Rice husk waste into various template-engineered mesoporous silica materials for different applications: A comprehensive review on recent developments

Hydrothermally modified rice husk derived silica and molybdenum sulphide embedded chitosan matrix for the removal of cationic dyes

The work reports the hydrothermal fabrication of a Chitosan/Silica/MoS2 (CSM) composite, leveraging chitosan as a structural framework and silica/molybdenum sulphide as inorganic fillers. Silica is sourced from the rice husk and incorporated into the composite to enhance the adsorption behaviour and thermal properties. The formation and the adsorption behaviour of the CSM composite were confirmed with the aid of FTIR, XRD, FE-SEM, EDX, TGA, XPS, BET, and HR-TEM analyses. The prepared adsorbent was used for removing the methylene blue (MB) and malachite green (MG) dyes from the aqueous solution, achieving adsorption capacities of 34.01 mg/g for MB and 29.85 mg/g for MG. Optimal dye removal occurred within 60 min at a pH of ∼11 and 125 mg of adsorbent dosage. The adsorption process followed the Freundlich isotherm and pseudo-second-order (PSO) kinetics by a regression coefficient of R2 > 0.99. Thermodynamic parameters illustrated the exothermic and spontaneous nature of adsorption. Regeneration tests confirmed the CSM composite's stability and reusability over five cycles. The adsorption mechanism involves electrostatic attraction, surface complexation, and hydrogen bonding. These findings indicate that the CSM composite is an effective adsorbent for removing dye pollutants from aqueous solutions.

Evaluation of biobased materials in the development of polymeric membranes for water capture and purification

The current study addresses the pressing issue of unsustainable water management, particularly in regions experiencing high water stress. It focuses on examining the viability of polymeric membranes composed of biobased materials, mainly chitosan, for various sustainable water management solutions. The membranes evaluated in the study were blends of PVC with either chitosan-silica or charcoal-silica, designed to enhance their functionality and performance. Scanning Electron Microscopy was used to analyze the fiber morphologies of the different membrane compositions. All tested membranes demonstrated robust mechanical properties. Notably, the PVC-Chitosan-Silica (8:2:4) membrane also showed good mechanical properties, combined with superior thermal stability. It excelled in functional tests, achieving water capture efficiencies up to 1.2 ml/g and lead removal rates as high as 92 %. Furthermore, this membrane displayed a lower mass loss at elevated temperatures, suggesting enhanced durability under thermal stress. These results underline the effective combination of chitosan and silica in improving the mechanical strength and thermal stability of polymeric membranes, making the PVC-Chitosan-Silica (8:2:4) particularly effective for advanced water management applications. The study illustrates the unique capabilities of chitosan and silica, advocating for their further exploration and optimization in future sustainable water treatment technologies, which could potentially lead to groundbreaking advancements in the field.

A promising mesoporous silica carrier material for the diagnosis and treatment of liver diseases: recent research advances

The therapeutic diagnosis of liver diseases has garnered significant interest within the medical community. In recent years, mesoporous silica nanoparticles (MSNs) have emerged as crucial nanocarriers for the treatment of liver ailments. Their remarkable diagnostic capabilities enable them to be used in techniques such as high-throughput mass spectrometry (MS), magnetic resonance imaging (MRI), near-infrared (NIR) fluorescence imaging, photoacoustic imaging (PAI), and ultrasonography (US), attracting considerable attention. Furthermore, the introduction of amino and carboxyl group modifications in MSNs has facilitated their use as drug delivery carriers for treating liver diseases, including hepatocellular carcinoma. This paper reviews the preparation methods, in vitro diagnostic capabilities, and in vivo therapeutic delivery systems of MSNs for liver disease treatment. It also summarizes relevant toxicity studies, aiming to provide a comprehensive overview of the diagnostic and therapeutic applications of MSNs in the treatment of liver diseases, particularly hepatocellular carcinoma. Through this review, we seek to offer theoretical insights into the potential of MSNs for diagnostic and therapeutic applications in liver disease treatment.

The role of biosilica and its potential for sensing technologies: A review

Efficiently managing agricultural waste while innovating to derive value-added products is a significant challenge in the 21st century. In recent decades, these by-products have been increasingly explored as alternative sources for materials such as biosilica. Biosilica is renowned for its high surface area, biocompatibility, chemical stability, and modifiable surface, which makes it suitable for various applications. Additionally, the biomineralization process-biosilicification-in living organisms like diatoms offers an eco-friendly pathway for silica production. Despite the potential applications of biosilica, research on its use in sensor technology remains limited. This review aims to address this gap by covering the primary methodologies for extracting silica from biomass, discussing key techniques for its characterization, and highlighting its potential for functionalization in diverse applications. Special emphasis is given to the utility of diatom-derived biosilicas in developing sensors for detecting gaseous molecules and biomolecules.

Nanosized MCM-41 silica from rice husk and its application for the removal of organic dyes from water

A novel synthesis of a nanometric MCM-41 from biogenic silica obtained from rice husk is here presented. CTABr and Pluronic F127 surfactants were employed as templating agents to promote the formation of a long-range ordered 2D-hexagonal structure with cylindrical pores and to limit the particle growth at the nanoscale level thus resulting in a material with uniform particle size of 20-30 nm. The physico-chemical properties of this sample (RH-nanoMCM) were investigated through a multi-technique approach, including PXRD, 29Si MAS NMR, TEM, Z-potential and N2 physisorption analysis at 77 K. The results were compared to those of a nanometric MCM-41 synthesized from a silicon alkoxide precursor. The adsorption capacity of RH-nanoMCM towards the cationic dye rhodamine B from aqueous phase was investigated at different initial dye concentrations by means of UV-vis spectroscopy. Insight into the non-covalent interactions between the dye molecules and the adsorbent surface was gained by means of 1H and 13C MAS NMR spectroscopy and FT-IR spectroscopy.

Porous Materials for the Heterogeneously Catalyzed Synthesis of High Value-Added Products: Latest Trends and Future Prospects

Heterogeneous catalysis currently stands as a foundational area in materials synthesis and applied chemistry. In this context, emphasizing the significance of heterogeneous catalysis in expediting chemical reactions and controlling the formation of desired products using porous materials represents an intriguing approach in the current technological landscape. This work delves into the synthesis and design of a variety of porous materials, encompassing microporous, mesoporous and macroporous materials (e. g. carbonaceous materials, metal oxides, MOFs, zeolites and functionalized analogues), alongside their properties and characteristics pivotal in heterogeneous catalysis. among others, and their subsequent modification, underscoring the significance of tailoring porous materials for specific catalytic applications.

Catalytic Oxidation of Acetone over MnOx-SiO2 Catalysts: An Effective Approach to Valorize Rice Husk Waste

Rice husk, a byproduct of rice production, poses significant environmental challenges due to disposal issues, while the emission of volatile organic compounds into the atmosphere further exacerbates these concerns. This study addresses both problems by exploring the potential of texturally enhanced SiO2, derived from Uruguayan rice husk, as a catalytic support for manganese oxides in the combustion of volatile organic compounds. SiO2 was synthesized from rice husk ash using a sustainable, acid-free pretreatment method, yielding a notably high silica purity of 96.5%-a level comparable to or exceeding previously reported values, highlighting the high silica quality inherent in Uruguayan rice husk. The catalytic activity was evaluated using acetone as a model volatile organic compound, achieving up to 90% conversion with 30 wt.% manganese oxide at 300 °C, with CO2 as the primary product. Furthermore, a 24 h stability test demonstrated consistent performance, maintaining a conversion rate of around 95.6 ± 2.5%. These findings suggest that high-purity SiO2 derived from Uruguayan rice husk, with its sustainability benefits, offers an effective solution for acetone removal when supporting an active phase such as manganese oxides, addressing both rice husk disposal and volatile organic compound emissions.

Mesoporous Silica with an Alveolar Construction Obtained by Eco-Friendly Treatment of Rice Husks

The high silicon content in rice plant waste, specifically rice husks, makes this waste by-product attractive for the extraction and valorization of silicon oxide, which is widely used as an inert support in catalysis, drug delivery and molecular sieving. The procedures currently used for the treatment of plant biomass make extensive use of mineral acids (HCl, H2SO4, HNO3), which, besides them being potential environmental pollutants, reduce the yield and worsen the chemical-physical properties of the product. In this study, an evaluation of the easy treatment of rice husks by benchmarking different, more eco-friendly carboxylic acids in order to obtain a mesoporous SiO2 with an alveolar structure and a relatively high surface area and pore volume (300-420 m2/g, 0.37-0.46 cm3/g) is presented. The obtained mesoporous silicas are characterized by worm-like pores with a narrow size distribution and a maximum in the range of 3.4-3.5 nm. The mesoporous structure of the obtained materials was also confirmed by TEM. The complete removal of the organic part of the rice husks in the final materials was evidenced by thermogravimetric analysis. The high purity of the obtained mesoporous silica was detected using ICP analysis (98.8 wt. %). The structure peculiarities of the obtained mesoporous silicas were also characterized by solid-state NMR and ATR-FTIR spectroscopies. The morphology of the mesoporous silica was investigated by SEM.

Silica-Derived Nanostructured Electrode Materials for ORR, OER, HER, CO2RR Electrocatalysis, and Energy Storage Applications: A Review

Silica-derived nanostructured catalysts (SDNCs) are a class of materials synthesized using nanocasting and templating techniques, which involve the sacrificial removal of a silica template to generate highly porous nanostructured materials. The surface of these nanostructures is functionalized with a variety of electrocatalytically active metal and non-metal atoms. SDNCs have attracted considerable attention due to their unique physicochemical properties, tunable electronic configuration, and microstructure. These properties make them highly efficient catalysts and promising electrode materials for next generation electrocatalysis, energy conversion, and energy storage technologies. The continued development of SDNCs is likely to lead to new and improved electrocatalysts and electrode materials. This review article provides a comprehensive overview of the recent advances in the development of SDNCs for electrocatalysis and energy storage applications. It analyzes 337,061 research articles published in the Web of Science (WoS) database up to December 2022 using the keywords "silica", "electrocatalysts", "ORR", "OER", "HER", "HOR", "CO2RR", "batteries", and "supercapacitors". The review discusses the application of SDNCs for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), supercapacitors, lithium-ion batteries, and thermal energy storage applications. It concludes by discussing the advantages and limitations of SDNCs for energy applications.

Pyrolysis kinetics and potential utilization analysis of cereal biomass by-products; an experimental analysis for cleaner energy productions in India

The optimal utilization of biomass relies heavily on the specific material and individual needs. Cereal biomass by-products can potentially be employed in thermochemical processes such as pyrolysis and gasification. To compare biomass sources, ultimate analysis, biochar potential, proximate analysis, thermal gravimetric analysis, price per megajoule generated heat, surface texture, and availability are used. A global survey of biomass wastes and opportunities for heat generation is presented in the current article. Here, nine different cereal-based agricultural waste products (barley, wheat, millet, oats, rice, rye straw, sorghum straw/stalk, and maize cob) are studied. Cereal wastes are compared based on calorific value, water content, volatile matter, ash content and ash chemical composition, bulk density, charring properties, availability, and transportation. According to the estimate, 156 million metric tonnes per year, or 6% of India's total emissions, could be eliminated by rice husk alone. Wheat straws, on the other hand, can cut emissions by 2%. Additionally, processing these nine feedstocks might result in the production of 40 GW of electrical energy, which would increase the installed capacity of India's national electric grid by 9%.

Recovery of Chlorosilane Residual Liquid to Prepare Nano-Silica via the Reverse Micro-Emulsion Process

In this paper, nano-silica particles were prepared from chlorosilane residue liquid using an inverse micro-emulsions system formed from octylphenyl polyoxyethylene ether (TX-100)/n-hexanol/cyclohexane/ammonia. The influence of different reaction conditions on the morphology, particle size, and dispersion of nano-silica particles was investigated via single-factor analysis. When the concentration of chlorosilane residue liquid (0.08 mol/L), hydrophile-lipophilic-balance (HLB) values (10.50), and the concentration of ammonia (0.58 mol/L) were under suitable conditions, the nano-silica particles had a more uniform morphology, smaller particle size, and better dispersion, while the size of the nano-silica particles gradually increased with the increase in the molar ratio of water to surfactant (ω). The prepared nano-silica was characterized through XRD, FT-IR, N2 adsorption/desorption experiments, and TG-DSC analysis. The results showed that the prepared nano-silica was amorphous mesoporous silica, and that the BET specific surface area was 850.5 m2/g. It also had good thermal stability. When the temperature exceeded 1140 °C, the nano-silica underwent a phase transition from an amorphous form to crystalline. This method not only promoted the sustainable development of the polysilicon industry, it also provided new ideas for the protection of the ecological environment, the preparation of environmental functional materials, and the recycling of resources and energy.