Influences of silver sulfide on the bioleaching of chalcopyrite, pyrite and chalcopyrite-containing ore

The effects of silver sulfide (Ag 2S) on the bioleaching of chalcopyrite and pyrite were investigated in this paper. It has been shown that Ag 2S enhanced the yields of bioleaching of chalcopyrite but inhibited the bio oxidation of pyrite. The addition of Ag 2S selectively increased the copper dissolution from the chalcopyrite containing ores in shake flasks with a recovery of 85.3% compared with 24.3% without Ag 2S, while slightly decreased the iron yields from 51% to 41.8%. The copper extraction of the chalcoopyrite containing waste rock in column leaching charged with 18 kg mass increased up to 21.7% in the presence of Ag 2S, while only 3.4% in the absence of the catalyst. The mechanism of Ag 2S catalysis could be explained well by the "Mixed potential model".

Preparation and characterization of hollow carambola-shaped silver sulfide microspheres using a microwave-assisted template-free method

A simple and convenient method, free of template, has been proposed to synthesize hollow carambolashaped Ag2 S microspheres with Ag NO3, thiourea（TU）, Na Cl and diethanolamine as reagents using a microwave-assisted method, at low temperatures of below 100 ℃. Powder X-ray diffraction（XRD）,scanning electron microscopy（FESEM） and high resolution transmission electron microscopy（HRTEM）were employed to characterize the morphology and composition of those microspheres. The results indicated that the hollow carambola-shaped silver sulfide microspheres（with high purity and homogeneous morphology） were prepared by an Ostwald ripening process. A possible formation mechanism of hollow carambola-shaped Ag2 S microspheres was proposed.

Influence of extracellular polymeric substances from activated sludge on the aggregation kinetics of silver and silver sulfide nanoparticles

Extracellular polymeric substances(EPS)in activated sludge from wastewater treatment plants(WWTPs)could affect interactions between nanoparticles and alter their migration behavior.The influence mechanisms of silver nanoparticles(Ag NPs)and silver sulfide nanoparticles(Ag_(2)S NPs)aggregated by active EPS sludge were studied in monovalent or divalent cation solutions.The aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek(DLVO)theory.The counterions aggravated the aggregation of both NPs,and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive force.Through extended DLVO(EDLVO)model analysis,in NaNO3 and low-concentration Ca(NO_(3))_(2)(<10 mmol/L)solutions,EPS could alleviate the aggregation behaviors of Cit-Ag NPs and Ag_(2)S NPs due to the enhancement of steric repulsive forces.At high concentrations of Ca(NO_(3))_(2)(10‒100 mmol/L),exopolysaccharide macromolecules could promote the aggregation of Cit-Ag NPs and Ag_(2)S NPs by interparticle bridging.As the final transformation form of Ag NPs in water environments,Ag_(2)S NPs had better stability,possibly due to their small van der Waals forces and their strong steric repulsive forces.It is essential to elucidate the surface mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide （Ag2S） nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands （Ag44（SR）30 and Agla（GSH）9） are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag2S nanoparticles with controllable sizes （4-16 nm） and switchable solvent affinity （between aqueous and organic solvents）. This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag2S nanopartides.

Mineralogical Characterization of a Polymetallic Sulfide Ore to Improve Silver Recovery

Based on the mineralogical characterization for the polymetallic sulfide ore, the way to improve silver recovery was studied. The results showed that silver was the most valuable metal whose grade was 448.82 g/t Ag, while 0.118% Cu, 1.65% Pb and 1.06% Zn may be comprehensively utilizated. The main silver-bearing minerals were argent and aregentite which accounted for 87.18% of total silver. Argentite and other metal minerals were distributed in the gangue minerals in complex forms. Argentite grains of 33.76% minus 50 μm indicated that a fine grinding scheme was necessary to enhance the degree of dissociation, and meanwhile selective grinding must be considered to prevent a complete grinding of coarse grains. The optimum regrinding fineness in the Cu flotation was determined as 73% minus 37 μm, while grains of 68.5% minus 74 μm in one-stage grinding remained unchanged as much as possible. Consequently, silver recovery increased to 2.68%, as well as the content of Pb simultaneously decreased from 7.26% to 2.68% in the Cu concentrate. From the lead pyrometallurgical point of view, recovering larger amounts of silver and lead at the expense of decreasing the grade of lead to a suitable level is not only economically viable for the plant, but also convenient for subsequent processing. Silver and lead recovery increased to 13.18% and 12.58%, respectively, while the Pb grade decreased from 53.1% to 46.12% for the Pb concentrate.

Preparation, Characterization and Properties of Graphene-silver Sulphide Hybrid

A facile and efficient strategy was reported for the preparation of graphene nanosheets-Ag2S hybrid by a simple hydrothermal process. First, Ag2S particles deposited on the surface of graphene oxide（GO） sheet. GO was then reduced by hydrazine hydrate to graphene. The results of X-ray diffraction（XRD） and Fourier transform infrared（FTIR） demonstrated the efficient reduction of GO to graphene. Transmission electron microscopy（TEM） image of the sample reveals the morphology of the architecture of graphene-Ag2S hybrid. Ultraviolet-visible spectroscopy（UV-Vis） and photoluminescence（PL） measurement were further employed to study the optical properties of the obtained nanocomposite. This work can be extended to design other graphene-based hybrid nanomaterials, and the as-grown architectures may hold promise for many applications.

水热法合成多孔Ag_2S敏化二氧化钛催化剂及其可见光催化活性(英文)

Porous Ag2S sensitized TiO2 catalysts were synthesized by the hydrothermal process.The crystallization and porous structure of the Ag2S/TiO2 composite photocatalysts were investigated by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,UV-Vis diffuse reflectance spectroscopy,and N2 adsorption.The Ag2S/TiO2 composites were mainly composed of anatase TiO2 and acanthite Ag2S.The absorption edge wavelengths of TiO2 and the Ag2S/TiO2 composite prepared with 3 mmol Na2S.5H2O were 400 and 800 nm,respectively,that is,the absorption edge of the composite had a pronounced red shift.The photocatalytic activity under visible light was investigated by the degradation of methylene blue with a UV-Vis spectrophotometer.The photocatalytic activities under visible light of the Ag2S/TiO2 photocatalysts were much higher than that of TiO2.

Template synthesis of silver indium sulfide based nanocrystals performed through cation exchange in organic and aqueous media

Heavy-metal-free silver based I-III-VI semiconductor nanocrystals(NCs),including ternary silver indium sulfide(AgInS_(2))and derivative quaternary silver indium zinc sulfide(i.e.,AgInZn_(2)S_(4))NCs,possess advantages of low toxicity,and size-tunable band gaps approaching near-infrared spectral range,which make them candidates for use in optoelectronic and biological devices.Herein,we report syntheses of AgInS_(2) based NCs starting from In_(2)S_(3) template,which have been performed both in organic and aqueous phase through cation exchange.As a result,ternary silver indium sulfide and quaternary silver indium zinc sulfide NCs are obtained in both organic and aqueous media,and confirmed to be orthorhombic AgInS_(2) NCs and hexagonal AgInZn_(2)S_(4) NCs,respectively.Furthermore,the aqueous AgInZn_(2)S_(4) NCs with red emission and low cytotoxicity are explored for the cancer cell imaging.

Defect chemistry for extrinsic doping in ductile semiconductor α-Ag_(2)S

As a new type of inorganic ductile semiconductor,silver sulfide(α-Ag_(2)S)has garnered a plethora of interests in recent years due to its promising applications in flexible electronics.However,the lack of detailed defect calculations and chemical intuition has largely hindered the optimization of material's performance.In this study,we systematically investigate the defect chemistry of extrinsic doping inα-Ag_(2)S using first-principles calculations.We computationally examine a broad suite of 17 dopants and find that all aliovalent elements have extremely low doping limits(<0.002%)in α-Ag_(2)S,rendering them ineffective in tuning the electron concentrations.In contrast,the isovalent elements Se and Te have relatively high doping limits,being consistent with the experimental observations.While the dopant Se or Te itself does not provide additional electrons,its introduction has a significant impact on the band gap,the band-edge position,and especially the formation energy of Ag interstitials,which effectively improve the electron concentrations by 2–3 orders of magnitudes.The size effects of Se and Te doping are responsible for the more favorable Ag interstitials in Ag_(2)S_(0.875)Se_(0.125) and Ag_(2)S_(0.875)Te_(0.125) with respect to pristine Ag2S.This work serves as a theoretical foundation for the rational design of Ag_(2)S-based functional materials.

Synthesis of Ag_(2)S nano-sized clusters and their chemical sensitizations in AgCl cubic and {100} tabular microcrystal imaging systems

In recent years much attention has been devoted to AgCl emulsion owing to its se-rial advantages and inimitable potential.But in the research of this emulsion a thorny problem remains unsolved till now,which is the improvement in sensitivity is always accompanied with high fog density.In this work 5 nm Ag_(2)S particles were prepared and used as novel sensitizers in AgCl cubic and{100}tabular microcrystal emulsions.The novel sensitizer shows an effective sensitizing ability for silver chloride emulsion,and it is superior to the traditional Na_(2)S_(2)O_(3) sensi-tizer because by using it comparatively high sensitivity can be obtained with lower fog density.So the above sensitizing problem is going to be effectively solved.To discover the evolution mechanism of the sensitizer clusters and explain their excellent sensitizing properties,diffuse reflectance spectroscopy(DRS)was used as a probe on the AgCl microcrystal surface.

Rationally designed synthesis of bright AgInS2/ZnS quantum dots with emission control

In the blossoming field of Cd-free semiconductor quantum dots(QDs),ternary Ⅰ-Ⅲ-VI QDs have received increasing attention due to the ease of the environmentally friendly synthesis of high-quality materials in water,their high photoluminescence(PL)quantum yields(QYs)in the red and near infrared(NIR)region,and their inherently low toxicity.Moreover,their oxygen-insensitive long PL lifetimes of up to several hundreds of nanoseconds close a gap for applications exploiting the compound-specific parameter PL lifetime.To overcome the lack of reproducible synthetic methodologies and to enable a design-based control of their PL properties,we assessed and modelled the synthesis of high-quality MPA-capped AglnS2/ZnS(AlS/ZnS)QDs.Systematically refined parameters included reaction time,temperature,Ag:In ratio,S:In ratio,Zn:In ratio,MPA:ln ratio,and pH using a design-of-experiment approach.Guidance for the optimization was provided by mathematical models developed for the application-relevant PL parameters,maximum PL wavelength,QY,and PL lifetime as well as the elemental composition in terms of Ag:ln:Zn ratio.With these experimental data-based models,MPA:ln and Ag:ln ratios and pH values were identified as the most important synthesis parameters for PL control and an insight into the connection of these parameters could be gained.Subsequently,the experimental conditions to synthetize QDs with tunable emission and high QY were predicted.The excellent agreement between the predicted and experimentally found PL features confirmed the reliability of our methodology for the rational design of high quality AlS/ZnS QDs with defined PL features.This approach can be straightforwardly extended to other ternary and quaternary QDs and to doped QDs.