Effect of Yttrium on Ce/Ni-Metakaolin Catalysts for CO2 Methanation.

In recent years, major economies have implemented carbon reduction and carbon neutrality policies. Furthermore, with advancements in science and technology, carbon dioxide (CO2) is now considered a valuable raw material for producing carbon-based fuels through hydrogenation. Various concentrations of yttrium (referred to as Y hereafter) were introduced to assess their influence on the catalytic performance of CO2 methanation. At a temperature of 300 °C, the catalyst exhibited an impressive CO2 conversion rate of 78.4% and maintained remarkable stability throughout a rigorous 100 h stability assessment. The findings suggest that the inclusion of yttrium (Y) promotes the formation of oxygen vacancies and alkaline sites on the catalyst. This, in turn, enhances the reducibility of nickel species, improves the dispersion of nickel particles, and plays a pivotal role in enhancing thermal stability. Furthermore, it offers an innovative design approach for creating highly efficient composite CO2 methanation catalysts by controlling particle size and harnessing synergistic catalytic effects at the metal/support interface.

Environmental regulation, green technology progress and haze reduction and carbon reduction.

Coordinated efforts to reduce haze and carbon emissions are important in promoting global climate governance and sustainable development. In this paper, based on prefecture-level data of China from 2005 to 2019, we investigate the impact of environmental regulatory intensity on the emissions of the concentration of PM2.5 and carbon dioxide (CO2). The research indicates that environmental regulation facilitates synergistic governance for PM2.5 reduction and carbon mitigation. Green technological advancement emerges as the primary mechanism through which environmental regulation achieves haze reduction and carbon mitigation. This conclusion remains robust after a series of robustness tests. Furthermore, the results from quantile regression reveal that the haze reduction and carbon mitigation effects of environmental regulation are subject to certain conditional dependencies. Environmental regulation exhibits a significant negative impact on carbon emissions across various quantile points. However, their influence on different quantile levels of PM2.5 concentration displays an asymmetric pattern. Finally, threshold regression findings suggest that there is no significant threshold effect of environmental regulation on CO2 emissions, but there are dual threshold effects on the PM2.5 concentration. Therefore, it is recommended that local governments judiciously implement environmental regulatory intensity, establish interregional policies for haze reduction and carbon mitigation, and fully harness the driving force of green technology to promote a comprehensive green transformation of economic and social development.

Enhancing Freeze-Thaw Resistance of Alkali-Activated Slag by Metakaolin.

Incorporating metakaolin (MK) into slag to prepare alkali-activated materials can reduce shrinkage and improve the durability of alkali-activated slag (AAS). But its durability under freeze-thaw conditions is unknown. In this paper, the effects of MK content on the freeze-thaw properties of AAS were investigated from the perspective of gel composition and pore solution. The experimental results showed that the addition of MK generates a gel mixture of C-A-S-H and N-A-S-H with a cross-linked structure and decreases the content of bound water and pore water absorption. With the increase of alkali dosage, water absorption decreased to 0.28% and then increased to 0.97%, and the leaching rate of ions was Ca2+ > Al3+ > Na+ > OH-. When the alkali dosage was 8 wt % and the MK content was 30 wt %, the compressive strength loss rate of AAS was 0.58% and the mass loss rate was 0.25% after 50 freeze-thaw cycles.

In-Situ Transformation of Li-ABW Zeolites Based on Li-Geopolymer.

Lithium batteries, as energy storage devices, are playing an increasingly important role in human society. As a result of the low safety of the liquid electrolyte in batteries, more attention has been paid to solid electrolytes. Based on the application of lithium zeolite in a Li-air battery, a non-hydrothermal conversed lithium molecular sieve was prepared. In this paper, in-situ infrared spectroscopy, together with other methods, was used to characterize the transformation process of geopolymer-based zeolite. The results showed that Li/Al = 1.1 and 60 °C were the best transformation conditions for the Li-ABW zeolite. On this basis, the geopolymer was crystallized after 50 min of reaction. This study proves that the formation of geopolymer-based zeolite occurs earlier than the solidification of the geopolymer and shows that the geopolymer is a good precursor for zeolite conversion. At the same time, it comes to the conclusion that the formation of zeolite will have an impact on the geopolymer gel. This article provides a simple preparation process for lithium zeolite, explores the preparation process and mechanism, and provides a theoretical basis for future applications.

Green location-oriented policies and carbon efficiency: a quasi-natural experiment from National Eco-industrial Demonstration Parks in China.

This paper investigates how National Eco-industrial Demonstration Parks (NEDP) in China affects carbon emission efficiency. The difference-in-differences (DID) strategy is used for analysis. This paper finds that the construction of NEDP is conducive to the improvement of carbon emission efficiency, and the findings remain robust through placebo tests and propensity score matching. Heterogeneity analysis shows NEDP construction has greater utility on carbon efficiency in non-resource-based cities as well as in environmentally friendly cities. The mechanism analysis found that green technology innovation, industrial restructuring, and the relocation of industrial enterprises are effective ways to improve carbon efficiency in NEDP. Finally, this paper finds that the construction of NEDP has obvious spatial spillover effects on carbon efficiency, which can effectively heighten the carbon efficiency level of this locality and nearby areas.

Low-temperature highly selective water delignification based on geopolymer materials.

Delignification pretreatment is the main source of high cost and high pollution in biomass processing. This paper reports on a simple cheap geopolymers-based highly selective and efficient pretreatment process for delignification under low-temperature water-cooking without discharging black liquor. The geopolymer with a SiO2/Al2O3 ratio of 4.4 showed the largest number of acidic sites and highest catalytic activity. Under mild reaction conditions (mGeopolymer/mFiber = 1/4, 90 min and 90 °C), the delignification rates of woody (eucalyptus) and herbaceous (bagasse) biomass increased by up to 38.90% and 62.20%, respectively. Moreover, the low-alkali black liquor produced by the new water delignification process facilitates subsequent water treatment, eliminating the need for alkali recovery. This study confirms the immense application prospects of geopolymers for the highly selective delignification of most biomass fibre. This study will develop a low-temperature water-cooking process for the delignification of papermaking or biomass processing without wastewater discharge.

Death-associated protein kinase 1 is associated with cognitive dysfunction in major depressive disorder.

We previously showed that death-associated protein kinase 1 (DAPK1) expression is increased in hippocampal tissue in a mouse model of major depressive disorde and is related to cognitive dysfunction in Alzheimer's disease. In addition, depression is a risk factor for developing Alzheimer's disease, as well as an early clinical manifestation of Alzheimer's disease. Meanwhile, cognitive dysfunction is a distinctive feature of major depressive disorder. Therefore, DAPK1 may be related to cognitive dysfunction in major depressive disorder. In this study, we established a mouse model of major depressive disorder by housing mice individually and exposing them to chronic, mild, unpredictable stressors. We found that DAPK1 and tau protein levels were increased in the hippocampal CA3 area, and tau was hyperphosphorylated at Thr231, Ser262, and Ser396 in these mice. Furthermore, DAPK1 shifted from axonal expression to overexpression on the cell membrane. Exercise and treatment with the antidepressant drug citalopram decreased DAPK1 expression and tau protein phosphorylation in hippocampal tissue and improved both depressive symptoms and cognitive dysfunction. These results indicate that DAPK1 may be a potential reason and therapeutic target of cognitive dysfunction in major depressive disorder.

Efficient preparation of red mud-based geopolymer microspheres (RM@GMs) and adsorption of fluoride ions in wastewater.

In this paper, red mud-based geopolymer microspheres (RM@GMs: 75-150 µm) was prepared by dispersion-suspension-solidification method to remove fluoride ions (F-). It was found that RM@GMs still had good mechanical properties and better F- removal effect at RM content reached 80 % of the total solid mass. The batch adsorption experiment results showed that the F- concentration (< 1.5 mg/L) reached the drinking water standard in 45 min at pH = 2 and RM@GMs dosage was 1 g/L. RM@GMs showed maximum adsorption capacity of 76.57 mg/g for F-, and the adsorption kinetics and isotherm fitted the pseudo-second-order kinetic and Langmuir isotherm model, respectively. RM@GMs exhibited excellent dynamic separation effect at the flow rate of 4 mL/min and column height of 1 cm. In addition, RM@GMs had good selectivity for F- in the competitive adsorption experiments and followed an order of: PO43- > > SO42- ≈ NO3- ≈ Cl-. In real seawater, natural surface water and tap water, RM@GMs still had excellent F- removal effect. The adsorption mechanism revealed that RM@GMs removed F- mainly through the synergistic effect of adsorption and ion exchange. Therefore, this paper provides the potential value for the large-scale utilization of RM in the application of F--containing wastewater.

Enhance the removal and immobilization of Cd(II) by the synthesis in situ of dithiocarbamate-geopolymer microsphere composite.

In this study, slag-based geopolymer microspheres (SGS) were combined with dithiocarbamate (DTC) to synthesize the composite adsorbent of SGS and DTC in situ (SGS-DTC). Synthesis was carried out with optimal dosages of 10 mL of EDA, 1.0 g of SGS, and 20 mL of CS2. The differences in material properties, performance, and mechanisms in the adsorption and immobilization of toxic Cd(II) in water between SGS and SGS-DTC were investigated. SGS-DTC showed better adsorption performance than SGS, irrespective of adsorbent dosage, pH, original content, and contact duration. Although after the Cd(II) adsorption, the immobilization performance at a different pH was better in the SGS-DTC than in the SGS, the immobilization performance was unaffected by changes in the other factors. For static adsorption, the adsorption rate of SGS-DTC (1.5 h) was faster than that of SGS (6 h); the Cd(II) adsorption capacity of SGS-DTC (211.2 mg/g) was almost twice that of SGS (116.7 mg/g), and correspondingly, the removal rate of SGS-DTC (99.75%) was nearly twice that of SGS (53.2%). For dynamic adsorption, the adsorption capacity of SGS-DTC was 389.78 mg/g, which is considerably higher than that of SGS (293.38 mg/g) in the Cd(II) solution prepared with deionized water. Furthermore, the adsorption capacity of the SGS-DTC was 299.26 mg/g, which is significantly higher than that of SGS (150.03 mg/g) in the Cd(II) solution prepared by the river water from Yongjiang, Nanning, Guangxi, China. One reason is that DTC was able to activate Si-O-Si without adsorption performance within SGS, thereby improving its adsorption and purification properties significantly. The other reason is that, after anchoring DTC on SGS, the specific surface area varied from 34.05-146.47 m2/g, the morphology was smooth-leaf-like, the pore volume was 0.13-0.20 cm3/g, and the pore size in SGS, was 14.75-5.60 nm. The high potential of SGS-DTC in removing and immobilizing heavy metal materials in wastewater is demonstrated in the results.

Thermal Catalytic-Cracking Low-Density Polyethylene Waste by Metakaolin-Based Geopolymer NaA Microsphere.

Metakaolin-based geopolymer microspheres (MGM) with hierarchical pore structures were prepared by suspension dispersion method in dimethicone at 80 °C. The hydrothermal modification of MGM was carried out at a lower temperature of 80 °C, and a NaA molecular sieve converted from metakaolin-based geopolymer (NMGM) with good crystal structure was prepared and applied in thermal catalytic cracking of low-density polyethylene (LDPE) reaction. The one-pot two-stage thermal catalytic cracking of LDPE was carried out in a 100 mL micro-autoclave under normal pressure. In this work, the optimal proportions and optimal reaction conditions of catalysts for NMGM thermal catalytic cracking of LDPE waste to fuel oil were investigated. The NMGM catalyst showed high selectivity to the liquid product of thermal catalytic cracking of waste LDPE. Under the reaction conditions of reaction time of 1 h and reaction temperature of 400 °C, the liquid-phase yield of thermal catalytic cracking of LDPE reached a high of 88.45%, of which the content of gasoline components was 10.14% and the content of diesel components was 80.97%.

A low-cost photo-evaporation inorganic membrane preparation and treatment of the simulated high salinity radioactive waste water.

Solar-driven desalination is an energy-saving and environmentally benign wastewater treatment technology. A method of in situ self-reduction of graphene oxide (rGO) by cheap geopolymer was introduced, and a photo evaporation membrane device (rGOPGC) for treatment of the simulated high salt liquid radioactive waste (HSLRW) was prepared in the present study. Compared with other rGO based photo evaporation membrane materials, geopolymer matrix has the advantages of low cost, reductant free, simple preparation process and mild conditions. After desalination of simulated seawater, the concentrations of Na+, K+, Ca2+ and Mg2+ ions reached the WHO standard, and the removal rates of radioactive I-, Cs+ and Sr2+ in the simulated high salinity wastewater reached 99.62%, 99.71% and 99.99% respectively; The evaporation rate of rGOPGC remained stable at 1.5 kg/m2/h after 16 cycles in high salinity environment. There was no obvious salt accumulation on the upper surface of the device, indicating its high stability. Furthermore, the evaporation performance at high temperature near the nuclear power plant (NPP) waste water was simulated and tested. Under one solar intensity and 35 °C ambient temperature, the evaporation rate of 1.75 kg/m2/h and the evaporation efficiency of 98.51% were achieved. The results indicated that the rGOPGC device is potential in the concentration evaluation of HSLRW.

Novel procedure of CO2 capture of the CaO sorbent activator on the reaction of one-part alkali-activated slag.

CaO derived naturally from limestone or dolomite is an inexpensive and widely available sorbent. Understanding the mechanisms of CaO carbonation at ambient temperature under the assistance of H2O is important for predicting the reaction of CaO in complex environments and designing novel CaO materials. In this study, we found that the reaction rate of alkali-activated slag is controlled by the CaCO3 layer on a partially carbonized CaO alkali activator. The size of the sorbent increased after the adsorption reaction and the physically adsorbed water in the pores accelerated the carbonation. The carbonation process was governed by CO2 diffusion. When the carbonation conversion rate reached 2-6%, the setting time increased rapidly with the increase in the carbonation rate. This is because the surface of the activator was modified by the thickened CaCO3 product layer, which increased the diffusional resistance and thus prolonged the setting time of the alkali-activated slag.

KOH-Activated Geopolymer Microspheres Recycle Co(II) with Higher Adsorption Capacity than NaOH-Activated Ones.

A new type of absorbent with high efficiency was synthesized by KOH-activated slag-based geopolymer microspheres (K-SGM), which exhibited higher adsorption capacities for recycling Co(II) (Q e,K-SGM = 192.31 mg/g, Q e,Na-SGM = 91.21 mg/g) than NaOH-activated ones (Na-SGM). During the Co(II) adsorption process, these two kinds of geopolymeric adsorbents could be combined with heavy metal ions to optimize each other and form heavy metal-grown aid adsorbents. The morphology of Na-SGM and K-SGM was different which varied from coarse pores to nanonetwork or nanosheets after Co(II) adsorption, and the Brunauer-Emmett-Teller (BET) surface areas of Na-SGM (10.46 m2/g) and K-SGM (22.96 m2/g) increased to 117.38 and 228.73 m2/g after Co(II) adsorption, respectively. The BET surface area of K-SGM is twice that of Na-SGM whether before or after Co(II) ion adsorption. The hydrated ionic radius of K and Na, the alkalinity degree of K+ and Na+, the electronegativity of Na-SGM and K-SGM surface, the BET surface area and Fourier transform infrared changes of CO3 2- and OH before and after Co(II) adsorption, and X-ray photoelectron spectroscopy analysis like the relative content of geopolymer gel and bridging oxygen bonds in the Na-SGM and K-SGM are the fundamental reasons for the obvious differences in Co(II) adsorption between Na-SGM and K-SGM.

Inhibition of Efflorescence in Na-Based Geopolymer Inorganic Coating.

Coating is one of the most important high-value-added application cases in geopolymer materials. However, efflorescence can easily cause discoloration and reduce the esthetic impression of the coating surface, thus limiting its application; hence, inhibition of efflorescence is one of the most important techniques in the application of geopolymer coatings. Efflorescence is a spontaneous behavior in a Na-based geopolymer, involving the migration of soluble alkalis. Alkalis are dissolved by water and diffuse to the material surface through nocuous pores, and then react with CO2 to produce white carbonate products. To inhibit efflorescence in geopolymer coating, this article reports a structure modification method using polydimethy siloxane (PS) and mica. To explore the inhibition mechanism, the effects of PS and mica on the pore structure, water absorption, alkali leaching, and efflorescence product were investigated. The experimental results showed that a harmful pore structure and instinctive water absorption of the geopolymer strongly contributed to efflorescence. PS and mica could reduce the pore size distribution and porosity and are helpful to establish a waterproof structure, leading to water absorption and the alkali leaching rate being significantly suppressed. Both high water glass and water content play a critical role in the increase of efflorescence, but even under a high content of water glass and water used in geopolymer coating, this method shows an 80-90% efflorescence reduction, which is much higher than that of other studies. In practical engineering, when the geopolymer coating is applied after modification, even if it is exposed to the field environment for a long time, there is no efflorescence deposit on the coating surface. It is feasible to limit water ingression in a geopolymer, which effectively blocks the efflorescence reaction process. This method is simple and practical and can be applied in practical engineering applications of geopolymer coatings conveniently.

One-Part Plastic Formable Inorganic Coating Obtain from Alkali-Activated Slag /Starch(CMS) Hybrid Composites.

Coating technology can be applied to decorate building constructions. Alkali-activated materials (AAM) are promising green and durable inorganic binders which show potential for development as innovative coating. In the paper, the possibility of using AAM composited with starch (CMS) as a novel plastic formable inorganic coating for decorating in building was investigated. The rheological properties, including plastic viscosity, yield stress, and thixotropy were considered to be critical properties to obtain the working requirements. Four different mixtures were systematically investigated to obtain the optimum formulation, and then were used to study their hardened properties, such as mechanical strengths (compressive, flexural, and adhesive strength), drying shrinkage, cracking behavior, and microstructure. Study results found that CMS could quickly and efficiently be hydrolyzed in an alkaline solution to produce organic plastic gel which filled in AAM paste, leading to the significant improvement of coating consistency, plastic viscosity, and thixotropy. The optimum coating composited with 15.40 wt% CMS shows a relatively stable rheological development, the setting time sufficient at higher than 4 h. Furthermore, CMS shows a significant positive effect on the cracking and shrinkage control due to padding effect and water retention of CMS, which results in no visible cracks on the coating surface. Although the mechanical strength development is relatively lower than that of plain AAM, its value, adhesive strength 2.11 MPa, compressive strength 55.09 MPa, and flexural strength 8.06 MPa highly meet the requirements of a relevant standard.

A Low-Cost Biomimetic Heterostructured Multilayer Membrane with Geopolymer Microparticles for Broad-Spectrum Water Purification.

Membranes have received wide interest in water purification. However, the development of a low-cost and eco-friendly membrane with the desired structure for broad-spectrum water purification still remains a great challenge. Inspired by the hierarchical structure and functions of wood, a heterostructured multilayer membrane fabricated through a facile and "green" layer-by-layer self-assembly method was reported in this study. Specifically, the hydrophilic geopolymer microparticles were doped into sodium alginate matrix to construct "xylem" layers with numerous microchannels, and chitosan was used to build "phloem" layers with dense structures. The resultant biomimetic multilayer membrane displayed a distinct heterostructure and provided the desired rejection to different kinds of pollutants including nanoparticles, soluble dyes, and heavy metal ions, as well as emulsified oil droplets. Furthermore, the biomimetic membrane exhibited a superior stability in a long-term operation and an excellent recyclability for multiple usages for oil droplets removal. The proposed biomimetic membrane prepared in a completely "green" way possesses great potential in practical application for water purification and separation.

Prepared self-growing supported nickel catalyst by recovering Ni (â ¡) from metal wastewater using geopolymer microspheres.

Here, new and effective microsphere adsorbents were synthesized by NaOH activating slag based geopolymer (Na-SGS). These microsphere adsorbents upset the adsorption equilibrium with the maximum Ni2+ adsorption capacity of 414.38 mg/g which is much larger than that of other geopolymer materials. After Ni2+ adsorption from simulated nickel electroplating wastewater, more active positions for the adsorption Ni2+ ions on Na-SGS were provided as shifts from the average pore diameter of 22.00-7.44 nm, the pore volume of 0.06 to 0.25 cm3/g, the Brunauer-Emmett-Teller (BET) surface area of 10.46-125.35 m2/g and the apparent change of new morphology. Moreover, the adsorbed Ni2+ species were distributed uniformly on Na-SGS. Thermodynamic performance reflected an exothermic, spontaneous and molecular disorder adsorption process, which can be easily controlled by the pH, dosage, initial concentration, contact time and temperature. Through the controllable adsorption, Na-SGS after Ni2+ adsorption (Na-SGS-Ni) was recycled and then reduced to be directly supported nickel catalysts (red-Na-SGS-Ni), which showed superior catalytic activity for CO2 methanation. Although the highest percent of CO2 conversation (XCO2 =99.54%) and methane selectivity (SCH4 =99.5%) are both at 300 °C, red-Na-SGS-Ni performed good XCO2 (99.48%) and SCH4 (98.2%) at low temperatures (100 °C).

Superhydrophobic Coatings Prepared by the in Situ Growth of Silicone Nanofilaments on Alkali-Activated Geopolymers Surface.

As a highly hydrophobic and good environmental durable material, silicone nanofilaments have shown great advantages in the construction of superhydrophobic coatings. However, the synthesis of these materials has always been limited to the application of trifunctional organosilane monomers under the action of acidic catalysts. For the first time, long-chain polymeric hydrogenated siloxane-poly(methyl-hydrosiloxane) (PMHS) was used to synthesize rapidly silicone nanofilaments in situ under alkaline conditions. A dense silicone nanofilament coating was obtained by PMHS + geopolymer layer on a smooth iron sheet, and achieved by one-step brushing of PMHS on the surface of a just-solidified alkali-activated metakaolin-based geopolymer coating at 120 °C for an hour of sealed curing. This composite coating was followed by a superhydrophobic composite coating with a contact angle of approximately 161° and a rolling angle of 2°. Consistent with this, laser scanning confocal microscopy and field-emission scanning electron microscopy images show the presence of micro- and nanoscale features that enable the entrapment of air when exposed to water and endow excellent superhydrophobic properties. Because geopolymer material has good adhesion ability with metal, ceramic, or other materials, the composite superhydrophobic coating is expected to be widely used.

N-Doped porous graphitic carbon with multi-flaky shell hollow structure prepared using a green and 'useful' template of CaCO3 for VOC fast adsorption and small peptide enrichment.

High N-doped porous graphitic carbons (S-NPGCs) with multi-flaky shell hollow structure were prepared by using CaCO3 as a green/useful template. S-NPGCs exhibit very fast adsorption for toluene (31 times that of HKUST-1) and effectively selective enrichment of small peptides with high inhibitory activity of angiotensin converting enzymes.

Facile synthesis of hierarchical N-doped hollow porous carbon whiskers with ultrahigh surface area via synergistic inner-outer activation for casein hydrolysate adsorption.

N-doped hollow porous carbon materials have attracted significant scientific interest in the field of peptide adsorption, drug delivery and catalysis. However, their facile synthesis is still a challenge due to the lack of an ideal template and effective route for high specific surface area (SSA). In this work, we report a facile approach for preparing N-doped hollow porous carbon whiskers (HPCWs) by using CaCO3 whiskers as a green template and double inner-activating agent. Two inner activators, CO2 and Ca(OH)2, are generated from the CaCO3 whisker template during the carbonization process. Among them, Ca(OH)2 was formed by H2O vapors reacting with the remaining template CaO. Attributed to the drastic synergistic effect of inner-activation (CO2 or Ca(OH)2) and outer-activation (KOH), the synthesized HPCWs exhibit ultrahigh SSA (3007 m2 g-1), the largest pore volume (2.63 cm3 g-1) and a controllable proportion of micropores (Sm/St, 60-86%). These intriguing pore structure characteristics of HPCWs endow with them rich target-oriented applications, as exemplified by their outstanding adsorption for casein hydrolysate (10 080 mg g-1), which is two orders of magnitude (102) higher than that of common porous materials. This facile and green synthesis strategy may pave a new way to prepare hollow porous carbon materials with the desired pore structure and high surface area for numerous applications.