Key Engineering Materials Vol. 659

Abstract: The study observes the use of a waste derived from high density polyethylene (HDPE) catalyst production as fillers in papermaking. The replacement of the industrial waste to two common fillers; calcium carbonate and clay, are of interest. The waste is in the form of bright slurry containing very fine particulates with titanium dioxide, calcium oxide and alumina, along with a small amount of chlorides. As-received HDPE waste of 0-30 wt% was added into a mixture of pulp stock to make handsheets. Cationic polyacrylamide was employed as a retention aid. The obtained handsheet samples were then dried and their properties were characterized and also compared with the handsheets holding carbonate and clay. Such properties included both physical and mechanical ones, i.e. apparent density, air resistance, brightness, opacity, smoothness, tear and tensile strength. The experimental results showed that the as-received industrial waste gave comparable outcomes to carbonate and kaolin clay. Improvement of the handsheet properties with the HDPE catalyst waste was discussed.

Abstract: In this work, the potential use of LDPE bags as containers in the SODIS application by simulated in an accelerated weathering tester (QUV), with respect to material safety and durability, was investigated. For the material integrity, a decrease in the elongation at break from 818% (at the beginning) to 21% (after 6 weeks of UV exposure) corresponded to the long UV exposure. A significant degree of mechanical degradation was evident during 2 to 4 weeks of UV exposure. The UV-Vis results showed that the UV transmittance of the bags, mostly in the UV-B region, decreased with longer duration of UV exposure. The FT-IR results showed a slight increase in carbonyl group, particularly observable in the bags exposed under UV for 3 weeks or longer. For the material safety, the amount of plastic additives that were leached into water was negligibily small and much lower than the limit of the safety standard. The results and analyses from this work provide insights into the feasibility of LDPE as an alternative material for SODIS containers and potentially be useful for future designs of SODIS containers to improve the disinfection and durability performances.

Abstract: Impure BiFeO₃ as a visible light photocatalyst for phenol degradation was synthezied via solid state method. The calcined temperatures of catalysts were studied. The characteristics of the catalysts were determined by XRD, SEM/EDS and BET. The catalysts were mainly composed of rhombohedral distorted perovskite-type BiFeO₃ phase with impurity phases (B₂Fe₄O₉, Bi₂₅FeO₄₀ and Bi₂O₃). Photocatalytic activity of phenol (5 mg/l) was studied in the impure BiFeO₃ illuminated with 200 w fluorescence lamps. The catalyst amount and initial pH value of phenol solution on the photocatalytic effiency have been also investigated. In the present experiments, the catalyst calcined at 800°C shows the highest activity. The optimum loading of impure BiFeO₃ and pH value were obtained to be 0.5 g/l and 6, respectively.

Abstract: For development of eco-friendly packaging foam from pomelo peel, physical and mechanical properties of the pomelo peel and effects of pomelo varieties, namely Kao-Nampueng, Thong-Dee, and Kao-Pan, on their properties were investigated. It was found that the pomelo variety showed somewhat significant effect on physical and mechanical of pomelo peel properties. Because of its thick peel with high moisture content (75-80%) and water activity (0.90-0.98), the peel weight accounted for almost half of the total fruit weight. Cell structure and pore size of the peel were examined using the environmental scanning electron microscope (ESEM). The result showed an open cell foam structure with pore size of approximately 151±31 µm. The pore size was more open and large towards the outer surface. Uniaxial compression tests on pomelo peel samples with and without flavedo showed good reproducible stress-strain curves despite its biological variation. Young’s moduli of both samples were calculated to be 200-300 kPa and 110-210 kPa, respectively. Moreover, the most important property of packaging foam is the ability to absorb energy during impact which can be characterised through the measurement of the onset strain of densification. It was found that the strain values at the maximum energy absorption efficiency (ε_cd) of peel samples with and without flavedo for all studied pomelo varieties were comparable and were approximately in the range of 60-65%. These preliminary results indicate very promising mechanical properties of pomelo peel as eco-friendly packaging foam although further modifications are required to improve their physical and shelf-stability properties.

Abstract: Industrial wastewater discharged into environments has been a serious and crucial problem, especially the wastewater from textile industry. It is one of the most harmful wastewaters due to their dark color, high COD and biotoxicity. Electrocoagulation is a technically easy, convenient and quick process that uses an electric field to neutralize the surface charges of contaminants in wastewater leading to coagulation and sedimentation. In this work, electrocoagulation (EC) process employed in the removal of dyes from real Batik wastewater was optimized. The optimum process conditions (∼60% color removal) for laboratory-scale were found to be: anode/cathode = Fe/Al, treatment time = 10 minutes, and electrode gap = 2cm with 30 kWh.m^-3 of energy consumption.

Abstract: The adsorption of ammonia gas on nanoparticle hydroxyapatite (HA) prepared from bovine bone was investigated. HA is well known as a good adsorbent for both of gas and liquid adsorbate. In this study, bovine bone was cleaned, calcined at 700 °C for 4 hrs and subsequently ground. The ground bovine bone powder was the starting material for synthesize of nanoparticle HA via precipitation. As-precipitated HA nanoparticles were filtered, washed and finally calcined at 500, 700, 1000 °C. Phase analyses were performed by X-ray diffraction (XRD) and the result showed that the higher the calcined temperature, the higher the degree of crystallinity. The result of ammonia (NH₃) gas adsorption indicated that as-precipitated HA with low crystallinity displayed better adsorption activity to NH₃ gas than calcined HA with high crystallinity.

Abstract: Activated carbon, zeolite and titanium dioxide are wildly used for removing the organic compounds in waste water. Although, these materials exhibit high performance (in powder form), reclaiming of these materials from the waste water treatment system is still hard. The objective of this study is to fabricate hollow cylinder activated carbon-zeolite samples which were used as a porous substrate. Various ratios of activated carbon, zeolite NaA and clay were mixed with special binder to form dough before extruded to be hollow cylinder shape. The hollow cylinder samples were cut into 2.5 cm long and then were fired at 600 °C for 2 hours under 5%CO₂+N₂ atmosphere. The fired samples were dip-coated with TiO₂-P25 and fired at 600 °C for 1 hour under 5%CO₂+N₂ atmosphere for testing the photocatalytic degradation of lignin solutions under UV light. The results showed that the strength of fired samples increasing with the ratio of clay increased. The XRD patterns of samples having clay addition showed peaks of zeolite and quartz. The physical properties, microstructure and photodegradation will be discussed.

Abstract: Hybrid composite for drinking water filter aids were prepared by slip casting method. The slip was prepared from the mixture of 17.41% of zeolite Na-A, 17.41% of activated carbon, 0.35% of ZnO nanoparticles, 8.7% of phenolic resin, 0.54% carboxymethyl cellulose and 55.59% of reversed osmosis water. The slip was mixed in a high speed ball mill for 15, 30, 45 and 60 minutes and was then poured into plaster molds for 3 hours in order to maintain hollow casting. The green body was dried and fired at several of firing temperature of 600, 650, 700 and 750 °C. The major characteristics of the composite filter were characterized as: mechanical strength, morphology, pore diameter and ion exchange ability by three points bending, scanning electron microscopy (SEM), mercury porosimetry and inductive coupled plasma-optical emission spectroscopy (ICP-OES), respectively.

Abstract: Organic contaminated wastes water from petrochemical industries can be removed by adsorbent and photocatalyst. In this work, the degradation rate of phenol have been studied at different ratios of activated carbon/NaA zeolite composite materials coated with TiO₂ photocatalyst which are easily to be fabricated into tubular shape by extrusion method. In addition, the foam-inserted composite can be floated on the surface of waste water for the higher phocatalyst activity. While the composite is the low cost adsorbent with high absorption and high ion exchange properties. In order to optimize the efficiency of material, the various ratios of activated carbon/NaA zeolite (3:1, 1:1 and 1:3) and amount of coated TiO₂ on the specimen’s surface was studied by UV/Vis spectrophotometer which related to phenol concentration. Moreover the various amount of phenolic resins (10, 20, 30, 40 and 50 wt%) at different reduction firing temperatures (600 and 650 °C) with soaking time of 1, 2 and 3 hours affected to the compressive strength of samples. For the characterization, XRD is used to characterize the phase and SEM is used to provide the morphology of the prepared composite materials.

Abstract: A wide application of magnesium aluminate spinel powder has attracted a number of studies concerning the preparation of magnesium aluminate spinel powder. In this study, a precursor for magnesium aluminate spinel was synthesized by a homogeneous precipitation method using urea as a precipitant. The precursor and the calcined powders were characterized by X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. After precipitation, the precursor was magnesium aluminium hydrate carbonate compound. By calcining, the precursor decomposed to MgO and an amorphous phase after calcining at 600°C. The formation of magnesium aluminate spinel via a reaction between MgO and the amorphous phase was observed after calcining over 800°C. The equiaxed magnesium aluminate spinel nanoparticles with particle size of 20-40 nm were obtained after calcining at 1100°C for 2 hours. Sinterability of the obtained magnesium aluminate spinel nanoparticles was also investigated by sintering compacts of magnesium aluminate spinel nanoparticles in the temperature interval of 1300-1650°C. Sintering temperature of 1600°C allowed the fabrication of dense magnesium aluminate spinel ceramics with relative density >95%.