Li Yun,Chang Cong,Jie Yafei,Jin Wei,Chen Yongming,Wan Xingbang,Tang Chaobo,Yang Shenghai
A promising copper–cobalt slag cleaning technique has been proposed, involving employing gypsum wastes as a sulfurizing agent to sulfurize copper, cobalt, and iron and enrich a condensed matte from copper–cobalt slag. This work thermodynamically investigated the phase conversion mechanism in the Cu 2 O–CoO–Fe 3 O 4 –FeO–CaSO 4 –C system, at the same time, calculated the equilibrium of the “matte–slag–gas.” The results show that CaSO 4 can be selectively reduced to CaS without self-decomposition to CaO and SO 2 . Cu 2 O and CoO lost in slag can be sulfurized by CaS to Cu 2 S and CoS. Fe x O y tended to stay in oxides. Whereas, in the “matte–slag–gas” equilibrium system, a matte containing Cu 2 S, CoS, FeS, Fe, Co, and Cu was obtained. In addition, industrial copper flash smelting slag was used to conduct beach-scale experiments to validate the thermodynamic modeling results and detect the copper and cobalt recovery efficiency. The experimental results reveal that more than 92% copper and 94% cobalt were recovered in matte. The sulfur and calcium in gypsum waste transferred to matte and cleaned slag, respectively. Thus, the values in the slag and gypsum wastes can be recycled simultaneously. Graphical Abstract
The vulcanization mechanism remains unclear due to the difficulty of characterization and the complexity of the vulcanization systems. In this work, a series of epoxy model systems were used to study the sulfur cleavage behavior, from which the study process of the vulcanization mechanism was significantly simplified and a brand new sulfur-only vulcanization mechanism was revealed by the FTIR and DSC analysis. Our studies suggest that thiyl radicals derived from the homolytic cleavage of sulfur play the dominant role in the vulcanization, while the heterolytic fission of sulfur cannot occur as expected because this reaction needs 200 °C. Nevertheless, sulfur anions, which are easy to be understood derived from the heterolytic cleavage of sulfur, are actually transformed from the thiol groups that are produced through the reaction of thiyl radicals abstracting α-H atoms of allyl groups in rubber, and this maybe the reason that vulcanization mechanism remains controversial for centuries.
Currently, about 10% − 20% of the world's copper production comes from bioleaching processes. On the one hand, the bioleaching residues accumulated over the years require harmless treatment. On the other hand, the gradual depletion of secondary copper sulphide ores has made refractory chalcopyrite the most important copper resource, but bioleaching of chalcopyrite has not yet achieved commercial success, and more efficient and cost-effective technologies need to be developed. To this end, the bioleaching residue-introduced thermal activation-leaching of chalcopyrite was investigated for the first time in this work. As the main or typical components of bioleaching residues, elemental sulphur, jarosite and covellite were selected as additives to chalcopyrite, which were thermally activated at 375 °C, 475 °C and 575 °C. The solubility of the activated products was evaluated using three leaching media including deionised water, dilute H 2 SO 4 (pH 1.85) and 10 wt% H 2 SO 4 , with a solid/liquid ratio of 0.5 g/10 mL. The leaching results showed that the highest Cu recoveries of the different groups were 96.10% (with jarosite added), 93.10% (with all three components added), 90.30% (with elemental sulphur added), 88.40% (chalcopyrite alone) and 88.00% (with covellite added). An improved Cu recovery of 5.32% with a significantly reduced iron leaching rate of 71.24% was obtained when all three additives were present. Combining the results of XRD, SEM, EDS, TG-DSC and predominance area diagram analysis, the sulphation mechanism of chalcopyrite induced by the thermal decomposition intermediates KFe(SO 4 ) 2 and K 2 SO 4 was proposed and the favourable sulphation atmosphere attributed to the formation of SO 2 and SO 3 was discussed. In addition, high-purity hematite was shown to be the main phase of the final solid product, achieving the simultaneous valuable and harmless transformation of the bioleaching residue.
危险品化学品经营许可证（带存储）