Search

Geothermal clay rich in kaolinite was first prepared into geopolymer binders. Preparation conditions of calcination on geothermal clay, Na 2 SiO 3 and NaOH combination in alkaline activator, and water content were studied. Thermal nature of the geothermal clay was characterized by TG-DSC and XRD measurements, which shows characteristics of kaolinite and cristobalite during calcination. Mechanical property, morphology and microstructure of the geothermal clay-based geopolymers were characterized by compressive strength measurements, SEM observation and NMR spectra analysis. With optimal synthesizing parameters, geothermal clay-based geopolymer possessed a compressive strength of 19.5 MPa, as well as a homogeneous geopolymeric gel with high percentages of Q 4 (2Al) and Q 4 (1Al) . As geothermal clay is supposed to be of intermediate dissolution reactivity in geopolymerization, this synthesis might extend the kinds of raw aluminosilicates in geopolymer formation. [ABSTRACT FROM AUTHOR]

Nanofluids showing enhanced thermal diffusivity and thermal conductivity have potential applications in the fields of thermal science, engineering, and sustainable energy. It is still a challenge, however, to facilely prepare nanofluids with good dispersion stability using an environmentally friendly method. In the present study, natural layered montmorillonite was exfoliated into two-dimensional montmorillonite nanosheets (MtNS) using a physical ultrasonic method in aqueous solutions. The obtained MtNS suspensions can be directly used as nanofluids without any further operation or any addition of dispersants. Owing to electrostatic repulsion and hydration repulsion among the MtNS nanoparticles in aqueous solution, MtNS/water nanofluids show excellent dispersion stability even over a long time. In addition, owing to the good light absorption ability of MtNS and the thermal diffusion properties of nanofluids, MtNS/water nanofluids exhibit outstanding photothermal conversion efficiency and dramatic solar thermal energy collection performance. Experimental results also proved that suspensions with a high MtNS concentration and small MtNS particle size increase the efficiency of solar energy harvesting. In addition, the stable dispersion of MtNS in fluids leads to extremely good suspension sustainability and recycling performance of the nanofluids. The facile and green preparation method, low cost, excellent dispersion stability, and good solar energy collection performance of MtNS/water nanofluids enable them to be promising solar energy collection mediums. The large-scale application of MtNS/water nanofluids can take full advantage of green solar energy, which can be used in green buildings and contribute to building a sustainable society. • MtNS/water with superior stability has been developed. • MtNS/water nanofluid can be prepared with facile and green method. • The electrostatic repulsion and hydration repulsion lead to stable suspension. • Outstanding photo-thermal conversion of MtNS/water has been proved. • MtNS/water nanofluid shows huge potential in solar energy utilization. [ABSTRACT FROM AUTHOR]

Silica tetrahedron (also called siloxane) is an important structure of clay minerals, the percentage of which influences the hydrophobicity, polarity and other surface properties on clay mineral surfaces. In this study, a novel method for surface wettability modification of talc through thermal treatment has been put forward. In this method, the symmetrical siloxane structures on talc basal surfaces were broken by transforming the nonpolar siloxane structure into a polar structure during the thermal treatment process, thus to decrease the hydrophobic components on talc surfaces, and therefore achieve the goal of surface wettability modification. This study was performed through the measurements of thermosgravimetric analysis and differential scanning calorimetry (TG-DSC), contact angle and wetting heat measurements, fourier transform infrared spectroscopy (FTIR), and 29Si-nuclear magnetic resonance spectroscopy (29Si NMR) as well as molecular dynamic simulations (MDs). The results indicate that the thermal treatment at 960 °C for only a very short time could greatly decrease the contact angle of water on talc surfaces. The mechanism could be attributed to that the thermal treatment leads to the disorder of some of the Si O bond length and O-Si-O bond angle in talc silica tetrahedron structure, which finally results in the disorder of the symmetrical siloxane structure and the formation of the amorphous silica phase. And the decrease of hydrophobic siloxane structures on talc surface gives rise to the relatively strong hydrophilicity on talc surfaces. This current method improves the wettability of talc without any addition of modifiers, which would be helpful of many applications of clay minerals, such as clay-polymer composites, filler materials, clay mineral dispersion in aqueous suspensions or mineral processing, etc. Unlabelled Image • Surface wettability modification has been achieved through thermal treatment. • Siloxane structure on talc surface influences the surface hydrophobicity. • Siloxane on talc surface transformed into amorphous silica when thermal treated. • The breakage of siloxane leads to decrease of the contact angle of talc surface. • Thermal treatment is promising in surface wettability modification of clay. [ABSTRACT FROM AUTHOR]

In this study, we introduced a solvent-free mechanochemical route to synthesize Li–Al layered double hydroxide through a two-step grinding of LiOH and Al(OH) 3 , in which the mixture powder with Li/Al molar ratio at 1/2 was first dry ground for 2 h and then wet ground for another 1 h with water addition without any heating operation. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The products possessed highly crystalline of Li–Al LDH phase with no evident impure phases, presenting an easy and effective preparation of Li–Al LDH by using solvent-free mechanochemical approach. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDH) have been extensively studied because of their unique characteristics. The available reviews have dealt with the applications of LDH normally prepared with aqueous solution approaches. Recently mechanochemical ways to synthesize LDH and intercalated LDH have received more and more attention from researchers and several mechanochemical processes have been reported. This article reviews the recent advances in the preparation and intercalation of layered double hydroxides by mechanochemical approaches. Although conventional solution methods for the syntheses of LDH were widely studied, several problems remain to be resolved; such as treatment of aqueous waste, high energy consumption, complex operation etc. It is believed that mechanochemical methods may have potentials to effectively overcome the difficulties and also to synthesize various new types of LDH with further development of this new technique. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are considered one of the most advanced energy-saving materials owing to their high thermal energy storage density during the phase transition process. To solve the leakage problem and poor thermal properties in PCMs, a three-dimensional (3D) hectorite aerogel, with an abundant porous structure, was synthesized to encapsulate octadecane (ODE) for preparing hectorite/octadecane composite PCMs with shape stability, large latent heat capacity, and good mechanical strength. The mechanical and thermophysical properties of the composite PCMs were investigated in depth in this study. Due to the high porosity characteristic of hectorite aerogel, the composite PCMs exhibited a large latent capacity of 196.70 J/g with an ODE loading rate larger than 85 wt%. It was also found that the aerogel played an important role in maintaining shape stability, as no significant leakage was observed during the phase-change process. In addition, the composite PCMs exhibited a compressive strength of approximately 2.4 MPa, suggesting good mechanical strength. The thermal stability was found to be excellent, considering that the thermal decomposition temperature of the composite was far higher than the phase change temperature. The excellent shape stability and thermal stability contributed to the outstanding recycling performance of the composite PCMs. The thermal management performance of the composite, in a building house model, was also tested to verify its superior thermal regulation function. Thus, these mechanically strong composite PCMs, with stupendous energy storage capacities and good form stabilities, can be applied in the energy storage and thermal management fields, thereby showing great potential for a sustainable society. • The composite PCMs showed perfect physicochemical compatibility and shape-stability. • Hectorite aerogel/ODE composite PCMs have large latent heat of 197.70 J/g with PCMs loading rate of 85.96%. • The composite PCMs show a great mechanical strength. • The composite PCM show prominent thermal management properties. [ABSTRACT FROM AUTHOR]

The shortage of fresh water is becoming a great challenge all over the world, solar desalination is an emerging green and sustainable strategy to produce clean water from seawater or waste water by utilization of renewable solar energy. However, the accumulation of salt will depress the long-term sustainable use of solar evaporators. In this work, a hydrogel evaporator with montmorillonite (Mt) and MoS 2 integrated layered structure has been fabricated for stable and efficient solar steam generation. The perfect hydrophilicity of Mt. can facilitate water transmission and salt redissolution speed. The vertical radial porous structure and low thermal conductivity of Mt. hydrogel ensures the shortest water transport path and superior heat localization performance. The upper MoS 2 layer has a light absorption rate of up to 92% in the entire solar spectrum (200–2500 nm), which enables an excellent solar to thermal conversion efficiency. Under a low solar irradiation intensity of only 1 kW·m−2, the Mt./MoS 2 double-layer aerogel can achieve a high evaporation rate of 1.31 kg·m−2·h−1. More importantly, the Mt./MoS 2 double-layer aerogel can produce freshwater with salt ions (Na+, K+, Mg2+, Ca2+) rejection rate over than 99.9%. The as-prepared solar evaporator aerogel is turned out to show good mechanical strength, superior water supply, excellent durability and outstanding desalination performances. As a result, the developed Mt./MoS 2 double-layer aerogel with low cost and high-quality of condensed water may provide a good prospect in solar desalination application and wastewater treatment. [Display omitted] • Mt. aerogels showed excellent water transmission and thermal insulation properties. • MoS 2 aerogels has good light absorption and solar-thermal conversion efficiency. • Mt./MoS 2 aerogels can achieve high evaporation rate under irradiation of 1 kW·m−2. • Mt./MoS 2 aerogels can produce freshwater with 99.9% salt ions rejections. [ABSTRACT FROM AUTHOR]

The exfoliation of montmorillonite (Mt) into nanosheets with mono or few-layer is significant for controllable preparation of Mt. functional nanocomposites, whereas Mt. nanosheets (MtNS) prepared in aqueous solutions usually encountered restack problems suffering from dehydration. In this work, anhydrous MtNS with few layers were successfully prepared through a novel gasification exfoliation method. The quality of morphology, structural and stability characteristics of MtNS were investigated by an atomic force microscope, scanning electron microscope, BET and turbidity. The anhydrous MtNS with a thickness of 0–5 nm were prepared by the liquid nitrogen (LN 2) gasification exfoliation. In addition, MtNS prepared through gasification exfoliation presented a looser interlayer structure, higher BET specific surface area and better dispersion stability than those prepared by ultrasonic exfoliation and freeze drying. Thus, the gasification exfoliation perfectly addressed the obstacle of nanosheet restacking. Moreover, molecular dynamics simulation found the LN 2 could enter the interlayer domain of Mt. When heating under 70 °C, the drastic gasification of LN 2 destroyed the weak interlayer binding force of Mt., leading to the successful preparation of anhydrous few-layered MtNS. These findings are expected to provide theoretical guidance for the scalable application of MtNS as functional materials. [Display omitted] • A novel gasification exfoliation method proposed to avoid restack of Mt nanosheets. • The prepared MtNS through gasification has similar thickness to that by sonication. • The G-MtNS possesses higher BET specific surface area than MtNS-FD. • The G-MtNS suspensions shows better stability than MtNS-FD suspensions. [ABSTRACT FROM AUTHOR]

Two-dimensional montmorillonite nanosheets (2DMMT), acrylic acid and acrylamide were used as raw materials to synthesize the three-dimensional reticular-structured hydrogel via hydrogen-bond, polymerization, amidation and electrostatic interactions. Morphology characteristics shown the porous structure of montmorillonite hydrogel, offering an open-access for Pb(II) to react with internal adsorption sites. Adsorption tests indicated that 2DMMT hydrogel could achieve the effective removal (99%) for high concentrated Pb(II) solution (125 mg/L) via small hydrogel dosage (1 g/L) within short contact time (60 min). High removal of Pb(II) (70%, adsorption capacity: 90 mg/g) could be still achieved even after five adsorption-regeneration cycles, achieving the long-term servicing for wastewater treatment with cost-optimal operation. Adsorption kinetics and isotherm tests indicating the homogeneous monolayer physical and chemical adsorption between Pb(II) and hydrogel, and the adsorption capacity of Pb(II) was controlled by the amount of adsorption sites on hydrogel. Characteristics of XPS and EDS revealed the adsorption mechanism of ion exchange, chelation reaction and chemical precipitation. Two-dimension montmorillonite with high surface area and fully-exposed active sites formed the reticular-structured hydrogel, showing high removal ability for Pb(II). [Display omitted] • Hydrogen-bond, polymerization, amidation and electrostatic interaction generated the 3D reticular-structured hydrogel. • 3D reticular structure offered an open-access for Pb(II) to react with internal adsorption sites in hydrogel. • Efficient removal for Pb(II) at high concentration is achieved via small dose of hydrogel within a short time. [ABSTRACT FROM AUTHOR]

Three-dimensional reduced graphene oxide/montmorillonite nanosheet aerogels (RGMTAs) have been successfully fabricated through hydrothermal method. X-ray diffraction and field-emission scanning electron microscope were used to characterize the structures of RGMTAs, and the electrochemical performance was investigated by electrochemical measurements. The restacking of reduced graphene oxide aerogel can be effectively inhibited without obvious structure change by using a small amount of montmorillonite nanosheets (Mts). The reduced graphene oxide/Mts aerogel shows enhanced electrochemical performance with a high specific capacitance of 275 F g−1 at a current density of 1 A g−1, and excellent rate capability. Moreover, though it is not conductive, excessive Mts only slightly increase the equivalent series resistance and charge transfer resistance. This work demonstrates that 2D Mts can reduce the restacking degree of graphene sheets, and the 3D reduced graphene oxide/Mt. nanosheet aerogel is a potential electrode material for supercapacitor applications. • 2D montmorillonite nanosheets can inhibit the restacking of reduced graphene oxide sheets. • Excessive montmorillonite nanosheets only slightly increase the equivalent series resistance and charge transfer resistance. • The reduced graphene oxide/montmorillonite nanosheet aerogel shows enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

MoS 2 and montmorillonite (MMT) nanosheets were hybridized through a simple in-situ hydrothermal synthesis in order to develop an efficient adsorbent, MoS 2 /MMT composite, for the removal of mercury from water. Raman, XRD, and FTIR results displayed the good hybridization of MMT and MoS 2. HRTEM images indicated that the active edges of MoS 2 were clearly exposed in the hybrid, demonstrating the vital role of MMT as eco-friendly, cheap and stable substrate for the growth of MoS 2. The overall adsorption process of Hg2+ on MoS 2 /MMT proved that the composite is highly efficient for the removal of Hg2+ from water, adsorbing up to 1836 mg/g of Hg2+, which outperformed most literature reported adsorbents. The adsorption kinetic and isotherm models could be well described by pseudo-first-order and Langmuir models, respectively. Furthermore, the Langmuir dimensionless constant, R L show that Hg2+ adsorption on the composite was found favorable to occur at the temperature of 25 °C and 35 °C. The XPS analysis revealed that the S sites and slight O sites were main contributors for the remarkable adsorption performance of MoS 2 /MMT composite on Hg2+ removal. This work suggests that MoS 2 supported on MMT substrate might be a promising adsorbent with high capacity and super efficiency for the removal of heavy metals from aqueous solution. Unlabelled Image • Preparation of MoS 2 /MMT composite through a simple in-situ hydrothermal method. • Efficient adsorptive removal of Hg2+ from water. • Investigation of kinetics and isotherm model. • Montmorillonite as supporting material to improve the dispersibility of MoS 2 in water. • Elucidating the underlaying adsorption mechanism. [ABSTRACT FROM AUTHOR]