Key Engineering Materials Vol. 800

Abstract: The processes of Zn²⁺ and Pb²⁺ extraction by bulk liquid membranes containing di (2-ethylhexyl) phosphoric acid and tri-n-octylamine during galvanostatic electrodialysis accompanied by electrodeposition of the metals were studied. The effects of the current density as well as of composition of the liquid membranes and aqueous solutions on the rate of zinc (II) and lead (II) transport were determined. It was demonstrated that a practically complete removal of zinc (II) and more than 90 % extraction of lead (II) from the feed solutions containing 0.01 M ZnSO₄ or 0.01 M Pb (NO₃)₂ was achieved during 1.0 − 5.0 h of electrodialysis. A possibility of effective transfer of zinc (II) into dilute solutions of sulphuric, hydrochloric, perchloric and acetic acids was shown. Adherent zinc and lead coatings with a fine-grained structure have been deposited on the platinum cathode. More than 75% of zinc (II) and about 60% of lead (II) was deposited from solutions of sulfuric acid and perchloric acid, respectively.

Abstract: Heavy metals are very toxic water pollutant. Their presence not only affect human beings but also animals and vegetation because of their mobility in aqueous ecosystem, toxicity and non-biodegradability [1].in the aim of removing heavy metals from aqueous solutions, an eco-friendly biosorbent was prepared from lagoon sludge by a humification process. The biosorption of Cd²⁺ and Al³⁺ ions from aqueous solutions was investigated as a function of initial pH,contact time, initial metal ions concentration, and temperature. Langmuir and Freundlich models were used to determine the sorption isotherm. Optimum pH for the removal of cadmium and aluminum was found respectively to be around 6 and 4 [2] . The equilibrium was obtained in 60 min with the pseudo-second-order kinetic model. The Langmuir model was a better fit with the experimental data for both cadmium and aluminum adsorption with a regression coefficient up to 0.99 and Q_max of 100 and 142 mg.g^-1 respectively for Cd²⁺and Al³⁺.

Abstract: In the present study, the waste shells were used as a new low cost and eco-friendly biosorbant for Orange G anionic dye removal from aqueous solutions. Experiments were conducted in batch mode, and the effect of pH of solution, contact time, and initial dye concentration. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and ICP-MS analysis for chemical analysis were used to characterize the obtained biosorbent. The results showed that the mussel shells are composed 73% of calcite and 26% of aragonite with some traces of aluminum, magnesium, sodium, silicium and zinc. The biosorption results show that the optimal pH was around 2 for efficient Orange G biosorption. The equilibrium was attained in 60 min. The kinetic analysis showed that the pseudo-second-order model is in good agreement with the experimental data. The biosorption isotherm was well described by Langmuir isotherm model, the maximumbiosorption capacity was 1000mg/g. The thermodynamic study revealed that the biosorption of Orange G onto mussel shell is spontaneous and exothermic.

Abstract: Ethylene vinyl-acetate copolymer (EVA) composite materials containing multiwall carbon nanotubes (MWCNT), graphene (Gr) and iron (III, IV) oxide (Fe₃O₄) nanoparticles where processed by melt blending. Film specimens were prepared by using compression moulding method. All nanoparticles content in samples was chosen equal to 20 wt.%. The material dielectric spectroscopy was used in a range of 10^-2 Hz to 10⁷ Hz to investigate nanoparticle effect on the dielectric active (ε’) and passive components (ε’’), specific electrical conductivity (σ’) and dielectric loss (tg) for the characterization of the dissipation of electromagnetic energy.

Abstract: As the demand for sustainable environment friendly materials increases, the biocomposites such as wood-polymer composite (WPC) have gained more attention in past years. Wood wastes and by-products like sawdust, chips, bark and wood residues as well as recycled polymers can serve as raw materials for production of WPC. However, there are still many issues obtaining WPCs, mainly a poor compatibility between a hydrophobic polymer matrix and a hydrophilic wood filler. In the present study, mechanical and mechanochemical activation of aspen wood waste were performed to increase their compatibility with recycled polypropylene matrix in the WPC, and the impact of both methods on the biocomposite properties were studied. It was found, that mechanochemical activation (MCA) of aspen wood particles leads to increased hydrophobicity of the obtained WPC compared to the WPC with mechanically activated (MA) particles. Work of adhesion with water was remarkably lower for the WPC modified by MCA which also correlates with moisture sorption results. Surface free energy of the WPC modified by MCA was lower compared to the WPC modified by MA, mostly due to decreased the polar component of surface free energy. The modulus of elasticity (MOE) were competitive for both the WPC formulations, however, MCA led to increased flexural strength of WPC compared to MA.

Abstract: In this study 3 samples of bio-composite materials with different proportion of hemp fibers in the PLA matrix were developed, their comparative analysis and certain mechanical properties were investigated. Bio-composite hemp and polylactide (PLA) fibers were evenly blended using carding technology. The obtained blanks were treated for thermosetting at a fixed temperature of 180°C and a pressure of 100 kN, as well as controlled heating, compression and cooling time were applied. The mechanical properties (tensile strength σ_t, elastic modulus E_t, relative extension ɛ_t) of composite material were determined.

Abstract: In this paper, the effect of unmodified halloysite nanotubes (HNTs) content on the chemical structure and the thermal and mechanical properties of blends based on starch-grafted-polyethylene (SgP) and high density polyethylene (HDPE) (70/30 w/w) nanocomposites was investigated at various filler content ratios, i.e. 1.5, 3 and 5 wt.%. The study showed the occurrence of chemical interactions between the polymer matrix and HNTs through OH bonding. Further, the addition of HNTs to the polymer blend led to an increase in the crystallization temperature of the nanocomposite samples, in particular at higher filler contents i.e. 3 and 5 wt.%, while the melting temperature remained almost unchanged. Tensile and flexural properties of the nanocomposite samples were however improved compared to the virgin blend with respect to the HNTs content ratio.

Abstract: End-of-life tyres and elastomer products are recognised by European Union as important valuable resource for circular economy. Current work introduces an analysis of devulcanised crumb rubber comminution technique by means of semi-industrial disintegrator DESI-15. For the estimation of grindability, the main kinematic parameter in the processing of materials was given the specific energy of treatment E_s in kWh/t. Grindability of devulcanised crumb rubber aggregates as a function of particle size of the specific energy of treatment was analysed. Classified devulcanised crumb rubber will be used as a component of composite materials for oil spills remediation and for design of composite materials for civil engineering applications.

Abstract: The aim of this research is to investigate and to evaluate the changes that occur on the surface of wood specimens, coated with three different coatings and exposed to artificial weathering. The three used coatings contain linseed oil and different types of pigments. Specimens of pine wood (Pinus sylvestris L.) were painted with one or two layers of coatings to evaluate the discoloration and changes in lightness. For all the tested coatings, discoloration and loss of lightness were observed for all specimens regardless of the applied coatings. Different rates of color changes were observed for the tested coatings. The presence of pigments in the coatings formulation delays the discoloration of wood; as also the composition of pigments plays a significant role in the process.

Abstract: The production of low-temperature clay lightweight aggregates is pursued eagerly as low energy and cost lightweight aggregate concrete (LAC) building blocks becomes more popular. Clay ceramic hollow spheres (CCHS) with waste glass (WG) additive was developed and studied as aggregate in cement composite. CCHS with diameter ranging in 6/8mm were produced by a sacrificial template technique with subsequent sintering under temperature of 900 °C and different WG content of 0, 5, 7 and 10 wt%. The effect of the sintering temperature and WG content on the physical properties and morphology of the CHS-cement composites were studied by means of optical microscopy and mechanical properties. Obtained composite materials were compared with commercially available lightweight fillers such as foamed glass granules and lightweight expanded clay aggregates (LECA). The results compressive strength of CCHS containing LAC is much higher from 4.8 to 7.1 MPa in comparison with the LECA-cement LAC - 3.5 MPa. Reduction of CCHS open porosity due to higher content of WG (10%) leads to lower absorption of cement paste, as result lower cement consumption, lower bulk density and compression strength. LAC with CCHS proved to be promising construction material due to low-temperature production process (i), widely available raw material (clay) and secondary material (glass cullet) use (ii), reduction of cement paste needed for material production (iii).