Synthesis of nanosilica from agricultural wastes and its multifaceted applications: A review

Innovative utilization of harvested mushroom substrate for green synthesis of silver nanoparticles: A multi-response optimization approach

In this work, harvested mushroom substrate (HMS) has been explored for the first time through a comprehensive optimization study for the green synthesis of silver nanoparticles (AgNPs). A multiple response central composite design with three parameters: pH of the reaction mixture, temperature, and incubation period at three distinct levels was employed in the optimization study. The particle size of AgNPs, UV absorbance, and the percentage of Ag/Cl elemental ratio were considered as the response parameters. For each response variable examined the model used was found to be significant (P < 0.05). The ideal conditions were: pH 8.9, a temperature of 59.4 °C, and an incubation period of 48.5 h. The UV-visible spectra of AgNPs indicated that the absorption maxima for AgNP-3 were 414 nm, 420 for AgNPs-2, and 457 for AgNPs-1. The XRD analysis of AgNPs-3 and AgNPs-2 show a large diffraction peak at ∼38.2°, ∼44.2°, ∼64.4°, and ∼77.4°, respectively, which relate to the planes of polycrystalline face-centered cubic (fcc) silver. Additionally, the XRD result of AgNPs-1, reveals diffraction characteristics of AgCl planes (111, 200, 220, 311, 222, and 400). The TEM investigations indicated that the smallest particles were synthesized at pH 9 with average diameters of 35 ± 6 nm (AgNPs-3). The zeta potentials of the AgNPs are -36 (AgNPs-3), -28 (AgNPs-2), and -19 (AgNPs-1) mV, respectively. The distinct IR peak at 3400, 1634, and 1383 cm-1 indicated the typical vibration of phenols, proteins, and alkaloids, respectively. The AgNPs were further evaluated against gram (+) strain Bacillus subtilis (MTCC 736) and gram (-) strain Escherichia coli (MTCC 68). All of the NPs tested positive for antibacterial activity against both bacterial strains. The study makes a sustainable alternative to disposing of HMS to achieve the Sustainable Development Goals (SDGs).

Properties and Performance of Oil Well Slurry and Cement Sheath Incorporating Nano Silica: A Review

The oil well cementing job is the operation in which a cement paste is pumped to fill the annulus behind the casing. Inclusion of nanomaterials in oil well cement results in improving the cement properties. This paper provides a comprehensive overview of incorporating nanosilica into oil well cement, addressing various aspects of the nanosilica manufacturing process, dispersion challenges, the impact on cement hydration and properties, as well as the operational challenges. The addition of nanosilica is found to enhance cement properties such as hydration rate, compressive strength at low temperatures, and resistance to deterioration at high temperatures. However, challenges arise, including increased viscosity and the need for higher water content. Dispersion of nanosilica into cement slurry remains a difficulty, compounded by the high manufacturing cost, limiting its practical application. The paper recommends further research to improve nanosilica dispersion, explore cost-effective raw materials, and overcome operational challenges for broader utilization in oil well cementing.

An innovative outlook on utilization of agro waste in fabrication of functional nanoparticles for industrial and biological applications: A review

The burning of an agro waste residue causes air pollution, global warming and lethal effects. To overcome these obstacles, the transformation of agro waste into nanoparticles (NPs) reduces industrial expenses and amplifies environmental sustainability. The concept of green nanotechnology is considered as a versatile tool for the development of valuable products. Although a plethora of literature on the NPs is available, but, still scientists are exploring to design more novel particles possessing unique shape and properties. So, this review basically summarises about the synthesis, characterizations, advantages and outcomes of the various agro waste derived NPs.

Sustainable Sources of Raw Materials for Additive Manufacturing of Bone-Substituting Biomaterials

The need for sustainable development has never been more urgent, as the world continues to struggle with environmental challenges, such as climate change, pollution, and dwindling natural resources. The use of renewable and recycled waste materials as a source of raw materials for biomaterials and tissue engineering is a promising avenue for sustainable development. Although tissue engineering has rapidly developed, the challenges associated with fulfilling the increasing demand for bone substitutes and implants remain unresolved, particularly as the global population ages. This review provides an overview of waste materials, such as eggshells, seashells, fish residues, and agricultural biomass, that can be transformed into biomaterials for bone tissue engineering. While the development of recycled metals is in its early stages, the use of probiotics and renewable polymers to improve the biofunctionalities of bone implants is highlighted. Despite the advances of additive manufacturing (AM), studies on AM waste-derived bone-substitutes are limited. It is foreseeable that AM technologies can provide a more sustainable alternative to manufacturing biomaterials and implants. The preliminary results of eggshell and seashell-derived calcium phosphate and rice husk ash-derived silica can likely pave the way for more advanced applications of AM waste-derived biomaterials for sustainably addressing several unmet clinical applications.

A State-of-the-Art Systemic Review on Selenium Nanoparticles: Mechanisms and Factors Influencing Biogenesis and Its Potential Applications

Selenium is a trace element required for the active function of numerous enzymes and various physiological processes. In recent years, selenium nanoparticles draw the attention of scientists and researchers because of its multifaceted uses. The process involved in chemically synthesized SeNPs has been found to be hazardous in nature, which has paved the way for safe and ecofriendly SeNPs to be developed in order to achieve sustainability. In comparison to chemical synthesis, SeNPs can be synthesized more safely and with greater flexibility utilizing bacteria, fungi, and plants. This review focused on the synthesis of SeNPs utilizing bacteria, fungi, and plants; the mechanisms involved in SeNP synthesis; and the effect of various abiotic factors on SeNP synthesis and morphological characteristics. This article discusses the synergies of SeNP synthesis via biological routes, which can help future researchers to synthesize SeNPs with more precision and employ them in desired fields.

Recent Advances on Porous Siliceous Materials Derived from Waste

In recent years, significant efforts have been made in view of a transition from a linear to a circular economy, where the value of products, materials, resources, and waste is maintained as long as possible in the economy. The re-utilization of industrial and agricultural waste into value-added products, such as nanostructured siliceous materials, has become a challenging topic as an effective strategy in waste management and a sustainable model aimed to limit the use of landfill, conserve natural resources, and reduce the use of harmful substances. In light of these considerations, nanoporous silica has attracted attention in various applications owing to the tunable pore dimensions, high specific surface areas, tailorable structure, and facile post-functionalization. In this review, recent progress on the synthesis of siliceous materials from different types of waste is presented, analyzing the factors influencing the size and morphology of the final product, alongside different synthetic methods used to impart specific porosity. Applications in the fields of wastewater/gas treatment and catalysis are discussed, focusing on process feasibility in large-scale productions.

The temporal profile of GH1 gene abundance and the shift in GH1 cellulase-producing microbial communities during vermicomposting of corn stover and cow dung

Vermicomposting is a promising method for corn stover management to achieve bioresource recovery and environmental protection. Most β-glucosidases, which limit the cellulose degradation rate during vermicomposting of corn stover, belong to glycoside hydrolase family 1 (GH1). This study was conducted with different earthworm densities to quantify the GH1 gene abundance and investigate the evolution of GH1 cellulase-producing microbial communities using qPCR and pyrosequencing. The results showed that β-glucosidase activity, GH1 gene abundance, TOC, and microbial communities carrying the GH1 gene were affected by processing time and earthworm density. After introducing earthworms, β-glucosidase activity increased to 1.90-2.13 U/g from 0.54 U/g. The GH1 gene abundance of treatments with earthworms (5.82E+09-6.70E+09 copies/g) was significantly higher than that of treatments without earthworms (2.48E+09 copies/g) on Day 45. Earthworms increased the richness of microbial communities. The relative abundances of Sphingobium and Dyadobacter, which are dominant genera harboring the GH1 gene, were increased by earthworms to peak values of 23.90% and 11.20%, respectively. Correlation analysis showed that Sphingobium, Dyadobacter, Trichoderma, and Starkeya were positively associated with β-glucosidases. This work sheds new light on the mechanism of cellulose degradation during vermicomposting at the molecular level.

A review on the emerging conversion technology of cellulose, starch, lignin, protein and other organics from vegetable-fruit-based waste

A large amount of vegetable-fruit-based waste (VFBW) belonging to agricultural waste is produced around the world every year, imposing a huge burden on the environment and sustainable development. VFBW contains a lot of water and useful organic compounds (e.g., cellulose, minerals, starch, proteins, organic acids, lipids, and soluble sugars). Taking into account the composition characteristics and circular economy of VFBW, many new emerging conversion technologies for the treatment of VFBW (such as hydrothermal gasification, ultrasound-assisted extraction, and synthesis of bioplastics) have been developed. This review summarizes the current literature discussing the technical parameters, process, mechanism, and characteristics of various emerging conversion methods, as well as analyzing the application, environmental impact, and bio-economy of by-products from the conversion process, to facilitate solutions to the key problems of engineering cases using these methods. The shortcomings of the current study and the direction of future research are also highlighted in the review.

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

Following the discovery of Stöber silica, the realm of morphology-controlled mesoporous silica nanomaterials like MCM-41, SBA-15, and KCC-1 has been expanded. Due to their high BET surface area, tunable pores, easiness of functionalization, and excellent thermal and chemical stability, these materials take part a vital role in the advancement of techniques and technologies for tackling the world's largest challenges in the area of water and the environment, energy storage, and biotechnology. Synthesizing these materials with excellent physicochemical properties from cost-efficient biomass wastes is a foremost model of sustainability. Particularly, SiO₂ with a purity >98% can be obtained from rice husk (RH), one of the most abundant biomass wastes, and can be template engineered into various forms of mesoporous silica materials in an economic and eco-friendly way. Hence, this review initially gives insight into why to valorize RH into value-added silica materials. Then the thermal, chemical, hydrothermal, and biological methods of high-quality silica extraction from RH and the principles of synthesis of mesoporous and fibrous mesoporous silica materials like SBA-15, MCM-41, MSNs, and KCC-1 are comprehensively discussed. The potential applications of rice husk-derived mesoporous silica materials in catalysis, drug delivery, energy, adsorption, and environmental remediation are explored. Finally, the conclusion and the future outlook are briefly highlighted.

Melioration of Paddy Straw to produce cellulase-free xylanase and bioactives under Solid State Fermentation and deciphering its impact by Life Cycle Assessment

Aiming towards zero waste management of Paddy straw (PS), the study offers a novel route for production of cellulase-free xylanase, using consortia of Trichoderma spp. under Solid State Fermentation (SSF) of PS valorized using nitrogen rich de-oiled neem cake (NC). Life Cycle Assessment (LCA) for enzyme production, performed using SimaPro software, depicted adverse impacts due to electricity consumption (92.84%) and use of ammonium sulphate salt (6.17%). Nonetheless, employing renewable energy and reducing salt consumption could help minimize these impacts. OHR-LCMS study of the partially purified enzyme revealed the presence of β-xylanase and α-L-Arabinofuranosidase. Enzymatic saccharification of various substrates enhanced the release of reducing sugars (mg/g) from corn cob (137.54 ± 0.96), pine needle (41.43 ± 1), sugarcane bagasse (105.17 ± 0.7), and PS (76.66 ± 1.29), demonstrating its applicability in the biofuel domain. LC-MS, ICMPS, and EDX profiling of the residual spent unravelled the manifestation of bioactives, minerals, and silica, playing an essential role as biopesticide and biofertilizer.

An Overview of Recent Progress in Nanofiber Membranes for Oily Wastewater Treatment

Oil separation from water becomes a challenging issue in industries, especially when large volumes of stable oil/water emulsion are discharged. The present short review offers an overview of the recent developments in the nanofiber membranes used in oily wastewater treatment. This review notes that nanofiber membranes can efficiently separate the free-floating oil, dispersed oil and emulsified oil droplets. The highly interconnected pore structure nanofiber membrane and its modified wettability can enhance the permeation flux and reduce the fouling. The nanofiber membrane is an efficient separator for liquid-liquid with different densities, which can act as a rejector of either oil or water and a coalescer of oil droplets. The present paper focuses on nanofiber membranes' production techniques, nanofiber membranes' modification for flux and separation efficiency improvement, and the future direction of research, especially for practical developments.

One-Pot Synthesis of Amine-Functionalized Nano-Silica via Sol-Gel Assisted by Reverse Micelle Microemulsion for Environmental Application

Amine modified nano-silica was prepared via a one-pot route and under very mild conditions in water in oil microemulsion with a non-ionic surfactant to study the effect of changing the amount of N-[3-(Trimethoxysilyl)propyl]ethylenediamine (DA) added to the synthesis mixture on the characteristics of the obtained nanocomposite such as morphology, crystallinity, surface charge, particle size, surface area, and accordingly the effect of all of these factors on the efficiency of the nanocomposite for the removal of heavy metal ions, namely zinc, from aqueous solutions. XRD, SEM, TGA, BET, DLS, FTIR, and pH0 analysis were performed for samples and the results showed a strong effect for the amount of DA added to the synthesis mixture on the characteristics of the obtained nanocomposites. It was found that increasing the amount of DA added to the synthesis mixture increased the pH0, hydrodynamic particle size obtained by dynamic light scattering analysis, and the particle size obtained by SEM. Sample prepared without the addition of DA (SNP) and the samples prepared with 1.5 mL of DA (SNP-1.5DA) showed a better adsorption performance compared to the samples prepared with 0.5 and 1.0 mL of DA (SNP-0.5DA and SNP-1.0DA, respectively). The main factor affecting the adsorption efficiency was found to be the available surface area for each nanocomposite, which was directly related to the degree of crystallinity as obtained by XRD analysis.