Novel method for recovering valuable metals from Sn ash: Vacuum carbothermal reduction-directional condensation.

Sn ash recycling is an industry with positive development prospects, as it provides better-protected resources, promotes sustainable development, and lays a solid foundation for future development. In this study, an innovative vacuum carbothermal reduction-directional condensation process was developed. The thermodynamic analysis results indicated that the initial reaction pressure and temperature for the carbothermal reduction of the system was 1-10 Pa and 998-1063 K, respectively. The saturation vapor pressure, separation coefficient, and condensation temperature of Sn, Pb, and Zn in the reduced products differed significantly, and their separation could be achieved by controlling the volatilization and condensation temperatures. A single-factor experiment investigated the effects of carbon ratio, temperature, and time on the reduction efficiency, direct yield, and recovery rate. The optimal experimental conditions were the ratio of MeO to C of 4:1, temperature of 1373 K, and time of 120 min. Sn, Pb, and Zn products were obtained at different positions. This process shortens the traditional process, reduces the reduction cost of Sn, and enables the implementation of the process, making it environmentally friendly.

Study on the behavior of clusters in the physical recovery of GaAs scrap.

Gallium arsenide (GaAs) is the most widely used second-generation semiconductor material. However, a large amount of GaAs scrap is generated at various stages of the GaAs wafer production process. Volatile GaAs clusters are inevitably generated during the process of GaAs vacuum thermal decomposition, resulting in lower purity of the recovered arsenic and the loss of gallium. In this study, thermodynamic analysis and dynamics simulation were combined to discuss the possibility of separating GaAs clusters and arsenic from a microscopic perspective. A vacuum thermal decomposition-directional condensation recovery process for GaAs scrap was proposed. By properly adjusting the separation parameters such as heating temperature, holding time and raw material size, high purity of gallium (99.99%) and arsenic (99.5%) were directly recovered under a system pressure of 1 Pa, heating temperature of 1323 K, holding time of 3 h, and GaAs scrap size of 2.5 cm. GaAs clusters were also recovered in powder form. The problem of difficult separation of GaAs clusters from arsenic was effectively solved by this method, and the purity of recovered arsenic was greatly improved. No additives are required and no waste liquid or gas emission in the whole process. The complexity of subsequent arsenic purification operations and the threat of arsenic containing waste to the environment were reduced as well.

Arsenic release pathway and the interaction principle among major species in vacuum sulfide reduction roasting of copper smelting flue dust.

The efficient release of arsenic in copper smelting flue dust (CSFD) with complicated production conditions and composition under the premise of environmental safety is difficult for the copper smelting industry. The vacuum environment is conducive to the volatilization of low-boiling arsenic compounds, which is beneficial to the physical process and chemical reaction of increasing the volume. In the present study, combined with thermodynamic calculations, the roasting process of pyrite and CSFD mixed in proportion in vacuum was simulated. Additionally, the release process of arsenic and the interaction mechanism of the main phases were performed in detail. The addition of pyrite facilitated the decomposition of stable arsenate in CSFD into volatile arsenic oxides. The results indicated that exceeding 98% of arsenic in CSFD volatilized into the condenser, while the arsenic content in the residue was reduced to 0.32% under optimal conditions. Pyrite could reduce the oxygen potential during the chemical reaction with CSFD, reacting with sulfates in CSFD to convert into sulfides and magnetic iron oxide (Fe3O4) simultaneously, and Bi2O3 would be transformed into metallic Bi. These findings are significant for developing arsenic-containing hazardous waste treatment routes and the application of innovative technical approaches.

Selective sulfidation-vacuum volatilization processes for tellurium and bismuth recovery from bismuth telluride waste thermoelectric material.

Bismuth telluride-based alloy materials are currently the best performing thermoelectric materials at near room temperature; however, their production and use generate waste (e.g., cutting waste and failed grains). There is also lack of efficient recycling strategies for the generated waste. In this study, a selective sulfidation-vacuum volatilization method is proposed for recovering bismuth telluride waste. The Gibbs free energies of the sulfidation reaction of bismuth telluride are calculated, the saturated vapor pressure of each substance is analyzed, and the composition of the products is predicted. Based on the differences among the sulfidation and volatile properties of bismuth and tellurium, by adding sulfur to bismuth telluride waste, the composition of the substances was regulated, and efficient separation of tellurium and bismuth was achieved. We combined theoretical calculations and experimental studies to investigate the effect of process conditions on the separation and recovery of tellurium and bismuth. The results show that bismuth was thoroughly sulfereted and tellurium was a pure metal when the mass ratio of sulfur to bismuth telluride was 0.168, the sulfidation temperature was 573 K, and the holding time was 60 min. After sulfidation of the bismuth telluride waste, the sulfides were telluride and bismuthous sulfide. The sulfides, that resulted from sulfureted bismuth telluride production, were treated via vacuum volatilization. The optimal vacuum volatilization condition was 873 K for 120 min. The purities of tellurium and bismuth sulfide obtained by the selective sulfidation-vacuum volatilization experiment were >99%. The distribution ratios of tellurium and bismuth were 98.46% and 99.59%, respectively. The method thoroughly separated tellurium and bismuth from bismuth telluride waste, considerably reducing the environmental and economic costs compared with those of the conventional processes.

Sustainable safe and environmentally friendly process to recovery valuable materials from hazardous waste InP.

With the rapid expansion of the market scale for indium phosphide (InP) semiconductors in high-tech industries such as optoelectronics and solar energy, the generation of hazardous waste InP has also increased dramatically, and the task of recycling waste InP is urgent. However, InP as a representative phosphide semiconductor is prone to produce highly toxic substances such as yellow phosphorus and PH3 in the recycling process, which discourages most companies from using it. In this study, a safe and efficient method of "vacuum decomposition-directional condensation (VD-DC)" is proposed to recover valuable materials from waste InP. In this method, briquetting pretreatment is used to improve thermal conductivity. At a decomposition temperature of 1123 K, system pressure of 30 Pa, and holding time of 3.5 h, indium with a purity of 99.43 wt% is obtained, and the direct yield reaches 98.54%. Non-toxic and stable red phosphorus with a purity of 98.14 wt% is recovered by converting the condensed yellow phosphorus at 573 K. Vacuum technology significantly reduces the decomposition temperature of InP and avoids the emission of waste water and waste gas, thus operating in an environmentally friendly manner.

Synergy of directional oxidation and vacuum gasification for green recovery of As2O3 from arsenic-containing hazardous secondary resources.

Arsenic, a hazardous material that is toxic for humans, enters the human body through soil, water, and air. Furthermore, metal smelting is known to produce arsenic-containing hazardous secondary resources (AHSRs), which cause irreversible damage to the total environment. Therefore, a novel, clean, and efficient arsenic fixation technology has been developed in this study for arsenic removal, which involves directional oxidation and vacuum gasification of AHSRs. Oxidation results revealed that physical phases containing arsenic (As, As2O3, As2Te3 and Cu3As) are selectively oxidized to As2O3 completely and thus classified as oxidative modulation products (OMPs). Meanwhile, approximately 98.82% As2O3 of OMPs convert into volatiles in the following gasification. Characterization results showed that As2O3 with 96.72% purity and uniform microscopic distribution was obtained in the form of monoclinic crystalline needle-like crystals. The proposed approach organically combines oxidation and volatilization properties of each element to facilitate clean and efficient separation as well as recovery of As2O3. No hazardous gas or wastewater is discharged during the entire process, thereby ensuring that arsenic is recycled in a sustainable and clean manner. Overall, this study provides a clean and low-carbon approach for recycling secondary resources containing arsenic.

Design of "turn-off" luminescent Ln-MOFs for sensitive detection of cyanide anions.

Two novel 2D lanthanide metal-organic frameworks (Ln-MOFs), namely {[Eu2(DBTA)3(DMF)2]·DMF}n (1) and {[Tb2(DBTA)3(DMF)2]·DMF}n (2) (H2DBTA = 2,5-dibromoterephthalic acid), have been successfully synthesized by the solvothermal method. Single-crystal X-ray diffraction results proved that the complexes possess the same topological structure of a (42·6)2(42·84)(47·63)2-connected net. The recognition of CN- from interfering anions with a low detection limit by "turn-off" luminescence makes them promising candidates for the highly selective and sensitive detection of the cyanide ion. The Ln-MOFs 1 and 2 exhibit excellent chemical sensing properties for CN- with efficiency, selectivity, and excellent performance in various mixed anions. The evaluation parameters, including the quenching constant and detection limit, have been investigated to obtain the detection performance for CN-.

The lead removal evolution from hazardous waste cathode ray tube funnel glass under enhancement of red mud melting and synthesizing value-added glass-ceramics via reutilization of silicate resources.

Waste CRT funnel glass (FG) is a typical hazardous waste produced by the electronics industry that contains toxic lead oxide, red mud (RM) is the first waste produced during alumina production. Both of these are extremely difficult to reuse. Here, we report a method to control FG waste, in which RM was used to enhance the removal of Pb from FG via a vacuum thermal process. The removed residual glass was utilized to create glass-ceramics. The results showed that RM can enhance the lead removal from waste CRT funnel glass by the vacuum thermal process. When 30% RM was added, the removal rate reached 98.54%. A significant mechanism of enhancing delead is investigated by a Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The results showed that the -Pb-O-Si-O- network structure was broken by the free calcium ions of RM. Afterward, valuable glass-ceramics with tetragonal-KAlSi2O6 and triclinic-CaSiO3 crystals were synthesized using the residual glass. The Pb, Ba, Cr, and Cu leaching concentrations of the glass-ceramics were well below the regulatory limit (5 mg/L) of the CA-EPA, as measured by the toxicity characteristic leaching procedure (TCLP) test. Overall, the results indicated that RM enhanced the removal of lead during the vacuum thermal process. The synthesis of value-added glass-ceramics reutilized silicate resources from waste cathode ray tube (CRT) funnel glass and RM.

Rapid Preparation of TiO2-x and Its Photocatalytic Oxidation for Arsenic Adsorption under Visible Light.

A rapid preparation method of TiO2-x by thermal treatment using H2TiO3 as the precursor was proposed compared with the static hydrogenation thermal treatment process. Its adsorption properties of arsenic under visible light were explored and investigated as well. Various colors of TiO2-x were prepared and characterized via XRD, TEM, BET, and so on. The results indicate that the method of rapid preparation is feasible. The TiO2-x exhibits a larger particle size that varied from 10 nm to 2 µm, and deeper color products were obtained as the treatment temperature increased from 600 to 900 °C. Light yellow TiO2-x was prepared after increasing the temperature from 600 to 900 °C, Ti4O7 and Ti6O11 with a dark color were formed under a H2 atmosphere at 1500 °C. The arsenic adsorption performances of some samples under visible light were tested, and reveal a high efficiency of TiO2-x in the photocatalytic oxidation arsenic adsorption under visible light, the conversion ratio of As(III) photocatalytic oxidation fluctuates around 2.85 mgAsg-1 h-1. In the absence of visible light, the adsorption capacities for As(III) and As(V) are 3.7 and 42.7 mg/g, respectively, at pH = 3. Under visible light condition, the adsorption capacity of As(III) increases sharply to 15.6 mg/g, which provides the foundation for a new application of TiO2-x in the field of arsenic adsorption.

Direct calciothermic reduction of porous calcium titanate to porous titanium.

A metallurgical material integration concept, using porous calcium titanate (CaTiO3) as raw material, was put forward for preparation of metallic titanium powder and porous titanium by calciothermic reduction. Porous metallic titanium was prepared by calcium vapor reduction at 1273 K for 6 h with two types of interconnected pores in titanium samples. The interconnected macropores about 50-300 µm were inherited from porous CaTiO3, and the micropores about 5-40 µm were made by leaching removal of byproduct CaO in reduction products. Metallic porous titanium was fabricated in Ca-dissolved CaO-CaCl2 molten salt mixtures by self-sintering and had a good interconnectivity inside with thickness about 155 µm and the porosities of the porous titanium are 65-81%.

A novel non-synonymous mutation in the homeodomain of HOXD13 causes synpolydactyly in a Chinese family.

PURPOSE: The 5' HoxD genes and their paralogs in the HoxD cluster are crucial for normal vertebrate limb development. Mutations in HOXD13 and HOXD13 have been found to cause human limb malformation. Here we describe a two-generation Chinese family with a variant form of mild synpolydactyly. METHODS: Sequence analysis of HOXD13 gene in a two-generation Chinese family with six individuals. RESULTS: Gene scan and linkage analysis suggested that HOXD13 might be responsible for the disease of this family. An LOD around 1.8 was observed at three markers (P=2E(-3)). We identified a novel c.893G>A (p.Arg298Gln) mutation in the HOXD13 homeodomain. And the mutation affected the transcriptional activation ability of HOXD13. CONCLUSION: This finding expands the phenotypic spectrum associated with HOXD13 mutations and advances our understanding of human limb development.