Utilization of Coal Gangue and Copper Tailings as Clay for Cement Clinker Calcinations

In order to avoid environmental pollution from Coal gangue （CG） and copper tailings （CT）, the utilization as cement clinker calcinations was experimentally investigated. Low-calcium limestone was also selected as another raw material. The clinker component and microstructure were analyzed by XRD and SEM. The experimental results showed that qualified cement clinker could be generated by substituting CG and CT compound for clay. While mixed with high-calcium limestone and low-calcium limestone, the calcinations temperature were 50 ℃ or 100 ℃ lower than that of clay. CT and CG contain oxygen-rich minerals and potential of geological rock energy. The energy of CG performs functions and drops down sintering temperature. The calcination time was shortened and the clinker sintering coal consumption reduced while substituting CG and CT for clay, and also served the reutilization of low-calcium limestone, CG and CT.

Recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation: process optimization and mineralogical study

Currently, the majority of copper tailings are not effectively developed. Worldwide, large amounts of copper tailings generated from copper production are continuously dumped, posing a potential environmental threat. Herein, the recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation was conducted; process optimization was carried out, and the corresponding mineralogy was investigated. The reduction time, reduction temperature, reducing agent (coal), calcium chloride additive, grinding time, and magnetic field intensity were examined for process optimization. Mineralogical analyses of the sample, reduced pellets, and magnetic concentrate under various conditions were performed by X-ray diffraction, optical microscopy, and scanning electron microscopy-energy-dispersive X-ray spectrometry to elucidate the iron reduction and growth mechanisms. The results indicated that the optimum parameters of iron recovery include a reduction temperature of 1150A degrees C, a reduction time of 120 min, a coal dosage of 25%, a calcium chloride dosage of 2.5%, a magnetic field intensity of 100 mT, and a grinding time of 1 min. Under these conditions, the iron grade in the magnetic concentrate was greater than 90%, with an iron recovery ratio greater than 95%.

Mineralogical characterization of copper sulfide tailings using automated mineral liberation analysis: A case study of the Chambishi Copper Mine tailings

As ore grades constantly decline,more copper tailings,which still contain a considerable amount of unrecovered copper,are expected to be produced as a byproduct of froth flotation.This research reveals the occurrence mechanism of copper minerals in typical copper sulfide tailings using quantitative mineral liberation analysis(MLA)integrated with scanning electron microscopy–energy dispersive spectroscopy(SEM–EDS).A comprehensive mineralogical characterization was carried out,and the results showed that almost all copper minerals were highly disseminated within coarse gangue particles,except for 9.2wt%chalcopyrite that occurred in the 160–180μm size fraction.The predominant copper-bearing mineral was chalcopyrite,which was closely intergrown with orthoclase and muscovite rather than quartz.The flotation tailings sample still contained 3.28wt%liberated chalcopyrite and 3.13wt%liberated bornite because of their extremely fine granularity.The SEM–EDS analysis further demonstrated that copper minerals mainly occurred as fine dispersed and fully enclosed structures in gangue minerals.The information obtained from this research could offer useful references for recovering residual copper from flotation tailings.

Reaction characteristics and kinetics of gallium in chlorination roasting of copper tailings using calcium chloride

The mineral composition of copper tailings was examined, and the phase analysis of gallium was conducted for recovery of the rare scattered metal gallium from copper tailings. The reaction characteristics and kinetics of gallium in the chlorination roasting of copper tailings were investigated in a tube furnace apparatus under different conditions, including roasting temperature, quantity of chlorination agent,roasting time, and airflow. Calcium chloride was chosen for the chlorination reaction because it is highly effective for volatilization of metals. The results show that gallium mainly exists in limonites in the form of oxides, and increases in roasting temperature, quantity of chlorination agent, and roasting time are conducive to increasing the chloridizing volatilization rate of gallium. The tailings gradually melt when the roasting temperature exceeds 900℃, resulting in a decrease in the chloridizing volatilization rate of gallium. The chloridizing volatilization rate of gallium reaches 78.86%at roasting temperature of 900℃ for 40 min, airflow of 0.1 m^(3)·h^(-1), and calcium content of 33.33 wt%. Study of the reaction kinetics of gallium in chlorination roasting shows that the values of activation energy both for chemically controlled anddiffusion-controlled reactionsare44.64and11.93 kJ·mol^(-1), respectively. This indicates that the chemical reaction serves an important function in the chlorination volatilization of gallium. Taken together, the results reveal the usefulness of tailings as a source of rare metals and provide a basis for gallium recovery and environmentally friendly disposal of copper tailings.

Preparation of Agarose Sulfate and Its Antithrombogenicity

As one of the seaweed polysaccharide, agarose has received much attention because of its biocompatibility. However, its application in biomedical field was limited with its biological inertia. Modification with some functional groups is needed to obtain agarose derivatives with biological activity and expand its applications. Consequently, agarose was sulfated with chlorosulfonic acid-pyridine with formamide as dispersing agent. The orthogonal test result showed that the optimal reaction condition was the reaction time being 4 h, the reaction temperature 65 ℃ and the ratio of chlorosulfonic acid to agarose 1-4（mL/g）. Two kinds of the insoluble agarose sulfate （below 37 ℃） were synthesized with degree of substitution （DS） being 0.17 and 0.43 respectively. Infrared spectroscopy （IR） and tac nuclear magnetic resonance （13C-NMR） spectroscopy results proved that C3_6 in agarose was sulfated. Their hydrophobic property and BSA adsorption capacity rose with increasing DS, while the adsorption of lib was reduced. The anti-clotting properties of agarose sulfate were significantly improved, and agarose sulfate could protect red blood cells from deformation after adsorption of BSA. These findings demonstrate that the cold-water insoluble agarose sulfate has a promise for applications as heoarin-like material in anticoagulation or endothelial re^enera＇Lion scaffold.

Diversity of free-living nitrogen-fixing microorganisms in wastelands of copper mine tailings during the process of natural ecological restoration

Biological nitrogen fixing is an important source of nitrogen input in the natural ecological restoration of mine wastelands. The diversity of nifH genes in railings samples under different plant communities in Yangshanchong and Tongguanshan wastelands in Tongling, was analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE） approach. The nitrogen-fixing microorganism community in the upper layer of tailings of Tongguanshan wasteland discarded in 1980 showed higher Shannon-Wiener diversity index than that in Yangshanchong wasteland discarded in 1991. The diversity of nifH genes in Yangshanchong wasteland of copper mine tailings did not display a consistent successional tendency with development of plant communities during the process of natural ecological restoration. Phylogenetic analysis of 25 sequences of nifH gene fragments retrieved from the DGGE gels indicated that there were mainly two taxa of free-living nitrogen-fixing microorganisms, Proteobacteria and Cyanobacteria living in the wastelands investigated, most of which were unique and uncultured. Canonical correspondence analysis （CCA） based on the relationship between band patterns of DGGE profile and physico-chemical properties of railings samples showed that the diversity of nifH genes in different tailing samples was mainly affected by loss of ignition, water content, pH and available Zn contents of wastelands. The dominant plant species and development period of plant communities by ameliorating pH, reducing the toxicity of heavy metals, increasing organic matter and water content affected the diversity and structure of the free-living nitrogenfixing microorganisms in wastelands of copper mine tailings.

Changes in the sorption, desorption, distribution, and availability of copper, induced by application of sewage sludge on Chilean soils contaminated by mine tailings

The effect of mine tailings and sewage sludge was evaluated on sorption, desorption, availability and distribution of copper in two soils, one high （sandy soil） and one low in copper （clay soil）. In both soils contaminated by mine tailings the copper sorption capacity and the affinity of the substrate for the metal decreased substantially compared to the uncontaminated soils, however, the sorption remained always high in the clay soil substrates. In the substrates with sandy soil, the high Cu content and lower clay content were determining factors in the lower magnitude of the sorption. Similarly, metal desorption was closely related to these two parameters, and it was higher in clay soil with lower pH. In general, the application of sewage sludge favored the sorption of Cu in soils contaminated and uncontaminated with mine tailings, and in all cases desorption decreased, an effect that remained for at least 30 days. Simple extraction of Cu with CaCl2 and diethylenetriaminepentaacetic acid gave contradictory results, so a careful choice of the procedure is required, depending on the level of metal in the soil and on the acting principle of the extracting agent. In that relation, more complete information on the changes in the metal forms was obtained by application of the sequential extraction procedure proposed by the European Community Bureau of Reference.