Cyanide-containing wastewater from the gold industry often contains high concentrations of sodium sulfate (Na2SO4) and sodium thiocyanate (NaSCN), resulting in large amounts of waste salts. This study presents, for the first time, the utilization of the reducing property of NaSCN to convert Na2SO4 waste salts into value-added products such as sodium disulfide (Na2S2), sodium sulfide (Na2S), and calcium sulfide (CaS), achieving the synergistic resource recovery of both salts. The pyrolysis of NaSCN alone, the co-pyrolysis of NaSCN and Na2SO4, and the effect of calcium oxide (CaO) on the pyrolysis process were investigated. Thermogravimetric analysis results indicate that, compared to carbothermal reduction, using NaSCN as a reducing agent can lower the theoretical reduction temperature of Na2SO4 by 267.3 K. The products from the pyrolysis of NaSCN alone are Na2S2, C, and N2(g). The solid products from the co-pyrolysis of Na2SO4 and NaSCN are Na2S2 and Na2S. In the Na2SO4-NaSCN-CaO system, the solid pyrolysis products are Na2S and CaS. The intermediate gaseous products CO(g) and CO2(g) generated during the pyrolysis of NaSCN significantly influence the reaction kinetics. At 973 K for 30 min, Na2SO4 can be completely reduced by NaSCN. In the Na2SO4-NaSCN-CaO system, however, the absorption of CO2(g) by CaO to form calcium carbonate (CaCO3) inhibits rapid pyrolysis at lower temperatures, requiring 60 min at 973 K to achieve complete conversion of SCN-ions. The reduction of Na2SO4 by NaSCN involves complex reactions among solid, liquid, and gas phases. Through in-depth analysis of the reaction process and thermodynamic equation fitting, it is confirmed that the rate-controlling step is the gas-solid interfacial reaction. The apparent activation energies for the Na2SO4-NaSCN and Na2SO4-NaSCN-CaO systems are 154.56 kJ & sdot;mol- 1 and 141.23 kJ & sdot;mol- 1, respectively.

Co-upcycling plastics with lithium-ion batteries (LIBs) into carbon nanotubes (CNTs) offers a promising high-value approach; however, it is hindered by the challenge of poisoning metal catalysts by carbon deposition and the uncontrollable particle growth. Here, we propose a co-upcycling strategy to convert spent LiNixCoyMn1-x-yO2 (NCM) and binary plastics-polyethylene terephthalate (PET) and other plastics-into NiCoMnOx/CNTs composites (or materials) for microwave absorption. During the pyrolysis, the generated pyrolysis gas reduces the NCM to NiCoMnOx and Li2CO3, and the NiCoMnOx catalyzes the decomposition of pyrolysis gas to generate CNTs. Importantly, Li2CO3 suppresses the growth of NiCo particles to below 100 nm and PET as both an etching agent and a carbon source, achieving a carbon conversion rate of 33% while preventing NiCoMnOx poisoning. After heat treatment at 800 °C, the resulting material exhibits favorable microwave absorption with an effective absorption bandwidth (EAB, RL <-10 dB) of 7.01 GHz at 2.41 mm. Life cycle analysis (LCA) shows that this strategy has obvious environmental benefits. Overall, PET is a general enabler to prepare (NixCoy)MnO/CNTs microwave-absorbing materials harnessing carbon from binary plastics and critical metals from battery materials, providing a sustainable solution for upcycling spent LIBs and plastic wastes.

The microstructure and corrosion behaviour of C26000 brass matrix composite were systematically investigated as a function of AlCoCrFeNi high entropy alloy (HEA) content by spark plasma sintering (SPS). The results demonstrate that increasing the content of HEA leads to significant grain refinement and a shift in the dominant grain orientation from the {111} to the {001} plane. At 20 wt% HEA addition, the composite exhibits reductions of 83.55% in the mass loss rate (0.064 mm/a), 43.75% in the dezincification corrosion depth (160.344 mu m), and 94.67% in the electrochemical corrosion rate (0.012 mm/a), compared to the unreinforced C26000 brass matrix. The enhanced corrosion resistance stems from the synergistic effect of a multi-principal element passivation film acting as a physical barrier against corrosive media and the HEA reinforcement improving the interfacial electrochemical stability of the brass matrix, thereby providing synergistic protection against corrosion. This study provides valuable insights for effectively enhancing the corrosion resistance of brass matrix composites using HEA reinforcements.

Microwave absorbing materials (MAMs) of the ferrite type are crucial for resisting electromagnetic radiation. This work proposed a novel high-temperature mechanochemical method (HTMC) to prepare zinc ferrite (ZnFe2O4). The effects of key process parameters on the microstructure and properties of ZnFe2O4 were investigated. The results indicate that the electromagnetic and microwave absorption (MA) performances can be influenced by the crystallization and dispersion degree of ZnFe2O4. Meanwhile, its MA originates from the good synergy between its dielectric losses (dipole polarization, interfacial polarization, conductive loss) and magnetic losses (eddy current loss, natural resonance, exchange resonance). The HTMC achieves the coupling effect of mechanical force and high-temperature, refining particles while promoting the reaction process. It not only effectively optimizes reaction conditions and shortens the reaction process, but also enables large-scale preparation. This work enriches the existing strategies for the preparation of high-performance ferrite-type MAMs and provides promising insight for engineering applications.

Abstract Metal-organic frameworks (MOFs)/MXene-derived aerogels exhibit significant application potential in the field of electromagnetic wave absorption (EMWA). In this study, bimetallic NiCu-MOFs/MXene-derived aerogels were fabricated, and the regulatory effects of MXene addition on their microstructures, compositions, and EMWA properties were systematically investigated. By leveraging the dynamic assembly behavior of NiCu-MOFs induced by water molecules and combining it with the hydrogen bonding interactions of MXene nanosheets, a composite aerogel with a “sphere-rod-sheet” hierarchical porous structure was successfully constructed. Benefiting from the synergistic effect between MXene and bimetallic oxides, the optimized aerogel demonstrates excellent EMWA performance: the minimum reflection loss (RL min ) is as low as −85.80 dB, and the effective absorption bandwidth (EAB, RL < −10 dB) reaches 5.68 GHz at a coating thickness of 2.93 mm. Additionally, this aerogel possesses characteristics such as ultra-low density and hydrophobicity. This research provides a theoretical basis and technical support for the design of lightweight, high-efficiency, and multi-functional integrated MOFs/MXene-based electromagnetic wave absorption materials.

Cyanide is a toxic pollutant and widely exists in the wastewater of gold smelters. With highly concentrated sulphate and thiocyanate, attaining selective removal of cyanide is an important task. In this paper, we prepared a zinc-based magnetic Layered Double Oxide (LDO) adsorbent for cyanide removal, named ZnAl-LDO/CoFe2O4. The adsorption product was subjected to pyrolysis to achieve complete removal of cyanide and regeneration of the adsorbent. With ferrocyanide as adsorbate, the maximum adsorption capacity of ZnAl-LDO/CoFe2O4 for total cyanide was 691.9 mg/g. Three kinds of cyanide-containing wastewater from a gold smelter were treated respectively, and the total cyanide concentration in the wastewater reached the emission standard (< 0.5 mg/L). The mechanism of ferrocyanide adsorption were surface complexation and the generation of Zn2Fe(CN)6·3H2O. The pyrolysis of the adsorption products allows the recovery of Zn in the form of Zn (g). The unreacted ZnAl-LDO in the product retains its original morphology and has a superior adsorption performance. Under optimal conditions, the adsorption capacity of the pyrolysis product was 223.6 mg/g.

Rationally constructed defects and heterogeneous interfaces within crystals can promote the electromagnetic wave absorption (EMWA) performance of microwave absorbing materials (MAMs). However, existing research in enhanced EMWA based on constructed defects and multiple heterogeneous interfaces in microcrystalline graphite (MG) remains insufficient. Herein, expanded microcrystalline graphite (EMG) with abundant pores and a laminar structure is derived from natural microcrystalline graphite. Subsequently, EMG/Mn0.4Zn0.6Fe2O4 (EMG/MZF) composites with excellent EMWA properties were synthesized via the high-temperature mechanochemical (HTMC) method under the guidance of composition and structural design. The continuous mechanical force during the HTMC process facilitates the introduction of defects and nonhomogeneous interfaces. Concurrently, the porous layered structure of EMG significantly improves the dielectric properties of the composites, which improves the impedance matching and increases the dielectric/magnetic loss synergy together with the magnetic MZF particles. When the EMG ratio is set to 8 wt%, the 8EMG/MZF achieves an RLmin of-56.9 dB at 13.4 GHz with a matching thickness of 1.6 mm, with an effective absorption bandwidth (EAB) that covers 11.6-16.3 GHz. Furthermore, the radar cross section (RCS) was simulated, revealing that the 8EMG/MZF reduces the RCS value of the perfect electrical conductor (PEC) layer by 21.8 dB m2, further confirming its potential for practical applications. Most importantly, the HTMC achieves large-scale preparation and demonstrates favorable potential for industrial applications. This work not only provides a promising strategy for the preparation of composites with superior EMWA, but also paves a novel insight for the multiscale design of high-performance MAMs based on natural MG.

Rationally designed structural defects and multi-heterointerface within crystals can be leveraged to modulate electronic structure of transition metal elements, thereby facilitating the exploration of high-performance microwave absorbing materials (MAMs). However, existing research into cation defects and oxygen vacancies based on MOFs/MXene derivatives remains insufficient, predominantly relying on semi-empirical methodologies. Herein, a novel dual-defect engineering strategy is proposed to design multi-heterointerface MnCoNi/MnTiO3@C@Ti3C2Tx (MCNCT) nanocomposites derived from trimetallic MnCoNi-MOF-74@Ti3C2Tx using electrostatic self-assembly and thermal treatment processes. Specifically, it involves deliberately manipulating metal source ratios to foster vigorous cation competition and govern the harmonious coexistence of oxygen and metal vacancies. Extended X-ray absorption fine structure (EXAFS) elucidated that defects alter local coordination structure, with isolated Mn coordinated to bridging oxygen and Mn/Co/Ni atoms. Simultaneously, asymmetric electronic structure was regulated by constructed heterogeneous interfaces, contributing synergistically defect-induced polarization, as confirmed by density function theory calculations. Therefore, M2C1N1CT achieves the minimum reflection loss (RLmin) of -78.47 dB at 2.10 mm, the effective absorption bandwidth (EAB, RL < -10 dB) of 6.25 GHz at 2.29 mm, and the reduction of radar cross section value for 34.27 dB m(2). This work provides meaningful insights into potential applications of high-performance MAMs in crystal-structure engineering and dual-defect engineering.

As a typical microwave absorption material (MAM), ferrite is frequently employed within the domain of electromagnetic wave absorption (EMWA). In this work, through adopting a novel and promising high-temperature mechanochemical (HTMC) method, pure-phase spinel Mn x Zn (1- x ) Fe 2 O 4 nanopowders (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) with a spherical structure were fabricated. The powders' chemical compositions and structures, microscopic morphology, and static magnetic characteristics (Ms, Mr, and Hc) were examined, along with their electromagnetic parameters and EMWA capabilities in 2-18 GHz. The outcomes demonstrate that the static magnetic characteristics and dynamic electromagnetic performances of the Mn x Zn (1- x ) Fe 2 O 4 nanopowders can be significantly affected by the manganese content. The static magnetic characteristics and EMWA performances of the as- prepared powders can all be enhanced with a promotion in manganese content, which may be related to the Zn2+ substitution. Among these, at a matching thickness of 4.4 mm, the MnFe2O4 powder obtains a minimum reflection loss of-54.7 dB (equivalent to 99.9997 % of the EMWA), at which point the effective absorption bandwidth approaches 3.9 GHz. The superior EMWA performance of as-prepared Mn x Zn (1- x ) Fe 2 O 4 nanopowders is attributable to the favorable cooperative impact between dielectric and magnetic losses, as well as the multiple reflection and scattering of electromagnetic waves between the Mn x Zn (1- x ) Fe 2 O 4 particles, which lengthens the dissemination path of electromagnetic waves and strengthens the loss effect. Therefore, the as-prepared MnxZn(1- x ) Fe 2 O 4 nanopowder can be utilized in the field of high-efficiency EMWA, and the HTMC method has considerable potential for the large-scale preparation of high-performance MAMs.

In this paper, pyrite is innovatively used as sulfur source, and its combustion heat is used to achieve effective detoxification of zinc leaching residue. Realize the treatment of waste with waste. The effects of several factors on the immobilization of hazardous components like Zn, Pb, As, and Cd were systematically investigated. The results show that under the condition of a roasting temperature of 975 degrees C, roasting time of 2.5 h, sulfur content of 20 %, and air flow of 0.8 m3 & sdot;h-1, the leaching concentrations of Zn, Pb, As, and Cd in the roasted residue were 15.9 mg & sdot;L-1, 0.1 mg & sdot;L-1, 1.72 mg & sdot;L-1, and 0.84 mg & sdot;L-1, respectively, all of which are below the limits of hazardous waste identification standard. Thermodynamic analysis of the pyrite roasting process revealed that the heat generated by its combustion facilitates the roasting process of zinc leaching residue. The combustion product SO2 can transform PbCO3 in the leaching residue into PbSO4, and Fe2O3 can convert ZnO, ZnS and ZnSO4 into ZnFe2O4. PbFe6(SO4)4(OH)12 transforms to PbSO4, Fe2O3 and SO3. CdO generates CdFe8O16Zn3 after roasting. As is immobilizated in the roasted residue in the form of FeAsO4. Magnetic separation was performed on the roasted residue to recover Fe, and the obtained concentrate had an Fe content of 54.20 %. The residue mass decreased by 25.73 % post-roasting, realizing "waste-treats-waste" through sulfur self-consumption and SO2 fixation.

Constructing a reasonable dielectric-magnetic synergistic effect is an effective way to prepare high-performance electromagnetic wave absorbers. In this paper, ZnFe2O4@SiO2/C composites with a close-packed structure were successfully synthesized by an efficient condensation reaction of a silane coupling agent and high-temperature mechanochemical technology. The silane coupling agent can effectively adjust the occurrence state of ZnFe2O4 and the graphite interlayer compound, so as to realize the adjustable electromagnetic parameters. When the ratio of silane coupling agent, deionized water, and anhydrous ethanol is 1:1:1, ZnFe2O4@SiO2/C composites achieve a minimum reflection loss value (RLmin) of -52.5 dB at a thickness of 1.87 mm and a maximum effective absorption bandwidth (EAB(max)) of 4.16 GHz at a thickness of 2.07 mm. In addition, the EAB covers 8-12 GHz at a thickness of 1.97 mm, achieving efficient absorption of X-band electromagnetic waves. Through the optimization of structure and composition, the problems of large thickness and limited electromagnetic wave performance of ZnFe2O4/C composites are effectively improved, which provides a way for the design and large-scale preparation of ZnFe2O4-based absorbers with high electromagnetic wave absorption performance in the X-band.

Constructing the magnetic/dielectric synergistic effect between ferrite and carbon materials is an important strategy to obtain microwave absorbers. ZnFe2O4 and graphite intercalation compounds (GICs) are creatively combined by high-temperature mechanochemical technology. The results show that ZnFe2O4 is attached to the surface and pores of graphite with special three-dimensional structure, the propagation path of microwaves in the composites can be extended, and polarization effects and magnetic loss of ZnFe2O4/C composites can be effectively enhanced. When the addition amounts of GICs is 10 wt%, the reflection loss (RL) of ZnFe2O4/C composite reaches -41.49 dB at a thickness of 4.5 mm, and the effective absorption bandwidth (EAB) reaches 3.92 GHz at a thickness of only 1.5 mm. This work provides a new idea for the synthesis of ZnFe2O4/C microwave absorbers agent by high-temperature mechanochemical technology.

Industrial acidic wastewater is typically treated using the neutralization precipitation method, which results in a significant amount of low-purity by-product gypsum that is difficult to utilize. In light of this issue, this paper proposes a new technology for the high purification of by-product gypsum in conjunction with acidic wastewater treatment. Using the technology of "seed crystal circulation-removal of impurities by acidity-gradient crystallization", the high-quality recovery of CaSO4 was realized in the form of high-purity gypsum whiskers. The results demonstrate that CaSO4.2 H2O can gradually dissolves and exposes the crystal nucleus when reintroduced into acidic wastewater with a high H2SO4 concentration (60 g/L). Upon the addition of acidic wastewater with a low H2SO4 concentration (12 g/L), the ratio of CaO/SO3 in the solution decreases, resulting in a decline in the nucleation rate of gypsum crystals. Newborn crystals easily grow along the (020) plane of CaSO4.2 H2O, forming CaSO4.2 H2O whiskers. Under the conditions of a 60 g/L H2SO4 concentration, a solid-liquid ratio of 10 g: 100 mL, a reaction time of 1 h, achieving a CaSO4 dissolution capacity of 3.9 g/L. Furthermore, the whiteness of high-purity gypsum can be increased from 19.93 % to 61.0 %, the content of CaSO4.2 H2O can be increased from 36.99 % to 95.75 %, and the length-diameter ratio can be increased to 75.8 when the reaction end point is controlled at pH= 1.03 and the reaction time is 120 min. Compared to conventional methods, this technology achieves simultaneous impurity removal and crystal morphology control through acidity-driven dissolutionrecrystallization, enabling direct conversion of low-grade gypsum into high-value whiskers.

In this investigation, a novel process for the synthesis of nano-ZrO2 powders based on high-temperature mechanochemical technology (HTMT) in a short process is proposed and HTMT nano-ZrO2 enhancement mechanism as an additive on the properties of B4C ceramics was systematically investigated. ZrO(OH)2 was used as a precursor, and ZrO2-B4C composites were prepared by optimizing the ball milling temperature and time in combination with the hot-press sintering technique. The results demonstrated that the high-temperature mechanical force causes the transition temperature of ZrO2 from monoclinic to tetragonal crystal system to be decreased to 500 °C. The ZrO2 treated by high-temperature ball milling at 600 °C/6 h exhibits lower microstress, higher crystallinity, and a particle size of only about 9.12 nm. HTMT nano-ZrO2 effectively controls the size of in situ generated ZrB2 particles in B4C ceramics, reduces interfacial porosity and grain coarsening, and promotes densification of B4C ceramics compared to commercially available nano-ZrO2. With the addition of 4 wt% HTMT nano-ZrO2, the composite showed optimal comprehensive properties: relative density of 99.75% (2.57 g/cm3), fracture toughness of 4.74 MPa/m1/2, flexural strength of 266.61 MPa, Vickers hardness of 31.14 GPa, and fracture mode with mixed mechanism of through-crystallization and along-crystallization.

The persulfate-based nonradical oxidation via the surface electron-transfer process shows great potential in wastewater purification. Herein, we explored for the first time the catalytic performance of two-dimensional hierarchical porous carbon nanosheets derived from 2D metal-organic framework materials for nonradical oxidation. 2D sheet-like MIL-88A was efficient and scalable synthesised by the thermal-assistant ball milling method. Three types of 2D hierarchical porous carbon nanosheets (gamma-Fe2O3/C, C, and Fe3C/C) were obtained by controlling the pyrolysis of 2D MIL-88A. The porous carbon nanosheets exhibited excellent persulfate activation and thiocyanate degradation performance, as evidenced by 99.9 % degradation of 11 mM thiocyanate within 15 min with 0.4 g/L catalyst and [Na2S2O8]: [SCN- ]= 6.0 at ambient pH (5.5). Quenching tests, electron spin resonance analysis, and electrochemical analysis revealed that the thiocyanate degradation process followed an electron transfer mechanism dominated by nonradical oxidation. Theoretical calculations demonstrated that incorporating nano gamma-Fe2O3 or Fe3C distributed uniformly on the sp(2) C=C carbon nanosheets significantly influenced the charge distribution and effectively improved electron transfer capability, achieving superior catalytic activity and robust interference resistance during treatment of real cyanide-containing wastewater.

The strongly alkaline sodium aluminate solution generated from high-sulfur bauxites during their refinement through the Bayer process contains sulfur, mainly in the form of thiosulfate (S2O32-) ions, which affects the quality of the target product (alumina). Consequently, the large-scale use of high-sulfur bauxites is severely limited, and methods of desulfurizing sodium aluminate solutions are urgently needed. To address this need, we herein prepared metal-organic framework (ZIF-8)-supported Co-doped TiO2 (Co-TiO2@ZIF-8) using a sol-gel method and low-temperature calcination under N-2 and examined the ability of this composite to photocatalyze the oxidative degradation of thiosulfate ions in sodium aluminate solutions. Co-TiO2@ZIF-8 retained the large specific surface area and rich porosity of ZIF-8, which reduced the agglomeration of TiO2 particles on the surface. The loading of Co-TiO(2 )endowed Co-TiO2@ZIF-8 with a mesoporous structure and thus increased its adsorption capacity. Compared with ZIF-8, Co-TiO2@ZIF-8 featured new functional groups, and the formation of Zn-C and N-Ti-O bonds confirmed the successful integration of Co-TiO2 with the ZIF-8 carrier. Consequently, the thiosulfate removal rates by Co-TiO2@ZIF-8 were 42 % and 26 % higher than those observed for the blank sample and pure TiO2 (light source = xenon arc lamp, oxidant = O-3, reaction time = 60 min), respectively. This high performance is primarily due to Co doping, which enhanced the efficiency of visible light utilization, and the photogenerated electron-hole pairs on the photocatalyst surface and hydroxyl radicals formed by the interaction of holes with the solution-phase OH- ions.

Herein, spinel Mn0.4Zn0.6Fe2O4 powders were fabricated utilizing a novel high -temperature mechanochemical method (HTMC), which achieves the coupling effect of high -temperature and mechanical force in a single process. The microstructure, chemical composition, magnetic properties, and electromagnetic wave absorption (EMWA) characteristics of the Mn0.4Zn0.6Fe2O4 powders were thoroughly considered in 2-18 GHz. The results reveal that with a matching thickness of 4.3 mm and a frequency of 6.2 GHz, S3 exhibits an effective absorption bandwidth that covers 4.56-7.48 GHz and has a minimum reflection loss (RLmin) of -43.8 dB. The excellent EMWA properties of the Mn0.4Zn0.6Fe2O4 powders can be ascribed to their effective cooperation between dielectric loss and magnetic loss as well as favorable impedance matching. Considering the performance enhancement generated by the distinctive coupling of multiple mechanisms in HTMC and the excellent EMWA properties of the as-prepared single Mn0.4Zn0.6Fe2O4 powders, it has significant potential in the field of fabricating efficient MAMs.

Combining magnetic loss materials with carbon -based substances is widely considered an efficient approach to synthesizing high -performance microwave absorbing materials (MAMs). Herein, natural microcrystalline graphite, which has abundant reserves but confined application throughout the world, was employed as the carbon source to synthesize Mn0.4Zn0.6Fe2O4/microcrystalline graphite (MZF/MG) nanocomposites for microwave absorption by a novelty and promising high-temperature mechanochemical method (HTMC). The morphology, chemical compositions, static magnetic properties, electromagnetic wave absorption (EMWA) performances in 2-18 GHz, as well as the EMWA mechanisms of the composites, were comprehensively explored. The experimental results indicate that the addition of MG has a positive effect on the improvement of the EMWA performance of MZF. By varying the MG content and matching thickness of the MZF/(5-20)MG composite, their EMWA properties can be easily adjusted. Among them, the MZF/15MG composite achieves a minimum reflection loss (R-Lmin) of -42.1 dB (corresponding to 99.994 % of the EMWA) and an effective absorption bandwidth (EAB, R-L < -10 dB) of 3.94 GHz (12.54-16.48 GHz) with a matching thickness of 1.3 mm. This study is anticipated to provide an insightful proposition for HTMC and MG being applied to the field of fabricating effective MAMs.

Ferrite is frequently employed as a high-efficiency microwave absorption material (MAM). Herein, a novel and prospective high-temperature mechanochemical (HTMC) method was employed to fabricate pure-phase spinel zinc ferrite powders with a spherical structure. After that, the chemical compositions and structures, microscopic morphology, static magnetic characteristics, and microwave absorption properties of the powders were examined. The powder achieves a minimum reflection loss of -54.7 dB at a matching thickness of 4.4 mm, at which time the effective absorption bandwidth approaches 3.9 GHz. The superior microwave absorption ability of the powders is attributable to the favorable cooperative impact between dielectric and magnetic losses. Therefore, the as-prepared zinc ferrite powders can be utilized as high-efficiency MAM. The HTMC method has considerable potential for the large-scale preparation of high-performance MAM.