Accelerating leaching of copper ore with surfactant and the analysis of reaction kinetics

To solve the problem of low permeability and lower extraction rates of high-mud ores, a surfactant was added as a penetrant to the pregnant leaching solution during column leaching tests. On the basis of the theories of physical chemistry and seepage flow mechanics, the mechanism by which seepage is enhanced under the effects of the surfactant was analyzed. The results show that the action modes of the surfactant were divided into four aspects: changing the wettability of the ore, reducing the viscosity of the leaching solution, adsorbing onto the surface of ore, and enhancing the permeability effect. The findings of column leaching tests demonstrated that permeability was substantially improved by the surfactant. In the later period of leaching, the permeability coefficient was two times higher than that of the control group. Meanwhile, the ore extraction rate increased by approximately 10%. During the leaching process, the surface tension of the solution did not substantially change, and that of the solution with surfactant increased slightly. The kinetics analysis of ore column leaching illustrated that the leaching processes were controlled by both internal diffusion(principal factor) and chemical reaction.

Geochronology and Geochemistry of the Late Cretaceous to Paleocene Intrusions in East Gangdese,Lhasa,Tibet and Their Tectonic Significances

In this study, we determined the granite ages in the middle to east Gangdese batholith. Zircon ages from these granites are 57.6-68.7 Ma, indicating that intrusions were formed in the Late Cretaceous to early Paleocene. The large-ion lithophile elements are highly enriched, whereas some high-field-strength elements are depleted. The Sr-Nd-Pb isotopic characteristics are similar to those of the Dianzhong volcanics in the Linzhou Basin, indicating the same origin and tectonic environment. The samples show positive εHf（t） values that are slightly lower than the values for the Linzizong volcanics, the Quxu intrusion, and other intrusions in middle Gangdese. We conclude that our samples, the Linzizong volcanics, and most main-collisional intrusions are derived from the same source with different ratios of crust and mantle input. On the basis of geological, geochemical, geochronological, and isotopic information, we conclude that the Late Cretaceous to Paleogene evolution of Gangdese can be divided into three stages. First, the collision began at 70-60 Ma, the same time as rollback of the Tethys Ocean slab. Second, during 60-50 Ma, slab breakoff triggered upwelling of the asthenosphere. Third, after 50 Ma, the Tethys Ocean slab＇s effect disappeared and the interaction between Indian and Asian crusts began influencing magmatism in Gangdese.

Sulfide mineral dissolution microbes: Community structure and function in industrial bioleaching heaps

Heap bioleaching is one of the most clean and economical processes for recovery of low-grade and complex ores, because the sulfide minerals are natural habitats for acidophiles capable of iron-and sulfur-oxidation. The most exciting advances in heap bioleaching are occurring in the field of microbiology, especially with the development of advanced molecular biology approaches. These chemolithotrophic microorganisms living in the acid mine environment fix N_2 and CO_2 and obtain energy for growth from soluble ferrous iron and reduced inorganic sulfur compounds during oxidation of sulfide minerals. The ferric iron as oxidant and sulfuric acid are a result of microbial activity and provide favorable conditions for the dissolution of sulfide minerals. Various microbial consortia were applied successfully in commercial bioleaching heaps around the world, and microbial community and activity were adapted related to the local climatic conditions, ore characteristics and engineering configuration. This review focuses on diversity of bioleaching microbes, their role in heap bioleaching processes, their community structure and function in industrial heaps and the relation to the ore characteristics and the engineering configuration, to give implications for optimizing leaching efficiency of heap bioleaching.

Linking leach chemistry and microbiology of low-grade copper ore bioleaching at different temperatures

The effects of temperature on chalcocite/pyrite oxidation and the microbial population in the bioleaching columns of a low-grade chalcocite ore were investigated in this study. Raffinate from the industrial bioleaching heap was used as an irrigation solution for columns operated at 20, 30, 45, and 60℃. The dissolution of copper and iron were investigated during the bioleaching processes, and the microbial community was revealed by using a high-throughput sequencing method. The genera of Ferroplasma, Acidithiobacillus, Leptospirillum, Acidiplasma, and Sulfobacillus dominated the microbial community, and the column at a higher temperature favored the growth of moderate thermophiles. Even though microbial abundance and activity were highest at 30℃, the column at a higher temperature achieved a much higher Cu leaching efficiency and recovery, which suggested that the promotion of chemical oxidation by elevated temperature dominated the dissolution of Cu. The highest pyrite oxidation percentage was detected at 45℃. Higher temperature resulted in precipitation of jarosite in columns, especially at 60℃. The results gave implications to the optimization of heap bioleaching of secondary copper sulfide in both enhanced chalcocite leaching and acid/iron balance, from the perspective of leaching temperature and affected microbial community and activity.

Geochronology and Geochemistry of the Tinggong Porphyry Copper Ore Deposit, Tibet

We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method.Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±0.28 Ma,15.02±0.25 Ma and 14.74±0.22 Ma,respectively.The ages of two granites are 50.48±0.71 Ma and 50.16±0.48 Ma.Light Rare Earth Elements （LREE） are enriched in the ore-bearing adamellite porphyries,which are high-K caic-alkaline and metaluminous,while Heavy Rare Earth Elements （HREE） and Y are strongly depleted,indicating an adakitic affinity.The Large Ion Lithophile Elements （LILE） of the adamellite porphyries are highly enriched,whereas some High Field Strength Elements （HFSE） are depleted.The diorite porphyry in this study is chemically similar to the adamellite porphyries,except that the Mg# of the diorite porphyry is a little higher,demonstrating more mantle contamination.Four samples from different rocks are selected for in situ zircon Hf isotopic analyses.The samples show positive εHf（t） values and young Hf model ages,indicating their derivation from juvenile crust.However,the adamellite porphyry and diorite porphyry formed in the Miocene exhibit more heterogeneous Hf isotopic ratios,with lower （Σ）Hf （t） values than the granites formed in the Eocene,suggesting the involvement of old Indian continent crust in their petrogenesis.The geochronology and geochemistry of the adamellite porphyries and the diorite porphyries indicate that they formed from the same source region in a post-collisional environment,but contaminated by crust and mantle materials in different ratios.The metallic minerals formed mainly during the older adamellite porphyry stage,but they were recycled and reactivated by the diorite porphyry intrusion.

Characteristics of Hydrogen-rich Coals in Southern China:Implications from Organic Geochemistry and Carbon Isotopic Compositions

The organic geochemical characteristics of hydrogen-rich coal in southern China were investigated synthetically through organic geochemistry and carbon isotope analyses.The results showed that the hydrogen contents of the test samples were more than 5.0% and the H/C atomic ratios were between 0.76-1.06.Samples were found to be composed mostly of Type Ⅱ-Ⅲ℃ kerogen,consistent with good hydrocarbon-generation potential.The R_(o)(0.54-1.10%)and T_(max)(430-453℃)values imply that the hydrogen-rich coals were in low maturity to mature stages.Stable carbon isotopic ratios(δ^(13)C_(org))of the samples used varied from −24.5‰ to −23.4‰,the barkinite content ranging from 13.9% to 83.3%,indicating a predominantly terrestrial origin with marine influence during coal formation.Some organic geochemical parameters showed corresponding changes as the hydrogen content increased from 5.0% to 7.0%,however,the source inputs changed significantly when hydrogen content was greater than 6.0%.Terrestrial higher plants gradually become predominant within the coal-forming materials,whereas this dominant position is not apparent at lower hydrogen contents,which is attributable to the strong seawater effect during the hydrogen-rich coal formation process.

Chalcocite(bio)hydrometallurgy-current state,mechanism,and future directions:A review

There has been a strong interest in technologies suited for mining and processing of low-grade ores because of the rapid depletion of mineral resources in the world.In most cases,the extraction of copper from such raw materials is achieved by applying the leaching procedures.However,its low extraction efficiency and the long extraction period limit its large-scale commercial applications in copper recovery,even though bioleaching has been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores.Overcoming the technical challenges requires a better understanding of leaching kinetics and on-site microbial activities.Herein,this paper reviews the current status of main commercial biomining operations around the world,identifies factors that affect chalcocite dissolution both in chemical leaching and bioleaching,summarizes the related kinetic research,and concludes with a discussion of two on-site chalcocite heap leaching practices.Further,the challenges and innovations for the future development of chalcocite hydrometallurgy are presented in the end.

Reduction behavior and kinetics of vanadium–titanium sinters under high potential oxygen enriched pulverized coal injection

In this work, the reduction behavior of vanadium–titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H2contents. Meanwhile, with the increase in CO and H2contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H2in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol. © 2017, The Author(s).

A nanoscale qualitative study on the role of sodium hydrosulfide in oxidized carrollite flotation

The surface species transformation of oxidized carrollite processing with NaHS and KBX was investigated.Flotation and contact angle tests indicate that the combination of NaHS and KBX takes a better flotation performance than adding NaHS or KBX alone.Thermodynamic analysis,X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FTIR) results confirm the stronger chemisorption of KBX occurs on the oxidized carrollite surface with NaHS,which is beneficial to remove the cobalt oxides,thus contributing to the superior floatability.Interestingly,less elemental sulfur was observed on the carrollite surface as the interaction of NaHS and KBX than adding NaHS alone.It suggests that elemental sulfur is not the main contributor to the restored floatability of oxidized carrollite through sulfidisation.This study provided a new perspective to correlate the surface species with xanthate adsorption and oxidized carrollite flotation through determining the various intermediate products.

Study on Modification and Test Technology of Nonexplosive and Irrestorable Fertilizer-grade Ammonium Nitrate

Based on a study of the relationship of ammonium nitrate （AN） explosion and its thermal stability, inert agents were added to AN for eliminating the explosive characteristic of AN and in order to be irrestorable. The results of using a large quantity of experiments and various testing technologies show that the improvement on thermal stability of modified AN is the basic reason for eliminating explosive characteristic of AN. The modification scheme was considered to have the following features： reliable and stable technology, market-demanded product, low investment and good economic returns. And during the revamping period, the normal production of AN will not be af- fected, and the economic, social and environmental benefits are good.