Search Results (6)

Kaolinite clay mineral with a layered silicate structure is an abundant resource in China. Due to its advantages of excellent stability, high specific surface area and environmental friendliness, kaolinite is widely used in environment decontamination. By using kaolinite as a carrier, the photocatalytic technology in pure photocatalysts of poor activities, narrow spectral responses, and limited electron transport can be overcome, and the nano-Ag disinfectant’s limitation of the growth and aggregation of nanoparticles is released. Moreover, pure kaolinite used as an adsorbent shows poor surface hydroxyl activity and low cation exchange, leading to the poor adsorption selectivity and easy desorption of heavy metals. Current modification methods including heat treatment, acid modification, metal modification, inorganic salt modification, and organic modification are carried out to obtain better adsorption performance. This review systematically summarizes the application of kaolinite-based nanomaterials in environmental decontamination, such as photocatalytic pollutant degradation and disinfection, nano silver (Ag) disinfection, and heavy metal adsorption. In addition, applications on gas phase pollutant, such as carbon dioxide (CO₂), capture and the removal of volatile organic compounds (VOCs) are also discussed. This study is the first comprehensive summary of the application of kaolinite in the environmental field. The review also illustrates the efficiency and mechanisms of coupling naturally/modified kaolinite with nanomaterials, and the limitation of the current use of kaolinite. Full article

Fly ash generated in the process of combustion of municipal waste is classified as hazardous waste. Its management today has become a significant problem. One of the methods of safe management of such ash may be using it for the production of concrete as a partial replacement for cement. Using immobilization, the number of hazardous compounds could be limited so that the obtained new material would be safe for the natural environment. Recovery of byproducts—in this case, fly ash—complies with the business models applied in the production cycle in the circular economy model. Such a solution may result in saving energy, limiting CO₂ emissions, reducing the use of natural resources, and management of dangerous waste. It should be added that concretes with the addition of hazardous waste would be used for industrial purposes according to the binding legal regulations. This article presents the influence of the addition of fly ash on the selected mechanical properties of concrete. Fly ash from the incineration of municipal waste was used as a partial replacement of CEM I concrete at amounts of 4%, 8%, and 18% of its mass. The compressive strength and flexural strength of such concretes were tested after 28 days of concrete curing. This article also presents the tests of the leachability of contaminants from fly ash and concretes produced with Portland cement CEM I. The test results confirm that immobilization is an effective process that limits the amount of contamination in the water extract. Zinc, lead, and chrome were almost completely immobilized by the C-S-H (calcium silicate hydrate) concrete phase, with their immobilization degree exceeding 99%. Chloride content also underwent immobilization at a similar level of 99%. The sulfates were immobilized at the level of 96%. The subject matter discussed in this article is essential because, to protect the natural environment and, thus, reduce the use of natural resources, it is increasingly necessary to reuse raw materials—not natural, but recycled from the industry. Waste often contains hazardous compounds. A proposal for their safe disposal is their immobilization in a cement matrix. An important aspect is reducing leachability from concrete as much as possible, e.g., using nanomaterials. The effectiveness of reducing the leachability of hazardous compounds with the proposed method was checked in this study. Full article

Siliceous natural nanomaterials (SNNMs), i.e., diatomaceous earth and natural zeolites, have a nanoporous structure with large active surfaces that adsorb cations or polarized molecules. Such nanoporous feature determines the effects related to SNNM utilization as low-risk plant protectants and soil improvers. This work used SNNMs from Romanian quarries as carriers for foliar fertilizers applied to stone-fruit trees, apricot and peach. We determined the effects of SNNMs on the physiology, yield and fruit quality of the treated stone-fruit trees. SNNM application determined impacts specific to the formation of particle films on leaves: reduced leaf temperature (up to 4.5 °C) and enhanced water use efficiency (up to 30%). Foliar fertilizers’ effects on yield are amplified by their application with SNNMs. Yield is increased up to 8.1% by the utilization of SNNMs with foliar fertilizers, compared to applying foliar fertilizer alone. Diatomaceous earth and natural zeolites promote the accumulation of polyphenols in apricot and peach fruits. The combined application of SNNMs and foliar fertilizer enhance the performance of peach and apricot trees. Full article

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO₂/CH₄ separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO₂ removal from CH₄, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO₂ plasticization, due to permeability decrease even at high feed pressure, up to 16 bar. Full article

This review aims to evaluate the scientific evidences for siliceous natural nanomaterials (SNNMs), natural zeolites, and diatomaceous earth, as biorationals. Both SNNMs are multifaceted agricultural inputs—plant protectants, plant biostimulants/plant strengtheners, soil improvers. The effects depend on the plant parts, where such siliceous natural nanomaterials (SNNMs) are applied. For stored grains, SNNMs act as plant protectants. Foliar applied SNNMs protect plants against biotic and abiotic stress—plant protectant and plant strengtheners. When applied to soil/roots, SNNMs stimulate root development and improve soil characteristics. These effects are related to the composition and porous (nano)structure of SNNMs. The large active siliceous surfaces of SNNMs are involved in: desiccation of the insects damaging stored grains, fungistatic effects against mycotoxigenic fungi and adsorption of their mycotoxins, desiccation of foliar pathogens and pests, stimulation of photosynthesis, release of soluble silicon species, improved soil characteristics. Similar to other biorationals from the category of basic substances with low risk, the SNNMs efficacy as plant protectants and plant health strengtheners is rather low. Complementary active ingredients should be used to enhance the effects of SNNMs on treated plants. For SNNMs applied as protectants of stored seeds, such strategy, of using complementary biorationals/low risk substances, proved to be highly effective. Full article