Key Engineering Materials Vol. 751

Abstract: Arsenic can be found in groundwater that is harmful to human beings. In this research, we present the potential uses of ZnO microparticles, ZnO and TiO₂ nanoparticles to removal arsenic in groundwater. The experiments of %arsenic removal upon using ZnO microparticles ZnO and TiO₂ nanoparticles were conducted in 25 mL of sample volume with 0.05 g of nanoadorpbents at pH 6. We found that the efficiency of arsenic adsorption increased with a reduction of particle size of theadsorbents. Upon using nanoadsorbents to remove arsenic from the solutions with the concentrations of 200-2000 ppb, we found that the %removal of arsenic decreased from 100% to 84% for ZnO nanoparticles and 100% to 97% for TiO₂ nanoparticles. Adsorption capacities upon using ZnO and TiO₂ nanoparticles were 0.85 and 0.99 mg of arsenic/g of sorbents, respectively. TiO₂ nanoparticles exhibited a better adsorption ability to arsenic than that ZnO because TiO₂ nanoparticles had a smaller average particle size and larger surface area allowed the adsorption of hydroxyl groups on the surface that could bond with in coming HAsO₄^2- via hydrogen bonding resulting in a better arsenic adsorptive capacity.

Abstract: Carbon nanoparticles (CNPs) were successfully synthesized from the mixture of used motor oil and benzene via a solution plasma process (SPP). The synthesis was achieved within a single step at room temperature and atmospheric pressure. The effects of mixing ratio between used motor oil and benzene on the physical and chemical properties of CNPs were investigated by means of field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The results revealed that there were no significant changes in morphological feature and chemical functional groups on CNPs at different mixing ratios. The CNPs exhibited the aggregates of fine particles with the diameter of about 20–30 nm. The crystallinity of CNPs was found to be slightly increase when synthesized under the presence of used motor oil, possibly due to the effect of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in used motor oil. We expect that the conversion of used motor oil into CNPs by SPP could be another attractive way to add the value to used motor oil prior to disposing.

Abstract: This research aims to use oil palm empty fruit bunch (EFB) fibers to reinforce epoxy resin for bumper beam in cars to replace epoxy/glass fiber composite. EFB fibers were extracted by two methods; chemical method by treating with 10-30% sodium hydroxide (% by weight of fiber) and mechanical method by steam explosion process at 12-20 kgf/cm² for 5 mins. Then, the obtained fibers were bleached by hydrogen peroxide. The results show that the chemical method can eliminate lignin better than the other and provided stronger fibers. Increasing of alkaline concentration yielded the decrease of lignin content and increase of cellulose content, while no significant difference on fiber size and strength was observed. In steam explosion method, increasing of pressure vapor affected to more dark brown color and disintegrated fibers. Therefore, the optimal method for preparing EFB fibers for reinforcement of epoxy composite was chemical treatment using 30%NaOH, followed by bleaching. Then, the EFB fibers extracted by chemical method at 30%NaOH were used for reinforcing epoxy composite with fiber contents of 0-10%w/w and compared to epoxy/glass fiber composite. The results show that flexural modulus did not increase with increasing fiber content. However, the chemical treated fibers can support composite from falling apart after testing like glass fiber reinforced composite with fiber contents upper than 7.5%w/w. Impact strength and storage modulus of alkaline treated palm fiber reinforced composites increased when fiber content more than 7.5%w/w. Thermal properties of composite, analyzed by DSC and DMTA, shows that the Tg increased with fiber content. Flexural modulus and thermal properties of EFB reinforced epoxy composites provided similar results to glass fiber reinforced composites. Therefore, EFB fiber reinforced epoxy composite could be an alternative green material for bumper beam in automobile.

Abstract: To attain the desirable strength of soil, soil reinforcement has been playing a pivotal role for many decades. Although there are many well-established methods to reinforce the soil, but now-a-days people are looking for low-cost reinforcing materials. In Bangladesh jute waste is not being used effectively, although jute production is quite good in amount. From this point of view in this study, jute fiber is selected as reinforcing material and focused on improvement of compressive strength of soil. Varying proportions of Jute fiber as 1%, 2%, 3% and 4% have been mixed with dry soil to make the samples to be tested. The result indicated that the sample prepared with 3% of jute fiber gives the highest value in Unconfined Compressive Strength (UCS) test and adding more than 3% of jute fiber tends to decrease the UCS value. As this study has been done keeping in mind about the embankment construction process in the coastal zones of Bangladesh, where grass turfing is done to protect soil from erosion and inorganic fertilizer is used to grow up the grass which has long-term effect on the environment. On the other hand, jute is 100% biodegradable, when it comes to contact of moist soil, after a certain period it acts as the natural fertilizer that helps to grow up the grass and make the root of grass stronger to hold the soil.

Abstract: This paper reports studies to investigate the relationships between hydrophobicity of biochar surface and soil water retention. The studied biochars were produced from acacia wood, cashew wood and bamboo. The resulting materials were oxidized via liquid oxidation to generate hydrophilic biochars containing oxygenated functional groups on the surface. All biochars were characterized and their ability as soil additives to enhance water retention was assessed. Our results suggest that hydrophobicity/hydrophilicity of biochars is not the major factor governing water retention ability of this particular soil. However, hydrophilicity of biochar helps improve soil permeability by providing better wettability to the soil.

Abstract: Biodegradable Polyethylene (PE) may be used in the fabrication of plastic films which can replace common films prepared from nondegradable polymers. A photodegradable polyethylene composite film was prepared by mixing titanium dioxide/poly(ethylene oxide) into the PE matrix (PE/TiO₂/PEO). The composites films were prepared using 0-3 wt.% of TiO₂ and 0-10 wt.% of PEO by melt mixing. It was then compression molded in to films at 180 ^◦C. The photo-degradation test was performed under 400 W UV lamp in the ambient air. The resulting composite materials were investigated by the Fourier transform infrared spectra (FTIR), Scanning electron microscope (SEM), weight loss monitoring, and Differential scanning calorimeter (DSC). The PE/TiO₂/PEO composites film showed a high photocatalytic activity, the weight loss rate of it is about two times higher than that of PE/TiO₂ film and ten times higher than that of neat PE film. The FTIR spectra films after UV irradiation showed that the carbonyl peak intensity for composite films the intensity is greater than that of neat PE film. The degraded PEO produced an acid and an aldehyde, which were able to facilitate PE degradation and the addition of PEO/TiO₂ brought about the facilitative effect of the PE degradation.

Abstract: Pure CeO₂ and Cu-doped CeO₂ nanoparticles with different doping amounts of Cu in the range of 0.5-2.0 wt.% were synthesized by the combination of homogeneous precipitation and impregnation methods. The effect of Cu on the correlation of structural, optical and photocatalytic properties of CeO₂ were studied. The XRD results indicated that phase structures of pure CeO₂ and Cu-doped CeO₂ nanoparticles were cubic fluorite phase and no other characteristic peaks related to Cu were detected. TEM images revealed that all samples were spherical in shape with the size less than 10 nm. The shift of absorption edge of Cu-doped CeO₂ catalysts, corresponding to a decrease of band gap energies from 3.2 to 2.8 eV, was also observed as the amount of Cu dopant increased. The photocatalytic performances of the Cu-doped CeO₂ exhibited higher activity than pure CeO₂ for photocatalytic degradation of methylene blue under visible light irradiation, and the CeO₂ doped with 1.0 wt.% Cu exhibited the highest photocatalytic activity.

Abstract: High efficiency BiOBr/GO composites photocatalyst were successfully synthesized via a facile precipitation method. The precursors were prepared by dissolving Bi (NO₃)₃.5H₂O and KBr in glycerol and distilled water, respectively. Various amounts (0.1-2 wt%) of graphene oxide were added into the mixed solution precursors, and stirred at room temperature to get precipitated powder without further heat treatment. The obtained products were characterized for phase, morphology, optical properties and surface area by X-ray diffraction (XRD), transmission electron microscopy (TEM), filed-emission scanning electron microscopy (FE-SEM), UV-Vis diffuse reflection spectroscopy (DRS) and Brunauer–Emmett–Teller (BET), respectively. The morphology and structure of as-synthesized samples were composed of numerous fine plates of BiOBr dispersed on the GO sheets. The photocatalytic activities of BiOBr/GO composites were evaluated by rhodamine B degradation under visible light irradiation. As the results, the significant increase in photodegradation of BiOBr/GO composite comparing with pure BiOBr was observed. Among all samples, the composite with 1 wt% of graphene oxide showed the highest photocatalytic performance.

Abstract: Over past decades, titanium dioxide-based materials have been recognized as effectively practical photocatalysts for purification of toxicity waste. However, pure TiO2 photocatalyst is highly active under ultraviolet illumination. In this work, the effort has been focused on the synthesis of titanium-rich materials starting from minerals ores ilmenite ores and leucoxene ores by ball-milling process in combined with hydrochloric acid leaching method with optimized conditions. Crystallinity and morphologies of as-prepared samples were characterized by X-rays diffraction technique and scanning electron microscope. The photocatalytic activities of both derived-materials were studied and compared by degradation of Rhodamine B organic dye as organic toxicity compound under ultraviolet light and visible light. The results illustrate that the leucoxene-derived sample exhibits superior catalytic performance to the sample derived from ilmenite ores due to the greater Ti-content of the starting leucoxene ores.

Abstract: In this research photocatalytic degradation of nanotitania synthesized via sol-gel method and coated on commercial unglazed ceramic tiles was investigated. The starting precursors were titanium (IV) tetraisopropoxide (Ti [OCH(CH₃)₂]₄; TIP), ethanol, hydrochloric acid and distilled water. Unglazed ceramic tiles were sintered at 900°C and 1100°C. The nanotitania based sols were applied on the tile surface using air-brush and calcined at 500°C for 3 h. The particle size of the synthesized TiO₂ varied in the range 8-20 nm. The photocatalysis of nanotitania was studied through the photodegradation of methylene blue solution under UVC irradiation using UV-Vis Spectrophotometer. The presence of nanotitania on unglazed ceramic tiles was confirmed by a scanning electron microscope equipped with energy dispersive X-ray spectrometer (EDS). Ceramic tiles sintered at 900°C gave higher % open porosity and hence higher amount of nanotitania embedded on the ceramic surface. The results showed that all unglazed ceramic tiles coated with nanotitania were able to show photodegradation of methylene blue.