Search Results (62)

Novel highly compressible and stretchable nanocomposite (NC) hydrogels were obtained by the free radical polymerization of N-vinylformamide (NVF) in aqueous solution in the presence of Laponite XLG (XLG) as the crosslinker and 2,2′-azobis(2-methylpropionitrile) as the initiator. The expected composition of the NC hydrogels was proved by FTIR, TEM, XRD, and TGA analyses. Swelling degree (SD) and mechanical measurements showed that the properties of the PNVF NC hydrogels were largely different from those of both PNVF hydrogels covalently crosslinked by N,N’-methylenebisacrylamide (MBA) and equivalent poly(N-vinyl-2-pyrrolidone) (PNVP) NC hydrogels. After an initial fast swelling stage, the PNVF NC hydrogels displayed a slow, but steady, SD increase with time, unlike the MBA-crosslinked and NVP hydrogels, which exhibited a much smaller SD change during their second swelling stage. The mechanical testing of the synthesized hydrogels by uniaxial compressive and tensile measurements showed much higher compressibility (>90%) and stretchability (up to ≈840%) in the PNVF NC hydrogels than both PNVP and MBA-crosslinked PNVF hydrogels (compressibility < 80%; stretchability up to ≈114%). Cyclic compression tests revealed higher values for both elastic character and mechanical stability in the PNVF NC hydrogels in comparison to the MBA-crosslinked and PNVP ones. These different mechanical properties were explained by the PNVF NC gels possessing a network made of homogeneously distributed crosslinking sites and flexible polymer chains, thus avoiding extensive chain breakage up to larger stress values. The PNVF NC hydrogels described here may find applications for water purification, due to their high clay content, as well as in the biomedical field based on the biocompatibility of both the polymer and crosslinking agent. Full article

The characterization and biomedical modification of bentonite clays from the Kalzhat deposit (Kzh), which is situated in Kazakhstan’s Zhetysu region, are the main objectives of this work. In order to improve the raw material’s structural qualities, the montmorillonite fraction was enriched, and coarse impurities were eliminated using the Salo method. The presence of meso- and micropores that guarantee high dispersity and specific surface area, as well as the prevalence of montmorillonite and kaolinite, was all confirmed by physicochemical analysis. Particle size measurements indicated finely dispersed structures with a propensity to aggregate, whereas thermal analysis demonstrated resilience under heating. After effective functionalization with silver nanoparticles, a porous hybrid system with improved surface reactivity was produced. These enhancements demonstrate the modified bentonite’s usefulness as a multifunctional carrier for the immobilization and controlled release of pharmaceuticals, with potential uses in drug delivery systems, antimicrobial coatings, and wound-healing materials. The material has potential use in sorption and environmental protection technologies in addition to its biomedical application. Overall, Kzh’s structural and functional performance is greatly improved by the combination of purification and functionalization with silver nanoparticles, highlighting its promise as a useful element in the development of next-generation polymer–composite systems. Full article

For deep purification of wastewater containing anionic dyes. In this study, cetyltrimethylammonium bromide (CTAB)-modified geopolymer-based hectorite was synthesized via a steam-assisted method using depolymerized illite-based geopolymer as the silicon source and CTAB as the modifier, enhancing its adsorption performance for anionic dyes. The product was characterized by methods such as X-ray diffraction, and the effects of parameters such as adsorbent dosage and pH on the adsorption process were investigated. Adsorption experiments revealed that when the CTAB addition was 20%, the adsorption performance for Congo red was optimal (99.79%, 997.92 mg·g⁻¹), far superior to that of hectorite without CTAB (66.64%, 666.40 mg·g⁻¹). The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model. Further comparison of changes before and after adsorption indicated that the adsorption mechanism primarily involved the combined effects of electrostatic interaction and hydrophobic effects. Additionally, after five adsorption–desorption cycles, the material maintained over 92% removal efficiency. By using different geopolymers as silicon sources to prepare CTAB-modified geopolymer-based hectorite, the high universality of this synthesis strategy was confirmed. This study provides a universal, green, and sustainable route for preparing efficient anionic dye adsorption materials and expands the high-value utilization of clay resources. Full article

The persistent contamination of water bodies by organic compounds, heavy metals, and pathogenic microorganisms represents a critical environmental and public health concern worldwide. In this context, polymer composite materials have emerged as promising multifunctional platforms for advanced water purification. These materials combine the structural versatility of natural and synthetic polymers with the enhanced physicochemical functionalities of inorganic fillers, such as metal oxides and clay minerals. This review comprehensively analyzes recent developments in polymer composites designed to remove organic, inorganic, and biological pollutants from water systems. Emphasis is placed on key removal mechanisms, adsorption, ion exchange, photocatalysis, and antimicrobial action, alongside relevant synthesis strategies and material properties that influence performance, such as surface area, porosity, functional group availability, and mechanical stability. Representative studies are examined to illustrate contaminant-specific composite designs and removal efficiencies. Despite significant advancements, challenges remain regarding scalability, material regeneration, and the environmental safety of nanostructured components. Future perspectives highlight the potential of bio-based and stimuli-responsive polymers, hybrid systems, and AI-assisted material design in promoting sustainable, efficient, and targeted water purification technologies. Full article

Among the main man-made water pollutants that pose a danger to the environment are oil products, heavy metals, and radionuclides, as well as micro- and nanoplastics. To purify such waters, it is necessary to use advanced methods, with sorption being one of them. The aim of this work is to develop a nano-functionalized composite, comprising magnetically responsive, thermally expanded graphite (TEG) and the natural clay bentonite, and to assess its ability to purify man-made contaminated waters. Throughout the course of the research, the methods of scanning electron microscopy, optical microscopy, dynamic light scattering, radiometry, and atomic absorption spectrophotometry were used. The use of the TEG–bentonite composite for the purification of the model water, simulating radioactively contaminated nuclear power plant (NPP) effluent, reduced the content of organic substances by 10–15 times, and the degree of extraction of cesium, strontium, cobalt, and manganese was between 81.4% and 98.8%. The use of the TEG–bentonite composite for the purification of real radioactively contaminated water obtained from the object “Shelter” (“Ukryttya” in Ukrainian), in the Chernobyl Exclusion Zone, Ukraine, with high activity, containing organic substances, including micro- and nanoplastics, reduced the radioactivity by three orders of magnitude. The use of cesium-selective sorbents for additional purification of the filtrate allowed for further decontamination of radioactively contaminated water with an efficiency of 99.99%. Full article

The main objective of this work is to develop a cost-effective and durable ceramic membrane for water purification. The low-cost ceramic membrane was fabricated using readily available materials, such as clays, aluminum oxide, and calcium carbonate, The membrane was fabricated by uniaxial pressing at different pressures and sintering temperatures, then tested using a scanning electron microscope (SEM) and XRD. The porosity of the resulting membrane was 38.7%, and the contact angle was 65° indicating good hydrophilicity for filtration applications. The main composition was 70% clay, 25% CaCO₃, and 5% alumina. The removal % for methylene blue was tested at varying concentrations, achieving up to 99% removal, an initial flux of 496.8 L m⁻² h⁻¹, and an average pore size of 2 µm. Furthermore, the research explores the effect of backwashing cycles and techniques on the membrane long-term performance. The results indicated that washing the membrane for four cycles to cleanness has achieved an improved efficiency of the membrane and % dye rejection. Back washing was achieved using no chemicals; only distilled water and drying were used. A preliminary costs assessment of the production for affordable membrane resulted in a value of 170 USD/m². The findings demonstrate that optimizing backwashing cycles is essential for prolonging the membrane lifespan and lowering operation costs. Full article

Addressing the technological bottlenecks in the efficient utilization of clay-type Li deposits in China, this study systematically investigates Li occurrence states and develops clean extraction processes using the Jinyinshan clay-type Li deposit in southern Hubei as a case study. The research aims to provide technical guidance for subsequent geological exploration and development of such deposits. Analytical techniques, including AMICS, EPMA, and LA-ICP-MS, reveal that Li primarily occurs in structurally bound forms within cookeite (82.55% of total Li), illite (6.65%), and rectorite (5.20%), with mineral particle sizes concentrated in fine-grained fractions (<45 μm). Leveraging process mineralogical insights, two industrially adaptable blank roasting–acid leaching processes were innovatively developed. Process I employs a full flow of blank roasting–hydrochloric acid leaching–Li-Al separation–Ca/Mg removal–concentration for Li precipitation–three-stage counter-current washing. Optimizing roasting temperature (600 °C), hydrochloric acid concentration (18 wt%), and leaching parameters achieved a 92.37% Li leaching rate. Multi-step purification yielded lithium carbonate with >99% Li₂CO₃ purity and an overall Li recovery of 73.89%. Process II follows blank roasting–sulfuric acid leaching–Al removal via alum precipitation–Al/Fe removal–freeze crystallization for sodium sulfate removal–Ca/Mg removal–concentration for Li precipitation–three-stage counter-current washing. Parameter optimization and freezing impurity removal achieved an 89.11% Li leaching rate, producing lithium carbonate with >98.85% Li₂CO₃ content alongside by-products like crude sodium chloride and ammonium alum. Both processes enable resource utilization of Al-rich residues, with the hydrochloric acid-based method excelling in stability and the sulfuric acid-based approach offering superior by-product valorization potential. This low-energy, high-yield clean extraction system provides critical theoretical and technical foundations for scaling clay-type Li deposit utilization, advancing green Li extraction and industrial chain development. Full article

The use of widespread and inexpensive clay minerals as adsorptive agents, as well as materials obtained by their chemical modification, can contribute to the solution of the problem of environmental pollution with antibiotics. This review considers the structural features of various natural clay minerals and the effect of these features on their sorption capacity. Based on the analysis of available papers (over the last 15 years, also including some fundamental basics over the last 20–30 years), it has been established that the main property of an antibiotic molecule affecting the ability to be adsorbed by a clay mineral is the hydrophilicity of the organic substance molecule. The leading properties that determine the ability of clays to adsorb antibiotics are the charge and area of their surfaces. The ability of antibiotic molecules to protonate and a partial change in the edge charge of mineral layers is determined by the acidity of the sorption solution. In addition, empirical evidence is provided that the most important factors affecting adsorption are the ionic strength of the sorption solution, the concentration of the adsorbent and adsorbate, and the interaction temperature. The diversity of the composition, structure, and properties of clay minerals allows them to be effective sorbents for a wide range of antibiotics. Full article

China is the world’s largest supplier of raw materials and is a major consumer of refractories. The environmental damage that results from the use of refractories has drawn increasing attention. Life cycle emissions of air pollutants and CO₂ associated with the refractory manufacturing industry between 2009 and 2021 were quantified in this study. Particulate matter, SO₂, and NO_x emissions decreased by 7.1% (1515 t), 23.6% (2982 t), and 27.8% (3178 t), respectively, over the aforementioned period despite refractory output volumes being relatively stable. Advancements in manufacturing and purification technologies and internal modifications within the industry played a significant role in these decreases. To sustain output while significantly lowering emissions, the industry shifted toward the production of new minimally polluting refractories and monolithic refractories and away from the production of highly polluting clay bricks. CO₂ emission was reduced by 1.36 million tons as a result of product modifications. A logarithmic mean Divisia index (LMDI) model was used to quantify the driving forces of five factors (pollution production coefficient, control technology level, economic development level, economic structure, and consumption structure) affecting emissions. Three different emission reduction scenarios were simulated, and potential emission reductions of 23.1–77.7% by 2030 were projected. Full article

This article analyses the necessity of employing an interdisciplinary approach in the geotechnical practice of designing, constructing, and operating industrial hydraulic structures—tailings dams of processing plants. Tailings dam failures often lead to irreversible consequences for the ecological state of the environment. The interdisciplinary approach involves treating the foundation soils of structures and anthropogenic tailings deposits as a multicomponent system. In this system, soil acts as a medium hosting groundwater of varying compositions and contamination levels, containing biotic components and their metabolic products, including the gaseous phase. It has been demonstrated that the justified application of this approach increases the operational safety of existing structures and the long-term stability of starter and tailings dikes built on weak clay foundation soils. Particular emphasis is placed on the biotic component and the dual role of subsurface microorganisms. These bacteria negatively impact the strength and load-bearing capacity of water- and water–gas-saturated clay soils in the foundation of the structures under consideration. The diverse biocenosis in groundwater simultaneously facilitates self-purification from petroleum hydrocarbons to undetectable levels. This aspect holds fundamental importance, as groundwater discharges into river systems. Full article

The purification of waste cooking oils (WCOs) through clay-based adsorption is an established recycling method, yet the relationship between clay composition and adsorption efficiency remains an area of active research. The aim of the present research work was to assess the performance of Maghnia bentonite in WCO decoloration and to gain information about the specific refining process. Thus, natural bentonite from the Maghnia region (Algeria) was investigated as an adsorbent for WCO refining for biolubricant production. The adsorption efficiency was evaluated under different conditions, achieving up to 70% decolorization at 10 wt% clay after 4 h of treatment. Structural characterization of the bentonite before and after adsorption was conducted using FT-IR spectroscopy, powder X-ray diffraction (XRD), and X-ray fluorescence (XRF) to assess compositional and morphological changes. FT-IR analysis confirmed the adsorption of organic compounds, XRD indicated minor alterations in interlayer spacing, and XRF revealed ion exchange mechanisms, including a reduction in sodium and magnesium and an increase in calcium and potassium. Adsorption kinetics followed a pseudo-second-order model, with desorption effects observed at prolonged contact times. The pHPZC of 8.3 suggested that bentonite adsorption efficiency is enhanced under acidic conditions. The high decoloration capacity of Maghnia bentonite, combined with the availability and the low cost of the material, suggests a possible industrial application of this material for WCO refinement, especially in lubricant production. Full article

In recent years, efforts have been made in developing new and more efficient water purification methods and the synthesis of catalysts with greater catalytic activity that are more stable and can be used in wide pH ranges. Pillared clays represent a viable alternative for removing organic contaminants. The clays, usually smectites, are modified by inserting inorganic pillars (Al, Zr, Cr, Fe, Ti, Ga, and Mn) between the layers of the clay, increasing its surface area, porosity, catalytic activity, and thermal stability. This review describes the importance of using pillared clays with different polyoxycations in Fenton, photo-Fenton, ozonation, wet catalytic oxidation of hydrogen peroxide, and photocatalysis processes. Pillared iron clays (Fe-PILCs) are promising catalysts capable of generating hydroxyl radicals that can oxidize organic contaminants, thus facilitating their removal. The current challenges of the PILC application at industrial scale are also discussed. Full article

The objective of this study is to utilize a simulation employing advanced oxidation processes (AOPs) from photodegradation to examine the treatment of textile effluents. The selection of textile effluents as the material to be degraded is justified by the significant volume of water containing dyes, such as methylene blue (MB), generated daily by the textile industry. Often, this water is discarded without undergoing effective treatment. The purification of textile effluents would enable the reuse of water within the textile production cycle, thereby promoting sustainability. This study focuses on AOPs, which are extensively utilized in photocatalytic processes. The catalytic precursor material consists of two types of clay: a commercial clay and a natural clay. The natural clay is pillared with Al and impregnated with Ce, while the commercial clay is also pillared with Al and impregnated with Ce. Both clays are also pillared with a mixed pillar of Al and Ce. This results in three comparable materials. These clays are characterized by the presence of montmorillonite as their predominant mineral component. The selected clays were commercial bentonite and natural clay (FCN). Photocatalytic performance validation tests were conducted using UV-Vis spectroscopy. Material characterization methods included crystallographic analysis (by X-Ray diffraction (XRD)), chemical composition (by X-Ray fluorescence (XRF)), morphological studies (by scanning electron microscopy (SEM)) and textural property analysis (by N₂ adsorption). The outcomes of these investigations offer signification insights into the potential applications of these materials in the treatment of textile effluents and the development of more sustainable processes within the textile industry. Furthermore, the results contribute to the advancement of photocatalytic material design. Full article

TiO₂ used for photocatalytic water purification is most active in the form of nanoparticles (NP), but their use is fraught with difficulties in separation from solution or/and a tendency to agglomerate. The novel materials designed in this work circumvent these problems by immobilizing TiO₂ NPs on the surface of exfoliated clay minerals. A series of TiO₂/clay mineral composites were obtained using five different clay components: the Na-, CTA-, or H-form of montmorillonite (Mt) and Na- or CTA-form of laponite (Lap). The TiO₂ component was prepared using the inverse microemulsion method. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, FTIR spectroscopy, thermal analysis, and N₂ adsorption–desorption isotherms. It was shown that upon composite synthesis, the Mt interlayer became filled by a mixture of CTA⁺ and hydronium ions, regardless of the nature of the parent clay, while the structure of Lap underwent partial destruction. The composites displayed high specific surface area and uniform mesoporosity determined by the size of the TiO₂ nanoparticles. The best textural parameters were shown by composites containing clay components whose structure was partially destroyed; for instance, Ti/CTA-Lap had a specific surface area of 420 m²g⁻¹ and a pore volume of 0.653 cm³g⁻¹. The materials were tested in the photodegradation of methyl orange and humic acid upon UV irradiation. The photocatalytic activity could be correlated with the development of textural properties. In both reactions, the performance of the most photoactive composites surpassed that of the reference commercial P25 titania. Full article

Rainwater and sewage are important pollution sources for surface water bodies. Vertical greening systems (VGSs) are extensively employed for these wastewater treatments due to the green and sustainable characteristics, as well as their high-efficiency in pollutant (organic matter, nitrogen, and phosphorus) removal. At present, more and more VGSs are designed with green buildings, serving city ecosystems. This study provides an overview of different kinds of VGSs for rain and sewage treatment, emphasizing their types, design, mechanisms, selection of plants, and growth substrate. Plants play a crucial role in pollutant removal, and different plants usually obtain different efficiencies of water treatment. Climbing plants and ornamental plants with fast growth rates are priority selections for VGSs, including Canna lilies, Jasmine, Grape vine, Boston ivy, Pittosporum tobira, Pelargonium australe, Mentha aquatica, and Lythrum salicaria. The substrate is the most critical part of the VGS, which plays an important role in regulating water flow, supporting plant growth, promoting biofilm growth, filtering pollutants, and adsorbing nutrients. The single substrate either has a blockage problem or has a short holding time. Therefore, a number of studies have mixed the substrates and integrated the advantages of the substrates to form a complementary effect, thereby improving the overall purification efficiency and stability. Novel substrates (sand, spent coffee grounds, date seeds, coffee grinds, reed-based, etc.) are usually mixed with coco coir, light-weight expanded clay, growstone, or perlite at a certain ratio to obtain optimum treatment performance. Moreover, plants in clay show more significant growth advantages and health statuses than in zeolite or soil. Operating parameters are also significant influences on the treatment performance. This review provides theoretical and technical support for designing sustainable, environmentally friendly, and cost-effective VGSs in treating rainwater and sewage. Full article