Concentration Of Sodium Sulfide Research Articles

Extraction and Characterization of Keratin Protein from Chicken Feathers using Alkaline Hydrolysis Method: Effects of Sodium Sulphide Concentration and Shelf-life Evaluation

This study investigated the extraction of keratin protein from chicken feathers through alkaline hydrolysis using sodium sulphide as a digesting agent. The protein was precipitated using hydrogen chloride and confirmed through biuret test, solubility test, sulfur test, and FTIR analysis. The effect of varying sodium sulphide concentrations (0.5 M, 0.75 M, and 1 M) on the extracted keratin was evaluated. Results showed that a higher concentration of sodium sulphide produced a higher yield of keratin, with 1 M producing 65.8% yield. However, the shelf-life of wet keratin extracted using 1 M concentration was four weeks, compared to six weeks for 0.5 M and 0.75 M concentrations. The dried keratin was unaffected after six weeks. The study suggests that a higher concentration of the reducing agent produced a higher yield of keratin protein but with a shorter shelf-life if drying was not carried out. The utilization of abundant waste generated by poultry industries is crucial in reducing pollution and creating opportunities for valuable product development. The extraction of keratin from chicken feathers provides an eco-friendly approach to waste management and creates opportunities for product development.

Reverse flotation separation of calcite/dolomite from hemimorphite based on their surface sulphophile and oxyphile affinity differences

This study attempts to selectively inhibit hemimorphite flotation using sodium sulphide and uncover the mechanisms behind it. With the use of a fatty acid collector, the flotation test results showed that sodium sulphide had a strong inhibition performance on hemimorphite flotation while having no adverse impact on calcite and dolomite flotation, which were consistent with the contact angle measurement results. According to the results of attenuated total reflectance-Fourier transform infrared spectroscopy and adsorption proportion measurement of sodium oleate, sodium sulphide can inhibit sodium oleate binding on hemimorphite surfaces while having no effect on calcite and dolomite surfaces. The sulphide species exhibited an extremely high binding affinity for the hemimorphite surface but not for the surfaces of the calcium/magnesium-bearing gangue minerals, as demonstrated by the X-ray photoelectron spectroscopy measurements. Because of the strong sulphophile affinity of zinc, when the sodium sulphide concentration was sufficiently high, an interface boundary layer of a liquid solution with the remaining sulphide species formed on the hemimorphite surface, preventing sodium oleate from binding on the hemimorphite surfaces and thus selectively inhibiting the hemimorphite flotation.

Interface-coupled PbSO4 dissolution and PbS precipitation and its effect on sulfidization flotation of anglesite

Anglesite sulfidization mechanism was systematically investigated using flotation tests, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and ultraviolet− visible diffuse reflectance spectroscopy (UV−Vis DRS). The activation effect of sodium sulfide on anglesite flotation was demonstrated by the flotation tests; however, sodium sulfide concentration must be properly controlled to avoid excessive sulfide ions causing flotation depression. The results of XPS, Raman, and UV−Vis DRS revealed that PbSO4 was replaced by PbS during anglesite treatment with a sodium sulfide aqueous solution. FESEM imaging shows the dissolution of PbSO4 and the precipitation of PbS nanoparticles during sulfidization. Thus, it can be suggested that the reaction of anglesite with a sodium sulfide aqueous solutionproceeds via an interface-coupled dissolution–precipitation mechanism: upon contact with a sodium sulfide aqueous solution, anglesite dissolution releases Pb2+ and SO42– into the fluid boundary layer, which becomes oversaturated with respect to PbS phase; then the PbS nanoparticles nucleate and grow on the surface of anglesite. The PbS nanoparticles grown on anglesite can improve the floatability of anglesite.

Effects of sodium sulfide concentration on the solid and solution chemistry of a biosolids slurry for phosphorus recovery and reuse

Municipal biosolids contain organic and inorganic phosphorus (P) that could be recovered for reuse as P fertilizer. Inorganic P compounds include iron phosphates that precipitate and/or adsorbed phosphate ions as a consequence of soluble iron addition in order not to exceed total phosphorus (TP) emission limits. The inorganic orthophosphate (o-Pi) minerals within biosolids can have low solubilities. One P recovery strategy is to maximize the dissolution of o-Pi from biosolids for reuse. Dissolving iron phosphates in biosolids by adding sodium sulfide was assessed as an o-Pi dissolution strategy. 10 % w/w biosolids slurries with a total phosphorus (TP) of 0.97 ± 0.03 mmol P/dry g were mixed with sulfide/TP (S2−/TP) molar ratios from 0 to 4 for up to 96 h. The maximum o-Pi concentration (48 ± 7 mM, or 42 ± 6 % of TP) was obtained for 4 S2−/TP after 24 h at room temperature (RT). Iron concentrations measured by colorimetry (ferrozine) reduced from 0.6 ± 0.1 mM to less than 0.01 mM (S2−/TP > 1). X-ray diffraction and FTIR suggest that sulfide treatment preferentially dissolved amorphous o-Pi-containing solids, vivianite, and minerals with iron, aluminum, phosphate, sulfate, and other subsitutions. Poorly crystalline erdite (NaFeS2 ·2H2O) was detected in products after S2−/TP treatment ratios ≥ 2. Incubation at RT or 37 °C did not affect the o-Pi concentrations for 0 or 4 S2−/TP over 47 h. Sulfide addition could also increase the risk of construction material corrosion, and reduce the efficiency of P recovery by precipitation. There are disadvantages to using sulfide to dissolve o-Pi from biosolids as a potential P recovery process.

Microscale exploration of the sulfidization flotation theory in malachite

With the gradual depletion of copper sulfide resources, efficient flotation technologies for the recovery of copper oxide minerals, such as malachite, have received significant attention. Although sulfidization plays a critical role in malachite flotation, the fundamental theory of sulfidization flotation remains uncertain in the context of practical industrial applications. In this study, evolution of the sulfide product morphology on the malachite surface was observed after treatment with various concentrations of sodium sulfide. In addition, the valence states and phase compositions of the sulfide products were investigated using different X-ray techniques. Furthermore, the evolution of the malachite surface morphology after the formation of a sulfide film was investigated, as were the interaction forces between the malachite and bubbles under the action of butyl xanthate. As a result, it was possible to directly observe the growth process of the sulfide film on the malachite surface, and the presence of Cu(I) was confirmed in the sulfide products. Moreover, the compositions of the sulfide products were investigated using X-ray techniques. The obtained results demonstrated that the sulfide film facilitated the formation of butyl xanthate product layers on the malachite surface, whilst also enhancing the interfacial interaction forces between the malachite and the bubbles.

Development of a Two-Stage Hydrometallurgical Process for Gold-Antimony Concentrate Treatment from the Olimpiadinskoe Deposit.

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R2) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As2S3 was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold-antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake.

Selective alkaline leaching of antimony from Low-grade refractory gold ores and process optimization

To eliminate the adverse effect of antimony on extracting of gold in matte smelting process from Sb-bearing refractory gold ores, the sodium sulfide leaching method was proposed to selectively remove antimony in advance. On the basis of the analysis and characterization of raw materials (XRD, SEM-EDS, mineralogical phase analysis, etc.), it can be detected that the antimony in refractory gold ores is mainly in form of stibnite with small quantities of oxides, and the gold is mainly wrapped up in sulfides and silicates. The effects of sodium sulfide and sodium hydroxide concentration, temperature, leaching time and liquid–solid ratio on the extraction rate of antimony and gold were discussed. Furthermore, the response surface method was applied to distinguish the interaction influence of process parameters on the antimony and gold extraction rate. It is detected that the polysulfides and thiosulfates are the main cause of associated leaching of gold. Furthermore, the regression equation model is established adopting the antimony extraction rate as response value, and it can be deduced that the relevance degree is Na2S concentration > temperature > NaOH concentration. Accordingly, the optimized process results are determined as follows: the extraction rates of antimony and gold reach 94.15% and 3.37%, respectively, under Na2S concentration of 85.66 g/L, NaOH concentration of 45.5 g/L, liquid–solid ratio of 1.5, leaching at 90 °C for 5 min, which are very consistent with the predicted values of the regression equation, proving the feasibility of the proposed optimization model.

Influence of hydrated Ca<sup>2+</sup> and Mg<sup>2+</sup> complexes on the sulfidization of smithsonite: Density functional based tight binding (DFTB+) study

Ca<sup>2+</sup> and Mg<sup>2+</sup> are the most dominating unavoidable ions in the smithsonite flotation. In this paper, the effect of Ca<sup>2+</sup> (Mg<sup>2+</sup>) on the surface of smithsonite sulfidization in a system where water molecules are present was investigated using density functional based tight binding (DFTB+) simulations for the first time. The results indicated that the adsorption of hydrated Ca<sup>2+</sup> complexes is stronger than that of hydrated Mg<sup>2+</sup> complexes on the hydrated smithsonite (101) surface. In addition, at low concentrations of sodium sulfide, there is no adsorption of HS- on the surface pre-adsorbed with hydrated Ca<sup>2+</sup> complexes, but only on the surface pre-adsorbed with hydrated Mg<sup>2+</sup> complexes. At high concentrations of Na<sub>2</sub>S, S<sup>2-</sup> weakens the adsorption of hydrated Ca<sup>2+</sup> complexes due to competitive adsorption, but the presence of S<sup>2-</sup> could desorb hydrated Mg<sup>2+</sup> complexes from the surface. The results compared the differences in effects of Ca<sup>2+</sup> and Mg<sup>2+</sup> on smithsonite sulfidization, which could provide an atomic scale basis for researching the surface sulfidization of oxide minerals.

ECOLOGICAL FEATURES OF SOAKING AND ASH PROCESSES IN THE PRODUCTION OF LEATHER

Ecological and colloid-chemical features of soaking-ash processes in processing of raw cattle leather materials at production of elastic leather for uppers of footwear according to operating and developed resource-saving technologies are investigated. To evaluate the effectiveness of the technological processes used a set of physic-chemical and operational properties of leather semi-finished products at different stages of its formation to the finished material. Resource-saving ecologically oriented technology of soaking and ash processes in leather production for shoe uppers from raw salted conserved materials – bull skins has been developed. Physicochemical, technological and ecological features of existing and developed technologies are studied. The developed technology due to the increase of process temperature provides more efficient use of chemical reagents, reduction of concentrations of environmentally hazardous reagents, process duration and energy consumption per unit of output. At the same time, the total consumption of chemical reagents is reduced by 2.2 times, and in the waste technological solutions the concentration of sodium sulfide and calcium hydroxide – by 2.9 and 4.4 times, respectively. However, the developed resource-saving environmentally friendly technology is characterized by a reduction in biological and chemical oxygen demand for the destruction of organic and inorganic substances in the waste soaking-ash solution after treatment of 1 ton of raw materials by 30.0 and 21.0%, respectively. By reducing the duration of the technological process by 2.3 times, the new technology can be considered as energy efficient. The developed resource-saving technology provides the formation of leather material for shoe uppers with an increased yield of 3.9%, and its performance properties meet the requirements of DSTU 3115-95. The results obtained in the development of environmentally friendly resource-saving technology of soaking ash processes for footwear leather uppers from raw cattle leather materials can be effectively used in the development of new innovative technologies for the manufacture of leather materials from a wide range of other raw materials.

INTENSIFICATION OF THE ABSORPTION OF OXYGEN BY WATER USING A ROTOR-PULSATING APPARATUS

One of the important components of the quality of food products is the quality of water used. A common way to remove unwanted impurities from water is aeration, i.e. the oxidation of chemical compounds in water by oxygen. Aeration devices with mechanical energy input in comparison with other groups of devices, namely with energy input with gas phase and with liquid phase, have low power consumption and additional mixing of the processed medium. The work presents a study of oxygen absorption in water in an experimental setup with rotor-pulsating apparatus for water treatment in beverage production technology. In this paper, the energy and technological parameters of aeration of a model aqueous solution of a certain concentration of sodium sulfide in an experimental setup with a rotor-pulsating apparatus as an aerator are determined. The experimental aeration setup allows conducting research in several modes and consists in particular of a vessel, a rotor-pulsating apparatus, two ejectors - one at the entrance to the rotor-pulsating, the other at the outlet, the recirculation pipeline. Air from the atmosphere enters each of the ejectors through a separate air duct. The aeration of the studied water took place in the recirculation mode for 20 minutes. Determination of the oxygen mass transfer rate is determined by the iodometric titration method on the rate of oxidation of sodium sulfite. Experiments were conducted without using a catalyst. It is determined that when placing the ejector unit at the rotor-pulsating apparatus inlet at the angular rotor unit velocity of 240.02; 270.18, and 300.02 s-1, the oxygen mass transfer rate is 1.39; 1.49 and 1.73 kg m3/h. At the location of the ejector unit at the outlet of the rotor-pulsating apparatus, the velocity of the oxygen mass transfer under the same conditions is 1.17; 1.36 and 1.63 kg m3/h respectively. However, the power consumption of the second scheme exceeds the power consumption by the first scheme by 50%.

Effects of Sodium Sulfide Concentration on the Solid and Solution Chemistry of a Concentrated Biosolids Slurry for Phosphorus Recovery and Reuse

Effects of Sodium Sulfide Concentration on the Solid and Solution Chemistry of a Concentrated Biosolids Slurry for Phosphorus Recovery and Reuse

Depression Mechanism of Sodium Sulfide in Flotation Separation of Molybdenite and Bismuthinite

ABSTRACT Sodium sulfide has been widely used as a bismuth depressant in the flotation separation of molybdenum–bismuth sulfide ores. However, the selective depression mechanism of sodium sulfide on bismuthinite remained unclear. In this study, the effect of sodium sulfide on the flotation performance of molybdenite and bismuthinite was systemically investigated through micro-flotation tests, bench-scale flotation tests, Fourier transform infrared (FTIR) measurements, adsorption experiments, and X-ray photoelectron spectroscopy (XPS) analyses. Micro-flotation tests indicated that sodium sulfide had excellent depressing effect on the bismuthinite in alkaline condition. The recovery of bismuthinite dramatically decreased from 86.7% to 16.5% with the concentration of sodium sulfide increased to 1 × 10−3 mol/L. By contrast, the depressing effect of sodium sulfide on the flotation of molybdenite was weak. The flotation recovery of molybdenite remained above 60% in the whole pH range tested. Surface analysis using FTIR and XPS analysis revealed that the surface of bismuthinite was covered by hydrophilic sulfide ions after treatment with sodium sulfide, which not only decreased its surface hydrophobicity but also prevented the subsequent adsorption of collector xanthate. While the surface of molybdenite was slightly affected and remained hydrophobic as indicated by high flotation recoveries. Bench-scale flotation tests confirmed that sodium sulfide could be used as an efficient depressant for flotation separation of molybdenite from bismuthinite. The work presented here not only provides a new perspective on the inhibition mechanism of sodium sulfide but also gives a theoretical support for the industrial application of sodium sulfide.

Leaching Kinetics of Antimony from Refractory Gold Ore in Alkaline Sodium Sulfide under Ultrasound

The leaching kinetics of antimony from refractory gold ore in alkaline sodium sulfide was investigated under ultrasound. The influence of factors such as stirring speed, temperature, the concentration of sodium hydroxide and sodium sulfide and particle size, was studied. The leaching kinetics has also been studied under convention and ultrasound. The experimental data are consistent with the shrinkage core model and the leaching rate is controlled by surface chemical reaction for both ultrasonic and the conventional method. Ultrasound increases the leaching rate of antimony from 81.2% to 93.1%. It can be seen that the rate constant kr of ultrasonic method at various temperatures is larger than that of the conventional method. The ultrasound reduces the apparent activation energy from 48.39kJ/mol to 33.88kJ/mol and reduces the apparent response series of sodium sulfide concentration from1.3 to 1.1. Comparing with conventional method, the ultrasound can greatly improve the antimony leaching rate, accelerate the leaching process and lower temperature and the concentration of sodium hydroxide and sodium sulfide. These advantages of ultrasonic method were also confirmed by the SEM analysis of the leached solid.

Oxidoreductase Activities in Oxyphilic Tissues of the Black Sea Ruff Scorpaena porcus under Short-term Hydrogen Sulfide Loading

Hydrogen sulfide can both exert a toxic effect and function as a signaling molecule in various physiological processes. Under conditions of experimental short-term hydrogen sulfide loading (HSL), activities of oxidoreductases (enzymes of energy metabolism and antioxidant defense)—malate dehydrogenase (MDH, 1.1.1.37), lactate dehydrogenase (LDH, 1.1.1.27) and catalase (1.11.1.6) were analyzed in oxyphilic tissues (brain, heart, gills) of the Black Sea sea ruff Scorpaena porcus Linnaeus, 1758. Two groups of fish were exposed for 5 min to different concentrations of sodium sulfide (37 and 75 µM Na2S) used as a hydrogen sulfide donor. High MDH and LDH activities were simultaneously detected in the brain structures and heart chambers, reflecting a similar potential of energy metabolism in these tissues, while enhanced LDH activity in the brain indicated anaerobization of the energy metabolism pathways. Differences in oxydoreductase activities were found between the first and fourth branchial arches, heart atrium and ventricle, as well as between different brain compartments. Under HSL, the gills exhibited some signs of hypoxemia (increasing darkening of the lamellae as the Na2S concentration moved upward) and metabolic depression. At a low Na2S concentration, HSL did not cause significant changes in oxidoreductase activities in the brain and heart, while upon a 2-fold increase in the Na2S concentration these changes became more pronounced. In the key oxyphilic structures (anterior brain compartments, heart ventricle) intense HSL led to a simultaneous increase in LDH and MDH activities, which was due to the ability of MDH to participate in anaerobic processes. The less O2-sensitive structures (medulla oblongata and heart atrium) exhibited almost no changes in MDH and LDH activities even in response to high-intensity HSL, suggesting a different mode of energy metabolism in these tissues. Under intense HSL, the oxidoreductases in the heart ventricles and anterior brain compartments demonstrated responses, which were similar to those under hypoxia/anoxia.

Escherichia coli-based synthesis of cadmium sulfide nanoparticles, characterization, antimicrobial and cytotoxicity studies.

The present research describes the synthesis of cadmium sulfide (CdS) nanoparticles from Escherichia coli under the influence of bacterial enzyme sulphate reductase and study on their cytotoxicity for applications in cancer therapy. Escherichia coli cells were used to synthesize CdS nanoparticles under different concentrations of cadmium chloride and sodium sulfide. The morphology of the nanoparticles was analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) was used for elemental analysis of nanoparticles. Fourier-transform infrared spectroscopy analysis (FTIR) was performed to assess the functional groups of the nanoparticles. Crystalline nature of nanoparticles was assessed using powder X-ray diffraction (XRD). Antibacterial studies of CdS nanoparticles were carried out on foodborne pathogens and cytotoxicity studies were carried out on Mus musculus skin melanoma (B16F10) and human epidermoid carcinoma (A431) cell lines. CdS nanoparticle showed more cytotoxic effect on cancer cells compared with standard 5-aminolevulinic acid (5-ALA). The Escherichia coli-synthesized CdS nanoparticles showed highest zone of inhibition in the ratio 4:1 of cadmium chloride and sodium sulfide on all tested bacterial strains. The nanoparticles were also tested for haemolytic activity on RBC cells, which exhibited lower cytotoxicity than sodium dodecyl sulphate which was used as positive control. The cytotoxicity of CdS nanoparticles assessed on A431 cells showed an inhibition of 81.53% at 100μM concentration while the cytotoxicity assessed on B16F10 cells showed an inhibition of 75.71% at 200μM concentration which was much efficient than 5-ALA which showed an inhibition of 31.95% at a concentration against B16F10 cells and 33.45% against A431 cells at a concentration of 1mM. Cadmium sulfide nanoparticles were thus found to be highly toxic on cancer cells compare with standard anticancerous drug 5-ALA.

АКТИВНОСТЬ ОКСИДОРЕДУКТАЗ В ОКСИФИЛЬНЫХ ТКАНЯХ МОРСКОГО ЕРША SCORPAENA PORCUS LINNAEUS, 1758 ПРИ КРАТКОСРОЧНОЙ СЕРОВОДОРОДНОЙ НАГРУЗКЕ

Hydrogen sulfide can exert a toxic effect and also function as a signaling molecule in various physiological processes. Under conditions of short-term experimental hydrogen sulfide loading (HSL), activities of oxidoreductases (enzymes of energy metabolism and antioxidant defense) - malate dehydrogenase (MDH, 1.1.1.37), lactate dehydrogenase (LDH, 1.1.1.27), catalase (1.11.1.6) – were analyzed in oxyphilic tissues (brain, heart, gills) of the Black Sea scorpionfish Scorpaena porcus Linnaeus, 1758. Two groups of fish were exposed for 5 min to different concentrations of sodium sulfide (37 and 75 μM Na2S) used as a hydrogen sulfide donor. High MDH and LDH activities were detected in the brain structures and heart chambers, reflecting a similar potential of energy metabolism in these tissues, while enhanced LDH activity in the brain indicated anaerobization of the energy metabolism pathways. Differences in oxydoreductase activities were found between the first and fourth branchialarches, heart atrium and ventricle, as well as between different brain compartments. Under HSL, the gills exhibited some signs of hypoxemia (increasing darkening of the lamellae as the Na2S concentration moved upward) and metabolic depression. At a low Na2S concentration, HSL did not cause significant changes in oxidoreductase activities in the brain and heart, while upon a 2-fold increase in the concentration these changes became more pronounced. In the key oxyphilic structures (anterior brain compartments, heart ventricle) intense HSL led to a simultaneous increase in LDH and MDH activities, which was due to the ability of MDH to participate in anaerobic processes. The less O2-sensitive structures (medulla oblongata and heart atrium) exhibited almost no changes in MDH and LDH activities even in response to high-intensity HSL, suggesting a different mode of energy metabolism in these tissues. Under intense HSL, the oxidoreductases in the heart ventricles and anterior brain compartments demonstrated responses, which were similar to those under hypoxia/anoxia.

Mechanism of silicate elution by hydrogen sulfide from bottom sediment in a brackish lake

Highly concentrated dissolved silicate was detected in pore water from anoxic-reducing sediment in Lake Nakaumi, a brackish lake. Silicate concentration also simultaneously increased with total hydrogen sulfide concentration during the summer. Generally, dissolved silicate is readily adsorbed onto ferric hydroxide and precipitates in an oxidative environment. In this study, we focused on the behavior of ferric hydroxide adsorbing silicate in sediment and determined that hydrogen sulfide was the main cause of dissolved silicate elution from ferric hydroxide adsorbing silicate because the hydrogen sulfide produced via microbiological processes in the anoxic-reducing environment was reducible for other metal oxides. According to laboratory experiments, silicate was released from ferric hydroxide by reacting with sodium sulfide, causing increasing elution of dissolved silicate from anoxic-reducing sediments with increasing concentration of sodium sulfide in the solutions. This result shows that hydrogen sulfide is very crucial for silicate release under a reducing environment. Therefore, in Lake Nakaumi, silicate would be released from the bottom after ferric hydroxide adsorbing silicate reacted with hydrogen sulfide in a summer reductive environment.

Ionic Liquids and Deep Eutectic Solvents and Their Use for Dissolving Animal Hair

In recent years, one of the priority areas of research in chemistry has become the processes carried out in an environment of liquid organic salts, the so-called ionic liquids (ILs), which are assessed as environmentally friendly or “green” alternatives to conventional organic solvents. ILs are non-volatile, highly polar solvents that dissolve many organic, inorganic, and organometallic compounds. Since they have no detectable vapor pressure, ILs are considered as potential substitutes for volatile organic compounds traditionally used as solvents. So-called deep eutectic solvents (DES) is a group of ILs that are liquid mixtures of a number of organic and (or) inorganic components taken in a certain ratio (eutectic or close to eutectic). DES deserve a special attention due to their negligible saturated vapor pressure, availability, low cost, as well as ability to dissolve at relatively high concentration of metal salts, metal oxides and various polymers. Particularly DES based on a mixture of choline chloride with urea (DES-1) or a mixture of choline chloride and adduct of urea with hydrogen peroxide (DES-2) give eutectics that are liquid at ambient temperature and have unusual solvent properties, including an ability to dissolve an animal hair in the presence of low concentration of sodium sulfide or ammonium thioglycolate. It was found that depending on the ratio between DES-1 and DES-2 in the mixture of two Deep Eutectic Solvents and the nature of sulfur-containing additive, the solubility of rabbit hair under used conditions, varies from 51% to 79%.

Selective removal of antimony from refractory gold ores by ultrasound

Ultrasound is used to enhance the removal of antimony from the refractory gold ores in alkaline sodium sulfide leaching process. The effects of ultrasonic time, temperature, reagent concentration and ultrasonic power on antimony removal are discussed. The removal rate of antimony reached 94.50% when ultrasonic time was 60 min, sodium hydroxide concentration was 1 mol/L, sodium sulfide concentration was 2 mol/L, ultrasonic power was 1500 W and temperature was 55 °C. Under the conditions, the removal rate of antimony without ultrasound is only 58.37%. The results show that ultrasound can significantly improve the removal efficiency of antimony and reduce the leaching temperature and time of antimony. The leaching rate of gold increased from 13.35% to 40.56% after antimony removal. Moreover, the leaching rate of gold after antimony removal reached 68.90% under ultrasound. Therefore, ultrasound not only enhances the removal efficiency of antimony, but also improves the leaching rate of gold. The improvement of the leaching rate of antimony and gold is attributed to that the mineral particles are broken up and pyrite is decomposed by ultrasound.

Mathematical modeling of bovine hides swelling behavior by response surface methodology for minimization of sulfide pollution in leather manufacture

Excessive utilization of such sulfides as sodium sulfide always results in serious wastewater pollution in the liming processing of leather manufacture, and thus the critical or optimal consumption of sodium sulfide is necessary. In this work, it was found that the swelling behavior of bovine hides is highly dependent on the liming time as well as temperature and the sodium sulfide concentration. In order to understand the swelling mechanism and optimize the swelling condition, a mathematical model was built based on the response surface methodology (RSM). As a result, the predicted values (Pva) were in good agreement with the experimental values (Eva) by analyzing the absolute as well as relative errors, and the optimized operation conditions were found to be performed in 0.85 wt% Na 2 S solution at 25 °C for 895 min, by which the polysaccharides in hair follicle are dissolve completely and meanwhile the collagen fiber bundles are swollen and disperse very well. • A mathematical model for bovine-hide swelling by sodium sulfide is established using RSM. • A way to reasonably use sodium sulfide in liming is proposed. • A theoretical basis for cleaner leather making technique is provided. • EVG staining combined with slice digital scanning is applied.