Selective flotation of chalcopyrite from pyrite via seawater oxidation pretreatment

The flotation separation of chalcopyrite from pyrite has attracted increasing attention due to the consumption of vast water resources and depressants.This study proposed the seawater oxidation pretreatment for non-depressant flotation separation of chalcopyrite from pyrite,as an effective and environmentally friendly strategy.Without the addition of depressants,seawater oxidation for 3 d effectively depressed pyrite flotation,with the highest recovery difference greater than 70%and a selectivity index greater than 6 between chalcopyrite and pyrite.The surface investigation showed that pyrite surface was more readily oxidized to form hydrophilic Fe oxidants/oxyhydroxides,as compared to that of chalcopyrite.Further UV-visible spectrophotometer and Fourier transform infrared spectrum(FTIR)results indicated that xanthate was less adsorbed onto the treated pyrite surface,resulting in un-floatable particles.Chalcopyrite surface was changed slightly due to seawater oxidation,thereby insignificantly affecting its flotation.The coordination theory was further used to reveal the combination mechanisms between xanthate and pyrite or chalcopyrite.This study therefore provides a promising strategy to effectively separate chalcopyrite from pyrite,especially in the freshwater-deficient area.

Peroxymonosulfate activation based on Co_(9)S_(8)@N-C:A new strategy for highly efficient hydrogen production and synchronous formaldehyde removal in wastewater

Formaldehyde(FA),as an important chemical raw material,has been widely used in many fields.However,the discharge of a large amount of FA-containing wastewater poses a serious threat to the environment and human health.Recently,the in-situ hydrogen energy release technology of hydrogen-containing stable liquid has been extensively explored due to its safe storage.Exploring a robust method to achieve FA removal and synchronous in-situ hydrogen release from FA containing wastewater is of great significant for environmental protection and energy crisis alleviation.Here,we have innovatively introduced peroxymonosulfate(PMS)activation technology into FA removal and hydrogen production simultaneously.The composite of nitrogen doped carbon coating Co_(9)S_(8)nanotubes(Co_(9)S_(8)@N-C)is employed as a proof of concept for FA decomposition and simultaneously hydrogen production based on PMS activation system.As expected,the Co_(9)S_(8)@N-C/PMS system presents much superior hydrogen production efficiency and satisfactory FA removal rate towards FA wastewater than those of common catalysis,photocatalysis and Fenton reaction in the basic condition in a wide range of FA concentration.The hydrogen yield reaches a value as high as 471μmol within 60 min,corresponding to a FA degradation rate of 30%with an initial FA concentration of 0.722 mol L^(-1).Characterizations and density functional theory(DFT)calculations suggest that the free radical process dominated by superoxide radical(O_(2)·^(-))and nonradical process dominated by singlet oxygen(^(1)O_(2)),which are induced by Co_(9)S_(8)@N-C/PMS system,are responsible for highly efficient hydrogen production via FA degradation.These generated O_(2)·^(-)and ^(1)O_(2)can extract·H from FA to form·OOH intermediate,which can further combine with the·H from water to produce hydrogen.This study provides an applicable technique for environmental purification and new energy development based on FA containing wastewater.