Search Results (139)

Chitosan has significant advantages due to its good biocompatibility and biodegradability. However, the original chitosan often has problems such as limited adsorption capacity and poor selectivity. Therefore, modifying chitosan to improve its adsorption performance has become an important research direction. This study adopted molecular dynamics simulations to explore the factors influencing the physical modification of chitosan and further conducted adsorption experiments with three different dyes. The results indicated that when combined with different clays, the interaction between chitosan and montmorillonite was more likely to occur, making it a suitable adsorbent for physical modification. As the molecular weight (MW) of chitosan increased, the <500 MW chitosan-modified bentonite exhibited the maximum adsorption capacity for different dyes, with the adsorption rates of 90.73% (methylene blue), 72.05% (methylene orange), and 32.28% (cresol red) at 20 mg/L, respectively. The adsorption kinetic and thermodynamic analysis indicated that the adsorption process is consistent with the pseudo-second-order kinetic model (R² > 0.99004), while lower temperature was more conducive to the adsorption process. The results would help determine the optimum synthetic conditions for chitosan-based composite materials and make positive contributions to the green development of agriculture. Full article

Historic blue bricks are fundamental to Beijing’s architectural heritage, yet cross-site compositional data for guiding material-compatible restoration remain scarce. This study applies WD-XRF, XRD, SEM, thermal expansion measurement, and physical property testing to 21 blue brick specimens from four Beijing-area sites spanning the Tang through Qing dynasties, with PCA and K-means clustering used to explore compositional grouping structures. Within this exploratory dataset, a compositional distinction separates the Ming and Qing Great Wall bricks: CaO falls from 7.7 to 1.5 wt.% as anorthite gives way to albite, while Qing specimens are denser (1.79 vs. 1.65 g·cm⁻³) with lower water absorption (15.9% vs. 20.9%). Two Wanping City bricks are strongly sulfate-enriched (SO₃ up to 9.8%), and WP-SE3 additionally carries a heavy chloride load (Cl 2.1%), masking their original clay signatures and illustrating how unrecognized weathering can distort compositional grouping and source-related interpretation from bulk chemistry. K-means clustering yields compositional types that overlap only partially with site boundaries, capturing raw material variation rather than site-specific manufacturing fingerprints. Despite constraints in sample size and physical property coverage, the integrated dataset offers preliminary compositional benchmarks and limited performance data to inform period-specific brick replacement at these heritage sites. Full article

The valorization of phosphogypsum (PG), a byproduct of phosphoric acid production, along with waste glass (WG) and silica fume (SF) into value-added materials has attracted growing attention in recent years. The present study aims to synthesize three types of porous geopolymers (GD, GDP, and GDG) using Tunisian clay and locally available mineral wastes, and to investigate their potential as low-cost adsorbents for the removal of methylene blue (MB) dye from aqueous solutions. The physicochemical characteristics of the raw precursors and the resulting porous geopolymers were analyzed using various techniques, including FTIR, XRD, BET, and SEM. Variations in Si/Al, Na/Al, and Ca/Al ratios play a critical role in the geopolymer structure. The high Ca/Al ratio in GDP (porous geopolymer from calcined clay and phosphogypsum) promotes the formation of C-A-S-H, leading to increased macroporosity, which favors adsorption capacity despite the presence of a more heterogeneous morphology. The results indicated that the maximum adsorption capacity (Qmax) for MB dye was obtained for the GDP sample, reaching 68 mg/g. Adsorption experiments revealed the successful removal of MB dye by geopolymers, with the Langmuir isotherm and pseudo-second-order kinetic models adequately describing the adsorption process. The MB uptake by geopolymers was facilitated by weak physicochemical interactions, including electrostatic attraction, hydrogen bonding, and π–π interactions. This study proposes a simple and effective alkali activation strategy that combines different industrial wastes within a single geopolymer system, resulting in improved porosity and adsorption efficiency. Overall, the findings highlight the potential of these waste-derived geopolymers as promising and sustainable adsorbents for wastewater treatment applications. Full article

The development of efficient and low-cost adsorbents for dye-contaminated wastewater remains an important challenge in environmental remediation. In this study, an interlayer-expanded polypyrrole/maghnite–Cu²⁺ nanocomposite (PPy/Mag–Cu²⁺) was successfully synthesized through purification of raw maghnite, sodium activation, Cu²⁺ ion exchange, and in situ oxidative polymerization of pyrrole. The obtained hybrid was characterized by X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, UV–Vis spectroscopy, scanning electron microscopy, and cyclic voltammetry. The results confirmed the successful incorporation of Cu²⁺ and polypyrrole while preserving the layered aluminosilicate framework. XRD analysis revealed a progressive increase in basal spacing from 17.49 Å for raw maghnite to 25.95 Å for the final nanocomposite, indicating effective intercalation and formation of an expanded hybrid structure. The adsorption performance of PPy/Mag–Cu²⁺ was evaluated for methylene blue removal under batch conditions. Adsorption was strongly influenced by contact time, pH, and initial dye concentration, with equilibrium reached after approximately 80 min and optimum removal at pH 9. Equilibrium data were best fitted by the Langmuir model, with a maximum monolayer adsorption capacity of 43.66 mg g⁻¹, while kinetic data followed the pseudo-second-order model. These findings demonstrate that PPy/Mag–Cu²⁺ is a promising and cost-effective hybrid adsorbent for cationic dye removal from aqueous media. Full article

This study aimed to investigate the effect of time and different disinfecting agents on nanocomposite filler composed of natural clay nanoparticles (modified and non-modified) added to maxillofacial silicone elastomers and readymade pigment additives. A total of 360 disk-shaped samples were divided into nine pigment-based groups, each with four subgroups (n = 10) exposed to different disinfectants: distilled water, 1% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and effervescent tablets. Color changes (ΔE) were measured before and after disinfection using a colorimeter. The ΔE values were assessed against perceptibility (ΔE = 1.1) and acceptability (ΔE = 3) thresholds. Nanoclay additives were also characterized using FTIR, XRD and EDX. Statistical analysis, including ANOVA and post hoc HSD tests, revealed that while all samples exhibited some color change, most remained below the acceptability threshold. Colorless silicone showed minimal, non-significant change according to perceptibility threshold (ΔE = 1.1). Blue pigments displayed significant change only with effervescent tablets. Red and mixed pigments showed perceptible changes with NaOCl, CHX, and effervescent tablets. However, nanoclay-containing specimens showed no significant perceptible alterations. Overall, despite minor perceptible changes in some pigments, all disinfecting agents tested resulted in color differences below the acceptability threshold, indicating their safe use for disinfecting maxillofacial silicone materials without compromising esthetics. Nevertheless, nanoclays are more reliable agents for the pigmentation of maxillofacial silicone as they show non-significant chromatic alteration. Full article

This article presents a comprehensive analysis of the polychrome paintings on the Flower Peking Opera Theatre in Bozhou, Anhui Province, China. A multi-technique approach was employed, including polarized light microscopy (PLM), X-ray fluorescence (XRF), micro-Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), and Herzberg staining to determine the composition and methodologies involved in the formation of the pigment layer, the white primer, and the ground layer. The analysis identified cinnabar (red), both artificial ultramarine and Prussian blue (blue), a mixture of barite and gypsum (white), a mixture of chromite and Prussian blue (green), and carbon black (black) in the pigment layer. The ground layer was found to consist of clay and plant fibers (cotton and hemp), while the white prime layer was primarily composed of barite and gypsum. This research provides insights for future conservation and restoration efforts. Full article

This study presents a comprehensive investigation of turbidity monitoring using two different types of polymer optical fiber (POF) sensors: the reflection–refraction type (RR-POF) and the gap type (Gap-POF). Both sensors were used to visualize and monitor the turbidity changes in suspensions with varying concentrations and different particle compositions, namely silica powder and clay particles. The experiments were conducted by introducing silica powder and clay into water at various concentrations, and the resulting turbidity was measured using both types of POF sensors. The results revealed a significant correlation between particle concentration and light intensity for both kinds of POF sensors. As the particle concentration increased, the light intensity decreased due to increased scattering and absorption effects. For both silica powder and clay suspensions, the light intensity stabilized at lower values as the concentration increased, with the Gap-POF sensor exhibiting higher sensitivity to turbidity changes, particularly at high particle concentrations. Additionally, the study found that the particle composition influenced the sensor response. Silica powder particles caused more irregular fluctuations in light intensity at higher concentrations due to their larger particle size and tendency to aggregate, while clay particles, due to their smaller size and better dispersion, resulted in more stable and gradual changes in light intensity. This highlighted the differences in optical responses between different particle types. Furthermore, the multi-wavelength measurements showed consistent results, with white and green lights exhibiting the strongest response to turbidity changes, while red and blue lights were less sensitive. This wavelength-dependent response was attributed to the scattering and absorption properties of the particles in the suspensions. Both RR-POF and Gap-POF sensors proved to be effective for turbidity monitoring, with Gap-POF demonstrating superior performance in high-concentration suspensions. The findings suggest that POF sensors, particularly Gap-POF, are highly suitable for real-time turbidity monitoring in various particle suspension systems. Full article

The fine clay content in reclaimed powder significantly influences the mechanical properties of cement-based materials. To promote the resource utilization of reclaimed powder in road engineering, using the methylene blue (MB) value as an indicator to evaluate the fine clay content of reclaimed powder, the influence of the MB value and proportion of reclaimed powder on the mechanical strength of cement-stabilized macadam was analyzed; fitting equations for the relationship between reclaimed powder proportion and mechanical strength were constructed; the required MB value and optimal proportion of reclaimed powder were clarified; the impact of MB value variation on mechanical strength under optimal proportion conditions was evaluated; and with mechanical strength consistency as the principle, equivalence analysis between reclaimed powder proportion and cement content was conducted. The results indicate that when the MB value of reclaimed powder is less than 5.0 g/kg, the MB value has no obvious influence on the mechanical strength of cement-stabilized macadam. With increasing reclaimed powder content, both the compressive strength and splitting tensile strength of cement-stabilized macadam first increase and then decrease, reaching peak values at reclaimed powder contents of 3.0–4.0% and 5.0–5.5%, respectively. As cement content increases, the strength-enhancing effect of reclaimed powder weakens. The MB value of reclaimed powder should be less than 5.0 g/kg with a content of 4%. When cement content is 3–4%, based on mechanical strength equivalence, a reclaimed powder content of 4% can replace at least 0.4–0.5% of cement content. Full article

This study presents the synthesis and characterization of novel kaolinite niobium and kaolinite titanium niobium nanocomposites and their application as heterogeneous photocatalysts. Utilizing a hydrolytic sol–gel route, we combined kaolinite with isopropyl alcohol, acetic acid, titanium (IV) isopropoxide, and ammonium niobium oxalate, followed by heat treatment at 400, 700, and 1000 °C. X-ray diffraction confirmed the retention of kaolinite’s characteristic reflections, with basal spacings indicating the presence of semiconductors on the external surfaces and edges. Heating treatment not allowing the crystallization of anatase until 1000 °C reveals that Nb⁵⁺ could inhibit the transition to titanium crystalline phases (anatase and rutile). The bandgap energies decreased with clay mineral support, averaging 2.50 eV, and absorbing up to 650 nm. The model reaction of terephthalic acid hydroxylation accomplished by photoluminescence spectroscopy demonstrated that KaolTiNb400 presented a higher rate of *OH production, achieving 591 mmol L⁻¹ min⁻¹ compared to pure KaolNb400 173 mmol L⁻¹ min⁻¹. Photodegradation studies revealed significant photocatalytic activity, with the KaolTiNb400 nanocomposite achieving the highest efficiency, demonstrating 90% removal of methylene blue (combining adsorption and degradation) after 24 h of UV light irradiation. These materials also exhibited promising results for the degradation of the antibiotics Triaxon^® (40%) and Loratadine (8%), highlighting their potential for organic pollutants’ removal. In both cases the presence of byproducts is detected. Full article

The purpose of this work was to develop and study catalytically active magnetic composites based on natural clays of Kazakhstan for their use in the process of catalytic wet peroxide oxidation (CWPO) of organic dyes. The synthesized materials, MnFe₂O₄/Shymkent and MnFe₂O₄/Ural, were obtained by intercalation of Fe²⁺, Fe³⁺, and Mn²⁺ ions into the interlayer spaces of natural aluminosilicates followed by heat treatment at 500 °C. The phase composition, morphology, and functional groups of the studied samples were characterized by the methods of elemental composition, X-Ray phase analysis, scanning electron microscopy, IR Fourier spectroscopy, and thermogravimetric analysis. The catalytic activity of the modified clays was evaluated in the decomposition reaction of methylene blue (MB) using hydrogen peroxide. To identify the influencing factors, adsorption experiments were conducted, including studying the effect of the adsorbent dose, the effect of pH on the degree of MB removal, and evaluating the activity of modified clays during the CWPO process under mild reaction conditions. The experiments were carried out at an initial dye concentration of C₀ = 50 mg/L, a catalyst dose of 0.25, 0.5, and 2.5 g/L, pH = 3 and 6, and a temperature of 50 °C. It was found that the degree of MB removal in adsorption experiments reaches 70% at a dose of 0.25 g/L and increases to 97.8–99% at 2.5 g/L. In terms of CWPO, with the addition of H₂O₂ complete degradation of MB was achieved within 120 min for MnFe₂O₄/Shymkent and 150 min for MnFe₂O₄/Ural. The high efficiency of the modified clays is explained by the formation of the MnFe₂O₄ ferritic spinel structure, an increase in porosity, specific surface area and hydrophilicity, as well as an improvement in the acid-base properties of the surface. The TGA results showed an increase in the thermal stability and uniformity of the composites. Thus, the developed magnetic composites can be considered as promising materials for the effective removal of organic pollutants from wastewater under mild CWPO conditions. Full article

“Miloschite”, a chromium-containing halloysite with intense blue hues, was first discovered in 1835 in Rudnjak, Serbia. Some of the collected “miloschite” samples remained in Serbia and are kept in the University Collection of Minerals and Rocks (Faculty of Mining and Geology, University of Belgrade) and in the Natural History Museum in Belgrade. During the 19th and 20th centuries, numerous studies examined this mineral. From the original samples collected at the type locality—initially described as “miloschite” and later confirmed to be varieties of halloysite enriched in chromium—subsequent interpretations of the authors on similar material from other localities worldwide led to a misinterpretation of “miloschite” as chromium-bearing kaolinite. This reinterpretation now requires revision. This investigation was carried out on an original sample employing techniques such as powder X-ray diffraction, thermal and various spectroscopic methods, along with assessments of cation exchange capacity, specific surface area, and color determination. Analyses reveal that “miloschite” primarily consists of chromium-bearing halloysite, where chromium is evenly distributed on the microscale and fills octahedral sites within the clay lattice. This research aims to reaffirm the status of “miloschite” as a significant geoheritage material from Serbia and to preserve its nomenclatural integrity as the chromium variety of halloysite. Full article

Eco-friendly clay-based adsorbents with low cost and high adsorption capacity for toxic dyes have attracted significant attention. In this study, a novel citric acid-modified sepiolite (CA-SEP) composite was developed for the efficient removal of methylene blue (MB) from aqueous solutions. The morphological, crystalline, and structural properties of the composite were characterized using XRD, FTIR, SEM, and BET analyses. Compared to pristine SEP, CA-SEP exhibited a 2.6-fold increase in adsorption capacity for MB and demonstrated excellent reusability. The effects of key parameters—including solution pH (2.0–10.0), contact time (0–300 min), adsorbent dosage (0.2–2.0 g/L), and initial MB concentration (10–150 mg/L)—on adsorption performance were systematically investigated. Modeling results indicated that the Sips isotherm provided the optimal fit for the equilibrium data. In kinetic studies, the adsorption process was best described by the pseudo-second-order model. The maximum adsorption capacity of CA-SEP for MB was estimated to be 40.61 mg/g. Moreover, the adsorbent retained high removal efficiency after five adsorption-desorption cycles, demonstrating good regenerability. These results indicate that CA-SEP is a highly efficient, sustainable, and economically viable adsorbent for the elimination of MB from contaminated water. 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

This work aims to design versatile hybrids fabricated by poly(hydroxypropyl methacrylate-co-glycidyl methacrylate) gels loaded with pristine montmorillonite, P(HPMA-co-GMA)/Mmt, by varying the clay content. Insights into design of epoxy-functional hybrids were provided by combining in situ copolymerization reactions with solution mixing to evaluate the effect of aluminosilicate addition on structure–property changes in (alkyl)methacrylate-based gels. Comprehensive analyses were conducted regarding the composition and structural properties of hybrids in the presence of Mmt. The hybrids exhibited excellent swelling, salt surfactant tolerance, and pH sensitivity depending on the composition. The higher the Mmt concentration, the lower the swelling ratio; however, the compressive moduli did not change monotonically with increasing Mmt from 0.80 to 2.20% (w/v). Dye adsorption revealed the effects of variables (dye type, pH, contact time, concentration) on adsorptive properties of hybrids towards cationic methylene blue (MB) and anionic sunset yellow, allura red, blue brilliant, carmoisine, and tartrazine dyes. Adsorption kinetics of MB obeyed pseudo-second-order model, and the maximum dye adsorption capacity for hybrids increased from 5.01 mg g⁻¹ to 16.42 mg g⁻¹, while adsorption isotherms were defined by the Freundlich model. The proposed hybrids have emerged as alternative materials that enable multiple uses of same adsorbent for the removal of different types of pollutants. Full article

Membranes were assessed on a bench scale for their performance in methylene blue dye separation. The sawdust, along with Brazilian clay and kaolin, were mixed and compacted by uniaxial pressing and sintered at 650 °C. The membranes were characterized by several techniques, including X-ray diffraction, scanning electron microscopy, porosity, mechanical strength, water uptake, and membrane hydrodynamic permeability. The results demonstrated that the incorporation of sawdust not only altered the pore morphology but also significantly improved water permeation and dye removal efficiency. The ceramic membrane had an average pore diameter of 0.346–0.622 µm and porosities ranging from 40.85 to 42.96%. The membranes were applied to the microfiltration of synthetic effluent containing methylene blue (MB) and, additionally, subjected to investigation of their adsorptive capacity. All membrane variants showed high hydrophilicity (contact angles < 60°) and achieved MB rejection efficiencies higher than 96%, demonstrating their efficiency in treating dye-contaminated effluents. Batch adsorption using ceramic membranes (M0–M3) removed 34.0–41.2% of methylene blue. Adsorption behavior fitted both Langmuir and Freundlich models, indicating mixed mono- and multilayer mechanisms. FTIR confirmed electrostatic interactions, hydrogen bonding, and possible π–π interactions in dye retention. Full article