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For the first time, the hydrophilicity of hemp shiv was modified without the compromise of its hygroscopic properties. This research focused on the use of sol–gel method in preparation of coatings on the natural plant material, hemp shiv, that has growing potential in the construction industry as a thermal insulator. The sol–gel coatings were produced by cohydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) using an acidic catalyst. Methyltriethoxysilane (MTES) was added as the hydrophobic precursor to provide water resistance to the bio-based material. Scanning electron microscopy (SEM) and focused ion beam (FIB) have been used to determine the morphological changes on the surface as well as within the hemp shiv. It was found that the sol–gel coatings caused a reduction in water uptake but did not strongly influence the moisture sorption behaviour of hemp shiv. Fourier transformed infrared (FTIR) spectroscopy shows that the coating layer on hemp shiv acts a shield, thereby lowering peak intensity in the wavelength range 1200–1800 cm −1 . The sol–gel coating affected pore size distribution and cumulative pore volume of the shiv resulting in tailored porosity. The overall porosity of shiv decreased with a refinement in diameter of the larger pores. Thermal analysis was performed using TGA and stability of coated and uncoated hemp shiv have been evaluated. Hemp shiv modified with sol–gel coating can potentially develop sustainable heat insulating composites with better hygrothermal properties.

In present study, nanospheres of CeO 2 are fabricated via utilizing a solvothermal mixed solvent technique at a low temperature. Using a three-electrode set up, the electrochemical activity of CeO 2 nanospheres in 2.0 M alkaline medium was evaluated. At a scan range of 5 mV s −1 , the material displayed large stability, the ability to work at high rates, and columbic efficiency, like specific capacitance value of 1435 F g −1 with specific energy of 87.89 Whkg −1 as well the power density of 1.0986 Wkg −1 . The outstanding outcome of the CeO 2 nanosphere is due to its mesoporous structure and high electrical double-layer capacitance of 6.35 mF. The nanospheres morphology of CeO 2 was responsible for increased conductivity that allows ions to pass easily, and the improved findings show that the procedure employed to make the oxides, which is beneficial for future generations and may be used to produce a variety of oxides that will resolve the energy issues. Graphical Abstract Highlights Controlled morphology of CeO 2 nanoballs was fabricated with efficient and economical solvothermal method. The capacitive properties of the CeO 2 nanoball were determined with three-electrode system under 2 M KOH. The electrochemical result of CeO 2 displays a high specific capacitance value of 1435 F g −1 , specific energy of 87.89 Wh kg −1 , and specific power of 1.0986 Wkg −1 . The enhanced supercapacitive property of CeO 2 was attributed to diverse morphology, larger surface area, and small crystallite size that permits faster ionic transport.

Activated alumina (AA) with metastable crystal phase and porous structure has shown great potential for fluoride ion removal. Conventional AA is obtained by direct calcination, which limits its fluoride adsorption ability due to the low surface area and limited active sites. In this work, a highly porous AA was synthesized by a sol–gel method, followed with supercritical drying (including ethanol supercritical drying and carbon dioxide supercritical drying) and calcination. The fluoride ion adsorption properties of AA were studied at different concentrations of fluoride in solution. The Langmuir model, Freundlich model, pseudo-first-order model and pseudo-second-order model were used to describe the adsorption process. The results show that the resulting AAs possess a high porosity and a high specific surface area (up to 660 m 2 /g). The fluoride adsorption capacity of AA increases with the increase of specific surface area and porosity (up to 119.2 mg/g), which is much higher than that of AA prepared by the traditional method (direct calcination). Moreover, all the fitted correlation coefficients of the four models exceed 90%, indicating both chemical and physical adsorption in AA. Graphical abstract Highlights Activated alumina (AA) was prepared by sol–gel method, followed with supercritical drying. The highest fluoride adsorption capacity of porous AA is 119.2 mg/g. The number of active sites of AA increases due to the high porosity and specific surface area.

To balance cost and performance of geopolymers, alkalinity of activating solution is critical. Alkalinity affects condensation that determines the final gel structures, but this effect is confounded by dissolution and is not understood from direct experimental evidence. In this study, we investigated effects of alkalinity on condensation for gels synthesized via a sol–gel method that eliminates dissolution process. As alkalinity increased, particle sizes of the gels increased as indicated by SEM, Si/Al ratios of the gels decreased but polymerization extent increased as supported by FTIR, 27 Al and 23 Na NMR, and composition analysis. The mechanism for the effects of alkalinity was proposed accordingly: (1) increasing alkalinity lowers the Si/Al ratio (i.e., more incorporation of Al) of the resulting products probably by affecting charging conditions of the Si and Al units; (2) the presence of Al(OH) 4 − units promotes their condensation with nearby species to increase the extent of polymerization; (3) enhanced condensation increases particle sizes of the gels even at microstructural level. This understanding on condensation independent of dissolution provides ways to control gel structures and Si/Al ratios and thus tailor properties accordingly, as well as to suggest a strategy (by altering Si/Al ratios during condensation) to develop kinetics-controlling admixtures. Highlights Condensation of geopolymer gel was studied independently of dissolution. Increasing alkalinity lowers Si/Al ratio (i.e., more incorporation of Al) of gel. More incorporated Al units enhance condensation with Si species. Enhanced condensation increases particle sizes of the gel at microstructural level.

Silica aerogels have been widely used as thermal insulators, but their fragility has hindered the potential applications. In this work, a novel way of improving aerogel skeletal structure was proposed where composites were reinforced by three functional layers of glass fiber (GF)/ carbon fiber (CF). Heat insulation performance of fiber-reinforced aerogel composites was also investigated in a simulated solar radiation system. Composites composed of three layers of fiber were prepared by a sol-gel process under ambient pressure drying. The results showed that, as three layers were all GF blankets, the composite heat conductivity increased with increasing glass fiber content. Flexural strength increased initially and reached a maximum at 20% glass fiber content before decreasing. To find a balance between promoting heat insulation performance and strengthening the composite structure, two layers of 5% glass fiber blankets were used as structure strengthening layers and one carding 5% carbon fiber as the heat insulation layer were recommended. Under these conditions, the composite showed extremely low thermal conductivity (0.031 W/m K), almost comparable to that of pure aerogel (0.036 W/m K) while maintaining high flexural strength (2.846 MPa), superior than previous studies. Composites with other ratios of glass/carbon fibers with sandwiched alignments also demonstrated better flexural strength and lower thermal conductivity than GF aerogel composites. This work provided an alternative way to prepare robust and sustainable heat insulation aerogel composites for practical uses. Highlights Heat insulation performance of silica aerogels composited with different ratios of glass fiber and carbon fiber was investigated. The flexural strength increased with increased glass fiber loading, and reached its highest value when glass fiber content was 20%. 5% carbon fiber inserted between the two 5% glass fiber layers was found the most ideal condition in terms of flexural strength (2.846 MPa) and thermal conductivity (0.031 W/m K).

In this study, optimization of the synthesis process parameters of sol-gel method using orthogonal experiment was first applied for CuFe 1.2 Al 0.8 O 4 catalysts in methanol steam reforming (MSR). OA 9 (4 4 ) orthogonal experiments were applied to optimize the synthesis process parameters by sol-gel method, including precursor copper source complexing agent, calcination temperature, and calcination time. The MSR performance was selected as the objective function. Results show that copper source has the greatest impact among the four factors on the catalytic performance. The catalytic performance of the catalyst synthesized by using copper hydroxide as the precursor copper source was much better than the other copper sources. For the other three factors, the order of important factors is: calcination time > complexing agent > calcination temperature. According to the results of range analysis, the optimal synthesis process parameters for CuFe 1.2 Al 0.8 O 4 with best MSR performance are as follows: the precursor copper source is copper hydroxide, the calcination time is 2 h, the complexing agent is ethanol and ethylene glycol, and the calcination temperature is 700 °C. The hydrogen production is 0.077 mol/min/g oat , the methanol conversion rate can reach >95%, and the hydrogen selectivity can reach 99%. CuFe 1.2 Al 0.8 O 4 spinel oxide catalyst which synthesized in this study has excellent catalytic performance for hydrogen production in MSR. Its low CO selectivity makes it a potential catalyst for producing high-purity hydrogen. Graphical Abstract Optimization of the synthesis process parameters of sol-gel method using orthogonal experiment was first applied for CuFe 1.2 Al 0.8 O 4 catalysts in methanol steam reforming (MSR). Its low CO selectivity makes it a potential catalyst for producing high-purity hydrogen. Highlights Orthogonal experiments were applied to optimize the synthesis process parameters by sol-gel method. Copper source has the greatest impact on the catalytic performance. The synthesized spinel has high hydrogen selectivity and low CO selectivity.

Pure Mn 3 O 4 and Mn 3 O 4 /rGO hybrid nanocomposites were synthesized by sol–gel based in situ reduction method. The structural properties of pure and nanocomposite materials were studied by XRD. The crystallite size of the Mn 3 O 4 nanoparticle was reduced in the nanocomposite as observed by XRD analysis. SEM and TEM images depict the spherical morphology of pristine Mn 3 O 4 nanoparticles and decoration of Mn 3 O 4 nanoparticle on rGO sheets. Raman spectra confirm the formation of Mn 3 O 4 /rGO nanohybrid composites as the A g mode of Mn 3 O 4 , D, and G bands of rGO were observed in the spectra. FTIR spectra confirm the presence of various functional groups of GO and the in situ reduction of GO into rGO. The electrochemical properties of the Mn 3 O 4 and Mn 3 O 4 /rGO composites were investigated by cyclic voltammetry analysis using 1 M KOH as an electrolyte. The cyclic voltammetry results show the pseudocapacitance behavior of Mn 3 O 4, whereas the hybrid nanocomposite exhibits the combined behaviors of pseudocapacitance and EDLC. The chronopotentiometry analysis demonstrated that the specific capacitance of Mn 3 O 4 /rGO nanocomposite (427 F g −1 ) was relatively higher than that of Mn 3 O 4 (136 F g −1 ) at 1 A/g. The impact of KOH electrolyte over the specific capacitance of a electrode material was comparatively analyzed with different electrolytes. The enhancement in the specific capacitance of the nanohybrid composite was attributed due to the strong electrode–electrolyte interaction of hybrid electrode material and synergetic effect of Mn 3 O 4 and rGO. Highlights Mn 3 O 4 /rGO nanocomposite was synthesized by sol–gel based in-situ reduction method. Crystallite size of the Mn 3 O 4 was reduced consistently while adding rGO 2 and 5%. TEM image confirms the spherical morphology of the Mn 3 O 4 nanoparticle (~10 nm) and Raman spectroscopy results confirm the formation of composites. Specific capacitance of the Mn 3 O 4 /rGO nanocomposite (427 F g −1 ) was higher than Mn 3 O 4 (136 F g −1 ). High specific capacitance of composite is due to the synergetic effect of Mn 3 O 4 /rGO.

The present work aims to synthesize hydroxyapatite (HAp) via green template addition using glutinous rice (GR) in combination with sol-gel route under various calcination temperatures (500–900 °C). The physicochemical properties of GR-HAp were analyzed using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. The utilization of GR as template in HAp synthesis resulted in the formation of GR-HAp particles that are less crystalline. Surface morphology revealed discrete, rod-shaped GR-HAp particles were formed at low calcination temperature (500–600 °C), while larger particles were formed as temperature was increased. Results confirmed that higher calcination temperature led to the transformation of HAp into various phases including β-Ca 3 (PO 4 ) 2 , CaO, and β-NaCa(PO 4 ). In addition, the formation of smaller, elongated GR-HAp particles with diameter of 75–180 nm and homogenous particle size distribution was attained at 900 °C. The antibacterial activity was evaluated via disc diffusion method against four Gram-positive bacteria including B. cereus , B. subtilis , S. aureus , and S. epidermidis , and two Gram-negative bacteria including E. coli and P. aeruginosa . The GR-HAp powder calcined at 900 °C showed strong antibacterial performance against all bacterial strains with inhibition zones ranging from 11.66–16.66 mm, which indicates its suitability to be utilized as a material in biomedical applications. Highlights Use of GR as template resulted in formation of less crystalline particles with reduced aggregation. Higher calcination temperature led to formation of β-Ca 3 (PO 4 ) 2 and β-NaCa(PO 4 ) phases. GR-HAp calcined at 900 °C showed strongest antibacterial performance against all bacterial strains.

A novel nanostructured Fenton-like catalyst based on La-doped MgFe 2 O 4 for enhanced carbamazepine degradation was prepared by facile sol-gel synthesis. The physicochemical properties of the obtained catalyst were studied by DTA-TG, XRD, FTIR, SEM-EDX, TEM, and nitrogen adsorption-desorption methods. The effect of calcination temperature on the structure and phase composition of the catalyst was assessed. The influence of the conditions of the catalytic process (dose of catalyst, H 2 O 2 concentration, and pH of model solution) on the efficiency of degradation of an antiepileptic drug, carbamazepine, was scrutinized. The performed studies provided a non-toxic and chemically stable Fenton-like catalyst which demonstrated enhanced efficiency in carbamazepine degradation. The optimal conditions were found as catalyst dose of 0.5 g L −1 , H 2 O 2 concentration of 20.0 mmol L −1 and pH of 6.0. The apparent pseudo-first-order rate constant reached up to 0.086 min −1 for MgLa 0.1 Fe 1.9 O 4 catalyst. Due to its high specific area and enhanced catalytic efficiency, the developed Fenton-like heterogeneous catalyst based on La-doped magnesium ferrite can be used for treating wastewaters polluted with pharmaceutically active compounds. Graphical abstract Highlights Fenton-like catalysts based on La-doped magnesium ferrite were obtained. Obtained catalysts were characterized by XRD, BET, SEM, TEM methods. MgLa 0.1 Fe 1.9 O 4 catalyst demonstrated high catalytic CBZ degradation.

The present investigation had made to synthesis of silica nanoparticle (SiNp) from Bambusa vulgaris leaves (BVL) ash by using sol-gel technique and it was utilized for the removal of Cadmium (Cd) and Congo red (CR) in aqueous solutions. Further, the synthesized adsorbent was characterized using instrumental techniques such as XRD, FTIR, FESEM–EDS mapping, TEM, BET, and Zeta potential. In addition, the batch mode technique (such as pH, adsorbent dose, and contact time) was carried out for optimization of Cd and CR removal. The adsorption behavior and capacity was calculated using different isotherms and kinetics. The obtained results of Cd and CR removal were optimized with following parameters such as pH 7, adsorbent dose (100 mg), and equilibrium time (30 min). Also, the adsorbent behavior was found suitable in Langmuir and Freundlich isotherm model and its maximum adsorbent capacity was 133 and 172 mg/g. The kinetic data were better fitted into the pseudo-second order model. The results concluded that the synthesized SiNp was the best adsorbent for the removal of metals, dyes and also economically sound techniques for disposal of agricultural waste. This investigation utilized Bambusa vulgaris leaves for synthesis of silica nanoparticle by sol-gel process and removal of Cadmium and Congo red. Bamboo species are considered one of the fast growing and high yielding plants. Mostly, it has been utilized for making of winnow, basket, fan, and pulp production. Indeed, as per previous reports this leaves are considered as waste; also they analyzed chemical properties of leaves. It contained higher percentage (more than 35%) of silica. Finally, we conclude that synthesized silica nanoparticle are eco-friendly and economically efficient adsorbent for removal of heavy metals as well as dyes in the aqueous solutions and also best solution for agricultural waste management. Highlights Silica nanoparticles were synthesized from Bambusa vulgaris leaves by sol-gel method. Silica nanoparticles were characterized using XRD, FTIR, FESEM–EDS mapping, TEM, BET, and Zeta potential. Cadmium and Congo red were removed using synthesized silica nanoparticles in batch mode. Maximum adsorption capacity (Q o ) of Cd and Congo red were 133, 172 mg/g, respectively.