Arsenic Sulfide Research Articles

Preliminary analysis on roles of metal\u2013organic compounds in the formation of invisible gold

The paper comprises new analytical data on the nature and occurrence of gold in solid pyrobitumen, closely associated with the main gold-bearing sulfide arsenic ores of the Bakyrchik gold deposit (Kazakhstan), related to post-collisional magmatic-hydrothermal origin. Gold mineralization of the deposit occurs mainly in the form of an “invisible” type of gold in the structures of arsenian pyrite and arsenopyrite, and the form of gold-organic compounds of pyrobitumen in carbonaceous-terrigenous sequences of Carboniferous formation. Microscopic and electron microscopic analysis, Raman and FT-Infrared analysis, mineralogical and three-step sequential extraction analysis (NH2OH·HCl, H2O2, HNO3 + HCl) has been carried out using 9 ore samples (from 3 different types of ores) for a comprehensive study of pyrobitumen and sulfide arsenic ores focusing mainly on organic matter. The sequentially extracted precious metal content of pyrobitumen reaches up to 7 ppm gold and other metals like Ag 4 ppm, Pt 31 ppb, and Pd 26 ppb, forming metal–organic compounds, while arsenic sulfide minerals incorporate 11 ppm gold, 39 ppm Ag, 0.49 ppm Pt. The enrichment of gold associating with organic matter and sulfide ore minerals was confirmed in this study. Organic matter was active in the migration of gold and the capture of gold by pyrobitumen. Moreover, the reductive organic matter agent released gold, most likely for the sulfide arsenic ore minerals. Pyrobitumen was a decisive factor in the concentration, transportation, and preservation of gold in the deposit.

Arsenic sulfide reverses cisplatin resistance in non-small cell lung cancer in vitro and in vivo through targeting PD-L1.

BackgroundRecent studies have found that programmed death ligand 1 (PD‐L1) might be involved in chemotherapy resistance in non‐small cell lung cancer (NSCLC). Arsenic sulfide (As4S4) has been recognized to have antitumor activities and enhance the cytotoxic effect of chemotherapy drugs. In this study, we aimed to verify the relationship between PD‐L1 and cisplatin (DDP) resistance and identify whether As4S4 could reverse DDP resistance through targeting PD‐L1 in NSCLC.MethodsThe effect of As4S4 and DDP on cell proliferation and apoptosis was investigated in NSCLC cell lines. The expression of p53 and PD‐L1 proteins was measured by western blotting analysis. The levels of miR‐34a‐5p, miR‐34a‐3p and PD‐L1 in cells were measured by real‐time qPCR analysis. Mouse xenograft models were established by inoculation with A549/DDP (DDP‐resistant) cells.ResultsDepletion of PD‐L1 inhibited DDP resistance in A549/DDP and H1299/DDP cells. As4S4 was capable of sensitizing A549/DDP cells to DDP by enhancing apoptosis. As4S4 upregulated p53 expression and downregulated PD‐L1 expression in A549/DDP cells. As4S4 increased miR‐34a‐5p level in A549/DDP cells. Inhibition of p53 by PFT‐α partially restored the levels of PD‐L1 and miR‐34a‐5p. Pretreatment with PFT‐α suppressed the apoptosis rate induced by cotreatment of As4S4 and DDP in A549/DDP cells. Cotreatment of DDP and As4S4 notably reduced the tumor size when compared with DDP treatment alone in vivo.ConclusionsUpregulation of PD‐L1 was correlated with DDP resistance in NSCLC cells. Mechanistic analyses indicated that As4S4 might sensitize NSCLC cells to DDP through targeting p53/miR‐34a‐5p/PD‐L1 axis.

Speciation characterization of arsenic-bearing phase in arsenic sulfide sludge and the sequential leaching mechanisms

Arsenic sulfide sludge (ASS) is a kind of deleterious waste which contains various valuable metallic elements, such as Re and Pb, which are always associated with arsenic-bearing phases in ASS. The leaching speed and efficiency of valuable elements may depend on the phase constitution. Here, we proposed a sequential leaching method to thoroughly understand the constitution of arsenic-bearing phase and the distribution of valuable elements in ASS. The results show that five major arsenic-bearing phases exist in ASS: amorphous As2S3, crystalline As4S4, As2O3, and As atoms dissolved into the lattice of PbS and PbSO4 phases. Re is mainly distributed in As2S3 and As4S4 phases. During the leaching process, the dissolution of As2O3 particles and As2O3 layers on the surface of As2S3/As4S4 particles occurs first. Then, the reaction between As2S3/As4S4 particles and copper sulfate happens. The order of leaching sequence is As2O3, amorphous As2S3 and crystalline As4S4. The majority of Re element exists in the solution while almost all Pb element remains in the solid residues, which is beneficial for the separation and purification valuable elements individually. This work not only detailed determines the arsenic-bearing species, but also provides significant theoretical bases for extracting valuable elements from ASS.

Oxidation Treatment of Arsenic Sulfide Slag

Research & Development in Material Science Oxidation Treatment of Arsenic Sulfide Slag Li Rui-bing1*, Yao Zhi-xin1, Zhang Ting-an2* and Yu San-san1 1Shenyang University of Chemical technology, Shenyang, China 2Northeastern University, Shenyang, China *Corresponding author: Li Rui-bing, Shenyang University of Chemical technology, Shenyang, Liaoning, 110142, China Zhang Ting-an, Northeastern University, Shenyang, Liaoning, 110819, China Submission: August 06, 2021;Published: August 17, 2021 DOI: 10.31031/RDMS.2021.15.000869 ISSN: 2576-8840 Volume 15 Issue 4

Orpiment in Colonial Williamsburg: Challenges with the Identification of Yellow Arsenic Sulphides in Historic Housepaints

Orpiment in Colonial Williamsburg: Challenges with the Identification of Yellow Arsenic Sulphides in Historic Housepaints

Direct one-stage plasma-chemical synthesis of chalcogenide films doped with ytterbium

In this paper we descried the plasma-enhanced chemical vapor deposition (PECVD) approach for preparation of the arsenic sulfide thin films modified by ytterbium. Radio frequency (40.68 MHz) plasma discharge at low pressure (0.1 Torr) was used for the initiation of chemical interactions between precursors. Arsenic monosulfide (As4S4), elemental high-pure S and Yb were employed as the starting materials. The composition of the films was controlled by regulating of the temperature of the ytterbium source supplied with external heater. The Yb concentration in the Yb:AsxSy films was from 1 to 7 at%. The chalcogenide materials were also studied by Scanning Electron Microscopy (SEM), Optical spectroscopy in the range of 250-1000 nm, and Raman spectroscopy.

Chemical solidification/stabilization of arsenic sulfide and oxide mixed wastes using elemental sulfur: Efficiencies, mechanisms and long-term stabilization enhancement by dicyclopentadiene

Large amounts of hazardous arsenic sulfide (As2S3) wastes are generated in many industries. These wastes, which are extremely unstable and can partially transform into highly soluble arsenic oxide (As2O3) and then transform into As2S3 and As2O3 mixed wastes (ASOW), are difficult to be solidified/stabilized using common binders. This study proposed a thermally initiated copolymerization method employing elemental sulfur (S8) to chemically solidify/stabilize ASOW. Under thermal conditions (140–200 °C), the elemental sulfur rings break and polymerize into diradical polymeric sulfur chains (•S-(S)m-S•). The ASOW is solidified/stabilized not only by transforming As2S3 into poly(As2S3-r-S) copolymers through copolymerization of •S-(S)m-S• with As2S3 but also by transforming As2O3 into As2S3 in the presence of poly(As2S3-r-S) copolymers. However, the sulfur chain in poly(As2S3-r-S) copolymers gradually crystallizes into S8 after long-term aging, resulting in the depolymerization of copolymers. Dicyclopentadiene (DCP) greatly improves the long-term stability of the solidified body through maintaining the sulfur chain form by forming highly stable poly(As2S3-r-S-r-DCP) copolymers. The solidified body showed high compressive strength (25.7 MPa) and low leaching concentration of arsenic (<1.2 mg L−1) even after 732 days of aging. This study provides a theoretical foundation for the S8-based chemical solidification/stabilization of ASOW as well as other sulfide-containing wastes.

Deposition of Arsenic from Nitric Acid Leaching Solutions of Gold–Arsenic Sulphide Concentrates

At present, the processing of refractory gold–arsenic sulphide concentrates is becoming more relevant due to the depletion of rich crude ore reserves. In the process of the nitric acid leaching of arsenic sulphide minerals, solutions are formed containing 20–30 g/L of arsenic (III). Since market demand for arsenic compounds is limited, such solutions are traditionally converted into poorly soluble compounds. This paper describes the investigation of precipitating arsenic sulphide from nitric acid leaching solutions of refractory sulphide raw materials of nonferrous metals containing iron (III) ions using sodium hydrosulphide with a molar ratio of NaHS/As = 2.4–2.6, which is typical for pure model solutions without oxidants. The work studied the effect of temperature, the pH of the solution and the consumption of NaHS and seed crystal on this process. The highest degree of precipitation of arsenic (III) sulphide (95–99%) from nitric acid leaching solutions containing iron (III) ions without seed occurs with a pH from 1.8 to 2.0 and a NaHS/As molar ratio of 2.8. The introduction of seed crystal significantly improves the precipitation of arsenic (III) sulphide. An increase in seed crystal consumption from 0 to 34 g/L in solution promotes an increase in the degree of transition of arsenic to sediment from 36.2 to 98.1% at pH = 1. According to SEM/EDS and XRF sediment data, from the results of experiments on the effect of As2S3 seed crystal consumption, acidity and molar ratio of NaHS/As on the precipitation of arsenic (III) sulphide and the Fetotal/Fe2+ ratio in the final solution, it can be concluded that the addition of a seed accelerates the crystallisation of arsenic (III) sulphide by increasing the number of crystallisation centres; as a result, the deposition rate of As2S3 becomes higher. Since the oxidation rate of sulphide ions to elemental sulphur by iron (III) ions does not change significantly, the molar ratio of NaHS/As can be reduced to 2.25 to obtain a precipitate having a lower amount of elemental sulphur and a high arsenic content similar to that precipitated from pure model solutions.

Co-treatment of copper smelting flue dust and arsenic sulfide residue by a pyrometallurgical approach for simultaneous removal and recovery of arsenic

As the typical hazardous arsenic pollutants, copper smelting flue dust (CSFD) and arsenic sulfide residue (ASR) are produced extensively during copper smelting process, which pose significant pressure on environmental protection and green development of the copper industry. This work proposed an economic, efficient, and applicable approach to treat waste with waste, in which the simultaneous removal and recovery of As from CSFD and ASR were realized by a roasting process, with adding sulfuric acid, at a relatively low temperature (300–350 ℃). The thermodynamic analysis and experiments confirmed that the main phases of As2S3 and S0 in the ASR were used as a reductant for reducing As(Ⅴ) in the CSFD, and the introduction of sulfuric acid favorably enhanced the thermodynamic driving force and greatly lowered the reaction temperature. The results indicated that removal and behavior of As were highly dependent on the mass ratio of ASR to CSFD, roasting temperature, and H2SO4 dosage. By regulating the parameters, the species As2S3, As2O5, and arsenate were all converted to volatile As2O3, which could be captured and deposited in cold water. In the optimized co-treatment, a satisfied As removal efficiency of 96.12% was achieved, while getting the 97.03% pure As2O3.

Structure of Arsenic Sulfide Cake and Solubility of Its Alloys with Sulfur

Structure of Arsenic Sulfide Cake and Solubility of Its Alloys with Sulfur

High-power mid-IR supercontinuum generation in fluoroindate and arsenic sulfide fibers pumped by a broadband 1.9–2.7 μm all-fiber laser source

We report the experimental demonstration of high-power supercontinuum generation in step-index fluoroindate (InF3) and chalcogenide (As2S3) fibers. A home-built fiber-based laser system with a broad spectrum spanning from 1.9 to 2.7 μm and delivering an output average power of 6.15 W was used as the pump source. A time-averaged power of 2.95 W covering the entire 2–5 μm wavelength range is obtained from an InF3 fiber. Cascading the system by adding an As2S3 fiber, the spectrum was extended up to 5.58 μm. Moreover, we present a supercontinuum with an average power of 440 mW and a spectrum extended to 4.17 μm generated by an As2S3 fiber pumped directly by a broadband (2.4–2.7 μm), silica-based laser source centered at 2.55 µm. Combined with a high degree of spectral flatness, the high-output supercontinuum power highlights the potential of the developed sources for use in a wide variety of applications.

PH-dependent photochemical transformation of arsenic sulfide sludge catalyzed by Fe ions under visible light irradiation

Arsenic sulfide sludge (ASS) is a typical precipitation product of acid smelting wastewater. Previous study reported that when exposed to sunlight, the release and oxidation of As(III) in ASS were markedly accelerated. However, the key factor to trigger the photocatalytic transformation of ASS is still unclear. Herein, we revealed that the coexisting Fe(II)/Fe(III) ions were critical to promote the photo-oxidation of released As(III) under visible light. We further validated that Fe(II)-stimulated photo-oxidation mechanism of As(III) in ASS was pH-dependent. In acid conditions, OH and SO4− were promoted by Fe(II)/Fe(III) cycling catalysis with the assistance of the reductive sulfur species from ASS, e.g. S2− and SO32−, and thus accelerated the oxidation of As(III). While in neutral conditions, the nascent ferric hydroxide colloids enhanced the oxidation rate of As(III) via photo-induced ligand-to-metal-charge transfer (LMCT) mechanism. These findings help in predicting and controlling the fate of real arsenic-containing sludge in sunlit environments.

The Application of Surface Plasmon Resonance with As2S3 Waveguide for Alcohols Identification

AbstractIn a composite structure, which contains dielectric‐metal interface, waves of electric charge densities can be initiated. The wave intensity decreases exponentially in adjacent media meaning that the wave closely localized at the interface does exist. Label‐free chemical sensors are realized as the propagation constant of the wave is highly sensitive to the refractive index. Surface plasmons can be excited by incident light flow directed at some specific angle (surface plasmon resonance) with a very sharp shape. In the present paper the possibility of identification of several most common alcohols such as methanol, ethanol, propanol, butanol, or pentanol, which have different refractive indices, has been studied. The structure is composed of a coupling prism made of rutile (TiO2), a thin gold film, and an amorphous arsenic sulfide (As2S3) thin film.

Arsenic removal from copper slag matrix by high temperature sulfide-reduction-volatilization

Arsenic contamination has been a major problem in copper slag utilization. Arsenic is easily incorporated into the silicate-based matrix, making the arsenic difficult to volatilize. In this study, pyrite was selected to depolymerize the matrix structure and volatilize the glassy arsenic by sulfide-reduction-volatilization reaction. The optimum technological parameters and mechanism of glassy arsenic volatilization by pyrite were further studied. The optimum operating parameters for glassy arsenic volatilization by pyrite were determined to be a temperature of 1200 °C, a holding time of 60 min, a heating rate of 5 °C/min, a basicity of 0.3, and a pyrite addition content of 15%. The arsenic volatilization ratio reached 80.9% under these experimental conditions. Besides, the mechanism of glassy arsenic volatilization was elucidated by XRD, XPS, FTIR, and SEM analyses. These results indicate that, with the increase in temperature, the pyrite decomposes to generate a variety of sulfur-based reducing substances (FeS, FeS1-x, S2(g)). Through “oxygen capture reaction”, these sulfur-based reducing substances depolymerize the bridging oxygen structure from the glass former ([AsO4], [FeO4], and [SiO4]) by the conversion of (Q2 +Q3)→(Q0 +Q1) and result in the precipitation of glass former ([AsO4], [FeO4] and [SiO4]) combining with the nearby cation. In this process, the glassy arsenic is released by the glass network and participates in reductive volatilization reaction with sulfur-based reducing substances, converting the glassy arsenic with high thermal stability to volatile arsenic oxide and arsenic sulfide. These findings provide a theoretical support for the in situ volatilization of arsenic in copper smelting and centralized control of arsenic contamination.

Efficient removal and recovery of arsenic from copper smelting flue dust by a roasting method: Process optimization, phase transformation and mechanism investigation

The efficient removal and recovery of arsenic from copper smelting flue dust have received widespread attention due to its extremely high toxicity and carcinogenicity. In this research, a roasting method used for treating the dust at a relatively low temperature (300–400 ℃), with adding sulfuric acid and bitumite, was proposed, in which the reduction of As(Ⅴ) and oxidation of arsenic sulfides were achieved simultaneously. It was proved by thermodynamic analysis and experiments that adding sulfuric acid was favorable for the removal of arsenic, through enhancing the thermodynamic driving force and promoting the transformation of arsenate and arsenic sulfides to As2O3. The phase transformation of arsenic was analyzed using XRD, SEM-EDS and XPS, which indicated that coal addition, roasting temperature and H2SO4 dosage play essential roles in arsenic removal. Based on the lab-scale experiments, the optimal conditions for arsenic removal were found to be at the roasting temperature of 300–400 °C, roasting time of 2–3 h, coal addition of 5% and H2SO4 dosage of 0.2–0.3 mL/g. Around 98% of arsenic was volatilized from the dust, while arsenic content in the residue was decreased to 0.57%. Eventually, arsenic was recovered as As2O3 with a high purity of 99.05%.

Effect of doping of molybdenum on the optical properties of glasses of the As—S system

This article discusses the spectral dependences of the absorption coefficient of thin arsenic sulphide films obtained by spin-coating, identified using a single-beam spectrophotometer in the wavelength range of 400–1000 nm. The effect of doping of molybdenum on the optical band gap is studied. While for a pure glass the band gap decreases with higher sulphur concentration, the opposite trend is observed in glass doped with molybdenum. Molybdenum doping also leads to an increase in Urbach energy. The obtained experimental curves are compared with theoretical ab-initio calculations.

Transformation behavior of the morphology, structure and toxicity of amorphous As2S3 during hydrothermal process

Arsenic sulfide sludge (ASS) is a typical hazardous waste in the non-ferrous smelting industry. In our previous study, ASS was effectively stabilized by hydrothermal treatment. However, the mechanism of hydrothermal stabilization is still unclear. Amorphous As2S3 is the main component of ASS. Therefore, in this work, the hydrothermal transformation behavior of amorphous As2S3 precipitated with NaAsO2 and Na2S·9H2O under acidic aqueous was investigated for a better understanding of hydrothermal stabilization process of ASS. It was found that under the conditions of 210 °C, initial pH 2 and solid-to-liquid (S/L) ratio 1:5, amorphous As2S3 floc gradually transformed to spherulitic particles and showed aggregation behavior with the extension of hydrothermal duration. The spherulitic particles were identified as orpiment, which was the crystalline arsenic mineral in the nature. Moreover, the As leaching concentration of hydrothermal products decreased remarkably with the transformation from amorphous As2S3 to orpiment. Under certain hydrothermal conditions, the As leaching concentration of amorphous As2S3 can be reduced from 139.4 mg/L to less than 5 mg/L. Hence, the mineralization from amorphous As2S3 to orpiment was the significant reason for the stabilization of arsenic sulfide during hydrothermal treatment. This paper provided a theoretical support for the hydrothermal stabilization of ASS.

Manikya Bhasma is a nanomedicine to affect cancer cell viability through induction of apoptosis

BackgroundAyurveda is an ancient medicine system practiced in the Indian sub-continent. Ayurvedic Bhasma is incinerated herbo-metallic/mineral preparations that consist of the particles in the range of nano/micrometers with therapeutic effects against different diseases. Manikya Bhasma (MB) is composed of purified ruby, orpiment, and purified arsenic sulfide. ObjectiveThis study was conducted to identify the potential of MB as a nanomedicine that can be used for the treatment of cancer. Materials and methodsBiophysical characterization to determine the morphology and composition of bhasma particles was done using several techniques such as DLS, FTIR, FETEM, FESEM, EDX, and XRD. Cell viability assays were conducted to identify the cytotoxic effect of MB against different cancer cell lines and also to determine the mode of death caused by MB. ResultsThe biophysical characterization of MB indicates that it is crystalline with a particle size of 70 nm. MB exhibits anticancer activity against MDAMB-231, HeLa, HCT-116, DLD-1, MG-63 cancer cells with an IC50 in the range of 105–155 μg/mL. MB induces oxidative stress in cancer cells, which in turn affects their cell-cycle with an accumulation of cells in the G1-phase. Also, apoptosis induced by MB involves loss of mitochondrial membrane potential, the release of Cyt c, activation of caspases, and DNA degradation. ConclusionOur study highlights the dual potential of MB as a nano-carrier to deliver the drugs and exerting cytotoxic effects against cancer cells.

Hydrothermal treatment of arsenic sulfide slag to immobilize arsenic into scorodite and recycle sulfur

Arsenic sulfide slag (ASS) is typically by-produced from arsenic-containing wastewater treatment. In this work, a novel hydrothermal treatment method with the assistance of Fe(NO3)3 (HT-Fe(NO3)3) was developed to detoxify ASS by transforming arsenic into scorodite and extracting sulfur in one step. After hydrothermal treatment, As(III) in ASS was oxidized and immobilized into the stable scorodite with a high As immobilization efficiency (~99%), and the toxicity leachability of arsenic-containing solid waste significantly reduced from 634.2 to 2.5 mg/L, well below the discharge standard of solid waste. Further study reveals that the nucleation and growth process was fit well by Avrami-Erofeev model and followed Ostwald step rule, which involved the As2S3 dissolution, formation of amorphous ferric arsenate and then crystallization within the amorphous precursor. In this process, sulfur originated from As2S3 played an important role by serving as the heterogeneous nuclei to decrease the barrier for the formation of amorphous ferric arsenate, and facilitated the transformation of as-formed scorodite from nano-sheet aggregates to the bulk and dense spherical polymorph, which further increased the stability of the arsenic contained solid product. This study will shed light on the development of new technologies for treatment of industrial solid waste and recycle of useful resources.

Removal of scorodite arsenic from gold ore in the form of AS2S3 and AS4S4

This paper discusses the removal of arsenic scorodite from the gold ore. Kinetic studies on the possibility of removal of arsenic in a compact shape of arsenic sulfide were carried out, which occupies a small volume. The reagent reaction order and activation energy are calculated. The limiting stage of the process occurred in the intradiffusion region, i.e. the rate of the process limits the diffusion supply of the reagent to the reaction boundary (or removal of products from it) through a layer of a solid substance (hematite-Fe2O3), formed during the sulphidization roasting, which is one of the decomposition products of scorodite. The reactions of decomposition of scorodite with the formation of arsenic sulfides are proposed, and the process of their progress confirmed by thermodynamic calculations and chemical analysis. The results of testing of sulphidization roasting on the gold-bearing refractory ore are presented, in which arsenic is mainly concentrated in scorodite. It was found that the recovery of arsenic in the form of As2S3 and As4S4 in sublimates is 92.1%. Comparative studies on the cyanidation of oxidized scorodite gold-containing ore and the cinder of sulphidization roasting were carried out. The industrial application of this technology provides an environmentally safe and efficient processing of such refractory gold-containing ores. The results show that sulphidization roasting increased the degree of gold recovery from 80% to 93.5% when the cyanide concentration increased from 1 kg/t to 1.75 kg/t.