Sepiolite Research Articles

Cooperative Effect of Chemical and Physical Processes for Flame Retardant Additives in Recycled ABS.

In the present work, the effectiveness of four non-halogenated flame retardants (FR) (aluminium trihydroxide (ATH), magnesium hydroxide (MDH), Sepiolite (SEP) and a mix of metallic oxides and hydroxides (PAVAL)) in blends with recycled acrylonitrile-butadiene-styrene (rABS) was studied in order to develop a more environmentally friendly flame-retardant composite alternative. The mechanical and thermo-mechanical properties of the obtained composites as well as their flame-retardant mechanism were evaluated by UL-94 and cone calorimetric tests. As expected, these particles modified the mechanical performance of the rABS, increasing its stiffness at the expense of reducing its toughness and impact behavior. Regarding the fire behavior, the experimentation showed that there is an important synergy between the chemical mechanism provided by MDH (decomposition into oxides and water) and the physical mechanism provided by SEP (oxygen barrier), which means that mixed composites (rABS/MDH/SEP) can be obtained with a flame behavior superior to that of the composites studied with only one type of FR. In order to find a balance between mechanical properties, composites with different amounts of SEP and MDH were evaluated. The results showed that composites with the composition rABS/MDH/SEP: 70/15/15 wt.% increase the time to ignition (TTI) by 75% and the resulting mass after ignition by more than 600%. Furthermore, they decrease the heat release rate (HRR) by 62.9%, the total smoke production (TSP) by 19.04% and the total heat release rate (THHR) by 13.77% compared to unadditivated rABS; without compromising the mechanical behavior of the original material. These results are promising and potentially represent a greener alternative for the manufacture of flame-retardant composites.

Ecological hybrid pigments with improved thermal, light, and chemical stability based on purpurin dye and different minerals for applications in polymer materials

A facile and cost-effective route was developed for the production of high-performance hybrid pigments by the stabilization of the natural red dye (purpurin) on mineral supports. For the first time, hydrotalcite (LDH), sepiolite (SEP), and aluminum-magnesium hydroxycarbonate (LH30) with different chemical compositions and structures were used as inorganic supports for purpurin. The physico-chemical properties of the prepared pigments were characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), color measurements, release kinetic experiments, and thermogravimetric analysis (TGA). Purpurin molecules were confirmed to have been successfully incorporated into the inorganic supports via interactions between the purpurin chromophore and Mg2+, Zn2+ and/or Al3+ ions from the mineral host. The interactions resulted in hybrid pigments with higher thermal stability and lower tendency to migrate, without changing the morphology of the minerals. The hybrid pigments were applied as new colorants for ethylene-norbornene copolymer. The polymer composites were subjected to long-term UV irradiation followed by color and mechanical measurements. The results suggest that purpurin-based hybrid pigments can act as durable and effective colorants. This work provides a novel approach for preparing stable and multifunctional hybrid pigments based on natural dyes and mineral supports.

Simple and eco-friendly fabrication of highly tolerant chitosan/alginate@sepiolite hybrid films on nylon textile for oil/water separation in harsh conditions

Because of the need of achieving efficient separation to oil/water mixture, the construction of separation coating with good mechanical strength and chemical resistance are highly desired. Although many polysaccharide-based coating for oil/water separation have been prepared, the poor durability and the environmentally unfriendly preparation process greatly restrict their applications. Herein, sepiolite (SP) was introduced into chitosan/alginate (CS/AG) matrix to produce nacre-like composite films with superb robustness and stability via a simple and green layer-by-layer (LbL) self-assembly technique. After the composite films are fabricated on nylon textile (NT), the hydrophilicity and underwater superoleophobicity of the NT surface are significantly improved. The composite coating also reveals excellent oleophobic stability after being subjected to corrosive liquids immersion, high-temperature treatment, strong abrasion, and organic solvents immersion. Furthermore, the modified NT is able to separate oil/pure water, oil/cold corrosive water, and oil/hot corrosive water mixtures with high filtration efficiency (>98.3 %). Especially, the separation to oil/hot corrosive solution mixtures can be repeated at least 40 times without obvious decrease of separation efficiencies. This investigation offers a new and eco-friendly strategy to prepare SP coating-based membrane materials with good superhydrophilicity, mechanical property, and recyclability for oily wastewater purification.

Enhanced hydrophilicity and promoted charge transfer in covalent triazine frameworks/sepiolite complexed via hydrogen bonding for visible-light driven degradation of antibiotics

Featuring strong visible-light absorption, tunable band gaps, structural diversity, and fully conjugated nitrogen-rich structures, covalent triazine frameworks (CTFs) are emerging as a class of promising semiconductor photocatalysts. However, limited by their poor hydrophilicity and fast charge carrier recombination, their photocatalytic efficiency in water is far lower than expected. Herein, a hybrid composite of sepiolite (SEP) and CTF with a tunable density was synthesized via an in situ CF3SO3H-promoted strategy. The resultant SEP@Th-CTF 2:1 composite exhibited excellent photocatalytic efficiency in the degradation of antibiotics under visible light, which can be attributed to its improved charge transfer and enhanced hydrophilicity. The interaction between sepiolite and Th-CTF via hydrogen bonding results in the transformation of photogenerated electron from Th-CTF to antibiotics. The combination of sepiolite with CTFs can improve photocatalytic performance, which is instructive to broaden the application of CTFs as semiconductors for efficient solar energy conversion in a water medium.

Adsorption properties and mechanism of sepiolite to graphene oxide in aqueous solution

Graphene oxide (GO) is widely used in various fields such as improving the performance of cement-based materials and making composite materials due to its large specific surface area and abundant oxygen-containing functional groups. However, it has also caused water pollution. To remove GO in aqueous solution, sepiolite (SEP) was used to adsorb it. The effects of pH, adsorbent quality, GO concentration, temperature and adsorption time on the ability of SEP to adsorb GO were investigated. The materials were characterized by SAP and laser particle size analyzer, and the adsorption performance and mechanism of SEP for GO were further analyzed by XRD, FTIR, SEM, TEM, XPS, AFM, and Zeta potential microscopic tests. The results showed that: 1) Under the conditions of temperature 303 K, pH = 3, adsorbent mass 30 mg, and initial concentration of GO 100 mg/L, the adsorption effect was the best, and the adsorption rate reached 94.8 %. 2) The adsorption reached equilibrium at 2160 min, and the adsorption process was more in line with the pseudo-second-order adsorption kinetic equation, and the adsorption behavior was controlled by chemical effects. 3) The adsorption of SEP to GO is more consistent with the Langmuir and Temkin adsorption isotherm model, and the reaction is a spontaneous, endothermic, and entropy-increasing process. Experiments showed that SEP had a strong adsorption capacity for GO, which provides a reference for the treatment of toxic GO in aqueous solution and the realization of water ecological protection.

Numerical and experimental analysis of refrigerating performance for hybrid nanolubricants with sepiolite additives

The use of nanomaterials in various forms and compositions provides the basis for the creation of high-performance structures in their application in many heating and cooling systems. In this study, the lubrication properties of rod-shaped Sepiolite (SP) and its various carbon composites Carbon Black (CB), Multi-Walled Carbon Nanotubes (MWCNT), and reduced Graphene Oxide (rGO) were investigated for the first time in a vapor compression cooling system. The cooling heat transfer performance was compared by analyzing the rheological and thermal behaviors using nanolubricants. The best improvement in cooling Coefficient of Performance (COP) was obtained by using SP-rGO nanoparticles. Compared to Polyol Ester (POE), the cooling performance COP increased by 23.6 % with the addition of SP-rGO. The strategy proposed here is simple and has great potential for producing high-efficiency cooling systems. In addition, the single-phase compressor motor was modeled with Finite Element Analysis (FEA) simulation in the experimental studies, and the simulation results were reported. According to the power loss data obtained from FEA simulation results, a total power loss of 119 W is determined as core losses of 44 W, winding losses of 65 W and frictional losses of 10 W for a 1 HP single-phase compressor motor. Thus, the electrical energy efficiency of the motor is approximately 86 %.

Effect of sepiolite on properties of silicone rubber/melamine/starch/sepiolite flame retardant composites

AbstractIn this work, a novel silicone rubber composite with low smoke, good mechanical property, and excellent flame retardant was prepared by introducing melamine (MEL), starch (St), and sepiolite (SEP) into SR. The effect of the amount of SEP on the mechanical properties of SR composites was investigated. The results showed that the mechanical properties were optimal when the amount of SEP was 30 phr. The tensile sections of the composites were characterized by SEM. The flame retardant properties of the composites were evaluated by oxygen index, vertical combustion, and cone calorimetry test (CCT). The thermal stability of the composites was tested by TGA. The flame retardant mechanism of the composites was also discussed. It was found that the strength and stability of the carbon layer of the composite were remarkably enhanced, and the flame retardant properties of the materials were improved with the addition of SEP. The SEM images of CCT carbon residues revealed that the carbon layer of the composite with SEP was more stable and had fewer cracks than that without SEP. This work provides new insights for the preparation of high‐performance SR composite.

Removal of trivalent chromium from aqueous solutions by natural clays: Valorization of saturated adsorbents as raw materials in ceramic manufacturing

Kaolinite/illite (KUb) and sepiolite (SEP) clays were used to study Cr(III) adsorption removal from aqueous solutions so that they could be utilized after saturation for ceramic manufacturing. SEP had a larger specific surface area and a higher PZC than KUb. The removal of Cr(III) was evaluated using a batch equilibration procedure at pHi = 4 and pHi = 6. Fast removal kinetics were observed for both clays. Maximum removal capacity was determined by changing the concentration of Cr(III) while keeping the concentration of clay constant and by altering the amount of clay while keeping the concentration of Cr(III) constant. In all situations, SEP had greater capacity than KUb, and capacity was greater for both clays at higher pHi. Not only did the pHi impact the removal capacity and efficiency, but so did the pH during adsorption and the initial concentration of Cr(III). Because of the higher PZC, the pHf for SEP was higher for the same pHi. The higher the pH and Cr(III) concentration, the higher the probability of Cr(OH)3 precipitation and the higher the removal capacity.Dried saturated clays were uniaxially pressed and sintered at 1000 °C for 2 h. The densities of the sintered materials were nearly identical to those of pure clay-based materials, but the compressive strengths were higher, which is significant for the use of saturated clays as raw materials in ceramic manufacturing. Leaching of Cr from SEP-based material was significantly higher than from KUb-based material probably due to the presence of CaCO3 in the SEP.

Effect of clay minerals on the flame retardancy of polylactic acid/ammonium polyphosphate system

The overview of the literature reveals the lack of comprehensive study on the effect of clay minerals in flame-retarded polylactic acid (PLA) composites. This research focuses on sepiolite (SEP) and montmorillonite (MMT) clay minerals and their impact on ammonium polyphosphate (APP)-based intumescent flame-retardant (IFR) system in PLA. The effects of the clay mineral types, their surface modification (O-SEP and O-MMT, respectively) and their concentration in PLA/APP composites on the flame-retardant properties were comprehensively evaluated through thermal and flammability tests. Overall, the sepiolite-containing samples showed the greatest decrease in pHRR and THR values at the 3 m/m% loading level. The sepiolites showed stronger interfacial interactions with the PLA matrix than the montmorillonites, and the organomodification proved to improve the compatibility of both types of clay minerals according to the dynamic mechanical analysis (DMA) results. Yet, the organomodification had a contradictory effect on the flame-retardant properties. In the case of sepiolites, it proved to be beneficial as the O-SEP added composite achieved a 60% decrease in the pHRR value and reduced the THR value to 60%. For montmorillonites, the improved compatibility by the organomodification with the PLA matrix seemed to hinder its flame-retardant effectiveness, as the critical point to its flame-retardant mechanism is the rapid migration and accumulation of the clay minerals towards the surface of the polymer.

Effects of Inorganic Passivators on Gas Production and Heavy Metal Passivation Performance during Anaerobic Digestion of Pig Manure and Corn Straw.

The treatment of livestock manure caused by the expansion of the breeding industry in China has attracted wide attention. Heavy metals in pig manure can pollute soil and water and even transfer to crops, posing harm to humans through the food chain. In this study, corn straw was selected as the additive and introduced into the anaerobic digestion. Sepiolite (SE), ferric oxide (Fe2O3), attapulgite (AT) and ferric sulfate (FeSO4) were used as passivators to compare the effects of these inorganic passivators on gas production and passivation of heavy metals during the process of the anaerobic digestion. When the dry mass ratio of pig manure to straw is 8:2, the gas production efficiency is optimal. SE, AT and ferric sulfate have a much stronger ability to improve gas production performance than Fe2O3. The total gas production increased by 10.34%, 6.62% and 4.56%, and the average methane production concentration increased by 0.7%, 0.3% and 0.4%, respectively. The influence of SE, AT and ferric sulfate on the passivation of heavy metals is much better than Fe2O3, and the fractions in biological effective forms of Cu and Zn reduced by 41.87 and 19.32%, respectively. The anaerobic digestion of mixed materials is conducive to the gas production and the passivation of heavy metals. Therefore, SE, AT and ferric sulfate are selected as composite passivators, and the optimal ratio of inorganic composite passivators i: AT 7.5 g/L, ferric sulfate 5 g/L and SE 7.5 g/L, according to the results of orthogonal experiments. This study can provide a theoretical basis for the safe application of biogas fertilizers.

Silanization of sepiolite with various silane coupling agents for enhancing oil uptake capacity

ABSTRACT Eskisehir sepiolite (SEP) was given a hydrophobic surface through acid treatment followed by silanization. The silanization process was realized with trimethoxy(octadecyl)silane (TMODS), (3-aminopropyl)triethoxysilane (APTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) coupling agents. The effects of temperature and reaction time on the silanization degree were studied within the ranges 25–50°C and 2–48 h, respectively. The efficiency of silanized SEP as an oil absorbent was investigated in pure olive oil media. The structural changes in sepiolite samples were monitored by X-ray diffraction (×RD), N2 adsorption (BET), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Fourier Transform Infrared spectroscopy (FTIR). Accordingly, maximum organic loading was achieved as 20.6% (w.) corresponding to 0.69 mmol silane/g SEP, when silanization was conducted with TMODS at 50°C for 24 h. Acid activation with hydrochloric acid removed the dolomite fraction and thus was in favor of silanization. The oil uptake capacities followed the order: GPTMS modified acid-activated SEP > APTES modified acid-activated SEP> TMODS modified acid-activated SEP > acid-activated SEP > SEP reaching as high as 2.77 ± 0.01 g/g at utmost. The augmentation in oil uptake capacity was not solely related to increased hydrophobicity, but also to altered surface area and porosity. Absorbed oil was recoverable at nearly 90% after three absorption – desorption cycles.

Selective catalytic depolymerization of lignin to guaiacols over Mo-Mn/sepiolite in supercritical ethanol

Lignin catalytic depolymerization (LCD) into liquid fuels and aromatic chemicals in supercritical ethanol systems is one of the most effective strategies for efficient utilization of biomass resources. In this study, a series of sepiolite (SEP) supported Mo-Mn catalysts with different Mn/Mo ratios were prepared and applied to LCD. Experimental results for lignin and 2-phenoxy-1-phenyl ethanol (PP) confirmed that Mo/Mn species promoted the breakage of β-O-4 bonds, Mn additive effectively inhibited the alkylation of intermediates, and Mn/Mo ratios distinctly affected the yields of lignin oil (LO) and guaiacols. All as-prepared Mn-Mo/SEP catalysts achieved approximately 100 % conversions of lignin and PP. Various characterization results demonstrated that Mn/Mo ratios could regulate the particle sizes of metal oxides as well as the concentration of oxygen vacancies (OV) and surface acidic sites. In 3Mn1Mo/SEP, the appropriate interaction among SEP, Mn and Mo species reduced the particle sizes of metal oxides and rendered the crystalline phase structure in a relatively complex state, which undoubtedly generated massive steps/corners on its surface and then enhanced the hydrogenation reaction. Furthermore, the 3Mn1Mo/SEP contained many OV and suitable distribution of Lewis and Brønsted acid sites, which facilitated the adsorption of oxygen-containing intermediates and further hydrogenation and deoxygenation. Therefore, 3Mn1Mo/SEP achieved 45.7 % of LO yield with an HHV of 32.31 MJ/Kg and the highest selectivity to phenols (85.61 %) and yield of guaiacols (308.9 mg/g lignin). In addition, the plausible reaction network for LCD was proposed based on the results of experiments and characterizations.

Synergistic removal of As(III) and Cd(II) by sepiolite-modified nanoscale zero-valent iron and a related mechanistic study.

Arsenic (As) and cadmium (Cd) are two highly toxic elements. In recent years, many newly synthesized chemical materials have been used widely for treatments of As- and Cd-contaminated effluents. However, most materials do not exhibit high efficiencies for simultaneous removal of As and Cd from water systems. Our study established a simple scheme for synthesizing a sepiolite (SEP)-modified nanoscale zero-valent iron (S-nZVI) for simultaneous removal of coexisting As and Cd from water and illuminated a possible underlying mechanism. Batch experiments showed that the maximum capacities for adsorption of As(III) and Cd(II) by S-nZVI were 230.29mg/g and 11.37mg/g, respectively, which represented better effects than those of other materials, as reported previously. Removal of Cd(II) depended on pH, but As(III) removal showed little dependence on pH. Coexisting ions such as phosphate (PO43-) and the conjugate base of humic acid (HA) significantly inhibited simultaneous removal of As(III) and Cd(II). In the mixed As(III)-Cd(II) system, the presence of As(III)-pretreated S-nZVI significantly enhanced Cd(II) adsorption by a factor of four over that seen for aqueous solution without As(III). XRD and XPS results showed that CdFe2O4 (Fe-O-Cd), Fe2As2O14 or FeAsO4 (Fe-O-As) were formed after As(III) and Cd(II) were captured by S-nZVI. However, a further zeta (ζ) potential analysis showed that the mechanism for As(III) and Cd(II) adsorption by S-nZVI is not just simple formation of the above chemicals, since the adsorbed As(III) increased the negative charge of S-nZVI; this suggested an electrostatic attraction between S-nZVI and Cd(II) and indicated that adsorbed As(III) created new sorption sites for Cd(II), which enhanced Cd(II) sorption via formation of ternary complexes (Fe-As-Cd). These results suggested that S-nZVI is a promising material for in situ remediation of heavy metal-contaminated groundwaters or paddy soils.

Calcareous Materials Effectively Reduce the Accumulation of Cd in Potatoes in Acidic Cadmium-Contaminated Farmland Soils in Mining Areas.

The in situ chemical immobilization method reduces the activity of heavy metals in soil by adding chemical amendments. It is widely used in farmland soil with moderate and mild heavy metal pollution due to its high efficiency and economy. However, the effects of different materials depend heavily on environmental factors such as soil texture, properties, and pollution levels. Under the influence of lead–zinc ore smelting and soil acidification, Cd is enriched and highly activated in the soils of northwestern Guizhou, China. Potato is an important economic crop in this region, and its absorption of Cd depends on the availability of Cd in the soil and the distribution of Cd within the plant. In this study, pot experiments were used to compare the effects of lime (LM), apatite (AP), calcite (CA), sepiolite (SP), bentonite (BN), and biochar (BC) on Cd accumulation in potatoes. The results showed that the application of LM (0.4%), AP (1.4%), and CA (0.4%) had a positive effect on soil pH and cations, and that they effectively reduced the availability of Cd in the soil. In contrast, the application of SP, BN, and BC had no significant effect on the soil properties and Cd availability. LM, AP, and CA treatment strongly reduced Cd accumulation in the potato tubers by controlling the total ‘flux’ of Cd into the potato plants. In contrast, the application of SP and BN promoted the migration of Cd from the root to the shoot, while the effect of BC varied by potato genotype. Overall, calcareous materials (LM, CA, and AP) were more applicable in the remediation of Cd-contaminated soils in the study area.

Simultaneously Improving Flame Retardant Performance, Thermal Stability and Conductivity of Copolymers of Polyethylene‐octene by Addition of a Ternary Composite Flame Retardant System

AbstractThe development of high efficiency and low‐cost refractories has always been a subject that attract people‘s attention. Although polyethylene‐octene copolymers (POE) has excellent mechanical properties, it is easy to be ignited, which seriously hinders its multi‐field applications. In this paper, a novel ternary composite flame retardant system, ammonium polyphosphate (APP)/expanded graphite (EG)/sepiolite (SEP), was proposed and applied to POE to prepare high flame‐retardant POE composites. The experimental results showed that the addition of SEP could play a good reinforcing role, so as to improve the mechanical properties of POE/APP composites. Thermogravimetric analysis (TGA) showed that when the ratio of EG and SEP was 1 : 1, the initial thermal decomposition temperature decreased significantly, which was conducive to the early degradation and carbonization of POE/APP composites. The thermal conductivity test showed that the addition of SEP can reduce the thermal conductivity of POE/APP composites. In addition, the flame retardant test results revealed that when the ratio of EG and SEP was 1 : 1, the oxygen index (LOI) increased to 25.3 %, the heat release rate (HRR) decreased to 140 kW/m2, the total heat release (THR) decreased to 70 MJ/m2, and the carbon layer produced by combustion was dense and uniform, which contribute to the great heat insulation. In conclusion, the addition of an appropriate amount of ternary compound flame retardant (EG/SEP/APP) could have an excellent synergistic flame retardant effect on POE/APP composites, and the processing method was simple and efficient, which would benefit to broad application of the prepared POE composites.

Enhanced pre-treatment of sepiolite on coal gasification wastewater: Performance and adsorption mechanism

As a simple and feasible treatment method, adsorption can be applied in the pretreatment of coal gasification wastewater (CGW) to remove high-concentration contaminants. This study initially selected granular activated carbon (PAC) and different clay materials (sepiolite (SPI), bentonite (BTE), kaolin (KL), diatomite (DTI) and attapulgite (APG)) as adsorbents, and results showed that chemical oxygen demand (COD) removal efficiencies of by PAC, SPI, DTI, KL, BTE and APG were 54.28 %, 44.19 %, 27.15 %, 17.68 %, 16.08 % and 5.58 %, respectively. In contrast, SPI and PAC had high adsorption capacity for high concentrations of organics. Ammonia nitrogen (NH3-N) removal efficiency by SPI exceeded 27 %, while the effective capacity of PAC was only 9.3 %. Moreover, pseudo-second-order kinetics better fitted kinetic data for PAC and SPI, revealing that the adsorption of organic pollutants on SPI is multi-molecular layer adsorption. The Sips model well described the adsorption process of contaminants by SPI, and more remarkably, the maximum adsorption capacity of SPI for COD was 438.4 mg/g. Accordingly, SPI and PAC both had significant removal effects on phenol, 2-methylphenol, 4-methylphenol, catechol and other refractory organic pollutants through gas chromatograph-mass spectrometer (GC-MS). Simultaneously, acute biotoxicity of CGW was greatly reduced after PAC and SPI adsorption treatment. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of strong polar hydration bonds enabled SPI to adsorb organic pollutants through intermolecular forces. SPI still exhibited more than 30 % of COD removal for CGW after 5 cycles. And COD and total phenol (Tph) removal efficiencies in the stable period reached 37.34 % and 31.04 % during the anaerobic process, respectively. Specially, the cost of removing COD per kilogram of SPI is only 2.73 ¥ while the cost of PAC is as high as 26.61 ¥. On the whole, this study provided an important insight for the feasibility application of SPI in the CGW pretreatment process.

Easy, fast, and clean fluorescence analysis of tryptophan with clays and graphene/clay mixtures

Clays (C) such as sepiolite (SEP) or bentonite (BEN) and their mixtures with graphene (G) have been used as sorbents in dispersive solid phase extraction (dSPE). Tryptophan (TRP) analysis by fluorescence combined with a sample preparation step using G/C 30/70 w/w mixture provides a quantitative TRP retention, independently of the amino acid concentration with a desorption process feasible in 80 mM aqueous solution of the surfactant Brij L23. Under these conditions, the detection and quantification limits are 3.5 and 11.8 µg L-1, respectively. Additionally, a novel, simple and inexpensive method has been developed to directly analyse TRP in real samples, in which the presence of matrix interferents typically limits to obtain accurate results. For the first time, BEN has been used as an effective clean-up sorbent for the fluorimetric analysis of TRP in beer, leading to results without statistical differences versus those of a reference HPLC method free of interferences, with recoveries of 90 % and 100 %. The proposed method can be applied to accurately analyse TRP in complex matrices in a direct, easy, fast and sustainable way.

Influence of minerals with different porous structures on thermochemical heat storage performance of CaCl2-based composite sorbents

Thermochemical heat storage has been successfully employed as a reliable solution for enhancing the utilisation of renewable energy. In this paper, we report novel composite sorbents fabricated by impregnating CaCl2 into porous minerals with different structural properties. Sepiolite (SP), diatomite (DT), and expanded perlite (EP) were chosen as the mesoporous, macroporous, and foamed macroporous matrices, respectively. The pore structure of the matrix exerts a vital influence on the loading of salt hydrates and the performance of the composite material. EP/Ca had the highest energy storage density of 2166 J/g with a water exchange amount of 1.20 g/g, while the energy storage densities of SP/Ca and DT/Ca were 1026 J/g and 1520 J/g, respectively. The foamed macropores of EP provided more space for salt hydrate loading, whereas DT and SP only possessed mesoporous pores with limited pore volumes, thus contributing to lower salt hydrate content. Moreover, EP/Ca exhibited good structural stability during heat storage cycles because of the foamed macroporous structure. In contrast, the restrictive effect of the holes of DT on the salt solution was low, thus causing DT/Ca leakage and caking. Therefore, EP was chosen as the most suitable matrix for supporting salt hydrates. Moreover, this work presents an excellent perspective for exploring new sorption heat-storage materials with low cost, mass production, and high performance.

Attapulgite as a cost-effective catalyst for low-energy consumption amine-based CO2 capture

The extensive heat duty of solvent regeneration has significantly hampered the industrial application of amine-based CO2 capture technology. Catalytic CO2 desorption with solid acid catalysts has recently emerged as a promising and competitive strategy for improving solvent regeneration performance. The reported catalysts have exhibited poor activities and are relatively expensive, which has slowed the large-scale implementation of this technique. In this work, three low-cost and environmentally friendly clay catalysts, namely, attapulgite (ATP), activated bentonite (K-10), and sepiolite (SEP), were used to catalyze the CO2 desorption in the CO2-loaded 5 M monoethanolamine (MEA) solution at 88 °C. The findings revealed that ATP, K-10, and SEP catalysts accelerated CO2 desorption, and the ATP demonstrated better catalytic activity in the early stage of the desorption process. In particular, the introduction of ATP significantly increased the CO2 desorption rate by 54–57% and reduced the relative heat duty by about 32%, compared to the blank test. The superior catalytic performance of ATP might be attributed to its favorable surface area and medium acid sites. The catalytic effect of ATP was confirmed using FT-IR and Raman techniques, and a potential catalytic desorption mechanism was proposed. Furthermore, the stability of activated ATP was demonstrated using 15 CO2 absorption-desorption cycles. These results demonstrated that ATP significantly contributes to the advancement of the amine-based CO2 capture process and has significant potential for large-scale deployment. This work may pave the avenue for developing abundant and inexpensive clay-based solid acid catalysts for low-energy consuming CO2 capture technology.

Curing, thermal, tensile and flammability characteristics of sepiolite/ethylene propylene diene monomer rubber composites with glut palmitate salt and silane coupling agents

AbstractThe main objective of this work is to compare the effectiveness of a newly synthesized glut palmitate (GP) salt and a commercially available (3‐aminopropyl) trimethoxysilane (APTMS) as coupling agents in sepiolite (SEP) filled ethylene propylene diene monomer (EPDM/SEP) composites. The unmodified and modified composites with different amounts of SEP were prepared with an open two‐roll mill and the morphology, cure characteristics, tensile properties, flammability, and thermal stability were studied. Fourier transform infrared spectroscopy (FTIR) analysis indicated shifting of the related absorption peaks and confirmed the interaction between composite with the GP salt and APTMS and the successful modification of sepiolite particles in EPDM/SEP composites. The maximum torque (MH), scorch time (ts2) and cure time (t90) of the modified EPDM composites decreased with both coupling agents. Thermal stability reduced in the presence of coupling agents but the reduction is more pronounced in the composite with GP salt due to low‐temperature degradation of the fatty acid. Compared with unmodified EPDM/SEP, the tensile strength of the modified EPDM/SEP with GP and APTMS enhanced by 15% and 52%, respectively but both elongation at break and modulus were lowered. GP and APTMS were efficient coupling agents in linking the SEP and EPDM matrix, reducing the rubber‐filler interaction (Qf/Qg) from 1.00 for the EPDM/SEP composites to 0.76 and 0.64 for the EPDM/GP/SEP and EPDM/APTMS/SEP composites, respectively.