Bentonite–Chitosan–Surfactant Composite with Antimicrobial, Antioxidant, and Mycotoxin Adsorption Properties

This study aimed to design a new composite with promising antimicrobial and antioxidant properties by a simple modification process of natural bentonite (B) with polysaccharide chitosan isolated from edible mushrooms Agaricus bisporus—ChM (sample B–ChM) and subsequently with a cationic surfactant—hexadecyltrimethylammonium bromide—HB (sample B–ChM–HB) for effective removal of mycotoxin zearalenone (ZEN). Characteri- zation confirmed the presence of ChM in B–ChM and both ChM and HB in B–ChM–HB. Compared to non- or slightly inhibitory activity of B and B–ChM, B–ChM–HB showed fungicidal activity against yeast Candida albicans and mycotoxigenic mold Aspergillus flavus, with a reduction of 6.00 log10 (CFU/mL) and 5.32 log10 (CFU/mL), respectively. B– ChM–HB showed a very high neutralization ability on •DPPH (89.03%–95.99%) in the concentration range of 0.625–5.0 mg/mL, the highest ferrous ion chelating ability (80.25%) at a concentration of 0.625 mg/mL, and did not induce lipid peroxidation in the linoleic acid model system. While B and B–ChM exhibited low adsorption of ZEN, its adsorption by B–ChM–HB was significantly higher. The equilibrium results of B–ChM–HB for ZEN were in accordance with the linear isotherm model at pH 3 and 7, pointing out that hydrophobic interactions (partitioning process) were relevant for toxin adsorption by the composite. Similar maximum ZEN adsorbed amounts under the applied experimental conditions (14.4 mg/g) at both pH values suggested that its adsorption was independent of the pH. This study reported for the first time that a novel composite of B with ChM and HB showed promising antimicrobial and antioxidant properties and was an efficient adsorbent for mycotoxin ZEN

Hydrothermal carbonization vs. pyrolysis in the race for sustainable solid biofuels: A comparative review

By 2050, global energy demand is expected to rise by 16–57%. At the same time, international agreements set the goal of reaching net-zero emissions. In that context, waste biomass appears as one of the renewable options that could serve as a solid fuel with a lower carbon footprint. Although it is widespread and to obtain, it comes with several drawbacks. High moisture and ash content, and a low calorific value (e.g., 10–16 MJ kg⁻1 biomass vs. 22–26 MJ kg⁻1 coal), explain why biomass cannot replace coal. Hydrothermal carbonization (HTC) and pyrolysis are two thermochemical routes being explored for turning waste biomass into carbon-rich products, known as hydrochar and biochar. These materials have shown promising fuel properties, with biochars in some cases reaching calorific values above 30 MJ kg⁻1, while hydrochar values are generally lower. In this review, we focus on HTC and pyrolysis, primarily through the changes they induce in biomass and the ways operating conditions shape the structure and fuel properties of the resulting chars. It is argued that the properties of the feedstock and the required end use largely determine the choice between these technologies. Direct comparison of HTC and pyrolysis in terms of combustion kinetics and pelletization remains limited. Therefore, this review considers combustion behavior, reaction kinetics, and pelletization, as they are crucial for advancing these materials toward practical energy applications. The goal is to outline what has been achieved so far, what can realistically be expected from these technologies, and where more research is still needed

Coupled experimental and theoretical investigation of an antidiabetic drug as a green corrosion inhibitor for low-carbon steel in acidic media

Pharmaceutical waste valorization offers a promising strategy for sustainable corrosion protection within a circular economy framework. In this study, the inhibition performance of expired metformin on low-carbon steel in 1 M HCl, simulating industrial acid pickling conditions, was systematically investigated. A comprehensive multi-technique approach was employed, combining weight loss measurements, electrochemical methods, and both qualitative and quantitative surface analyses, including scanning electron microscopy (SEM) and digital image analysis using MIPAR software, to evaluate inhibition efficiency over a concentration range of 100–600 ppm. The results reveal that metformin exhibits optimal inhibitory performance at 400 ppm, achieving maximum inhibition efficiencies of 84.9% (weight loss), 86.3% (LPR), 87.0% (EIS), and 89.4% (PDP). Quantitative surface analysis further confirms this trend, indicating 92.8% uncorroded surface area at the optimal concentration. Potentiodynamic polarization measurements demonstrate that metformin acts as a mixed-type inhibitor, suppressing both anodic metal dissolution and cathodic hydrogen evolution reactions. Furthermore, spin-polarized density functional theory (DFT) calculations demonstrate that the inhibitor-metal interaction is governed by chemisorption, driven by charge transfer from nitrogen lone pairs in metformin to vacant Fe 3d orbitals, leading to Fe N coordinate bond formation. These findings demonstrate the effectiveness of expired metformin as a sustainable corrosion inhibitor and highlight the advantage of integrating quantitative surface analysis with electrochemical and computational approaches for a more rigorous and objective evaluation. This work contributes to the development of environmentally friendly corrosion protection strategies and supports the principles of green chemistry and circular economy

Valorization of fruit and vegetable pomace: Development of zinc-enriched nutriceutical

Zinc deficiency is recognized as a global public health concern, affecting populations of all ages. This study aims to develop zinc supplements (nutraceuticals) based on by-products of the fruit and vegetable processing industry. Dehydrated apple and beetroot pomace powders were enriched with vitamin C and zinc via fluid-bed wet granulation, producing granules with substantially improved flowability (Carr's index reduced by up to 45%, Hausner ratio by up to 25%, while bulk and tapped density were reduced by up to 25% and 40%, respectively). Microbiological and long-term storage stability was demonstrated by low water activity (aw) (≤0.3), moisture content (<10%), and glass transition temperatures (Tg=29-34°C) well above standard storage conditions. The formulated nutraceuticals exhibited stronger antioxidant activity compared to the starting powders, as well as significant anti-hyperglicemic activity. Furthermore, the enhanced bioaccessibility of zinc was confirmed upon in vitro digestion of granulated samples using atomic absorption spectrometry and differential pulse voltammetry. The present findings demonstrate that apple and beetroot pomaces can be successfully valorized as sustainable and functional matrices for zinc-enrichment, free of gluten, artificial sweeteners, colorants, preservatives, anti-caking agents, and anti-nutritional factors such as phytic acid

Thermodynamic and Kinetic Analysis of Lead Leaching from Pretreated Pb–Ag Jarosite Sludge by Chloride Solution

Waste products of zinc hydrometallurgy, such as Pb–Ag jarosite sludge, represent a significant environmental problem due to toxic properties associated with elevated lead content. At the same time, this material has economic value, making its valorization beneficial from both ecological and financial perspectives. This study investigates the chloride leaching of pretreated Pb–Ag jarosite sludge, which underwent sulphation roasting followed by water leaching. The experiments were conducted with a constant solid/liquid ratio of 1:20, a stirring rate of 150 rpm, and using a 4 mol dm3 MgCl2 solution as the leaching agent, while temperature (40–80 ◦C) and leaching time (up to 120 min) were varied. The results showed that temperature significantly affects the lead leaching degree, with the highest (95%) achieved at 80 ◦C after 60 min. Kinetic analysis revealed a diffusion-controlled mechanism, with an activation energy of 18.40 kJ mol−1. Due to the characteristics of the leaching curve, the process was divided into four segments, with corresponding activation energies determined for each segment (16.48, 11.80, 13.88, and 20.50 kJ mol−1). The proposed MgCl2 system enables efficient lead leaching with a reduced amount of leaching agent, thus representing a more sustainable approach to the valorization of Pb–Ag jarosite sludge

Hierarchical Microporous Miscanthus-Derived Activated Carbon Enables Entropy-Driven High-Efficiency Dye Removal

Thermochemically treated lignocellulosic biomass represents a sustainable route to high-performance activated carbons for water purification. In this study, a miscanthus-derived activated carbon (ACM) was synthesized via one-step high-temperature KOH activation and evaluated for methylene blue (MB) removal from aqueous solutions. ACM exhibits a high specific surface area (SSABET = 1290 m²/g), dominant microporosity, and a hierarchical pore structure, enabling rapid dye diffusion. Adsorption kinetics follow a pseudo-second-order model, while intraparticle diffusion analysis reveals a two-stage mass-transfer mechanism. The weak pH dependence suggests that electrostatic interactions are not the sole controlling factor. Equilibrium data are best described by the Redlich-Peterson isotherm, indicating heterogeneous surfaces and mixed adsorption behavior. The maximum adsorption capacity increases from 410.2 to 463.8 mg/g as temperature rises from 298 to 318 K, confirming endothermic adsorption. Thermodynamic parameters indicate spontaneous, entropy-driven adsorption. FTIR analysis shows that MB uptake is predominantly governed by strong non-covalent interactions, including π–π stacking and hydrogen bonding with ACM surface functionalities, with partial contribution from pore filling rather than classical chemisorption. Reusability tests demonstrate an 80.7% removal efficiency after three adsorption–desorption cycles without detectable mass loss, highlighting ACM as a cost-effective and sustainable sorbent for wastewater treatment

Sustainable Hydrochars from Winery Waste for the Efficient Removal of Organophosphorus Pesticides and Synthetic Dye

The removal of water pollutants, specifically the organophosphorus pesticides chlorpyrifos (CHP) and azinphos-methyl (AZM), as well as the dye Rhodamine B (RB), was investigated through the valorization of grape pomace, an abundant agricultural byproduct. For the first time, hydrochars derived from grape pomace were utilized as adsorbents for these contaminants following KOH activation (HCK) and pyrolysis at 400 °C (PHC). The study aimed to evaluate the adsorption performance, determine the optimal conditions, and elucidate the adsorption mechanisms. Physicochemical characterization using SEM, FTIR, BET surface area analysis, stability, and pHPZC measurements revealed distinct differences in surface morphology, functional groups, porosity, and surface charge. Under optimized conditions, maximum adsorption capacities reached 751.0, 3.98, and 1.39 mg g−1 for RB, CHP, and AZM, respectively, on HCK, and 616.0 (RB), 30.10 (CHP), and 9.15 mg g−1 (AZM) on PHC, indicating that the selected hydrochars efficiently removed the investigated pollutants from water. Kinetic modeling demonstrated pseudo-first-order adsorption for RB and CHP on HCK and pseudo-second-order adsorption for AZM on HCK and all pollutants on PHC. Thermodynamic analysis confirmed that adsorption processes were spontaneous and favorable, with enhancements dependent on temperature. These findings suggest that HCK is particularly effective for cationic dyes, while PHC exhibits greater affinity toward organophosphorus pesticides, offering complementary applications and providing new mechanistic insights into hydrochar-based pollutant removal

Effect of cyclic simulation cooling and solidification during high pressure die casting

This is a case study on how successive simulation cycles influence the cooling and solidification during high pressure die casting. The casting model is made for a mounting frame for recessed lighting and the material used is aluminum alloy for the casting and the die is made from H11 tool steel. A total of 8 simulations were made with various conditions. Two different die opening criteria were used, first is that the liquid phase of the casting reaches 0%, and second that the casting cools down to 450 °C. After the casting is removed from the mold five different cooling times were simulated (5s, 10s, 30s, 60s, 120s) for the duration of 10 cycles with stationary air of 20°C as a cooling medium. The most optimal cooling time was determined to be 30 seconds, and for this criteria the number of cycles was increased 100. However, 100 cycles were simulated as solidification only with the assumption that the casting cavity was filled to 100%, even if the flow simulations of the 10 cycles showed a maximum of 99.977%. Depending on the cooling time the overall time needed to finish 10 cycles of casting was between 11 and 27 minutes, while 100 cycles took around 3 hours according to the simulations. For the 100 cycles for the first condition the cycle time grew from 74 to 107 seconds, while for the second it grew from 75 to 126 seconds. Once more operating parameters are acquired from the manufacturer, casting failures can be avoided by using simulations to properly maintain equipment

Uklanjanje boje reaktivna crna 5 primenom kompozitnog fotokatalizatora na bazi titanijum(IV)-oksida

U ovom radu izvršena je fotokatalizovana reakcija razgradnje boje reaktivna crna 5 (RB5) pod dejstvom lampe koja imitira Sunčevo zračenje. Tokom eksperimentalnog rada varirani su reakcioni parametri, kao što je kontaktno vreme (0-120 min), distanca lampe od rastvora (5 - 20 cm), količina fotokatalizatora (0,05-0,25 g/L) i početna koncentracija boje (10-30 mg/L). Kao fotoaktivni materijal korišćen je sintetisani kompozit TiO2-Y2O3. Kinetika razgradnje boje je pratila krivu pseudo-prvog reda (R2=0,98), sa izračunatom konstantom brzine od 0,064 min-1. Smanjenje koncentracije boje sa vremenom mereno je primenom ultravioletne-vidljive (UV-Vis) spektoskopije. Nakon 120 min, u rastvoru nije primećeno prisutvo zaostale boje, te se predloženi postupak tremana vodenog rastvora boje može smatrati efikasnim. Ovakvi sistemi mogu pronaći primenu i u uklanjanju drugih tipova industrijskih boja, kao i drugih klasa organskih zagađujućih materija prisutnih u vodama