／20％时,采用硫化法除重金属,浸出液中的Fe、Pb杂质含量达到1mg／L,已经满足制备工艺要求。     

Preparation of nanostructured goethite by chemical precipitation in a rotating packed bed

Nanostructured goethite was successfully prepared at 25°C by chemical precipitation in the rotating packed bed in which the rotational speed was 1800 rpm, the flow rate of aqueous FeCl₃ with a concentration of 0.3 mol/L was 0.5 L/min, and the flow rate of aqueous NaOH with a concentration of 0.9 mol/L was 0.5 L/min. The prepared nanostructured goethite had an average crystallite size of 20 nm and a needle shape with a mean length of 500 nm. Moreover, the prepared nanostructured goethite exhibited the Type-III isotherm for N₂ adsorption-desorption with a BET specific surface area of 23 m²/g. The rotating packed bed with the chemical precipitation approach yielded a rate of preparation of nanostructured goethite of about 19 kg/day. The adsorption capacity of the prepared nanostructured goethite was examined using the adsorption of dyes in water. Based on the Langmuir model, its maximum adsorption capacity for Reactive Red 2 was 29.1 mg/g, and its maximum adsorption capacity for Orange G was 24.5 mg/g. Accordingly, the prepared nanostructured goethite can be used as a potential adsorbent for removing dyes from water.     

Negative effects of dissolved organic compounds on settling performance of goethite in Bayer red mud

Goethite, a typical iron-containing monomineral in red mud, was synthesized under the simulated Bayer digestion condition during the alumina production. The effects of dissolved organic compounds including sodium formate, sodium acetate, sodium oxalate, sodium salicylate and disodium phthalate on the settling performance of goethite slurries were studied. The settling performance of the slurries was also investigated with the addition of self-made hydroxamated polyacrylamide flocculant (HCPAM). The adsorption mechanism of dissolved organic compounds on the goethite surfaces was studied by FT-IR and XPS, respectively. The results show that the addition of organic compounds lowers the settling performance of the slurries and a deterioration in settling performance is observed in the order of sodium oxalate > sodium salicylate (～ disodium phthalate) > sodium formate > sodium acetate. Moreover, HCPAM can efficiently eliminate the negative effects of sodium formate, sodium acetate and sodium oxalate on the settling performance of the goethite slurries, but it can only partially improve the settling performance of the goethite slurries containing sodium salicylate or disodium phthalate. FT-IR and XPS results show that these organic compounds are chemically adsorbed on the goethite surface.     

Destruction and removal efficiency of PICs by various iron ores during sintering-exploratory testing

Worldwide,iron ore sintering is the largest industrial single source of dioxin emissions^1-3.Conversely, some ores may help in reducing emissions,because of their aptitude of（a） adsorbing and（b） oxidising or decomposing TOC and dioxins^4,5.Such dioxin abatement abilities were tested for five types of ores,representing major ore origins（Australia,Brazil,and South Africa ）,minerals（magnetite,haematite,goethite,pisolite ）,and properties,e.g.porosity,and Loss on Ignition（LOI） values.In total,11 exploratory experimental runs were conducted on iron ores,to test the oxidation in air of four different organic trace test substances:acetone, chloroform,n-hexane,and toluene contained in a test gas were led simultaneously over the ore over a preestablished temperature program.Each test comprehends a first part with a programmed temperature rise,a brief soaking period at the temperature maximum（>400℃）,and a ballistic cooling part.The concentration of the four organics is continuously monitored by Mass Spectrometry（MS） operating in a full-scan mode（m/e < 100）. Exploratory experiments allowed differentiating the ores tested according to the Destruction & Removal Efficiency（DRE） attained.To check the results the products of oxidation in the effluent were sampled on Tenax and identified.Also,the dioxin load remaining on several test residues was examined and found to be quite limited （pg I-TEQ/g）.     

Eu(Ⅲ)在针铁矿及磷酸根改性针铁矿上的吸附

采用静态法研究了Eu(Ⅲ)在针铁矿及磷酸根改性的针铁矿上的吸附行为,测定了（25±1）℃下的吸附边界及吸附等温线,探讨了FA的存在对吸附的影响。实验结果表明,pH对吸附的影响较大,pH＝4～6为Eu(Ⅲ)在针铁矿上的吸附边界,磷酸根改性的针铁矿的吸附边界明显向低pH移动。Eu(Ⅲ)在针铁矿及磷酸根改性的针铁矿上的吸附更符合Freundlich等温线。Eu(Ⅲ)在针铁矿上的吸附主要是通过表面配位进行的。     

某印尼低品位红土镍矿的微观结构及晶体化学(英文)

为深入研究红土镍矿的镍富集原理,利用电子显微镜、扫描电镜、X射线衍射分析以及电子探针微区分析对含镍0.97%的某印尼低品位红土镍矿的工艺矿物学进行研究,以了解镍钴有价金属的分布及赋存状态。实验表明:该矿样主要矿物为针铁矿(含量约为80%),镍含量约为0.87%;含镍、铁、镁的结晶水硅酸盐矿物((Mg,Fe,Ni)2SiO4)的含量约为15%,如利蛇纹石((Fe,Ni,Al)O(OH))和橄榄石((Mg,Fe,Ni)3Si2O5(OH))等,镍含量约在1.19%左右;其它含量较低的物相为赤铁矿、磁赤铁矿、铬铁矿和石英等,这些矿物的镍含量极低。钴土矿是含钴矿物,分析发现该矿物往往有较高的镍和钴含量。微观检测发现:红土镍矿微观结构复杂,不同矿物之间共生普遍,主要矿物的微观结构松散,因而传统选矿方式很难实现镍的富集。     

Mineral‐induced degradation of halogentated organic pollutants from aquatic systems

Several laboratory tests were conducted to examine Fe(II) as an enhancing agent in the dehalogenation of CHC1₃ in batch mode. The CHC1₃ degradation was found to be negligible when only Fe(II) is present as a reductant in the (aqueous) reaction system. However, in the presence of Fe(II) coated goethite, the rate of CHC1₃ degradation was enhanced to some extent. This observation can be explained by considering a surface mediated electron transfer step in the overall process. Substantial increase of the degradation rate was observed when the goethite particles first coated with fulvic acid were employed in the adsorption of Fe(II) for the degradation of CHC1₃.