The knowledge of zeta potential is a very useful indicator of the stability of dispersed systems. This is especially important in many industrial processes, such as e.g. mineral processing, purification of water and many others. This article deals with the investigation of the electrokinetic behavior of goethite, quartz and clay minerals depending on pH and the presence of inorganic dispersants: sodiumhexamethaphosphate (SHMP), sodiumpyrophosphate (SPP) and sodium silicate (SS). All studies are conducted on natural samples, taken from Omarska iron mine (Bosnia and Herzegovina) by measuring the zeta potential. From the experimental results, it was found that the increase of the suspension pH resulted in an increase in the negative charge of all three tested samples. The clay did not show any isoelectric point (IEP). Quartz showed isoelectric points at pH about 2.6 and close to 2 in the absence and presence of sodium silicate in suspensions, respectively. Goethite showed isoelectric points at pH 6.7 and 4.95 in the absence and presence of sodium silicate in suspensions, respectively. An IEP could not be detected when the SHMP and SPP were used and the surface charge is negative from pH 2 to pH 12 in all tested samples. The addition of SHMP provided the highest negative zeta potential, i.e. the most stable dispersion, in all three tested samples.Keywords: zeta potential, isoelectric point, goethite, quartz, clay, inorganic dispersants.
This paper analyzes the quantitative and qualitative recovery of pedunculate oak (Quercus robur) logs processed in the modern sawmilling facility of “Drvoprodex” d.o.o. in Srbac, Bosnia and Herzegovina. The research was conducted through a combination of direct measurements during two operational shifts, encompassing 185 logs and company-maintained production records. Logs were classified into three quality grades, with detailed analysis of dimensions and produced assortments, including lamellae (grades A–C), rustic-grade elements (R class), and friezes. The overall recovery from debarked log volume reached approximately 30%, aligning with the lower end of typical industry expectations for oak flooring production. Friezes dominated in quantity (2,376 pcs), particularly in 70 mm width, while lamellae and R-class elements showed optimal yields at 135 mm and 215 mm widths. Regression analysis confirmed a statistically significant positive influence of log diameter on both recovery rate and daily processing volume. While advanced equipment such as a band saw head rig, CNC optimizer, and multi-blade rip saws are employed, several older machines occasionally limit throughput, underscoring the need for further modernization. Importantly, about 70% of the log volume remains as sawmill residue, including slabs, edgings, sawdust, and bark. Recommendations are made for systematic valorization of these co-products: coarse residues can be chipped for biomass energy or panel manufacturing, while sawdust and bark can serve for pellet production or biochemical extraction (e.g. tannins). Enhancing residue utilization would increase material efficiency and economic sustainability, aligning the mill with circular economy principles and near-zero-waste production goals.Keywords: oak sawmilling, log recovery, wood processing.
Laser-induced graphene (LIG) has been the subject of extensive research over the past decade and has found promising applications in physiological monitoring processes in both sports and medicine. Its excellent characteristics, such as good electrical conductivity, piezoresistivity, flexibility, and low-cost production, make it a suitable material for use in wearable electronics and sensors. Poly(dimethylsiloxane) (PDMS) has attracted attention as a substrate for wearable sensors due to its good biocompatibility, elasticity, and mechanical characteristics. However, since its structure contains no readily carbonizable atoms, PDMS must be modified with glycol additives such as diethylene glycol (PDMS/DEG) and ethylene glycol (PDMS/EG) to enable graphene induction. This paper presents the laser induction of graphene on a PDMS/DEG and PDMS/EG composite, electronic testing, and physicochemical characterization. By optimizing laser parameters, LIG with the lowest electrical resistance was obtained, with PDMS/DEG samples showing superior surface morphology compared to PDMS/EG. Raman spectroscopy revealed the characteristic D, G, and 2D bands typical for graphene. The assignment of bands in infrared spectroscopy (FTIR) and SEM micrographs confirmed the structure of graphene. Characterization revealed that the optimal glycol compound concentration in PDMS is 20 wt.%. In the future, this material has the potential to be used for measuring physiological processes and limb movements.Keywords: laser-induced graphene, PDMS, sensors, diethylene glycol, ethylene glycol.
The remarkable applications of flexible and wearable sensors in human motion detection and health monitoring have attracted considerable attention from both academic and industrial communities. Wearable strain sensors for finger-motion monitoring demand materials that combine high conductivity, flexibility, long-term durability, fast response, and stable interfaces. Here we report a MXene–polyurethane (PU) platform built on an MDI/HBP/PDMS network with 50 wt% soft segments (PU-50) that serves as a biocompatible, elastic substrate for a Ti₃C₂Tₓ conductive layer. MXene-PU composites were characterized by scanning electron microscopy (SEM), tensile testing and electrical measurements. SEM confirms the intended morphologies: layered, lamellar MXene stacks that form percolating pathways and a PU microphase-separated morphology between soft and hard segments. Three device variants were evaluated under finger flexion with increasing frequency: MXene on neat PU, PU with 1 wt% pure MXene in the bulk (PUMX), and PU with 1 wt% functionalized MXene (PEG-MXene) in the bulk (PUMP). Time-resolved resistance measurements acquired every 20 ms yielded clear, low-hysteresis ΔR/R₀ waveforms across all frequencies, with a consistent performance hierarchy in which PUMP exhibited the lowest baseline drift and the most stable cycle-to-cycle response, while the neat PU device displayed the largest resistance modulation amplitude. On-surface drawing tests on the neat-PU-MXene sensor further demonstrated pattern-robust sensitivity, producing distinct, repeatable temporal signatures for triangle, circle, and square trajectories with rapid baseline recovery and minor residual offsets. The obtained results validate MXene–PU as a fast, stable, and comfortable candidate for wearable finger motion sensors. They also identify mild interface optimization—via functionalized MXene in the substrate—as an effective way to enhance signal stability and suppress baseline drift while preserving signal fidelity across frequencies. This motivates future work on long-term stability, environmental compensation, and integration with compact wireless readout for multi-gesture recognition.Keywords: MXene, polyurethanes, tensile testing, wearable sensors, finger-motion sensing.
Fenton processes, in which hydrogen peroxide in the presence of divalent iron ions generates hydroxyl radicals (•OH), are widely used for the degradation of organic pollutants (phenols, antibiotics, dyes). In this review, red mud is analysed as a cheap source of iron ions in Fenton processes. Raw red mud can be used without additional modifications, but to increase the catalytic efficiency, its modification is required, which includes chemical reduction, carbothermal treatment or doping with metals. Particular attention is given to photo-Fenton and electro-Fenton processes, where red mud doped Cо, Sn or Cе, or in combination with reduced graphene oxide and biochar, allow the generation of not only hydroxyl radicals (•OH) but also singlet oxygen (1O2) and superoxide radicals (•O2–), achieving ≥99% pollutant removal. At the same time, the synthesised catalysts showed high stability and reusability. Based on a comparative analysis of more than 30 studies, it is concluded that red mud represents a cheap source of iron ions for heterogeneous Fenton processes, with significant potential for industrial application.Keywords: Fenton process, hydroxyl radicals, organic pollutants, red mud.
