This study is focused on technology development for microplastic removal from wastewater using a sorption process, which would be suitable not only as a tertiary stage of purification in wastewater ...treatment plants but also for other waters, e.g., process water and surface water. Therefore, cheap natural materials such as zeolites and bentonites were tested as possible sorbents. This study aims not only at sorbent selection but also at their possible modification by a special water regime improving sorption efficiency and lifetime. Microplastic particles of the majority of common types of plastics were prepared by a newly developed abrasion technique from various plastic items used at home, thus microplastic particle sizes and shapes corresponded to the real microplastics found in waters. Based on results with high reproducibility, a novel method for microplastic characterization based on Raman spectroscopy in combination with SEM/EDX was developed. The removal of microplastics from waste water was tested not only at the laboratory scale but also in a developed semi-operational sorption unit at a real wastewater treatment plant throughout the year with the efficiency of over 90%.
The fluctuation of relative humidity and temperature in the surrounding environments of wood products is an important parameter influencing their mechanical properties. The objective of this study ...was to investigate the complex relationship between the moisture content and mechanical properties of wood as a critical aspect in the design of durable and reliable structures. Over a period of 669 days, a simulated type of experiment was conducted, during which the moisture content and external temperature were continuously measured in a compact profile of Norway spruce (Picea abies (L.) KARST.). The data were processed using quadratic and cubic models to establish a predictive model. It was found that the quadratic models slightly outperformed the cubic models when considering time lags greater than six days. The final model demonstrated a significant improvement in explaining the variance of the dependent variable compared to the basic model. Based on these findings, it can be concluded that understanding the relationship between the moisture content and temperature of wood samples plays an important role in wood’s efficient use, particularly for timber constructions. This understanding is vital for accurately predicting the mechanical characteristics of wood, which, in turn, contributes to the development of more durable and reliable structures.
The Scots pine (Pinus sylvestris Linnaeus) is one of the most important commercial tree species in Central Europe, yet we know very little about the variability of its wood properties. The aim of ...this study is to primarily analyse the impact of different tree growth rates and site characteristics on the shrinkage of Scots pine wood. The investigated forest stands are located at two sites of the Czech Republic that are characteristic for Scots pine silviculture. At each site, sample trees were selected from two stands representing two variants of the silvicultural treatment, i.e. a clear-cutting and shelterwood system with long regeneration period. Wood shrinkage in radial and tangential directions and volumetric shrinkage were determined in accordance with Czech standards. Lower values of shrinkage were found out in forest stands regenerated by the shelterwood method. The wood in the central part of the trunk shows lower shrinkage values than in the basal part in both stands. The unambiguous effect of the horizontal position in the trunk stem was demonstrated in forest stands regenerated by the clear-cutting method, whilst stands regenerated by the shelterwood method showed a more even distribution of shrinkage along the trunk width. Furthermore, it was found that the shrinkage of the Scots pine has a medium dependence on wood density.
The present paper deals with the measurement of coat thickness on wood using an ultrasonic measurement method. Exterior wood coatings (waterborne acrylate dispersions) with coating film thickness ...between 80 - 115 µm were examined. The non-destructive film thickness measurement used a Sursonic ultrasound measuring device, enabling measurement of the thickness of thin films on non-ferromagnetic and simultaneously non-conductive materials. The device also enables measurement of very thin layers of coating films, where the transit time of an ultrasound pulse through the film is shorter than the time width of the pulse. The accuracy of measurement using this measuring device was determined; destructive measurement using a light microscope was chosen as a reference measurement method. Differences in the results measured using the destructive and non-destructive methods were recorded; nevertheless, in most cases, these differences are smaller than the uncertainty of measurement using the light microscope. It can be concluded, therefore, that the results of the two compared methods match over the entire range of thickness of 80 - 115 µm. The largest differences in the measurement readings from the destructive and non-destructive methods were identified in the range of 97 - 103 µm.
The stability of wood materials in harsh environments requires a durable superhydrophobic (SH) coating. In this paper, a sustainable SH coating, suitable for interior and exterior applications of ...wood, was produced by reinforcing with bio based carnauba-wax two matrices, i.e. Epoxy resin or polydimethylsiloxane (PDMS). Fluorine-free dodecyl-terminated silica nanoparticles (DDT-SiO2), prepared through a chemical procedure, have been used to increase the hydrophobicity of all coating formulations. A novel approach for the wood substrate preparation was proposed and tested. The results showed that long-term water-repellency of the SH coatings can be enhanced by solvent/ultrasonic pre-treatments, controlling the chemical and morphological characteristics of the wood substrate before coating. The formulation containing wax exhibited a contact angle of 172° and a sliding angle <3° when applied on a clean/micro-structured wood surface subjected to solvent pre-treatments. The PDMS-based coating displayed excellent durability to water impact test, 120 cycles outdoor weathering/aging and severe environments (i.e. chemicals, ultrasonic and sea-water) than Epoxy one. While wax decreased the transparency of Epoxy-based coatings, the synergistic effect on the durability of the coating was evident. The superior characteristics of non-wetting, mechanically durable and resistance to finger-touch test of wax-PDMS-DDT-SiO2 coating were attributed to the hierarchical structure caused by carnauba-wax self-assembly and interwoven morphology. In fact, the wax helps keep the “PDMS-NPs” lotus-like structures tightly connected, producing a robust surface. The self-cleaning test, carried out using commonly used liquids and colored water, confirmed the admirable performance of the PDMS-based coating, guaranteeing also aesthetic property. The surface treatment obtained can be considered “eco-friendly” as it is composed of vegetable carnauba-wax containing nanoparticles modified with non-fluorinated compounds.
•Physicochemical changes on pretreated wood through solvent/ultrasonic pretreatment ensure stability of coating over-time.•The hierarchical structure caused by wax self-assembly and interwoven morphology enhanced the coating durability.•Durability of superhydrophobic coatings based on PDMS and epoxy was evaluated.•Mechanical water impact, finger-touch, chemicals, ultrasonic, sea-water and outdoor weathering tests were measured.•A robust, self cleaning wood surface with good aesthetic characteristic was found.
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•Material from cheap raw materials and cheap adhesive was produced.•Wheat and rapeseed straw particles were enzymatically treated.•Enzymatic treatment affected the properties of ...particles, but not the properties of boards.•The highest erosion of surface was reached via a combination of xylanases and pectinases.•No difference between the properties of wheat and rapeseed boards was observed.
The paper deals with the possibility of using post-harvest crop residues, namely winter wheat straw and winter rapeseed straw for the purpose of producing particleboards. In order to increase particle surface energy, particles were treated with enzymes prior to application of the adhesive; xylanases, pectinase, and a combination of both. The effect of the enzymatic treatment on the properties of the treated particles was monitored and, after the production of the boards, the influence of particle treatment on the mechanical and physical properties of the composites was also monitored. The effect of enzymatic modification on the properties of wheat and rapeseed particles was observed. The enzymes used influenced the particle surface morphology, their surface energy and equilibrium moisture content. Only the combination of pectinase and xylanase (Texazym SER 7) increased the surface energy of wheat surface from 26 mN/m (untreated) to 30 mN/m. The greatest erosion of the surface was achieved by the combination of xylanases and pectinases. After enzymatic treatment both wheat and rapeseed straw exhibited higher equilibrium moisture content. The increase of moisture of wheat straw was from 11.9 %–13.2 % and of rapeseed straw from 12.4 %–13.44 %. Although the selected enzymes had an effect on the properties of the particles, the effect of the enzymatic treatment on the equilibrium moisture, the internal bond strength and the bending characteristics of the produced particleboards were not observed. Produced boards reached low mechanical properties, internal bond strength reached values form to 61–99 mN/mm2.
Post-harvest crop residues are an interesting raw material for the production of composite materials. However, their surface often contains waxy and siliceous substances, which can cause adhesion ...problems. Therefore, various surface pre-treatment methods have been developed to increase the surface tension of these particles and hence to improve adhesive adhesion. The influence of hydrothermal, chemical, plasma and enzymatic treatment was investigated. The aim of the paper is to evaluate the effect of pre-treatments of post-harvest crop residues on the nature of joint failure and adhesive dispersion on the particles. The evaluation is based on microscopic analysis of particles obtained from the rupture area after internal bonding tests. The nature of bond failure and adhesive dispersion on the particle surface is evaluated. The results show a clear influence of material pre-treatment on the failure bond of the bond and, to a large extent, correlate with the mechanical properties of composites published in previous studies. The most suitable treatment appears to be a plasma treatment at a properly adjusted intensity. Conversely, the unsuitable treatment was alkaline, which, although it increased adhesion, deteriorated the overall mechanical properties. Hydrothermal treatment could be also considered as an industrially suitable method.
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