Phosphogypsum is a solid waste generated in the process of manufacturing phosphate fertilizers. A current high-value-added utilization approach involves preparing it into the widely utilized alpha-hemihydrate gypsum (alpha-HH) via the conventional hydrothermal synthesis method. Nevertheless, this method is time-consuming and energy-intensive. Microwave hydrothermal synthesis emerges as a more favorable alternative owing to its strong penetrating power and rapid heating rate. Consequently, in this study, a comparative investigation was conducted on the synthesis of alpha-hemihydrate gypsum using the conventional hydrothermal method and the microwave hydrothermal method. Density-functional theory (DFT) was employed to conduct a systematic analysis of how EDTA affects the synthesis of alpha-HH. In addition, a series of material characterization techniques were employed to clarify the underlying modification mechanism. Experimental results indicate that, under identical parameters, both methods produced alpha-HH gypsum after 4 h of hydrothermal treatment. However, the microwave hydrothermal method yielded products with superior performance. With the addition of 1.2 % EDTA under microwave hydrothermal conditions, the resulting sample exhibited an average L/D ratio of 1.46 and a compressive strength of 39.26 MPa-51.8 % higher than that achieved by the conventional hydrothermal method-while reducing energy consumption by 105.4 % under the same treatment duration. These findings demonstrate that EDTA can ionize carboxyl groups, enabling them to form stable complexes with Ca2 + on the surface of alpha-HH via coordination. This process hinders the growth of the crystal c-axis and thereby regulates the crystal morphology, establishing EDTA as an effective crystal modifier. Consequently, microwave hydrothermal synthesis of alpha-hemihydrate gypsum proves to be more efficient than the conventional hydrothermal method and exhibits favorable environmental and economic advantages.

Two types of poly(ionic liquids) (PILs), namely linear PILs (LPILs) and reticulated cross-linked network PILs (RPILs), were synthesized and evaluated for the adsorption of gold thiosulfate complex ([Au(S2O3)2]3- ) from thiosulfate solutions. Experimental results showed that the adsorption of [Au(S2O3)2]3- on the PILs followed the pseudo-second-order kinetic model, indicating that the adsorption process was dominated by chemical adsorption. In terms of adsorption thermodynamics, the bromide-based LPIL fitted the Hill adsorption model, whereas the other PILs followed to the Freundlich model. The main interactions between the PILs and [Au(S2O3)2]3- were electrostatic attraction and anion-It interactions, and ion exchange dominated the gold adsorption process. The RPILs exhibited higher gold adsorption capacities than the LPILs. However, gold desorption was more readily achieved with LPILs, primarily owing to their weaker affinity for gold species. In addition, the perchlorate-based LPIL showed good adsorption selectivity and recyclability toward [Au(S2O3)2]3- . This study provides a promising strategy for the efficient separation and recovery of gold from thiosulfate media.

Modifying the adsorption structure of thiosulfate on the gold electrode surface offers a promising strategy to mitigate the passivation phenomenon and enhance gold dissolution efficiency. To investigate this, thiol functional groups—known for their strong affinity to gold surfaces—were employed. Following surface modification with varying concentrations of 3-mercaptopropionic acid (3-MPA), the scanning voltammetry curves of the gold electrode in thiosulfate solution exhibited notable changes. At an applied potential of 0.2V, electrolysis experiments demonstrated that the 3-MPA-modified electrode enabled a higher amount of gold dissolution. Raman spectroscopy further revealed that 3-MPA adsorption occurs concurrently with gold dissolution and effectively eliminates passivation products generated on the electrode surface at high potentials. Combined with XPS characterization and molecular simulation, the results confirm that gold dissolution proceeds via the formation of a gold–3-MPA intermediate, which significantly lowers the reaction energy barrier. Although 3-MPA alone cannot dissolve gold, its adsorption onto the gold surface effectively facilitates the dissolution process—an effect that is equally observable when 3-MPA is directly introduced into the solution. These findings demonstrate that functional groups with affinity for gold not only play a role in the recovery of Au(S2O3)3-2from solution, but also facilitate the gold dissolution process. Furthermore, the relevant results provide valuable insights for optimizing the efficiency of thiosulfate-based gold leaching.

Thiosulfate leaching has been regarded as an environmentally benign alternative to the toxic cyanidation process for the gold recovery. However, the efficient extraction of gold from thiosulfate solutions remains a significant challenge. To address this issue, an ionic liquid (IL)-based extraction system was developed. A benzylfunctionalized IL was identified as the optimal extractant, enabling ultra-fast and highly efficient recovery of gold under optimal conditions, including a gold concentration of 10 mg/L, an extraction time of 1.0 min, an aqueous to organic phase volume ratio (A/O) of 150 and an extraction efficiency of 98.2%. The extraction of gold was found to proceed via an ion-pair mechanism and was governed by the synergistic effects of hydrophobic interaction, pi-pi stacking, and hydrogen bonding. The proposed IL-based extraction system was successfully applied to the extraction of gold from the thiosulfate leachate of gold ore and exhibited excellent selectivity. These results demonstrate that the benzyl-functionalized IL-based extraction system provides an effective and rapid approach for the highly efficient extraction of gold from thiosulfate solutions.

The limited recovery efficiency of gold ions from leaching solutions remains a critical challenge hindering the widespread application of thiosulfate leaching processes. Although zinc powder cementation demonstrates operational simplicity and broad applicability as a mature recovery method, its practical implementation faces two persistent issues: excessive zinc consumption and undesirable copper coprecipitation, which compromise the recyclability of copper-ammonia thiosulfate solutions. Recent advancements employing electrogenerative devices have significantly reduced zinc consumption; however, copper co-deposition persists, particularly during multi-cycle operations. To address this issue, this study proposes the addition of ethylenediamine (en). Experimental results show that after adding 5 mmol/L en to a solution containing 5 mmol/L Cu2+, 0.5 mol/L NH3, 0.1 mol/L S2O2-3and 10 mg/L Au, the copper loss decreased from 32.2% to 6.3% after five cycles, while the gold recovery maintained greater than 99.2%. The Cu (II) complex ions recovery efficiency improved from 18.0% to 88.0% after gold deposition, which ensured that the leaching solution returns to the leaching stage for recycling. Density functional theory calculations and molecular dynamics simulations reveal that en preferentially coordinates with copper ions, forming more stable copper-ammonia-en complexes and thus effectively suppressing their tendency to deposit.

Freeze–thaw cycles (FTCs) can disturb nitrogen transformations and promote nitrous oxide (N₂O) release in subsurface wastewater infiltration systems (SWIS). However, the microbial mechanisms linking community shifts to N₂O fate remain unclear. In this study, metagenomic analysis combined with 15NO₃− isotope tracing was conducted to assess FTCs impact on microbial composition, nitrogen-cycling gene profiles, and N₂O generation in SWIS. FTCs significantly reshaped the community and increased the relative abundances of Nocardioides, Bradyrhizobium and Sphingomonas. Functional profiling revealed a gene imbalance at the denitrification terminal step: high-frequency FTCs slightly increased nirK abundance but markedly decreased nosZ. Consistent with this, 15NO₃− tracing showed that the N₂O fraction rose from 28.75% in the first cycle to 31.63% in the fifth cycle, indicating a shift toward incomplete denitrification. Machine-learning analysis further identified N₂O fate indicators, denitrification genes, and microbial taxa associated with the FT response. These results indicate that FTCs enhance N₂O accumulation in SWIS mainly by weakening nosZ-mediated N₂O reduction rather than uniformly stimulating upstream denitrification. This study provides mechanistic evidence for controlling N₂O emissions from SWIS in seasonally frozen regions.

Microwave hydrothermal synthesis can provide a sustainable way to prepare tobermorite, which can potentially efficiently solidify heavy metals by replacing calcium or silicon within its structure of tobermorite. In this paper, the feasibility of microwave hydrothermal process in solidifying heavy metal zinc (Zn) was investigated. The tobermorite was prepared from fumed silica and calcium hydroxide at Ca/Si of 0.83. The Zn-substituted tobermorite (Zn-tobermorite) was then prepared by adding Zinc chlorine under the Zn/Ca ratios of 0.05, 0.1, 0.15, 0.2, respectively. Additionally the characterisation of hydration product and the leaching behaviour of immobilised Zn was detected. Results indicated that the primary reaction products under both microwave and conventional hydrothermal conditions were Zn-tobermorite, tobermorite, gyrolite, hemimorphite, and reinhardbraunsite. During the synthesis of Zn-tobermorite, Zn2+ ions substituted for Ca2+ at an optimal Zn/Ca ratio of 0.15, achieving a Zn immobilization efficiency of 99.9 %. The microwave-assisted hydrothermal process reduced the synthesis time by approximately 85 % from 14 h to 2 h compared to conventional methods, while maintaining similar immobilization performance. This work offers a sustainable and time-efficient approach for heavy metal immobilization, showing significant potential for large-scale environmental remediation in industrial settings.

Non-fired artificial aggregates currently face several challenges, including low solid waste utilization rates, insufficient strength, and intricate preparation processes. These issues significantly impede their industrial application. In this research, all-solid-waste artificial aggregates were prepared by blending magnesium slag and calcium carbide slag in different proportions, followed by curing under CO2 conditions at 0.1 MPa and a concentration of 99.99 %. The study examined the impacts of varying solid waste ratios on the cylinder compressive strength, 1-h water absorption, apparent density, carbonation products, and microstructure of the all-solid-waste artificial aggregates. Additionally, it elucidated the carbonation reaction mechanisms and the action mechanisms of different minerals. The results indicated that with the addition of calcium carbide slag, the strength of the allsolid-waste carbonated artificial aggregates initially increased and then decreased. Sample C50M50 (comprising 50 % magnesium slag and 50 % calcium carbide slag) exhibited the maximum cylinder compressive strength of 15.12 MPa. At this composition, the 1-h water absorption and apparent density of the aggregates were 14 % and 1593 kg/m3, respectively. Moreover, the carbonation products of magnesium slag mainly consisted of uncarbonated particles, calcite, and decalcified silica gel, while those of calcium carbide slag were predominantly calcite. After the CO2 curing of aggregates with appropriate proportions of solid waste, sufficient carbonation products, such as calcite and decalcified silica gel, formed a stable spatial structure among particles. This, in turn, enhanced the physical properties of the aggregates. This research offers novel perspectives and fundamental theoretical references for the low-carbon preparation of all-solid-waste artificial aggregates and the synergistic resource utilization of multi-source solid wastes and CO2.

Titanium gypsum, a byproduct of the TiO2 industry, is a significant source of environmental pollution. Its high water content and poor crystallinity make it challenging to utilize effectively. The extensive stockpiling of titanium gypsum not only occupies valuable farmland but also poses severe threat to the surrounding ecological environment and human health. To address these issues, the microwave hydrothermal method was employed to convert titanium gypsum into alpha-hemihydrate gypsum (alpha-HH) and a crystal modifier was incorporated to enhance the strength of its products. The modifying effects of three modifiers, succinic acid (SA), glutaric acid (GA), and maleic acid (MA), on the alpha-HH crystal morphology were systematically investigated, and their modification mechanisms were elucidated. The results reveal that GA had negligible impact on alpha-HH, while SA and MA effectively modulated its morphology from acicular to short columnar shape. By doping 0.1 % MA, alpha-HH crystals with an average aspect ratio (L/D ratio) of 1.1 and a compressive strength of 36.7 MPa were obtained; by doping 0.5 % SA, alpha-HH crystals with an average L/D ratio of 1.24 and a compressive strength of 32.5 MPa were achieved, meeting the national standard for alpha 30 (JC/T 2038-2010). The preferential adsorption of organic acid modifiers at the end face of alpha-HH accounts for this morphological shift phenomenon. Furthermore, the structure of organic acids also influences their modification effect; specifically, SA and MA with a carboxyl group spacing two carbon atoms apart exhibit synergistic crystal modulation effects. The presence of neighboring hydroxyl groups and cis-double bonds in MA enhances its function in Ca2 + complexation as well as surface modulation on alpha-HH crystals, resulting in better modification effect. This study provides novel insights into rational modifier selection for preparing alpha-HH crystals

The compressive strength of autoclaved aerated concrete (AAC) mainly varies depending on the type and quantity of hydration products as well as the pore structure. Recycled concrete powder (RCP), calcium carbide slag (CCS), fly ash (FA), and Phosphogypsum (PG) were employed to prepare AAC, which is in line with the development direction of green building materials. Nevertheless, the variation rule of hydration and microstructure of AAC fabricated from the aforementioned solid wastes along with the autoclaved curing time and the mechanism need to be clarified urgently. This study explored the influence of different autoclaved curing durations on the compressive strength, hydration products, microstructure, and pore structure of AAC composed of RCP and other diverse solid wastes under the autoclaved condition of 180 degrees C. The obtained findings indicate that the compressive strength of the samples attained the maximum value of 8.2 MPa at 9 h of autoclaved curing at 180 degrees C, which is 127.78% higher than that of 1 h compressive strength. As the autoclaved curing time increased from 1 h to 10 h, the average pore size initially decreased from 37.047 nm to 22.54 nm and subsequently increased slightly to 23.455 nm. During this process, a significant transformation occurred where C-(A)-S-H gradually converted into tobermorite. The morphology of tobermorite evolved from sheet-like to plate-like and finally to fibrous structures. The accumulation of fibrous tobermorite not only refined the pore structure but also improved the compressive strength. However, an overly long autoclaved curing time (> 9 h) led to the transformation of tobermorite to xonotlite, resulting in a 10.67% decrease in strength and a 4.06% increase in the average pore size.

Microplastics and antibiotics often coexist in aquatic environments as composite pollutants, and their dynamic migration and transformation processes under hydraulic forces exacerbate ecological and health risks. This study investigates the interfacial interactions between polystyrene (PS) microplastics and sulfamethoxazole (SMX) as model pollutants under coupled aging and hydrodynamic forces conditions. By integrating experimental testing, structural modeling, and particle-flow field simulation, the underlying mechanisms are systematically elucidated. Results indicate that aging treatment significantly roughens the PS surface, increasing specific surface area while introducing oxygen-containing functional groups. The interactions between PS and SMX are primarily governed by electrostatic attraction, hydrophobic interaction, hydrogen bonding, and it-it conjugation, with the adsorption capacity of aged PS increasing approximately 1.17 fold. CFD-DEM simulations further reveal that at low hydrodynamic energy, PS-SMX complexes predominantly accumulate at the bottom and remained stable. While hydrodynamic forces increased, the complexes will diffusion and redistribution, leading to partial desorption of SMX. This study provides theoretical support for the synergistic management of microplastics and antibiotics under complex hydrodynamic conditions.

This research delves into the properties of sintered ceramsite from muck, enhanced with municipal waste incinerated fly ash (MWIFA), using microwave sintering technology. It specifically investigated the effects of the MWIFA mix ratio, sintering temperature, and holding time on ceramsite’s key performance, including one-hour water absorption, porosity, and apparent density. The microstructural attributes were quantified through X-ray diffraction (XRD) and scanning electron microscopy (SEM), coupled with an evaluation of ceramsite’s capability to solidify heavy metals. The results demonstrate that ceramsite prepared with a 10

This study aims to investigate a new type of low-carbon activation technology: microwave activation, and its potential influence on the volcanic ash activity of coal gasification slag (CGS) when used as a supplementary cementing material.Mechanically ground coal gasification slag (CGS-30) was subjected to microwave activation at varying power levels (500 W, 800 W, and 1000 W). The pozzolanic activity was assessed through activity index testing and the compressive strength of Portland cement (PC) paste containing 30% slag. Simultaneously, microstructural changes were analyzed using a range of advanced characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry (ICP), nuclear magnetic resonance (NMR), backscattered electron (BSE) imaging, and thermogravimetric analysis (TG). The results demonstrate that microwave treatment substantially enhances the reactivity of CGS. An optimal microwave power of 800 W was identified, at which the activity index of CGS-30 reached 94.31% after 28 days, and the compressive strength of the blended cement paste increased by 22.51% compared to untreated samples after 7 days. Microwave activation facilitates the transformation of crystalline SiO₂ into an amorphous phase, reduces the degree of polymerization within the silicon-oxygen network, and enhances the leaching rate of Al³⁺ ions, thereby increasing the availability of surface-active components. This research offers valuable insights into the development and application of microwave-activated CGS as a supplementary cementitious material.

Microwave hydrothermal synthesis is gaining increasing attention for its volumetric heating nature, which offers potential for reducing energy consumption and production time in the preparation of tobermorite. In this study, calcium hydroxide and fumed silica were utilized as raw materials to synthesize tobermorite through microwave hydrothermal synthesis. The impact of different synthesis times and temperatures on the microstructure of tobermorite was investigated, followed by an exploration of the mechanism underlying crystal structure formation during microwave heating. The results indicate that under identical temperature conditions, optimal parameters for microwave hydrothermal synthesis of tobermorite include a liquid-to-solid ratio of 30 mL g–1, a temperature of 220 °C, and a duration of 1.5 h. Compared with conventional hydrothermal synthesis requiring 14 h, the microwave method only takes approximately 9

The design of cost-effective electrocatalysts with excellent performance is imperative for water splitting. Herein, novel heterostructured NiS/Ni3S4/Ni3S2/NF electrocatalysts were successfully prepared by hydrothermal synthesis in a one-pot process, exhibiting efficient activity in the oxygen evolution reaction (OER) with a low overpotential of 237 mV at 10 mA cm-2 and a corresponding Tafel slope of 30.44 mV dec-1 in 1.0 M KOH. The overall electrocatalytic water splitting cell voltage was only 1.51 V at 10 mA cm-2 in KOH when using NiS/Ni3S4/Ni3S2/NF as the anode and platinum on carbon (Pt/C) as the cathode. Density functional simulations further revealed that the exceptional activity primarily stems from the coupling interactions between Ni3S2(110)/Ni3S4(100) interfaces, which not only optimizes the adsorption free energy of OER intermediates but also enhances catalytic performance. This synthetic strategy provides an avenue for expanding other cost-effective multiphase metal heterostructures.

Although the early strength of lightweight porous concrete (LPC) is relatively low, employing the carbon dioxide (CO2) mineralization curing technique can enhances both its early strength and facilitate CO2 sequestration. Nevertheless, there remains a lack of comprehensive research on how CO2 concentration, temperature, and mineralization time collectively affect LPC's properties. This study investigated the combined impact of CO2 concentration, temperature variations, and different durations for mineralization on the characteristics of solid waste-based lightweight porous concrete blocks (RSFAC). The experimental parameters included a range in CO2 concentration from 20% to 60%, temperatures spanning between 20 degrees C to 80 degrees C, and varied mineralization times lasting between 10 min up to 4 h. The obtained findings reveal that the mineralized LPCs exhibited favorable compressive strength along with a desirable pore structure. The analysis of the interaction effect indicates that the combination of CO2 concentration and temperature surpassed that of either temperature or mineralization time alone. This can be attributed to rapid diffusion of CO2 into RSFAC during the initial stage when both CO2 concentration and temperature were increased. Specifically, a temperature of 60 degrees C with a 40% concentration of CO2 facilitated Ca2+ dissolution within pores while promoting uniform distribution of calcium carbonate (CaCO3) in crystalline form known as calcite. Compared to the RSFAC 1 d compressive strength at 20 degrees C, the RSFAC 1 d compressive strength at 60 degrees C was enhanced by 58%. With the increase in temperature and mineralization time, the impact of CO2 concentration on compressive strength enhancement diminished. Specifically, a temperature of 60 degrees C and a mineralization time of 2 h promoted the mineralization reaction and accelerated concrete hydration, thereby improving its mechanical strength. By employing a CO2 concentration of 32%, a temperature of 58 degrees C, and a mineralization time of 115 min, the compressive strength at 7 d can reached up to 3.53 MPa. These findings provide valuable theoretical support for industrial applications involving CO2 mineralization curing in RSFAC.

The limitations of gangue, including its low strength, high water absorption, and poor bonding capacity with the concrete matrix, restrict its extensive use in construction materials. In this study, various fly ash-cement slurry with different water-cement ratios (0.3, 0.35, 0.4, 0.45, and 0.5) were initially employed to encapsulate the coal gangue aggregate (CGA) at a fly ash dosage of 10 %. Subsequently, synergistic CO2 mineralization conditioning was applied (with a CO2 concentration of 20 %, pressure of 0.1 MPa, humidity at 70 %, and temperature set to 20 degrees C) to enhance the modification process for CGA. The study aimed to investigate how the combined effects of fly ash-cement slurry encapsulation and CO2 mineralization influence the physical properties and microstructure of CGA while analyzing the strengthening mechanisms involved in modifying coal gangue aggregate concrete (CGC). The findings revealed that the synergistic modification through CO2 mineralization coupled with fly ashcement slurry encapsulation was significantly more effective than using only fly ash-cement slurry for enhancing CGA properties. At a water-cement ratio of 0.35, there was a reported increase in apparent density by 3.85 %, a decrease in crushing value by 29.37 %, and only a modest rise in water absorption by 9.9 %. The reaction between encapsulated fly ash-cement slurry and CO2 mineralization produced numerous hydrated calcium silicate gels and CaCO3 products that filled CGA pores-resulting in a porosity reduction of 36.54 %-and improved workability for CGC with an increase in slump by 54.29 %. Additionally, CO2 mineralization enhanced the interfacial transition zone (ITZ) between mortar and CGA; consequently, the elastic modulus of ITZ increased by 8.75 %. The compressive strength of modified CGC rose by 27.14 %, while chloride ion permeability decreased by 32.74 % along with an improvement in water resistance coefficient by 7.2 %. Furthermore, this modified CGC can achieve cost savings up to 13.16 % while reducing carbon emissions from CO2 by approximately 13.43 %. This research offers valuable technical insights for advancing industrial applications and maximizing coal gangue utilization.

Titanium gypsum (TG), a byproduct of the titanium dioxide industry, is recognized as a significant contributor to environmental pollution due to high water content, poor crystallinity and other characteristics that make it difficult to be reused/recycled effectively. This study evaluated the feasibility to recycle TG to produce alpha-hemihydrate gypsum via microwave hydrothermal method, wherein tricarballylic acid (TA) was employed as modifier to modulate the crystallization of alpha-HH. The impact of TA dosage on the characteristics of alpha-HH crystals is comprehensively assessed through a series of microscale analyses. The findings reveal a notable reduction in the Length/Diameter ratio (L/D ratio) of alpha-HH crystals, diminishing from 17.79 to 0.96, in response to the incremental introduction of TA, ranging from 0 % to 0.13 %. An optimum TA dosage of 0.1 % is found to yield a commendable compressive strength of 37.4 MPa. Additionally, this study validates the interaction between TA and alpha-HH crystals. Based on the experimental results, it is further postulated that microwave heating is conducive to expediting the rate of Ca2+ and SO42- ion accumulation at the (002) surface, thus altering the degree of solution supersaturation and consequently accelerating the growth kinetics of alpha-HH crystals. This study offers valuable insights into the utilisation of this methodology in various industrial and scientific applications.

The utilization of recycled concrete powder (RCP) in cement-based materials was greatly limited by its low reactivity. This work aimed to activate the activity of RCP by microwave radiation. The effects of microwave radiation at different power (300-800 W) on the grindability, phase assemblage, microstructure and activity index of RCP were studied. Subsequently, 30% RCP was incorporated into cement paste to prepare RCP-PC pastes. The setting time and compressive strength of blended pastes were tested, and the microstructure and hydration products of hardened pastes were also investigated by SEM and TG. Results show that microwave radiation not only promoted the dissociation of RCP particles, but also induced the amorphous transition of crystalline phases in RCP. As a result, the grindability and activity index of RCP were significantly improved. When subjected to microwave radiation at 800 W, the activity index of RCP was increased from 53% to 75% at 7 d and from 59% to 79% at 28 d, respectively. Furthermore, compared to the cement paste with raw RCP, the initial and final setting time of the microwave activated RCP-PC paste was shortened, and the early compressive strength was enhanced. This work was expected to develop a novel method for the activation of RCP, thus promoting its recycling and utilization in cement-based materials.