Innovative methodology for comprehensive utilization of arsenic-bearing neutralization sludge.

Arsenic-bearing neutralization (ABN) sludge is a classical hazardous waste commonly found in nonferrous metallurgy. However, the current storage of these hazardous wastes not only has to pay costly hazardous waste taxes but also poses significant risks to both the environment and human health. To address these issues and achieve the comprehensive utilization and minimization of ABN sludge, this study proposes a new combined process. The process involves selective reduction roasting, leaching, and carbonation, through which, the arsenate and gypsum in the ABN sludge were recovered in the form of As(s), high-purity CaCO3, and H2S. The selective reduction behaviors of arsenate and gypsum were investigated through thermodynamic analysis and roasting experiments. The results indicated that the 95.35 % arsenate and 96.55 % gypsum in the sludge were selectively reduced to As4(g) and CaS at 950 °C by carbothermic reduction. The As4(g) was condensed to As(s) and enriched in the dust (As, 96.78 wt %). In the leaching process, H2S gas was adopted to promote the leaching of CaS, and resulted in 97.41 % of CaS in the roasted product was selectively leached in the form of Ca(HS)2, leading to a 74.11 % reduction in the weight of the ABN sludge. Then, the Ca(HS)2 was subjected to capture CO2 for the separation of Ca2+ and S2-. The result depicted that 99.69 % of Ca2+ and 99.12 % of S2- were separated as high-purity (99.12 wt %) CaCO3 and H2S (24.89 vol %) by controlling the terminal carbonation pH to below 6.55. The generated H2S can be economically converted to sulfur by the Clause process. The whole process realized the comprehensive resource recovery and the minimization of the sludge, which provides an alternative solution for the clean treatment of hazardous ABN waste.

New Insight into Elastic Mechanical Properties and Anisotropies of Crystal Defect α-Quartz from DFT Calculation.

To reveal the cleavage mechanism of α-quartz in the grinding process of nonferrous metal ores, mechanical and charge properties of α-quartz crystals are investigated using the density functional theory. Based on the elastic constant matrix, the bulk and shear moduli were calculated before and after the α-quartz with oxygen atom defects. The results show that the ratios of bulk and shear moduli (B/G) were 0.87 and 0.95, respectively, which indicated that at the same stress level, it was easier to fracture without O-vacancy defects than with O-vacancy defects. The mapping surfaces indicated that the O-vacancy defect increased the bulk-, shear-, and Young's moduli, and Poisson ratio while decreasing the hardness. The anisotropy index (AL and AU) was calculated which illustrated that the O-vacancy can result in an increased anisotropy; meanwhile, the bulk anisotropy index (AB) increased strongly about two times. The anisotropy analysis shows the dominance crystal cleavage of the (011) plane in the shear stress and the dominance crystal cleavage of the (111) plane in the normal stress. The electron localization function α-quartz show that the O-vacancy defect can decrease the Si-Si length from 3.703 to 2.442 Å, which indicated that the O-vacancy formed the new covalent bonds between silicon atoms. Our work provided a systematic approach containing the mechanical, anisotropic, and electronic properties of mineral crystals to explain the cleavage behavior of crystals.

Recovery of zinc and extraction of calcium and sulfur from zinc-rich gypsum residue by selective reduction roasting combined with hydrolysis.

A novel process that includes selective reduction roasting followed by hydrolysis was proposed in this work to recover zinc, and efficiently extract calcium and sulfur from hazardous zinc-rich gypsum residue (ZGR) waste for high-purity of CaCO3 and sulfur production. The selective reduction behaviors of ZGR during the reduction roasting were investigated in detail based on thermodynamic analysis and roasting experiments. The effect of roasting temperature, carbon dosage and time on the selective reduction of ZGR was comprehensively investigated, and the results indicated that ZnO and CaSO4 in the ZGR can be selectively reduced to Zn(g) and CaS, respectively. The volatile Zn(g) was oxidized to ZnO and enriched in the dust, which can be used as a secondary zinc resource. Moreover, the hydrolysis behaviors and leaching kinetic of CaS during hydrolysis were studied intensively. Results depicted that in the H2S-H2O system, the CaS in the roasted product can be selectively and efficiently dissolved into the leachate. Furthermore, the kinetic analysis revealed that the hydrolysis of CaS conformed to the internal diffusion reaction control model in the shrinking core model and the apparent activation energy Ea = -12.02 kJ/mol. The obtained hydrolysate with low impurities could be used to capture CO2 for the production of high-purity sulfur and CaCO3. Iron and other impurities in the roasted product were concentrated into the leaching slag in the form of metallic iron and akermanite. The whole process realized the recovery of zinc, and the selective and effective extraction of calcium and sulfur, which could provide an alternative process for the large-scale treatment of these hazardous wastes.

[Dynamic characteristics of brain networks in patients with irritable bowel syndrome based on functional magnetic resonance imaging].

The disorder of brain-gut interaction is an important cause of irritable bowel syndrome (IBS), but the dynamic characteristics of the brain remain unclear. Since there are many shortcomings for evaluating brain dynamic nature in the previous studies, we proposed a new method based on slope calculation by point-by-point analysis of the data from functional magnetic resonance imaging, and detected the abnormalities of brain dynamic changes in IBS patients. The results showed that compared with healthy subjects, there were dynamic changes in the brain for the IBS patients. After correction by false discovery rate (FDR), significant abnormalities were only found in two functional connections of the right posterior cingulate gyrus linked to left middle frontal gyrus, and the right posterior cingulate gyrus linked to left pallidus. The above results of the brain dynamic analysis were totally different from those of the brain static analysis of IBS patients. Our findings provide novel complementary information for illustrating the central nervous mechanism of IBS and may offer a new direction to explore central target for patients with IBS.

Production and resource utilization of flue gas desulfurized gypsum in China - A review.

Flue gas desulfurized gypsum (FGD gypsum), mainly originates from thermal power plants, smelters, and large-scale enterprise boilers. This article reviews the production in China and the latest beneficial utilizations of FGD gypsum. China is a large coal-consuming country and has always had serious SO2 emissions. Therefore, the Chinese government has implemented a large number of desulfurization measures since 2006. With continually increasing energy consumption and increasingly stringent environmental requirements, the production of FGD gypsum has exceeded 108 tons. The basic properties and the current beneficial applications of FGD gypsum are summarized here. The practical application of FGD gypsum in four fields-building materials, agriculture, material synthesis, and soil-and its impact on the environment, are analyzed. Finally, a new direction is proposed for the future utilization of FGD gypsum.

Dynamic characteristics of brain networks in patients with irritable bowel syndrome based on functional magnetic resonance imaging / 生理学报

The disorder of brain-gut interaction is an important cause of irritable bowel syndrome (IBS), but the dynamic characteristics of the brain remain unclear. Since there are many shortcomings for evaluating brain dynamic nature in the previous studies, we proposed a new method based on slope calculation by point-by-point analysis of the data from functional magnetic resonance imaging, and detected the abnormalities of brain dynamic changes in IBS patients. The results showed that compared with healthy subjects, there were dynamic changes in the brain for the IBS patients. After correction by false discovery rate (FDR), significant abnormalities were only found in two functional connections of the right posterior cingulate gyrus linked to left middle frontal gyrus, and the right posterior cingulate gyrus linked to left pallidus. The above results of the brain dynamic analysis were totally different from those of the brain static analysis of IBS patients. Our findings provide novel complementary information for illustrating the central nervous mechanism of IBS and may offer a new direction to explore central target for patients with IBS.

Immobilization and enzymatic properties of glutamate decarboxylase from Enterococcus faecium by affinity adsorption on regenerated chitin.

Glutamate decarboxylase (GAD, EC 4.1.1.15) is an important enzyme in gamma-aminobutyric acid biosynthesis and DL-glutamic acid resolution. In this study, the Enterococcus faecium-derived GAD was successfully immobilized by regenerated chitin (RC) via specific adsorption of cellulose-binding domain (CBD). The optimal binding buffer was 20 mmol/L phosphate buffer saline (pH 8.0), and the RC binding capacity was 1.77 ± 0.11 mgcbd-gad/grc under this condition. The ratio of wet RC and crude enzyme solution used for immobilization was recommended to 3:50 (g/mL). To evaluate the effect of RC immobilization on GAD, properties of the immobilize GAD (RC-CBD-GAD) were investigated. Results indicated RC-CBD-GAD was relatively stable at pH 4.4-5.6 and temperature - 20-40 °C, and the optimal reaction pH value and temperature were pH 4.8 and 50 °C, respectively. When it was reacted with 5 mmol/L of follow chemical reagents respectively, the activity of RC-CBD-GAD was hardly affected by EDTA, KCl, and NaCl, and significantly inactivated by AgNO3, MnSO4, MgSO4, CuSO4, ZnSO4, FeCl2, FeCl3, AlCl3, CaCl2, and Pb(CH3COO)2. The apparent Km and Vmax were 28.35 mmol/L and 147.06 µmol/(gRC-CBD-GAD·min), respectively. The optimum time for a batch of catalytic reaction without exogenous pH control was 2 h. Under this reaction time, RC-CBD-GAD had a good reusability with a half-life of 23 cycles, indicating that it was very attractive for GABA industry. As a novel, efficient, and green CBD binding carrier, RC provides an alternative way to protein immobilization.

Pneumatic separation for crushed spent lithium-ion batteries.

Pneumatic separation was used to separate the valuable current collectors and harmful separators in spent lithium-ion batteries (LIBs) to avoid the plastic pollution caused by the separators in this study. Theoretical calculations for suspension velocities of the current collectors and separators indicate that they could be separated under special conditions. Furthermore, a special Z-shaped pneumatic separator was used to separate the current collectors and separators for the first time. Experiments for manually cut samples indicate that the efficiency of pneumatic separation is approximately 100% with the sizes and airflow velocities in the range of 3-4 cm and 6.96-7.8 m/s, respectively. Furthermore, industrial experiments of pneumatic separation indicate that the recoveries of the current collectors and separators are approximately 99.23% and 98.64%, respectively. Computer simulations of the separation process indicate that the turbulence and the changes in high-speed zones in the pneumatic separator benefit the separation of current collectors and separators. In conclusion, pneumatic separation is a promising technology to separate crushed current collectors and separators.

Pyrolysis and physical separation for the recovery of spent LiFePO4 batteries.

In this study, a novel process consisting of pyrolysis and physical separation was proposed to comprehensively recycle spent lithium ion batteries (LIBs). The discharge and pyrolysis behaviors of spent LIBs, the recovery of electrolyte from the spent LIBs by low-temperature volatilization, and the recovery of valuable materials from the pyrolytic residues through physical separation were studied in detail. The results indicated that approximately 99.91% of the organic electrolytes was recycled, and the lithium salt (LiPF6) in the batteries was disposed by pyrolysis process. The active materials could be effectively separated from current collectors after the pyrolysis under N2 at 550 °C for 2 h. The pyrolytic gas was mainly composed of light alkenes, and the pyrolytic tar was mainly composed of aromatic long chain alkenes and light alcohols. Pyrolytic residues were recycled by color sorting, high-pressure water cleaning and flotation processes, and about 99.34% of Al, 96.25% of Cu, and 49.67% of cathode active materials were recovered from the spent LIBs. Finally, electrochemical tests indicate that the cathode active materials obtained by the process can be used to produce new batteries.

Sulfidation mechanism of ZnO roasted with pyrite.

Sulfidation is a widely used technology to improve the floatability of oxidized metal minerals or to stabilize the heavy metals in various wastes. The sulfidation mechanism of ZnO with pyrite was detailedly studied by thermodynamic calculation and roasting experiments. The sulfidation behaviors, phase transformations, microscopic morphology and surface properties were investigated by TG-DSC, ICP, XRD, SEM-EDS, and XPS analysis. The results indicate that the nature of the sulfidation is the reaction of ZnO with the gaseous sulfur generated by the decomposition of pyrite. Pyrite instead of sulfur as the sulfidizing agent can not only relieve the volatilization loss of sulfur but also enhance the formation of liquid phase and thus facilitate the growth of ZnS particles. The sulfidation reaction belongs to surface chemical reaction and relates to the migration of oxygen from the inside of ZnO to its surfaces. The presence of carbon not only eliminates the release of SO2, but also decreases the decomposition temperature of pyrite and promotes the sulfidation of ZnO. The addition of Na2CO3 promotes the sulfidation of ZnO at lower temperatures (below 850 °C) and enhances the growth of ZnS particles but has a negative effect on the sulfidation at higher temperatures.

Mechanism study on the sulfidation of ZnO with sulfur and iron oxide at high temperature.

The mechanism of ZnO sulfidation with sulfur and iron oxide at high temperatures was studied. The thermodynamic analysis, sulfidation behavior of zinc, phase transformations, morphology changes, and surface properties were investigated by HSC 5.0 combined with FactSage 7.0, ICP, XRD, optical microscopy coupled with SEM-EDS, and XPS. The results indicate that increasing temperature and adding iron oxide can not only improve the sulfidation of ZnO but also promote the formation and growth of ZnS crystals. Fe2O3 captured the sulfur in the initial sulfidation process as iron sulfides, which then acted as the sulfurizing agent in the late period, thus reducing sulfur escape at high temperatures. The addition of carbon can not only enhance the sulfidation but increase sulfur utilization rate and eliminate the generation of SO2. The surfaces of marmatite and synthetic zinc sulfides contain high oxygen due to oxidation and oxygen adsorption. Hydroxyl easily absorbs on the surface of iron-bearing zinc sulfide (Zn1-xFexS). The oxidation of synthetic Zn1-xFexS is easier than marmatite in air.