Search Results (411)

The paper deals with the concept of how to regulate structure formation in the interfacial transition zone (ITZ) between the Ordinary Portland Cement (OPC) matrix and basalt to ensure the durability of basalt fiber-reinforced concretes. It has been demonstrated that the alkali–silica reaction (ASR) can be transformed from a destructive (negative) process into a constructive one in OPC concrete through activation by sodium water glass combined with the incorporation of an Al₂O₃-containing additive, namely metakaolin. Alkaline activation increased the compressive strength of OPC basalt fiber-reinforced concrete by 1.6–1.9 times. The formation of stable zeolite-like hydration products within the Na₂O-CaO-Al₂O₃-SiO₂-H₂O system promoted self-healing of the ITZ. This resulted in a 5.6-fold increase in ITZ microhardness compared to the cement matrix, as well as transforming expansion into shrinkage of concrete with a final value of 0.01 mm/m after 360 days. The structure-forming processes in the ITZ ensured a 1.14-fold increase in the compressive strength of 180-day alkali-activated OPC basalt fiber-reinforced concrete compared to its 30-day strength, in contrast to a 0.92-fold decrease in the strength of the non-modified OPC analog under conditions accelerating the development of ASR. Full article

Mineral substrates for indoor horticulture systems critically determine plant water availability and irrigation demand. However, integrative assessments linking pore structure, water retention, and evaporation dynamics of commonly used mineral growing media remain scarce. A total of nine distinct mineral substrates were investigated: expanded clay, expanded slate, pumice, perlite, zeolite, vermiculite, lava granules, brick chips, and clay granules. To assess the impact of granulometry, pumice was tested in three different grain sizes (1–3 mm, 4–7 mm, 7–14 mm), resulting in a total of 11 experimental samples. Samples were characterized using scanning electron microscopy (SEM), suction experiments, and evaporation tests at 30%, 50%, and 70% relative humidity (RH) at 23 °C. Bulk density ranged from <0.12 g·cm⁻³ (perlite, vermiculite) to >0.99 g·cm⁻³ (zeolite, brick chips), while volumetric water content varied from 11.0 vol.% (expanded clay) to 46.6 vol.% (vermiculite). Plant-available water content (AWC) ranged from 2.7 vol.% (expanded clay) to 30.9 vol.% (clay granules). These results demonstrate that pore interconnectivity, rather than total porosity, is the decisive driver of hydraulic performance. Finer pumice fractions increased water retention by ~16% compared to coarser fractions. All substrates exhibited a two-phase evaporation profile, with initial rates ranging from 1.9 to 5.6 g·h⁻¹ at 30% RH. Clay granules showed the most temporally stable evaporation, with only a 37% rate reduction over 48 h, compared to 66% for perlite. While conducted under controlled laboratory conditions, these findings provide a quantitative basis for targeted substrate selection and blending to optimize root-zone hydration, irrigation efficiency, and hygrothermal performance in permanent indoor horticulture systems. Full article

In the era of increasing generation of various waste streams, the possibility of utilizing them as secondary resources is of utmost importance and fully corresponds to the goals of the circular economy. Industrial residues from the pulp and paper industry, such as biomass combustion ash (FARP) and sludge from industrial wastewater treatment (PPWS), together with natural zeolite as a modifying additive, represent valuable sources enabling their integrated valorization. The present study aims to investigate the potential for their reuse through the development of sustainable material blends. A comprehensive analysis of the chemical composition and morphology of the obtained mixtures was carried out using inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate a tendency for the formation of mineral matrices dominated by calcium–sulfur–oxygen (Ca–S–O) phases, with the presence of calcium sulfate and aluminosilicate structures. The blends are associated with the formation of stable crystalline structures exhibiting potential pozzolanic activity. In this way, carbon is captured and fixed in a stable mineral form. The obtained results suggest the potential of these blends for use in low-carbon systems focused on waste valorization and carbon retention. The materials may be suitable for applications in construction, soil remediation, and environmental technologies, contributing to closing the resource loop “from farm to table and back again”. Full article

Improving nitrogen (N) use efficiency in olive cultivation is essential to address the environmental burden of N fertilizers, whose recovery efficiency rarely exceeds 55%. This study evaluates the agronomic and environmental performance of chabazite-rich zeolite as a soil amendment to enable 50% N-fertilizer reduction in olive growing. A seven-year field experiment (2017–2023) was conducted at two sites in Emilia-Romagna (Italy)—one irrigated (Brisighella) and one rainfed (Bertinoro)—comparing four autochthonous varieties under zeolite amendment (ZEO, 50% N) versus conventional fertilization (CNT, 100% N). Vegetative growth, productive parameters, oil quality and environmental impacts (Life Cycle Assessment, ISO 14040/44) were monitored. Under irrigation, ZEO maintained vegetative and productive equivalence with CNT, sustaining commercially viable yields (0.5–2.3 t ha⁻¹). Under rainfed conditions, variety-specific responses emerged: Colombina exhibited 126.2% greater trunk diameter and near-universal fruiting competence (88.9% vs. 29–35% productive plants) under ZEO, while Capolga showed treatment convergence. LCA revealed higher per-unit environmental impacts for ZEO during early orchard phases due to front-loaded extraction burdens, progressively offset by annual N-input reductions. These findings demonstrate that zeolite amendment enables agronomically viable 50% N-fertilizer reduction, with efficacy modulated by water regime and genotype. Full article

This study addresses the challenge of separating powdered zeolite adsorbents by developing biomass-supported composites via in situ crystallization of zeolites NaA (LTA) and NaX (FAU) within lead tree wood. Wood was mixed with precursor gels and subjected to hydrothermal treatment, yielding composites and external zeolite powders. Phase formation and morphology were confirmed by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The zeolite content in the composites was estimated from TGA to be approximately 10 wt.% for LTW–NaA and ~2 wt.% for LTW–NaX. Cu(II) adsorption was evaluated under controlled conditions and analyzed using Langmuir and Freundlich models together with Giles classification. The NaA powder showed the highest capacity (q_m ≈ 210 mg g⁻¹), while composite performance reflected zeolite loading. When normalized by zeolite mass, the composites exhibited comparable or enhanced capacities relative to powders, suggesting improved accessibility of active sites. NaA-based materials displayed H-type isotherms, whereas NaX-based materials showed L-type behavior, indicating different adsorption mechanisms. These results demonstrate that framework topology and biomass confinement jointly influence adsorption and that the composites are promising, easily recoverable adsorbents, with further work required to assess regeneration and long-term stability. Full article

The purpose of this study is the exploration of the catalytic performance of a ZSM-5 zeolite produced from iron-rich fly ash, without any additional iron loading, in removing paracetamol via a heterogenous Fenton reaction. The structural and textural characterization by powder X-ray diffraction and N₂ adsorption isotherms showed that a pure ZSM-5 phase was synthesized, but lower crystallinity and textural parameters were obtained when compared with commercial ZSM-5. The XPS analysis revealed significant amounts of iron and yttrium, which enhanced the electronic properties of the samples’ surface when compared with iron-impregnated commercial ZSM-5. The catalytic reaction was followed through UV-spectroscopy and kinetic models were applied to the data; the best fit was obtained for a pseudo-first-order model. All fly ash-based zeolites showed increased paracetamol removal when compared with commercial iron-loaded ZSM-5, which may be attributed to the more disordered structure, able to accommodate large paracetamol species (dimers). On the other hand, the effect of yttrium on the electronic properties of iron sites may increase the ^●OH radical formation, thus increasing the paracetamol removal rate, despite the progressive drop on paracetamol removal upon regeneration–reuse cycles due to Fe leaching. Full article

The critical role of lithium in powering the new energy economy necessitates prioritizing efficient extraction methods. This study investigates a novel zeolitic imidazolate frame work (ZIF-8)-coated manganese-based lithium-ion sieve (LIS) for enhanced lithium recovery. The precursor of LIS, Li_1.6Mn_1.6O_4, was synthesized via the hydrothermal method, followed by acid pickling to obtain the spinel lithium-ion sieve H_1.6Mn_1.6O₄. The material was then immersed in a 2-methylimidazole/Zn(NO₃)₂ solution, undergoing ultrasonic-assisted hydrothermal growth to form H_1.6Mn_1.6O₄@ZIF-8 composites. Under optimized conditions (30 °C, pH = 11, 24 h), the composite demonstrated superior lithium extraction performance compared to single-phase adsorbents, reaching 26.62 mg/g in the solution with 250 mg/L Li⁺. The adsorption capacity of the composite increased with Li⁺ concentration and reaction time. The adsorption kinetics followed a pseudo-second-order kinetic model and were dominated by chemisorption. The H_1.6Mn_1.6O₄@ZIF-8 composite exhibited an enhanced Li⁺ partition coefficient K_d of 118.3 in a mixed solution containing ions such as Li⁺, Mg²⁺, K⁺, and Ca²⁺, each with a concentration of 250 mg/L (pH = 12); good structural stability with manganese dissolution of 1.6%; and a capacity retention of approximately 79.5% after five cycles (C_Li⁺ = 250 mg/L). Full article

The limited high-temperature resistance of Ordinary Portland Cement (OPC) remains a critical challenge for fire-exposed and industrial concrete structures. Its performance deterioration above 500 °C is associated with dehydration and recrystallization of hydration products, leading to structural degradation of the cement matrix. To address this limitation, partial clinker replacement with fly ash combined with sodium water glass activation was proposed to enhance thermal stability. Physico-chemical analysis revealed the absence of portlandite and the formation of C-A-S-H and zeolite-like N–C–A–S–H phases in the fly ash-containing alkali-activated Portland cement. Upon heating, C-A-S-H phases sintered into stable high-temperature calcium aluminosilicate phases and zeolite-like phases underwent topotactic recrystallization into feldspathoid-type structures, preserving matrix integrity at high temperatures. The optimized composition region of cement system (fly ash—12.0–16.5 wt. %, density of water glass—1220–1240 kg/m³) was characterized by residual strength ≥ 50%, while compressive strength at 28 days was ≥80 MPa, exceeding the residual performance typically reported for conventional OPC systems under similar conditions (5–35%). The study was devoted to revealing the potential of low-emission Portland cements in high-temperature-resistant concretes through the utilization of fly ash. The mechanism that controls the compressive strength and temperature resistance of such cements has been demonstrated. Full article

While temperature and acidity dominate the design of zeolite catalysts for olefin cracking, the role of reaction time as an independent variable governing pathway dynamic remains elusive. This study integrates experimental and simulation methods to unravel the dynamic competition among carbenium ion cracking, thermal cracking and Confined Catalytic Radical (CCR) pathways during 1-pentene cracking on H-ZSM-5 zeolite at 650 °C. Analysis of the optimum performance envelope (OPE) curves for cracking products revealed that, in the initial reaction stage, the CCR mechanism significantly enhances ethylene yield. As the reaction time prolongs, C₅+ olefins in the gas phase undergo further cracking on the zeolite surface, markedly increasing the contribution of the carbenium ion pathway. Molecular simulations indicate that C₅+ olefins exhibit stronger adsorption capacity but lower diffusion coefficients on H-ZSM-5, and this adsorption–diffusion disparity is a key factor influencing the evolution of 1-pentene cracking pathways. Concurrently, thermal cracking reactions are also enhanced with increasing residence time, which is unfavorable for ethylene formation. This work elucidates the time-dependent evolution of 1-pentene cracking pathways and the regulatory role of intraparticle mass transfer, providing a theoretical basis for optimizing light olefin selectivity through the adjustment of reaction time and catalyst structure. Full article

The production route for cement clinker, including the clinkerization protocol and temperature, is highly dependent on the selection of raw materials. Natural resource reserves used in cement manufacturing are steadily declining due to rapid urbanization and the growing demand for building materials. Consequently, there is an urgent need to identify alternative resources, potentially from cost-effective primary raw materials or waste products. This study aims to evaluate the feasibility of incorporating recycled concrete as construction and demolition waste (C&DW) with unconventional clayey materials (bentonite and zeolite) into clinker synthesis at a reduced temperature of 1300 °C. The effect of mechanical pretreatment of the clinker raw meal, applied for durations of 10 to 30 min, was investigated. Mix designs combining traditional and alternative raw materials, along with different mechanical pretreatment durations, were systematically tested to assess their impact on raw meal clinkerization and the resulting cement mechanical properties. Despite variations in raw meal composition, the produced clinkers consistently exhibited phase compositions comprising C₃S, C₂S, C₃A, and C₄AF, as confirmed by XRD, FTIR, and SEM/EDS analyses. Among the studied raw materials, clayey components played a dominant role in controlling the formation of the main cement minerals, demonstrating that zeolite and bentonite can effectively substitute standard clays. Additionally, C&DW did not impede clinkerization; rather, it functioned as a silica source, replacing quartz sand. Short mechanical pretreatments (10 min) enhanced the content of cement minerals, whereas longer treatments adversely affected clinkerization. This study offers new insights into cement clinker production at reduced temperatures through the use of C&DW combined with unconventional clayey materials. The clinkerization temperature was reduced by approximately 100 °C from the conventional 1400–1450 °C, while still producing cements with mechanical performance comparable to ordinary Portland cement (OPC). The resulting zeolite- and bentonite-based cements, either mechanically untreated or subjected to short pretreatment, are potentially suitable for structural concrete applications, while cements produced with longer mechanical pretreatments may be more appropriate for lower-demand or non-structural uses. Full article

Gamma-valerolactone (GVL) can be used as a renewable solvent, flavoring agent, and precursor to produce liquid fuels and fine chemicals. GVL is mainly produced by the efficient hydrogenation of levulinic acid and its esters over a wide range of bifunctional catalysts under harsh conditions because high temperature is generally required for GVL formation. So far, the hydrogenation of levulinic acids/esters under mild conditions remains a great challenge. In this study, 2 wt.% Ru was loaded onto ZSM-5 zeolite (MFI) via a deposition–precipitation method and further wrapped by crystallization, forming a core–shell structure. Moreover, the wrapped Ru catalyst was coated with a petal-like layer of Mg₃Si₄O₉(OH)₄ (MgSiO₃) via a hydrothermal reaction in a Mg(NO₃)₂ solution, thereby introducing alkalinity and achieving spatial separation of Mg and Ru. This dual-functional catalyst reduces the inhibitory effect of Mg on the Ru active center and enables efficient preparation of GVL from ethyl levulinate (EL) under mild conditions, achieving 100% EL conversion and 98% GVL selectivity in the aqueous phase at 80 °C in 2 h under 0.5 MPa of H₂. Full article

Cement stabilization is widely used to improve the mechanical performance of bentonite-rich soils; however, the behavior of cement-stabilized bentonite under highly alkaline conditions remains unclear. This study aims to elucidate the degradation mechanisms of the mechanical properties of cement-stabilized bentonite exposed to NaOH solutions with concentrations ranging from 1 to 8 mol/L. Unconfined compressive strength (UCS) tests were combined with XRD, ²⁹Si NMR, and MIP to characterize mineral phases, silicate structure, and pore structure of the stabilized soils. Increasing alkalinity led to pronounced strength deterioration, with the 90 d UCS decreasing from 2.56 MPa to 0.25 MPa, corresponding to a reduction of approximately 90%. Microstructural analyses indicate that elevated alkali content inhibits cement clinker hydration, promotes the formation of zeolitic crystalline phases, induces depolymerization of the silicate network with the mean chain length decreasing from 6.4 to 3.5, partially transforms montmorillonite from a 2:1 to a 1:1 layer structure, and results in significant pore coarsening, as reflected by an increase in the most probable pore size from 62.53 to 1054.52 nm. These coupled effects weaken the integrity of the gel network and account for the continuous reduction in mechanical strength with increasing alkali concentration, providing a mechanistic basis for understanding the alkali-induced weakening behavior of cement-stabilized bentonite and offering guidance for its engineering application in alkaline environments. Full article

Metal–organic frameworks (MOFs), particularly Zeolitic Imidazolate Framework-8 (ZIF-8), are promising photocatalysts; however, their practical application is limited by a wide band gap (~3.85 eV), which restricts light absorption mainly to the ultraviolet region. This limitation was addressed by synthesizing a series of cobalt-doped ZIF-8 materials, Co(x)ZIF-8 (x = 0, 2.5, 5, 7.5, and 10 wt%), using a cost-effective aqueous synthesis route. Structural and compositional analyses using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) confirmed the formation of phase-pure ZIF-8 topology, with no significant change in nanoparticle morphology upon the partial substitution of Zn²⁺ by Co²⁺ ions within the framework. UV–Vis diffuse reflectance and Tauc plot analysis revealed a systematic and substantial reduction in the optical band gap (Eg) with increasing Co content, indicating enhanced visible-light absorption capability. All Co(x)ZIF-8 samples exhibited superior photocatalytic activity compared to pristine ZIF-8 under light irradiation. Among them, Co(2.5)ZIF-8 displayed the highest apparent reaction rate constant for pollutant degradation, while Co(5)ZIF-8 achieved the highest overall degradation efficiency (~87%) after 40 min. The enhanced photocatalytic performance is attributed to the synergistic effects of band-gap narrowing and the presence of Co²⁺ ions, which act as effective charge-trapping centers and suppress electron–hole recombination. Electrochemical measurements further demonstrated that Co(5)ZIF-8 exhibits the highest current density (most negative J) at large negative potentials (e.g., J ≈ −0.105 A cm⁻² at E = −2.0 V), indicating superior intrinsic catalytic activity. These findings highlight cobalt-doped ZIF-8 as a highly tunable and efficient photocatalyst with strong potential for environmental remediation applications. Full article

This study presents a sustainable valorization strategy for wastewater treatment plant (WWTP) residual sands through their hydrothermal conversion into a dual-phase FAU/LTA zeolite and evaluates its adsorption performance toward methylene blue (MB) as a model cationic contaminant. The synthesized material (ZEO-RS) exhibited a low Si/Al ratio (~1.7), well-developed FAU supercages with minor LTA domains, and high structural integrity, as confirmed by XRD, FTIR, XRF, SEM and PZC analyses. ZEO-RS demonstrated rapid adsorption kinetics, reaching approximately 92% of equilibrium uptake within 30 min and following a pseudo-second-order kinetic model (k₂= 2.73 g·mg⁻¹·h⁻¹). Equilibrium data were best described by the Langmuir isotherm, yielding a maximum adsorption capacity of 34.2 mg·g⁻¹ at 20 °C, with favorable separation factors (0 < r_L < 1), while Freundlich fitting indicated moderate surface heterogeneity. Thermodynamic analysis revealed that MB adsorption is spontaneous (ΔG° = −11.98 to −12.56 kJ·mol⁻¹), mildly endothermic (ΔH° = +5.26 kJ·mol⁻¹), and entropy-driven (ΔS° = +0.059 kJ·mol⁻¹·K⁻¹). FTIR evidence, combined with pH-dependent behavior, indicates that adsorption proceeds via synergistic electrostatic attraction, pore confinement within FAU domains, and partial ion-exchange interactions. Desorption efficiencies conducted under mild acidic, neutral, and alkaline conditions resulted in low MB release (1–8%), indicating strong dye retention and high framework stability. Overall, the results demonstrate that WWTP residual sands are an effective and scalable low-cost precursor for producing zeolitic adsorbents, supporting their potential application in sustainable water purification and circular-economy-based wastewater treatment strategies. Full article

A cobalt-containing zeolitic imidazolate framework (ZIF-67) was carbonized by different routes to composite materials (cZIFs) composed of metallic Co, Co₃O₄, and N-doped carbonaceous phase. The effect of the carbonization procedure on the water pollutant removal properties of cZIFs was studied. Higher temperature and prolonged thermal treatment resulted in more uniform particle size distribution (as determined by nanoparticle tracking analysis, NTA) and surface charge lowering (as determined by zeta potential measurements). Surface-governed environmental applications of prepared cZIFs were tested using physical (adsorption) and electrochemical methods for dye degradation. Targeted dyes were methylene blue (MB) and methyl orange (MO), chosen as model compounds to establish the specificity of selected remediation procedures. Electrodegradation was initiated via an intermediate reactive oxygen species formed during oxygen reduction reaction (ORR) on cZIFs serving as electrocatalysts. The adsorption test showed relatively uniform adsorption sites at the surface of cZIFs, reaching a removal of over 70 mg/g for both dyes while governed by pseudo-first-order kinetics favored by higher mesoporosity. In the electro-assisted degradation process, cZIF samples demonstrated impressive efficiency, achieving almost complete degradation of MB and MO within 4.5 h. Detailed analysis of energy consumption in the degradation process enabled the calculation of the current conversion efficiency index and the amount of charge associated with O₂^•−/^•OH generation, normalized by the quantity of removed dye, for tested materials. Here, the proposed method will assist similar research studies on the removal of organic water pollutants to discriminate among electrode materials and procedures based on energy efficiency. Full article