Novel technology on preparation of double-layered pellets for sulfur and arsenic-bearing gold concentrates

Double-layered pellet （DLP） roasting is a novel pretreatment method for sulfur and arsenic-bearing gold concentrates. In this process, preparation of DLPs is a fundamental step which is required to produce DLPs with favorable mechanical strength and thermal stability. Studies were carried out to investigate the affecting factors and conditions on the preparation and properties of DLPs. The results show that moisture content has significant influence on DLPs preparation. With the increase of moisture content in the range of no more than 9.8%, drop resistance and compressive strength of green DLPs are raised and the pelletizing dynamics is improved accordingly. The optimum conditions are determined as moisture content of 9.8%, coating time of 14-16 min, drying temperature 〈80 ℃and drying gas velocity 〈1.2 m/s. When DLPs prepared under these conditions are roasted at 600 ℃ for 1 h, favorable removal and solidifying rates can be obtained, in which the removal rates of arsenic and sulfur are 94.38% and 82.55%, and the solidifying rates of arsenic and sulfur reach 99.62% and 99.79%, respectively. These results promise industrial application of DLP roasting.

Valence variation of arsenic in bioleaching process of arsenic-bearing gold ore

The concentration and variational trend of As3 +and As 5+,the bacterial resistance for the As 3+and As 5+and converting conditions from As3 +to As 5+were analyzed.The additive was used to prompt the bacterial leaching efficiency by changing valence state of arsenic.The results show that the concentration of As 3+ is larger than that of As 5+ in the lag phase.The concentration of As 3+ decreases in the log phase,and is lower than that of As5 +.HQ-0211 typed bacteria express better resistance for As 3+and As 5+and remain growing when the concentrations of As3 +and As 5+are above 6.0 g/L and 12.0 g/L,respectively.It is found that Fe 3+cannot oxidize As3 +singly as strong oxidant in the leaching system,but can cooperate with pyrite or chalcopyrite to do that.The oxidation of As 3+ is prompted with addition of H2O2.The bacterial activity is improved in favor of bacterial leaching efficiency.NaClO restrains the bacterial growth to depress leaching efficiency because of the chloric compounds affecting bacterial activity.

Source of Ore-Forming Fluid and Material in the Baiyun Gold Deposit, Liaoning Province, NE China: Constraints from H-O-S-Pb Isotopes and in-situ Analyses of Au-Bearing Pyrites

The Baiyun deposit is a large gold deposit at the western end of the Liaoji rift zone in Liaoning Province, which has produced both auriferous quartz-vein type and altered-rock type mineralization. The ore bodies are mainly hosted in schist from the Gaixian Formation of the Liaohe Group. A detailed field geological survey showed that the quartz-vein type gold ore bodies are distributed in the near EW-trending and occur in the extensional tectonic space of schist in the Gaixian Formation, and the altered-rock type gold ore bodies are distributed in the near EW-trending structural belt and occur near in the Gaixian Formation of biotite schist, biotite granulite, marble and the upper footwall of dike. To further elucidate the source of ore-forming fluid and material in the Baiyun gold deposit, the H-O isotopes for quartz, S and Pb isotopes, in-situ trace elements for sulfides from quartz-vein and altered-rock type mineralization were studied. The H-O isotopic δD_(V-SMOW) and δ^(18)O_(H2O) values of the auriferous quartz range were from-88.8‰ to-82.2‰ and-1.95‰ to 4.85‰, respectively, suggests that the ore-forming fluids were mainly magmatic water with minor meteoric water. The distribution ranges of in-situ S isotopic compositions of Au-bearing pyrite in the quartz-vein type and altered-rock type ores were-8.38‰–-10.47‰(with average values of-7.89‰) and 11.38‰– 17.52‰(with average values of 11.55‰), respectively, indicating that the S isotopic compositions of the two ore types were clearly different. The in-situ Pb isotopic ratios changed almost uniformly, which showed that they had the same lead isotopic source. Based on the analysis of S and Pb isotopic compositions, the metallogenic materials in the Baiyun gold deposit were primarily from deep magma, and some wall rock materials may have been mixed in the metallogenic process. Co/Ni diagram shows that most Au-bearing pyrites have magmatic-hydrothermal or sedimentary alteration properties, and Au/As ratios were between 0.001 and 0.828(the average value was 0.07), indicating that the ore-forming fluid in the Baiyun gold deposit may have been deep magma. Combining the geological, trace element, and isotopic data, as well as data from previous studies, we propose that the Baiyun gold deposit is a magmatic-hydrothermal ore deposit.