Efficient recovery of zinc and copper from copper smelting slag (CSS) by cooperative modification with a composite medium of FeS-O2.

Efficient recovery of valuable metals from copper smelting slag (CSS) can not only alleviate the pressure from resource scarcity, but also has important practical significance for the realization of green and sustainable production in the copper smelting industry. In this paper, a composite medium of FeS-O2 is used as a synergistic modifier to transform the solid-state valuable metals in CSS into leachable state of sulphates, and achieves efficient and comprehensive recovery of zinc and copper through neutral leaching. XRD, FTIR, XPS, etc and comparative analysis methods are used to deeply analyze the characteristics of occurrence phase and transformation rules of valuable metal in CSS, roasted slag and leached slag. The results show under the optimal roasting conditions of TRoasting = 650 °C, M(copper slag): M(FeS) = 1:1, V(O2): V(Ar) = 1:6 and tHolding = 90 min, the recovery rate for zinc is approximately 95.1 %, and that for copper is 99.3 %, almost all of which is recovered. These findings provide a new method and process foundation and theoretical support for the efficient resource utilization of CSS.

Flexible synthesis of high-performance electrode materials of N-doped carbon coating MnO nanowires for supercapacitors.

The MnO/C composites were obtained by co-precipitation method, which used Mn3O4nanomaterials as precursors and dopamine solution after ultrasonic mixing and calcination under N2atmosphere at different temperatures. By studying the difference of MnO/C nanomaterials formed at different temperatures, it was found that with the increase of calcination temperature, the materials appear obvious agglomeration. The optimal calcination temperature is 400 °C, and the resulting MnO/C is a uniformly dispersed slender nanowire structure. The specific capacitance of MnO/C nanowires can reach 356 F g-1at 1 A g-1. In the meantime, the initial capacitance of MnO/C nanowires remains 106% after 5000 cycles. Moreover, the asymmetric supercapacitor was installed, which displays a tremendous energy density of 30.944 Wh kg-1along with a high power density of 10 kW kg-1. The composite material reveals a promising prospect in the application of supercapacitors.

Ultrasonic power combined with seed materials for recovery of phosphorus from swine wastewater via struvite crystallization process.

Recovering P via struvite crystallization is an effective way to utilize the resources in swine wastewater. At present, the main challenges of traditional struvite crystallization process are the long reaction time and insufficient removal efficiency. In this study, a novel method to promote struvite crystallization process through ultrasound (US) combined with seed materials is proposed to overcome these defects. We systematically study the effects of US, seed materials, and ultrasonic power on nutrient recovery. The experimental results show that under the conditions of pH 9.5 and MgCl2:P molar ratio1.4:1, the addition of 2 g/L pre-synthesized struvite as the seed materials can increase the P removal rate to 91.56%, whereas, the addition of 80 W ultrasonic power for 15 min can make the P removal rate reach 94.18%. Meanwhile, the combination of US and struvite seed crystals can achieve a maximum P removal efficiency value of 97.66% in which 10 min for the reaction time is enough. The products are characterized using XRD, SEM, and FTIR to determine the phosphorus removal mechanism of ultrasonic power combined with seed induction. The shearing effect of US is found beneficial to affect the surface morphology of the seed crystals, which provides more nucleation sites to enhance crystal nucleation and growth. The removal efficiency comparison reveals that this combined technology performs an excellent removal effect.

The removal of organic impurities from industrial waste salt by pyrolysis.

The presence of organic impurities hinders the resource utilization of industrial waste salt (IWS). In this study, pyrolysis treatment was chosen to remove these organic impurities. The optimal process parameters for the pyrolysis of organic impurities were as follows: a temperature of 500 °C and a holding time of 20 min. Under these optimal conditions, the total organic carbon (TOC) removal rate was 96.32%, inducing a decrease in the TOC mass fraction from 1.88 to 0.08%. Fourier transform infrared spectroscopy (FTIR) results obtained during this process showed that prolonging the pyrolysis time (10-70 min) for IWS resulted in a gradual decrease in the relative content of characteristic functional group, such as C-O in ether groups, and the disappearance of functional group, such as benzophenone carbonyl group and ester carbonyl. Organic impurities can release gas-containing compounds that destroy the initially smooth IWS surface, and the resulting particles with rough and irregular shapes fuse into large or lumpy particles during the pyrolysis process. GC‒MS results clearly showed that the number of different semivolatile organic compounds in the IWS was reduced from 35 to 19 as a result of the pyrolysis process. Correspondingly, organic impurities with molecular formulas containing 5-10 carbon atoms converted into compounds containing 6-20 carbon atoms. These findings provide theoretical support for IWS resource utilization.

Process parameters and biological mechanism of efficient removal of Cd(II) ion from wastewater by a novel Bacillus subtilis TR1.

The safe treatment of heavy metals in wastewater is directly related to the human health and social development. In this paper, a new biological strain has been isolated from electroplating wastewater, which can effectively remove metal ions in wastewater. The results of 16 S rDNA sequencing analysis and NCBI GenBank database comparison show that the strain belongs to a novel Bacillus genus and names Bacillus subtilis TR1 with the accession number of OL441606. The removal rate of Cd(II) reaches to 85.68% with the conditions of pH = 7, C0Cd(II) = 20 mg L-1, t = 48 h, m = 0.1 g, and T = 35 °C. The biological removal mechanism of Cd(II) is in-depth studied by FTIR and XRD combined with third-generation sequencing. The results indicate that Bacillus subtilis TR1 removes Cd(II) mainly through two synergistic pathways, namely, extracellular chemisorption and intracellular bioaccumulation: 1) The groups carried on the surface of the strain, such as -COOH, -NH, -OH and C-H, have good chemisorption properties for Cd(II) and easily form cadmium containing chelation (-COO-Cd(II), -N-Cd(II), etc.) with these groups. The appearance of TR1 strain changes from cylindrical to spherical after Cd(II) adsorption, which is due to the biotoxicity of Cd(II); 2) Cd(II) exchanges on the surface of TR1 strain with K and Na ions released from the intracellular cytoplasm and enters the cytoplasm under the transfer of biological transport medium. This part of Cd(II) is converted into its own components by anabolic enzymes and accumulates in the cytoplasm. These data provide a new biological agent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Effects of incineration and pyrolysis on removal of organics and liberation of cathode active materials derived from spent ternary lithium-ion batteries.

Removing organics via thermal treatment to liberate active materials from spent cathode sheets is essential for recovering lithium-ion batteries. In this study, the effects of incineration, N2 pyrolysis, and CO2 pyrolysis on the removal of organics and liberation of ternary cathode active materials (CAMs) were compared. The results indicated that the organics in the spent ternary cathode sheets comprised a residual electrolyte and polyvinylidene fluoride (PVDF) binder. Moreover, the organics could be removed to promote the liberation of CAMs via incineration, N2 pyrolysis, and CO2 pyrolysis. When the temperature was <200 °C, the chemical properties of the volatilized ester electrolyte remained unchanged during both N2 and CO2 pyrolysis, indicating that the electrolyte can be collected by controlling the pyrolysis temperature and condensation. Furthermore, PVDF binder decomposition occurred at 200-600 °C. The optimal temperatures of incineration, N2 pyrolysis, and CO2 pyrolysis were 550, 500, and 450 °C, respectively, and these treatments increased the liberation efficiency of CAMs from 81.49 % to 98.75 %, 99.26 %, and 97.98 %, respectively. In addition, heat-treated CAMs required less time to achieve adequate liberation. Following three thermal treatment processes, the sizes of the CAM particles were mainly concentrated in the ranges of 0.075-0.1 mm and <0.075 mm. Furthermore, for all types of CAMs examined, the Al concentration decreased from 1.09 % to <0.35 %, which increased the separation efficiency and improved the chemical metallurgical performance.

Seroprevalence of Toxoplasma gondii infection in sheep and cattle in Shanxi Province, North China.

Toxoplasmosis is a worldwide zoonotic disease caused by infection with the intracellular protozoan parasite Toxoplasma gondii, posing significant economic losses to the livestock industry. As a major livestock province, little is known of the prevalence of T. gondii infection in sheep and cattle in Shanxi Province, North China. In this study, a total of 1962 blood samples from cattle (n = 978) and sheep (n = 984), collected from 11 administrative cities in Shanxi Province, were examined for antibodies against T. gondii by using the indirect enzyme linked immunosorbent assay (ELISA) kits commercially available. The results showed that antibodies to T. gondii were detected in 306 of the 978 cattle serum samples (31.29%, 95% CI 28.38-34.19), ranging from 12.64% to 60.00% among the different cities. The overall seroprevalence of T. gondii in sheep was 17.78% (175/984, 95% CI 15.40-20.17), ranging from 2.22% to 41.11% among the different administrative cities. The T. gondii seroprevalence was associated with the management mode and geographical location. This is the first report of T. gondii seroprevalence in cattle and sheep in Shanxi Province, North China, which provides baseline data to plan future control strategies for T. gondii infection in this province.

Solventing out crystallization-basic magnesium carbonate percipitation for thorough phosphorus removal from ammonium tungstate solution.

The ammonium tungstate solution obtained by leaching scheelite with phosphate contains a large amount of phosphorus. For production of qualified ammonium paratungstate products, phosphorus must be deeply removed from the ammonium tungstate solution. In this study, a novel process for ammonium phosphate recovery and deep phosphorus removal from the solution was proposed. First, ammonium phosphate was crystallized and separated from the ammonium tungstate solution by blowing ammonia and cooling. Results showed that the crystallization ratio of phosphorus was above 95% under the conditions of an ammonia concentration of 4.18 mol/L, an initial phosphorus concentration ranging from 15 g/L to 30 g/L, a holding time of 60 min and the temperature of 20°C. Then, the small portion of phosphorus remaining in the ammonium tungstate solution was further deeply removed by basic magnesium carbonate percipitation. The phosphorus removal efficiency was above 99% and tungsten loss was less than 0.22% under the following conditions: the basic magnesium carbonate stoichiometric ratio was 1.5, the initial phosphorus concentration was ranging from 0.5 to 4 g/L, the reaction time was 120 min and temperature was 25°C. After phosphorus removal, the concentration of phosphorus in the ammonium tungstate solution was below 10 ppm, which meant deep phosphorus removal was achieved.

An emission-free controlled potassium pyrosulfate roasting-assisted leaching process for selective lithium recycling from spent Li-ion batteries.

Recycling critical metals from spent Li-ion batteries (LIBs) is important for the overall sustainability of future batteries. This study reports an improved sulfation roasting technology to efficiently recycle Li and Co from spent LiCoO2 LIBs using potassium pyrosulfate as sulfurizing reagent. By sulfation roasting, LiCoO2 was converted into water-soluble lithium potassium sulfate and water-insoluble cobalt oxide. Under optimal conditions, 98.51% Li was leached in water, with a selectivity of 99.86%. More importantly, sulfur can be recirculated thoroughly, and the sulfur atomic efficiency can be significantly enhanced by controlling the amount of potassium pyrosulfate. Li ions from the water leaching process were recovered by chemical precipitation. Furthermore, application of this technology to other spent LIBs, such as LiMn2O4 and LiNi0.5Co0.2Mn0.3O2, verified its effectiveness for selective recovery Li. These findings can provide some inspiration for high efficiency and environmentally friendly recovery metal from spent LIBs.

Comparative Antigenicity and Pathogenicity of Two Distinct Genotypes of Highly Pathogenic Avian Influenza Viruses (H5N8) From Wild Birds in China, 2020-2021.

To date, there have been three epidemic waves of H5N8 avian influenza worldwide. The current third epidemic wave began in October 2020 and has expanded to at least 46 countries. Active and passive surveillance were conducted to monitor H5N8 viruses from wild birds in China. Genetic analysis of 10 H5N8 viruses isolated from wild birds identified two different genotypes. Animal challenge experiments indicated that the H5N8 isolates are highly pathogenic in chickens, mildly pathogenic in ducks, while pathogenicity varied in BALB/c mice. Moreover, there were significant differences in antigenicity as compared to Re-11 vaccine strain and vaccinated chickens were not completely protected against challenge with the high dose of H5N8 virus. With the use of the new matched vaccine and increased poultry immune density, surveillance should be intensified to monitor the emergence of mutant strains and potential worldwide spread via wild birds.

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.

The selective adsorption performance and mechanism of multiwall magnetic carbon nanotubes for heavy metals in wastewater.

The safe treatment of heavy metals in wastewater is directly related to human health and social development. In this paper, a new type of recyclable adsorbent is synthesized through the oxidation of enhancer and modification with magnetic nanoparticles. The new adsorbent not only inherits the advantages of multiwall carbon nanotubes (6O-MWCNTs), but also exhibits a new magnetic property and further improved adsorption capacity, which is conducive to the magnetic separation and recovery of heavy metals. The adsorption results indicate that multiwall magnetic carbon nanotubes (6O-MWCNTs@Fe3O4) have a good performance for Pb(II) selective adsorption, with a maximum adsorption capacity of 215.05 mg/g, much higher than the existing adsorption capacity of the same type of adsorbents. Under the action of an external magnetic field, 6O-MWCNTs@Fe3O4 that adsorbed metal ions can quickly achieve good separation from the solution. The joint characterization results of FTIR and XPS show that under the action of both coordination and electrostatic attraction, the C=O bond in the -COOH group is induced to open by the metal ions and transforms into an ionic bond, and the metal ions are stably adsorbed on the surface of 6O-MWCNTs@Fe3O4. Pb(II) has a stronger attraction than Cu(II) and Cd(II) to the lone pair of electrons in oxygen atoms to form complexes, due to the covalent index of Pb (6.41) is more larger than that of Cu (2.98) and Cd (2.71).These data provide a new type of recyclable adsorbent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Investigation of organic impurity and its occurrence in industrial waste salt produced by physicochemical process.

Industrial waste salt is classified as hazardous waste to the environment. The organic impurity and its occurrence in industrial waste salt affect the salt resource utilization. In this paper, composition quantitative analysis, XRD, TG-DSC, SEM/FIB-SEM coupled with EDS, FTIR, XPS and GC-Ms were chosen to investigate the organic impurity and its occurrence in industrial waste salt. The organic impurities owe small proportion (1.77%) in the specimen and exhibit weak thermal stability within the temperature of 600°C. A clear definition of organic impurity, including 11 kinds of organic compounds, including aldehyde, benzene and its derivatives etc., were detected in the industrial waste salt. These organic impurities, owing (C-O/C-O-C, C-OH/C = O, C-C/CHx/C = C etc.)-containing function group substance, are mainly distributed both on the surface and inside of the salt particles. Meanwhile, the organic substance may combine with metal cations (Ni2+, Mg2+, Cu2+ etc.) through functional groups, such as hydroxide, carbonyl etc., which increases its stability in the industrial waste salt. These findings provide comprehensive information for the resource utilization of industrial waste salt from chemical industry etc.

Synthesis and Hydration Characteristic of Geopolymer Based on Lead Smelting Slag.

Lead smelting slag (LSS) has been identified as general industrial solid waste, which is produced from the pyrometallurgical treatment of the Shuikoushan process for primary lead production in China. The LSS-based geopolymer was synthesized after high-energy ball milling. The effect of unconfined compressive strength (UCS) on the synthesis parameters of the geopolymer was optimized. Under the best parameters of the geopolymer (modulus of water glass was 1-1.5, dosage of water glass (W(SiO2+Na2O)) was 5% and water-to-binder ratio was 0.2), the UCS reached 76.09 MPa after curing for 28 days. The toxicity characteristic leaching procedure (TCLP) leaching concentration of Zn from LSS fell from 167.16 to 93.99 mg/L after alkali-activation, which was below the limit allowed. Meanwhile, C-S-H and the geopolymer of the hydration products were identified from the geopolymer. In addition, the behavior of iron was also discussed. Then, the hydration process characteristics of the LSS-based geopolymer were proposed. The obtained results showed that Ca2+ and Fe2+ occupied the site of the network as modifiers in the glass phase and then dissociated from the glass network after the water glass activation. At the same time, C-S-H, the geopolymer and Fe(OH)2 gel were produced, and then the Fe(OH)2 was easily oxidized to Fe(OH)3 under the air curing conditions. Consequently, the conclusion was drawn that LSS was an implementable raw material for geopolymer production.

Optimized bimetallic nickel-iron phosphides with rich defects as enhanced electrocatalysts for oxygen evolution reaction.

Exploring low-cost and outstanding bimetallic phosphides to substitute noble metals as electrocatalysts for oxygen evolution reaction (OER) in alkaline media is essential for renewable energy technologies. Herein, bimetallic nickel-iron phosphides nanoparticles (P-NiFe-800 NPs) with rich defects have been synthesized through gas annealing at 800 °C and phosphorization using uniform nickel-iron nanocubes (NiFe NCs) as precursor. At optimized calcination temperature, the obtained P-NiFe-800 NPs are composed of uniform nanoparticles with the rough surface, which suggests the larger surface area and more exposed rich active sites than other samples for OER. The introduction of P element to binary nickel-iron metals can optimize the crystalline and electronic structures of NiFe NCs and thus enhance electrocatalytic properties. Owing to the distinct morphological structure and synergistic effect between nickel-iron and phosphorus, P-NiFe-800 NPs demonstrate superior electrocatalytic activities for OER with lower overpotential of 270.1 mV to achieve a current density of 10 mA cm-2, smaller Tafel slope of 39 mV dec-1, lower electrochemical impedance spectroscopy (EIS) value, bigger determined double-layer capacitance (Cdl) of 2130 uF cm-2 and prominent stability than NiFe NCs, NiFe-600 NPs, NiFe-700 NPs, NiFe-800 NPs, NiFe-900 NPs, P-NiFe NCs, P-NiFe-600 NPs, P-NiFe-700 NPs and P-NiFe-900 NPs. The optimized phosphorization is helpful for fabricating the bimetallic phosphides as efficient catalysts for OER.

Formation mechanism of zinc-doped fayalite (Fe2-xZnxSiO4) slag during copper smelting.

The interactions between Fe2SiO4 and ZnO play an essential role in the recovery of zinc from copper slag. The dissolution and substitution mechanism of ZnO in fayalite were investigated by using TG-DSC, XRD, PPMS DynaCool, XPS, Mossbauer and SEM-EDS analyses and compared with MS calculation results. The results indicate that the dissolution and substitution are actually processes of the penetrating dissolution of Zn(II) ions that can be divided into three steps: 1) ZnO dissociates into Zn1-yO and Zn(II) ions; 2) Zn(II) penetrates the gap of the octahedron outer layer to substitute Fe(II) sites in the internal structure of SiOFe(II) (M2) to form (Fe2-x, Znx)SiO4; 3) Fe(II) is forced to migrate to the surface of (Fe2-x, Znx)SiO4 to form (Zn1-y, Fe(II)y)O. These findings can be derived the occurrence state and distribution of zinc in copper slag theoretically.

Cotreatment of MSWI Fly Ash and Granulated Lead Smelting Slag Using a Geopolymer System.

Municipal solid waste incineration fly ash (MSWI FA) and granulated lead smelting slag (GLSS) are toxic industrial wastes. In the present study, granulated lead smelting slag (GLSS) was pretreated as a geopolymer precursor through the high-energy ball milling activation process, which could be used as a geopolymeric solidification/stabilization (S/S) reagent for MSWI FA. The S/S process has been estimated through the physical properties and heavy metals leachability of the S/S matrices. The results show that the compressive strength of the geopolymer matrix reaches 15.32 MPa after curing for 28 days under the best parameters, and the physical properties meet the requirement of MU10 grade fly ash brick. In addition, the toxicity characteristic leaching procedure (TCLP) test results show that arsenic and heavy metals are immobilized effectively in the geopolymer matrix, and their concentrations in the leachate are far below the US EPA TCLP limits. The hydration products of the geopolymer binder are characterized by X-ray diffraction and Fourier transform infrared methods. The results show that the geopolymer gel and Friedel's salt are the main hydration products. The S/S mechanism of the arsenic and heavy metals in the geopolymer matrix mainly involves physical encapsulation of the geopolymer gel, geopolymer adsorption and ion exchange of Friedel's salt.

Co-treatment of flotation waste, neutralization sludge, and arsenic-containing gypsum sludge from copper smelting: solidification/stabilization of arsenic and heavy metals with minimal cement clinker.

Flotation waste of copper slag (FWCS), neutralization sludge (NS), and arsenic-containing gypsum sludge (GS), both of which are difficult to dispose of, are major solid wastes produced by the copper smelting. This study focused on the co-treatment of FWCS, NS, and GS for solidification/stabilization of arsenic and heavy metals with minimal cement clinker. Firstly, the preparation parameters of binder composed of FWCS, NS, and cement clinker were optimized to be FWCS dosage of 40%, NS dosage of 10%, cement clinker dosage of 50%, mill time of 1.5 h, and water-to-binder ratio of 0.25. On these conditions, the unconfined compressive strength (UCS) of the binder reached 43.24 MPa after hydration of 28 days. Then, the binder was used to solidify/stabilize the As-containing GS. When the mass ratio of binder-to-GS was 5:5, the UCS of matrix can reach 11.06 MPa after hydration of 28 days, meeting the required UCS level of MU10 brick in China. Moreover, arsenic and other heavy metals in FWCS, NS, and GS were effectively solidified or stabilized. The heavy metal concentrations in leachate were much lower than those in the limits of China standard leaching test (CSLT). Therefore, the matrices were potential to be used as bricks in some constructions. XRD analysis shows that the main hydration products of the matrix were portlandite and calcium silicate hydrate. These hydration products may play a significant role in the stabilization/solidification of arsenic and heavy metals.