Thermal energy storage plays a crucial role in energy conservation and environmental protection. Research on thermal energy storage of phase change materials (PCM) has been standing in the forefront ...of science. Several evident defects exist in the phase change materials such as low thermal conductivity and leakage during the phase change process. Meanwhile, the clay mineral materials have relatively high thermal conductivity and excellent adsorbability, which can successfully remedy the defects resided in PCM. Thus, the researches on clay mineral-based form-stable phase change materials (FSPCM) were reviewed in this paper. Nine kinds of clay mineral materials were summarized, that is kaolin, diatomite, sepiolite, montmorillonite, perlite, SiO2, attapulgite, vermiculite and fly ash. The large specific surface area and prominent porous structure of clay mineral materials can successfully prevent the flow and leakage of PCM within the clay mineral-based FSPCM. Hence, this paper can partly serve as a reference for thermal energy storage and conservation.
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•Novel organo-clays are renowned organics adsorbents with wide availability and cost-effectiveness.•Synthesis and characterization of various gemini surfactants for organo-clays are ...described.•Adsorption performances and mechanisms are compared on tunable organo-Mts, organo-Vts and organo-SiNSs.•Potential precursors and modifiers are proposed for promising organo-clays.
Novel organo-clays functionalized with gemini surfactants are one of the most prevalent adsorbents covering a vast range of organic pollutants. The adsorption performances, mechanisms and regenerabilities of organo-clays are closely associated with their interlayer structure, resulting from variations of modifier and/or the precursor. To this end, a comprehensive view of organo-clay adsorbents is described from two angles: preparation and adsorption. The synthetic routes of gemini surfactants (abbr. geminis) tuning the structure and morphology of organo-clays have been summarized, with the geminis examining on different layer charged precursors (vermiculite, montmorillonite and silica nanosheets with the layer charge decreasing). A systematic summarization, comparison and future prospection about the fate of novel organo-clays is achieved, including functionalization by gemini surfactants varying in alkyl chains, spacers, head groups and functional groups, adsorption and desorption towards specific pollutants, and novel characterization methods. The adsorption isotherms, kinetics, thermodynamics as well as additional interactions are compared and overviewed significantly. Furthermore, the limitations, differences and directions of organo-clay adsorbents are discussed.
•EVM benefited the encapsulation of PEG and decreased its supercooling extent.•A theoretical calculation method was applicable to predict the thermal conductivity enhancement ability of Ag NW.•Latent ...heats and thermal conductivity of PEG–Ag/EVM ss-CPCMs maintained simultaneously reasonable.
A series of novel polyethylene glycol-silver nanowire/expanded vermiculite shape-stabilized composite phase change materials (PEG–Ag/EVM ss-CPCMs) were prepared by physical blending and impregnation method to overcome liquid leakage during phase transition and enhance the thermal conductivity of PEG. In these PEG–Ag/EVM ss-CPCMs, PEG served as the phase change material for thermal energy storage; Ag NW served as thermal conductivity enhancement filler; EVM acted as the supporting material to provide structural strength and prevent the leakage of melted PEG. SEM analysis results indicated that Ag NW wrapped with PEG was well dispersed and enwrapped inside the pores and surfaces of EVM due to capillary force and surface tension. It was found that the maximum encapsulation capacity of PEG in all PEG–Ag/EVM ss-CPCMs with good shape stability was 66.1wt.%. The thermal conductivity of PEG–Ag/EVM ss-CPCMs could be greatly enhanced by the prepared Ag NW with a length of 5–20μm and a diameter of 50–100nm. A theoretical calculation method was developed to predict and evaluate the thermal conductivity enhancement ability of Ag NW. The predictions were consistent with experimental results. The thermal conductivity of PEG–Ag/EVM ss-CPCM19.3 reached 0.68W/mK, which was 11.3 times higher than that of pure PEG, and corresponding phase change latent heat was 96.4J/g. The supercooling extent of PEG in PEG–Ag/EVM ss-CPCMs decreased approximate 7°C because the EVM could act as a heterogeneous nucleation center to promote the crystallization of PEG. FT-IR and TGA results showed that the PEG–Ag/EVM ss-CPCMs exhibited excellent chemical compatibility and thermal stability.
This research presented six natural clay minerals (NCM) evaluated for the effectiveness of NH4+ adsorption from aqueous solution. For the first time, the NH4+ adsorption capacities of kaolinite, ...halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite were examined and compared in the same study. All the NCM were fully characterized by XRD, SEM/EDS, XRF,FTIR, CEC, zeta potential and nitrogen adsorption-desorption isotherms to better understand the adsorption mechanism-property relationship. Adsorption kinetics showed that the adsorption behavior followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the NCM studied, vermiculite (50.06mg/g) and montmorillonite (40.84mg/g) showed the highest ammonium adsorption capacities. Our results revealed that the cation exchange is the main mechanism for the NH4+ adsorption. Additionally, negatively charged surface, water absorption process and surface morphology of NCM might also contribute to the high adsorption capacity for the NH4+. The maximum adsorption capacities for all NCM were rapidly obtained within 30min with a dosage of 0.3g/25mL at pH of 7. The results illustrated that the NCM have significant potential as economic, safe and effective adsorbent materials for the NH4+ adsorption from the aqueous solution.
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•Vermiculite and montmorillonite showed the highest ammonium adsorption capacities.•Cation exchange was the main mechanism onto NCM.•The structure and surface properties of NCM are the key for the highest adsorption.•Parameters such as contact time, dosage and pH affecting NH4+ adsorption•The adsorption isotherms and kinetic models were investigated.
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•An ether-spacer-containing Gemini surfactant was used as modifier for three organo-clays.•Modifier structure and wettability have significant influence on the adsorption performance ...of organo-clays.•The adsorption capacity of organo-vermiculite (BDEE-Vt) towards CR is up to 298 mg g−1 at 55 °C.•The larger layer charge of the clay, the more hydrophobic of the particle, the more CR adsorbed.
Clay minerals (vermiculite, montmorillonite and silica nanosheets) with diminishing layer charge were modified by a novel Gemini surfactant, 2,2′-bis(dodecyldimethylammonio)-ethyl ether dichloride (BDEE) for the first time. The resultant products were certified by FT-IR, Elemental analysis (EA), TG, SEM and XRD, which indicated that the BDEE in vermiculite (Vt), montmorillonite (Mt) and silica nanosheets (SiNSs) adopted different arrangements. Adsorption capacities as a function of contact time, concentration of the Congo red (CR) and temperature were explored in detail. The results showed that the saturated sorption amount of BDEE-Vt, BDEE-Mt and BDEE-SiNSs up to 298, 154 and 64 mg g−1 at 55 °C within 120 min, respectively. Interestingly, the order of adsorption capacities of these organo-clays were agreed with the sequences of the layer charge and the hydrophobicity of particles characterized by Lipophilic to Hydrophilic Ratio (LHR), which further proved the importance of hydrophobic interaction to CR adsorption onto organo-clays. The pseudo-second-order and Redlich-Peterson models were more suitable for the adsorption data of each adsorbent. Thermodynamic parameters showed that the processes of absorbed CR on BDEE-Vt and BDEE-Mt were endothermic and spontaneous, while BDEE-SiNSs was endothermic and non-spontaneous converted to spontaneous with temperature increasing. This work provides theoretical guidance for further design of highly efficient modifiers and high-performance organo-clay adsorbents.
•Expanded vermiculite/carbon (EVMC) was prepared by in-situ sucrose carbonization.•The form-stable composite PCM of paraffin/EVMC were fabricated.•The maximum absorption of paraffin in the ...paraffin/EVMC is 53.2wt.%.•We developed a new way to enhance the thermal conductivity of the organic PCMs.
Paraffin/expanded vermiculite with modified porous carbon layer was prepared in the study. In the composite phase change materials (PCM), expanded vermiculite was impregnated with sucrose in the layer and then carbonated in situ in order to enhance thermal conductivity and improve the adsorption capacity of expanded vermiculite, which acted as a carrier material in the preparation of the form-stable PCM. SEM images showed the morphology of expanded vermiculite had been changed after carbonation. A series of micro-pores had been formed among the layers of expanded vermiculite with the diameter ranging from several microns to 120μm. Thermal properties of the composite PCM were determined by differential scanning calorimeter (DSC) analysis. According to DSC analysis results, when the paraffin adsorption reached 53.2wt.%, latent heats of the composite PCM were respectively 101.14J/g at the freezing temperature of 48.85°C and 103J/g at the melting temperature of 53.1°C. TGA results showed that the form-stable composite PCM presented good thermal stability. Due to the formation of carbon structure in the layer of expanded vermiculite, the thermal conductivity of the supporting materials was improved, thus slightly decreasing the extrapolated onset melting temperature of pure paraffin. Furthermore, the results of FT-IR analysis and thermal cycling tests showed that the form-stable composite PCM had good chemical stability and thermal reliability after 200melting/freezing cycles. The form-stable composite PCM with good thermal properties, thermal reliability, and chemical stability is the promising PCM for the low-temperature thermal energy storage applications.
Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in ...liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film‐forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few‐layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)‐based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.
2D fillers can comprehensively upgrade the performance of solid polymer electrolytes, including thermal and dimensional stability, mechanical strength and elasticity, ionic conductivity, interfacial stability, and operation voltage. 2D fillers are advantageous over 0D and 1D fillers in providing higher effective interface with polymers in solid polymer electrolytes and withstanding the matrix's deformation in the solid polymer electrolytes under external force.
•Vermiculite could prolong the thermophilic phase and speed up organic matter loss.•Vermiculite could reduce the nitrogen loss by decreasing the NH3 emissions.•10% vermiculite reduced the NH3 ...emissions by 26.39% compared with the control.•Vermiculite could be used to alleviate the compost salinity.
This study investigated the effects of adding vermiculite to the food waste composting process. Four treatments with varying vermiculite percent compositions, 0%, 5%, 10% and 15% (w/w, wet weight of food waste basis) mixed with initial food waste were designed and then composted for 42 days. Results show that adding vermiculite prolongs the thermophilic phase, speeds up the organic matter loss, reduces the NH3 emissions and electrical conductivity values. Compared to the control, the amount of nitrogen loss through NH3 emissions in the treatments of 5%, 10% and 15% vermiculite decreased by 9.89%, 26.39% and 18.65%, respectively. Finally this work suggests that vermiculite is a suitable additive for food waste composting, especially when the makeup of the compost is 10% vermiculite.
Novel EVM/SrBr2 composite sorbents with different salt contents were developed for low-temperature thermal energy storage (TES). Simulative sorption experiment was conducted to obtain the sorption ...kinetics diagram and identify threshold salt content that composite sorbents can hold without solution leakage. Distribution of salt embedded in EVM was observed by extreme-resolution scanning electron microscopy (ER-SEM). Thermochemical characterizations including desorption performance and desorption heat were fully investigated by analyzing simultaneous thermal analyzer (STA) results. Results reveal that sorption process of composite sorbents is divided into three parts: water adsorption of EVM, water adsorption of SrBr2 crystal and liquid-gas absorption of SrBr2 solution. Since SrBr2 solution can be hold in macrospores of EVM, water uptake and energy storage density are greatly increased. It appears that the composite sorbent of EVMSrBr240 is a promising material for thermal energy storage, with water uptake of 0.53 g/g, mass energy storage density of 0.46 kWh/kg and volume energy storage density of 105.36 kWh/m3.
•Vermiculite/SrBr2 composite sorbents were developed for thermal energy storage.•Water uptake of composite sorbents is divided into three phases.•Energy storage density of each sorption phase is evaluated via calculations.•EVMSrBr240 is chosen as optimal sorbent without solution leakage.
Solid state lithium metal batteries are the most promising next‐generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due ...to the excellent flexibility, manufacturability, lightweight, and low‐cost processing. However, fatal drawbacks of the SPE such as the insufficient ionic conductivity and Li+ transference number at room temperature restrict their practical application. Here vertically aligned 2D sheets are demonstrated as an advanced filler for SPE with enhanced ionic conductivity, Li+ transference number, mechanical modulus, and electrochemical stability, using vermiculite nanosheets as an example. The vertically aligned vermiculite sheets (VAVS), prepared by the temperature gradient freezing, provide aligned, continuous, run‐through polymer‐filler interfaces after infiltrating with polyethylene oxide (PEO)‐based SPE. As a result, ionic conductivity as high as 1.89 × 10−4 S cm−1 at 25 °C is achieved with Li+ transference number close to 0.5. Along with their enhanced mechanical strength, Li|Li symmetric cells using VAVS–CSPE are stable over 1300 h with a low overpotential. LiFePO4 in all‐solid‐state lithium metal batteries with VAVS–CSPE could deliver a specific capacity of 167 mAh g−1 at 0.1 C at 35 °C and 82% capacity retention after 200 cycles at 0.5 C.
A vertically aligned 2D materials filler for solid polymer electrolytes is demonstrated. The aligned, continuous, run‐through polymer‐filler interfaces enhance the ionic conductivity, Li+ transference number, mechanical modulus, and electrochemical stability of solid polymer electrolytes. LiFePO4 in lithium metal batteries with the electrolyte could deliver a specific capacity of 167 mAh g−1 at 0.1 C at 35 °C.
