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Summary Catalytic electrodes play an indispensable role in electrochemical devices. As the pursuit of high activity dominates the research focus, limited attention was paid to the recycling technologies. Existing methods often only allow for recovering specific metallic substance without restoring the functionality of the electrode. Herein, we report a general, non-destructive method based on high-temperature pulse annealing to enable direct reuse of catalytic electrodes. The high temperature ensures complete decomposition of byproducts; meanwhile, the rapid annealing maintains the original physiochemical property, and thus the performance of the catalyst. Using the Li-air battery as a model system, we can regenerate a Ru-loaded electrode for 10 times after each cycling operation, thus extending its lifetime by nearly 10 folds. Our method can be readily applied to other electrochemical systems where catalytic electrodes are prone to deactivation by byproducts. This study paves a new way toward highly sustainable operation of electrochemical devices.

The vanadium flow battery (VFB) is widely regarded as one of the most reliable large-scale energy storage technologies due to its flexible design, long cycle life, and high safety. However, novel electrodes for VFBs with a well-suited structure by cost-effective manufacturing processes are still highly sought after to penetrate the growing energy storage market. Here, we demonstrate a holey three-dimensional (3D) wood-based electrode for VFBs, which was engineered by the facile perforation and carbonization of earth-abundant, low-cost, and sustainable wood. The 3D-wood electrode inherits the intrinsic, vertically-aligned channels (i.e. low tortuosity structure) of the original crude wood material, which provides fluent electrolyte transport paths in the flow battery system. Furthermore, small holes (approximately 1.3 ​mm) are drilled across the 3D-wood electrode in the perpendicular direction to connect the parallel channels, thereby enabling ion exchange and reducing flow resistance. The concentration polarization is significantly reduced during the charge and discharge process in VFB, due to these electrode modifications. The porous structure of the 3D-wood electrode, with a high specific surface area of 216.77 ​m2 ​g−1 and oxygen functional groups, provides sufficient reaction sites for vanadium cations to enhance the electrochemical reactivity of VFBs. The superior structure of the 3D-wood electrode ensures the feasibility in VFBs and offers a promising direction for developing flow battery electrodes through pore engineering of earth-abundant biomaterials.

Aerosol spray coupled with high-temperature pyrolysis is an emerging technique for continuous manufacturing of nanomaterials at large scale that demonstrates extremely high production efficiency. Current aerosol spray techniques using a tube furnace can only attain a low temperature range (generally 95%), during which salt decomposition and particle nucleation/growth occur. The high temperature critically enables homogeneous mixing of elements in the resultant nanoparticles and the short residence time is key to suppress particle growth and agglomeration. Compared with the traditional aerosol spray pyrolysis, the carbonized wood reactor can achieve a record high temperature (≥2000 K), a much shorter residence time (∼tens of milliseconds), highly efficient, uniform heating, and provide a platform for continuous nanomaterial manufacturing for a broad range of applications.

Summary The ability to alloy different elements is critical for property tuning and materials discovery. However, general alloying at the nanoscale remains extremely challenging due to strong immiscibility and easy oxidation, particularly for early transition metals that are highly reactive. Here, we report nanoscale alloying using a high-temperature- and high-entropy-based strategy (T∗ΔSmix) to significantly expand the possible alloys and include early transition metals. While high-temperature synthesis favors alloy formation and metal reduction, the high-entropy compositional design is critical to further extending the alloying to strongly repelling combinations (e.g., Au-W) and easily oxidized elements (e.g., Zr). In particular, we explicitly characterized a record 15-element nanoalloy, which showed a solid-solution structure featuring localized strain and lattice distortions as a result of extreme mixing. Our study significantly broadens available compositions of nanoalloys and provides clear guidelines by utilizing the less-explored entropic chemistry.

Hyperglycemia-induced endothelial dysfunction is generally believed to be the basis of diabetic vascular complications. Dopamine receptors is known to play an important protective role in diabetes. However, the protective effect of dopamine receptors against hyperglycemia-induced endothelial damage in diabetic rats is still unknown. In the present study, we established a cell model of hyperglycemia-induced endothelial dysfunction by treating human umbilical vein endothelial cells (HUVEC) with high glucose. MTT and lactate dehydrogenase assays results showed that high glucose treatment significantly reduced the cell viability and down-regulated dopamine D4 receptor. Pre-treatment with PD168077, a specific D4 receptor agonist, greatly improved endothelial cell viability and decreased apoptosis. Furthermore, pharmacological inhibition of phosphoinositide 3-kinase (PI3K) and endothelial nitric oxide synthase (eNOS) eliminated the protective effect of D4 receptor against endothelial injury. More importantly, the expression level of D4 receptor was also dramatically down-regulated in the arterial endothelium of rats with streptozotocin-(STZ)-induced diabetes, and the STZ-induced impairment of acetylcholine-induced vasodilation was reversed by activation of D4 receptor. In conclusion, our results indicated that dopamine D4 receptor protected against hyperglycemia-induced endothelial dysfunction via the PI3K/eNOS pathway, which may provide a novel strategy in the treatment of diabetes.

Graphitic carbon has attracted tremendous research interest in recent years owing to its exceptional thermal and electrical properties that arise from the ordered sp2 hybridized carbon structure. Due to its high activation energy, graphitization is often energy- and chemical-intensive. In addition, the electrical conductivity of graphitized materials has always been limited by the presence of intrinsic defects. In this paper, we propose a new method to convert lignin-based biomass into highly crystalline graphitic carbon by a Joule heating process. The Joule heating utilizes the internal resistance of a reduced graphene oxide/lignin (rGO-lignin) carbon film to heat the sample to up to 2500 K within 1 h. The annealing of lignin at this high temperature is found to remove impurities and intrinsic defects, as well as to initiate the graphitization process. Amorphous lignin carbon can be converted into short-range ordered and graphitic carbon with an ultrahigh electrical conductivity of 4500 S/cm, significantly higher than the original 6.4 S/cm. The microstructure change underlying this high electrical conductivity was further probed through electron microscopy and chemical analysis. This highly crystalline, electrically conductive graphitized lignin-carbon is expected to be useful for numerous applications where high conductivity and corrosion resistance are desired.

Although the novel sulphoaluminate-magnesium potassium phosphate cementitious composite (SAC-MKPC) has the advantages of rapid setting, high early strength, and excellent water resistance, MKPC factories traditionally use dead burnt magnesite as raw material, which requires a high consumption of primary energy sources. This research was mainly focused on investigating the feasibility of using magnesium sulphate, calcium oxide, and aluminium oxide in the preparation of the SAC-MKPC composite clinker at low-temperature. Two different CaO:Al2O3:MgSO4 molar ratios, namely 4:3:37.7 and 4:3:16.15, were calcined at temperatures ranging from 1200 to 1350 °C, with a spacing of 50 °C. The results showed that the composite clinker was successfully obtained by calcining a mixture of magnesium sulphate, calcium oxide, and aluminium oxide at 1250–1350 °C, which is 150–250 °C lower than the temperature used in the dead burnt magnesite production. In the clinker system, yeelimite, periclase, and anhydrite were the main mineral phases and the hydration products consisted mainly of K-struvite, ettringite, residual periclase, and yeelimite. The CaO:Al2O3:MgSO4 molar ratio yielding the best mechanical properties was 4:3:37.7. The compressive strength of the hydration products reached 31 and 70 MPa after 2 h and 1 day, respectively. The scanning electron micrographs of the hydration products showed a relatively dense structure, covered by ‘amorphous materials’ generated during the preparation process. The elemental composition of the amorphous materials included O, Mg, Al, P, S, K and Ca, and derived mostly from the cementation of MKPC and AFt.

Lightweight porous concrete is a popular energy-saving building material. However, the raw materials required to prepare this concrete paste are extracted from natural resources, and its early compressive strength is so low that it cannot be used for applications with a short casting time. In order to improve the early compressive strength and reduce energy and resource consumption during preparation, this study proposes using only solid wastes to prepare the pastes for lightweight porous concrete that can be ready to use in a short time. This was achieved by sintering a mixture of aluminum dust, flue-gas desulfurization gypsum, carbide slag, and red mud to obtain a cementitious material (CM). Then, other solid wastes (14.26 wt% flue-gas desulfurization gypsum, 9.9 wt% fly ash, and 1 wt% carbide slag) were blended with the CM to prepare ready-to-use lightweight porous concrete (RLPC), which was successfully prepared using only industrial solid wastes as the raw materials. The minimum thermal conductivity obtained was 0.15 W/m·K, and the maximum 28-d compressive strength obtained was 3.57 MPa for an RLPC dry density of ∼600 kg/m3. In addition, the 4-h and 1-d compressive strengths were up to 1.31 MPa and 1.57 MPa, respectively, which is even higher than the 28-d compressive strength of most conventional foamed concretes. Finally, our life cycle assessment showed that the preparation of RLPC has a lower environmental impact than that of conventional foamed concrete.

Surface contamination and degradation are two main issues leading to performance decay of ceramic-based solid-state electrolytes (SSEs). The typical strategies used to clean surface contaminants and restore ceramic materials involve mechanical polishing or high temperature thermal treatment. However, mechanical polishing can cause other side reactions and cannot clean contaminants on the grain boundaries of SSEs, while conventional thermal treatment using a furnace is often energy- and time-intensive, as the heating and cooling processes are slow. In this work, we for the first time demonstrate a high temperature thermal pulse technique for rapid ceramic surface processing. As a demonstration, we cleaned a garnet-based Li conductive SSE featuring lithium carbonate surface contamination in less than 2 s. The thermal pulsed garnet SSE exhibits an improved ionic conductivity of 3.2 × 10−4 S/cm—a two-fold increase compared to the starting material. Symmetric cells featuring the thermal pulsed garnet SSE can cycle at current densities up to 500 µA/cm2, while control cells short-circuit at a current density of 100 µA/cm2.

Organic pollutants in wastewater have raised great concerns because of their considerable risk to human health and the ecosystem. Although Fenton reaction of advanced oxidation process represents a promising water treatment strategy. However, continuous consumption and low utilization efficiency of H2O2 limit its practical application. Herein, we propose photocatalytic in-situ production and activation H2O2 at triphase interface to reach excellent removal efficiency for contaminants. The triphase interface configuration allows oxygen rapid diffusion from the air to the surface of photocatalyst and avoids the problem of poor mass transfer of oxygen in solution. Meanwhile, using the Z-type heterojunction MIL-101(Fe)/g−C3N4 as model photocatalysts could largely promote the photo-induced electrons and holes separation efficiency to further improve reaction efficiency. As a result, the triphase photocatalytic system achieved an in-situ H2O2 production rate of 4370 μmol h−1 (greater than5 times higher than the diphase control) and a superior degradation efficiency for organic pollutants (model pollutant: methyl orange, concentration: 10 ppm, 99% removal rate in 130 min, while only 21% in diphase control) with a 17.5 times higher reaction rate constant. Therefore, the triphase photocatalytic system realized the highly efficient degradation of organic pollutants in wastewater by solar-driven, in-situ generation and activation of H2O2 with high catalytic activity and minimized oxygen transport limitation, thus providing a green and sustainable strategy for wastewater treatment and broadly environmental remediation.

Because the disposal of phosphogypsum (PG) can lead to serious contamination of the air, soil, and water, recycling of PG has attracted wide attention. This study investigated the effect and solidification of phosphorus in the production of calcium sulfoaluminate (CSA) cement using PG as the sole CaO source. The effects of three phosphorus impurities (Ca3(PO4)2, CaHPO4, Ca(H2PO4)2) on the decomposition of CaSO4, formation of minerals, microstructure of the clinker, and the hydration and mechanical properties of the cement were studied. Experimental results show that Ca3(PO4)2 and Ca(H2PO4)2 promoted the decomposition of CaSO4 and the formation of clinker minerals with the increase in P2O5 content, whereas CaHPO4 showed a promoting effect only when the P2O5 content was more than 1.5 wt%. The increase in phosphorus incorporation in Ca2SiO4 leads to the transformation of β-Ca2SiO4 to α′-Ca2SiO4 and then to Ca7Si2P2O16. The presence of three phosphates in the clinker enhanced the growth of crystal grains and the generation of a liquid phase. Compared with Ca4Al6SO16 without phosphorus, the hydration reaction of phosphorus-bearing Ca4Al6SO16 started later and ended earlier, and the reaction time was shorter. The presence of phosphorus impurities reduces the 1-day strength of CSA cement but does not affect the development of the 3-day and 28-day strengths. Considering environmental aspects, the solidification of phosphorus in the production of CSA clinker were quantified by measuring the distribution of elements. The results indicated that phosphorus is solidified by Ca4Al6SO16, Ca2SiO4, and Ca4Al2Fe2O10, and Ca2SiO4 has a stronger ability to solidify phosphorus than the other two minerals. Ca3(PO4)2 is more difficult to solidify than CaHPO4 and Ca(H2PO4)2. This study is of great significant to guide the large-scale clean utilization of PG in the production of CSA cement.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer related death which needs novel drugs to improve patient outcome. Survivin overexpresses in HCC and contributes to HCC malignant progression. In this study, we established a Survivin-targeted drug screening platform, a cell model HepG2-Sur5P-EGFP-Sur3U stably transfected with lentivirus carrying an EGFP expression cassette, in which the EGFP expression was regulated by the upstream Survivin promoter and downstream Survivin 3'-UTR. By using this platform, we screened and easily identified one of matrine derivatives, WM-127, from hundreds of matrine derivatives. WM-127 was demonstrated to be a strong Survivin inhibitor that inhibited cell proliferation, induced cell cycle arrest and apoptosis of HCC cells, and suppressed the growth of HCC xenografted tumors in nude mice, suggesting that WM-127 might be a promising drug for HCC treatment. WM-127 exhibited less cytotoxicity in normal cells. Mechanistic studies showed that WM-127 suppressed the activity of Survivin/β-catenin pathway and the expression of Bax to induce cell cycle arrest and apoptosis. Taken together, we constructed an economical, practical, efficient and convenient cell platform for screening the Survivin-targeted drugs from the enormous diversity of chemicals or factors, which would be a potential tool for antitumor drug research and development.

Energy-saving materials in buildings enable meaningful reduction of indoor energy consumption and are critical to develop a carbon-neutrality society. Accordingly, lighting in modern buildings should be properly managed toward energy-efficient buildings. Here, we developed a broadband light-management cellulose composite film, composed of 75 wt% cellulose bonded by phenol formaldehyde resin, which shows a high transparency (~86%) and haze (~90%) for effective light propagating and scattering, and more importantly, a superior anti-ultraviolet capability (~83% absorptance and ~17% reflectance), thus enabling a soft, uniform, large areal, and safe illumination of the sunlight in buildings toward a comfortable, healthy yet energy-saving environment. In addition, our cellulose composite film features a strong mechanical strength (140 MPa tensile strength) and superior robustness (e.g., high hydro-stability with a high wet strength of 135 MPa, thermal stability and fire-resistance ability, as well as excellent impact absroption capacity), proving its durability for long-term indoor or outdoor applications. The cellulose composite film is synthesized by a simple and scalable calendaring-like process which can be fully compatible with current paper-making industry. These integrated merits of our cellulose composite film make a promising candidate for energy efficient building applications toward a sustainable society.

Summary High-entropy alloy nanoparticles (HEA NPs) are an area of interest due to their interesting structural features, large compositional space, and high potential for catalytic applications. While many HEA NPs have been successfully synthesized and characterized, little is known about the impact of composition on structural features. This work utilizes element-specific X-ray spectroscopy techniques to compare 5- and 15-element HEA NPs with shared elements, aiming to understand the impact that adding additional elements to an HEA has on its structure and properties. Here, we report significant differences between HEA-5 and HEA-15. In particular, the 3d elements show different oxidation behavior associated with different bonding properties. Varied bonding properties are also observed in the 4d and 5d elements. These results provide an understanding of the impact composition plays on the HEA structure, which will serve to aid in the fine-tuning of structure and properties of HEAs through adjusting their composition.

Large-scale construction 3D printing (C3DP), which is also known as green building construction is an innovative method that can save time, materials, and labor costs. The suitable printing materials should have the properties of good fluidity, excellent early strength, appropriate setting time, suitable viscosity, and cost-effectiveness. Among the main concerns of the construction 3D printing, the clogging of the material induced by premature setting and poor fluidity of the concrete is a significant one. It hinders the pumping capacity of concrete materials from the mixer to the extruder and reduces the overall efficiency of the C3DP process. The existing literature has proposed a variety of materials for C3DP, but there is still no standard information on the material selection. Therefore, it is necessary to solve the problem of material clogging while obtaining the above-mentioned characteristics suitable for printing materials. In the present study, the suitable printing properties for C3DP material were obtained to solve the clogging problem. The composition based on industrial solid waste was used to prepare this material. The use of this material in C3DP was proved to be cost-effective. Suitable setting time (33 min), good fluidity (181 mm), and excellent compressive strength (10.4 MPa and 78.2 MPa for 2 h and 28 days, respectively) were realized. These suitable properties were obtained by adding the phase change material (PCM) at different temperatures. In addition, due to the phase change characteristics, PCM has been proven to effectively solve the clogging problem of material. Furthermore, optimized material was used to print 3D structures with different shapes. We believe that this work can provide innovative ideas for the promotion of green building construction and the production of high-value products.

Iron-rich calcium sulfoaluminate (IR-CSA) cement is a low-carbon cement that contains small amount of aluminum. In this study, IR-CSA cement preparation method using gypsum as the source of calcium oxide was developed. The effects of iron on the decomposition of gypsum, formation of phases, microstructure of the clinker, and hydration of cement paste were investigated. The results indicated that the decomposition of gypsum and the formation of the target phase were first slightly promoted and then hindered when the iron content in the raw material increased. The presence of iron enhanced the growth of crystal grains and densification of the microstructure in the clinker. The early hydration behavior of IR-CSA cement mainly depended on the hydration of the iron-bearing ye’elimite and ferrous phases. Furthermore, the incorporation of iron into mineral phases was studied. The maximum incorporation content of Fe2O3 in ye’elimite and belite phase reached 19.36 wt%, expressed as C4A2.61F0.39 S - , and 2.83 wt%, respectively. The chemical composition of the ferrous phase was similar to that of C4AF, and its mineral phases were C2F, C6AF2, C4AF, and C6A2F from the center to the edge. Finally, the feasibility of preparing IR-CSA cement using phosphogypsum as the sole calcium oxide source was evaluated for engineering applications. This unique preparation method reduces the use of aluminum in raw materials and thus promotes recycling of iron-containing or low-aluminum-containing industrial solid waste materials.

Summary A tree is a living energy-water system. Intensive study of tree-derived natural wood is of great significance for the sustainable development of human civilization and reduced dependence on nonrenewable resources. Here, we report on the mesostructures of several natural wood materials as well as their thermal conductivities and mechanical properties. We found that natural wood, including hardwood and softwood, possesses excellent hydrophilicity, an interconnected pore network, low thermal conductivity, and various mechanical properties. Inspired by the critical ecological energy-water nexus, high-efficiency solar steam generation based on natural wood is demonstrated in this work. The variation in multiple natural wood microstructures results in significantly different solar steam generation performances, with the more porous wood showing higher evaporation efficiency based on our results. The inherent rich mesostructures, aligned microchannels, and favorable hydrophilicity enable natural wood materials to be applied in many other fields of the energy-water nexus.

Solid waste-based calcium sulfoaluminate (SW-CSA) cement is a type of low carbon cement that uses solid waste as raw material. It is usually used to prepare lightweight porous concrete (LPC) due to its short setting time. However, high water absorption of LPC based on SW-CSA cement limits its extensive application. Water repellent can be mixed into binder material to reduce the water absorption of LPC, but it may affect the hydration properties of SW-CSA cement paste, which influences the performance of LPC correspondingly. Calcium stearate (CS), sodium oleate (SO) and sodium methyl siliconate (SMS) are three familiar commercial water repellents. To find the suitable internal mixing water repellent for LPC based on SW-CSA cement, the effects of three CS, SO and SMS on the water absorption, hydration, compressive strength, fluidity, and setting time of SW-CSA cement paste were explored. Besides, the properties of LPC with CS and SO added were also studied. The results indicated that using CS as the water repellent could reduce the 1 day water absorption of SW-CSA cement paste by 45.9% and the water absorption of LPC by 33.0%. It also reduced the setting time of SW-CSA cement paste and increased the final compressive strength of LPC, which was conducive to the preferred rapid setting and high compressive strength of LPC. The hydrophobicity of SW-CSA cement paste with SO was better than that of SW-CSA cement paste with CS. But using SO and SMS as the water repellent retarded the early hydration of SW-CSA cement and prolonged the setting time of SW-CSA cement and reduced the final compressive strength of SW-CSA cement paste. Therefore, SO and SMS can’t be used as the internal mixing water repellent of LPC based on SW-CSA cement, while CS is a promising internal mixing water repellent of SW-CSA cement to prepare LPC.

Nanomaterials comprising earth-abundant elements show great potential as substitutes for scarce, expensive materials in energy conversions, but degradation and contamination issues in working environments severely limit their practical applications. Here we report a facile and scalable strategy to synthesize ultrathin-graphene-coated cobalt nanoparticles which are achieved by the application of an electrical current pulse to a carbon-based substrate and by generating a transient high temperature of up to 1500 K in 50 ms to induce the nanoparticle growth and graphene coating. Thickness of the graphene shell is effectively controlled to be under three atomic layers, favorable for charge transfer and electrocatalytic applications. Our one-step synthetic strategy provides a universal, scalable and cost-effective approach for the fast synthesis of metal-carbon core-shell nanoarchitectures for energy conversion applications.

Highly efficient broadband light management to enhance the light trapping inside active layer is critical for many energy conversion devices such as thin film solar cells and photoelectrochemical cells. In this work, we demonstrate highly transparent, mesoporous wood composite via fast extraction of lignin along naturally formed low tortuosity channels followed by fast filling of polymers. The transparent wood displays a high optical transmittance and at the same time a high haze in a broad wavelength range between 400 nm and 1100 nm. With such unique optical properties, the transparent wood composite with cellulose nanofibers can be utilized for a range of optoelectronics, especially for solar cells and wide-angle lighting where light management is crucial to enhance device operation efficiency. We demonstrate that the newly developed transparent wood composite can function as a broad range light management layer and substantially improve the overall energy conversion efficiency by as much as 18% when simply coated with a GaAs thin film solar cell. Our research on wood based light management material provides an attractive platform for future development embracing green, disposable optoelectronic devices with efficient light management.

Most ferroelectric transitions occur ultrafast and are time independent. However, here in (1-x) (Bi0.5Na0.5)TiO3-xBaTiO3, we have found a ferroelectric phase transition induced solely by increasing waiting time at certain temperatures (isothermal phase transition). Through cooling, a unique metastable state between a relaxor ferroelectric and a ferroelectric is unveiled, which in essence is initially a short-range ordered glassy state and then can evolve into a long-range ordered ferroelectric state through the isothermal process. It is also found that these isothermal ferroelectric transitions only occur within a specific temperature region with different waiting time needed. These features of isothermal phase transition can be understood by Landau theory analysis with the consideration of random defects as a competition between the thermodynamically favored long-range ordered state and the kinetically frustrated short-range ordered glassy state from random defects. This study offers a precise experimental as well as a phenomenological interpretation on the isothermal ferroelectric transition, which may help to further clarify the intricate structure-property relationship in this important lead-free piezoelectric material and other related systems.

A sulfoaluminate high-performance cementitious material (SHCM) was prepared using flue gas desulfurization (FGD)-gypsum, coal gangue, limestone tailings, and aluminum ash as raw materials. The composition of the SHCM clinker, mechanics and hydration properties of the SHCM, and heavy metal leaching characteristics of the SHCM pastes were studied. The results showed that the mineral phases of the SHCM clinker were similar to that of ordinary sulfoaluminate cement (SAC) clinker, mainly including calcium sulfoaluminate and dicalcium silicate, and the key differences were that the SHCM clinker had an excessive content of calcination-formed anhydrite and contained some gehlenite. The 3-day and 28-day compressive strength of the SHCM mortars reached up to 45.7 MPa and 67.8 MPa, respectively, and a continuous strength gain was observed in the later age, unlike that in the case of ordinary SAC. The cumulative hydration heat during the first 3 days of the SHCM was 283 J/g, which is lower than that of ordinary SAC under the same conditions. Additionally, the SHCM pastes also showed good immobilization ability of heavy metals in the hydration process, with the leaching concentrations of Zn, Cr, As, and Cu much lower than the limits of Chinese National Standard, and with retention ratios of Zn, Cr, As, and Cu in SHCM pastes over 90%, at each hydration age. This work provides a practical and effective way to transform industrial solid wastes to value-added, high-performance and green sulfoaluminate cementitious material.

Industrial by-product gypsum is a waste by-product containing mostly calcium sulfate. Problems related to its storage and utilization have become a bottleneck restricting the development of various industries. The authors investigated the feasibility of co-producing calcium sulfoaluminate cement and sulfuric acid through the mass utilization of industrial by-product gypsum. The CaSO4 and CaO derived from the partial decomposition of industrial by-product gypsum are used to form calcium sulfoaluminate clinker minerals, and the SO2 released during the production of calcium sulfoaluminate clinker is collected and transformed into sulfuric acid. The experimental results show that calcium sulfoaluminate cement can be prepared using the decomposition of industrial by-product gypsum, and its mineral formation, compressive strengths, and microstructure are satisfactory. According to the theoretical calculation, the concentration of SO2 released during the production of calcium sulfoaluminate clinker could reach 7.55% thereby meeting the required concentration for the preparation of sulfuric acid. A life cycle assessment also showed that the co-production of calcium sulfoaluminate cement and sulfuric acid using the decomposition of industrial by-product gypsum has a lower environmental impact than the conventional production process. In this study, a promising and environmentally friendly method for the mass utilization of industrial by-product gypsum, effectively eliminating the environmental contamination caused by its accumulation, is described.

Ferric-rich calcium sulfoaluminate (FR-CSA) cement is a type of low-carbon cement. Common CSA needs to consume a large number of bauxite during the preparation process. In FR-CSA, Fe2O3 can act as an alternative for Al2O3 by shaping some iron-bearing minerals (Ca4Al2Fe2O10 (C4AF), Ca2Fe2O5 (C2F), and Ca4Al6−2xFe2xSO16 ( C 4 A 3 - x F x S - )). In order to reduce the use of Al2O3 and optimize the iron-bearing mineral compositions in the FR-CSA clinker, this study investigated the effect of CaSO4 batching in raw material on the formation of C4AF and C 4 A 3 - x F x S - at 1250 °C. It was proved that CaSO4 plays an important role and the maximum incorporation amount of Fe2O3 could be 16.18 wt% in C 4 A 3 - x F x S - , thereof x in the subscripts being 0.33. With the CaSO4 contents in the targeted clinker increasing from 0 to 10 wt%, the effective utilization rates of both Al2O3 and Fe2O3 significantly increased. When the excess amount of CaSO4 was >10 wt%, the effective utilization rate of Fe2O3 increased but that of Al2O3 decreased. The findings in this research can contribute to the mineral optimization of FR-CSA cement clinker and the improvement of effective utilization of Al2O3 and Fe2O3. The production of high-performance FR-CSA cement becomes possible by the substitution of solid wastes containing relatively low Al2O3 content for bauxite.

Sulfoaluminate cement (SAC) is a quick-repairing engineering material, and it has advantages of an early strength, rapid hardening, and more importantly, a low sintering temperature. In the conventional SAC industry, natural gypsum, bauxite and limestone are used extensively as the main raw materials, which requires more natural-resource consumption, and emits greenhouse gases. Our group developed a novel technology to produce SAC green materials by using industrial solid waste (ISW) as raw material. The major mineral phases of the SAC green-materials clinker were C 4 A 3 $ and C2S, the main hydration products were a C–S–H phase and AFt crystals, and the microstructure was dense. The hydration products had excellent mechanical properties; their compressive strength reached 75 MPa after 3 days of curing. To enhance the ISW value-added, three-dimensional printing materials, foam concrete block and high-water filling materials were developed based on the SAC green materials. CO2 emissions were reduced by 58% in SAC preparation by using ISW compared with conventional SAC preparation. Full use of the ISW to produce high-performance SAC green materials is a sustainable option and a possible path to decrease CO2 emissions in the SAC industry.

Flue gas desulfurization (FGD) gypsum is an industrial by-product of the desulfurization process. The gross product of FGD gypsum has reached 550 million tons in China by 2016 and quite a portion was discarded. The purpose of this study is to investigate the feasibility of an innovative concept of producing the CSA cement based on sulfur recovery and entirely made of the FGD gypsum to replace natural gypsum and limestone as CaO and SO3 sources. A mixture of industrial solid waste was calcined under different calcination conditions to study the decomposition behavior of FGD gypsum and properties of CSA cement made from the FGD gypsum. Experimental results show that it is feasible to use the FGD gypsum to entirely supply the CaO and SO3 of this cement, the optimized calcination temperature is between 1270 and 1310 °C, and the suitable retention time is 60–100 min. The highest compressive strengths of 63.3, 85.3, 102.8 MPa were attained at 1, 3, and 28 d, respectively when the temperature was kept at 1310 °C for 60 min. Results also indicate that the FGD gypsum decomposition, which is mainly influenced by calcination temperature, retention time and alumina–silica ratio, has a significant impact on the clinker mineral phase formation. The novel technical idea developed in this research can greatly improve the utilization of FGD gypsum and may reduce about 50% of CO2 emission in routine production.