Key Engineering Materials Vol. 751

Abstract: Graphene oxide (GO) powder was synthesized by modified Hummer’s method. Bismuth vanadate (BiVO₄) nanoparticle was synthesized by solvothermal method at 100 and 200°C for 3h. Composite graphene oxide and bismuth vanadate (GO/BiVO₄) nanoparticle were synthesized by mixed oxide method in weight ratio of 0.20:1.00. The physical and chemical properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and surface area analyzer (BET). The photocatalytic degradation of methomyl performance was determined by high performance liquid chromatograph (HPLC). Composite GO/BiVO₄ nanoparticle at 200°C for 3h was the highest photocatalytic degradation of methomyl.

Abstract: Bismuth vanadate (Bi₂VO_5.5) powder has been successfully prepared by microwave method. Bismuth nitrate and ammonium vanadate were used as the starting precursors with the mole ratio of 2:1 in 2-propanol. The microwave power was 500 Watt for 2-6 min. The yellow powder was obtained and calcined at 500°C for 2h. The structure was identified by X-ray diffraction (XRD). The morphology was investigated by scanning electron microscopy (SEM). The chemical composition was determined by energy dispersive X-ray spectrometry (EDXS). The functional groups were investigated by fourier transform infrared spectrometry (FTIR) The photocatalytic degradation of methylene blue (MB) using Bi₂VO_5.5 powder was studied by ultraviolet-visible spectrophotometry (UV-Vis).

Abstract: The objective of this work was to investigate the characteristics of polyaniline-chitosan membrane by SEM, FTIR, tensile strength and percentage elongation and to determine the adsorption behavior of reactive dyes (Yellow 145, Red 195, Blue 222) onto the polyaniline-chitosan membrane. The removal of reactive dyes was investigated in a batch experiment. Parameters influencing the adsorption including pH (2-10), contact time (0-150 min), equilibrium study (30 min to 16 h) and initial concentration (10, 25, 50, 100, 250 and 500 mg×L^-1) were studied at room temperature. The dye concentrations were determined by a UV/VIS Spectrophotometer at the wavelengths 423, 540 and 620 nm for Yellow 145, Red 195 and Blue 222, respectively. The results indicated that the tensile strength and percentage elongation of polyaniline-chitosan membrane were 0.032 kN/mm² and 15.53%, respectively. It was found that optimum pH for adsorption of all dyes on polyaniline-chitosan membrane was pH 2. When the adsorption time increased, the adsorption efficiency increased accordingly. The adsorption equilibrium was found to be reached at 3 h in all adsorptions. Moreover, the isotherm study showed that the polyaniline-chitosan membrane adsorption corresponded to Freundlich model. Moreover, it was also found that polyaniline-chitosan membrane exhibits higher adsorption efficiency for reactive dyes than chitosan.

Abstract: The adsorption of reactive dye (RB 222) onto cross-linked chitosan-rice husk ash composite beads was investigated. BET, SEM and FTIR methodologies were used to characterize the properties of the composite beads. The results indicated that the BET surface area values of cross-linked chitosan-rice husk ash composite beads were 4 .740 m² /g . The effects of various parameters on the adsorption behavior of composite beads including pH (2-12), temperature (20°C, 30°C and 40°C), and initial concentration (10-850 mg/L) were studied. The dye concentrations after adsorption process were measured using a UV/VIS Spectrophotometer at 611 nm. For the effect of pH on reactive dye (RB 222) removal, the highest value of dye removal was obtained at pH 2. The isotherm study was fitted by Freundlich Isotherm. Moreover, thermodynamics of adsorption was also found that the △G^o had negative values. It indicates the feasibility of adsorption process at temperature below 40°C.

Abstract: The electrocoagulation/flotation (ECF) technique has been regarded as a safe, efficient and environmentally friendly technique for contaminants removal in aqueous solution. In this research, an electrocoagulation cell was constructed using aluminum metal as electrodes. The constructed electrocoagulation cells were then utilized for the removals of organic dye from model solutions. To enhance flotation, sodium dodecyl sulfate (SDS) was added as a surface active agent. Some operational parameters namely electrolysis time, applied voltage, and SDS concentration were investigated. It was found that the optimum conditions were electrolysis time of 30 minute, applied voltage of 5 V, and SDS concentration of 200 ppm. Under these optimum conditions, the removal of organic dye was 84%. It was concluded that addition of SDS to ECF system may facilitate better and efficient removals of organic dye from aqueous solutions.

Abstract: In this research, the researchers study the fabrication of oil absorption, hydrophobic polyurethane (PU) sponge for application in an oil-spill cleanup model. Virgin PU is initially hydrophilic. PU is made hydrophobic by incorporating hydrophobic silica aerogel (SA) into PU 3D porous structure by stirring method and UV-treatment method. UV-irradiation promotes the attachment of SA onto the PU surface. Varying UV irradiation time and concentration of SA is done to attain an optimal attachment of SA on PU. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), contact angle measurements (CA) are used to determine the adhesion of SA on PU. The loadings of SA with and without UV-treatment are compared. Results show that SA-PU with UV-treatment has more loading of SA than SA-PU without treatment. FT-IR spectra and SEM micrographs verify the results. Moreover, the SA-PU is tested for oil absorption to simulate oil-spill cleanup. The findings show fast (less than 3 seconds), recoverable oil-spills cleanup with simple method of preparation. In addition, SA-PU with UV treatment has higher absorption rate and %absorption efficiency when compared to original PU and SA-PU without UV treatment.

Abstract: In this work, rubber-TiO₂-rGO (RT-rGO) composite sheets were successfully prepared by a simple latex mixing-casting method using TiO₂ and natural rubber latex with different amounts of rGO loading. The prepared RT-rGO sheet samples were characterized by XRD, FT-IR, Raman, SEM and EDS techniques. The photocatalytic properties of the prepared RT-rGO sheets as catalyst were evaluated using methylene blue (MB) dye solution under UV light irradiation. The result indicated that all the composite sheets loaded with rGO had better photocatalytic activities than the sheet without rGO loading. RT-rGO6.2% sheet showed the highest removal efficiency of 93.3% which has the rate constant (k_app) as 98.2 times higher than the unloaded sheet. Furthermore, the efficiency of the RT-rGO sheet upon the repeated usage was also studied. The result indicated that the sheet could be easily used, recovered and reused many times with no need for the cleaning in between successive uses. Thus, the RT-rGO sheet appears to be an attractive-material for the wastewater treatment or the water purification industry.

Abstract: The goal of this work was the synthesis and the improvement of viscosity of surfactant with carboxymethyl cellulose (CMC) from different types of agriculture wastes to reduce a quantity of wastes. Cavendish banana peels, corn silk and bagasse as agricultural wastes were selected to synthesis CMC by extraction with NaOH to cellulose. Then cellulose was modified by reacting with monochloroacetic acid to obtain CMC which was investigated the functional group by Fourier Transform Infrared Spectrometer (FTIR). Moreover, a 0.5 wt% of synthesized CMC was prepared in 14 wt% of sodium lauryl sulfate (SLS) solution to estimate viscosity by rotational viscometer, transparency by visible spectrophotometer and stability by observation, comparing with commercial thickener (PEG400). The results showed that CMCs of all three agriculture wastes can increase the viscosity of the surfactant solution and more increase than solution with PEG400. The SLS solution containing the CMC of corn silk provided the highest viscosity of 22.4 Cp by rotation speed of 250 rpm. However, the values of transparency and stability of surfactant solution with CMCs are slightly lower than that of solution with PEG400, except for the addition of CMC from bagasse, it was precipitated in yellow color in a short time.

Abstract: Being abundant and hazardous solid waste, the utilization of fly ash was sought. This study aimed to convert coal fly ash into zeolite using reflux method combined with microwave and ultrasonic pretreatments. Fly ash was reacted with NaOH 2 M, ultrasonicated for 30 minutes and irradiated using microwave for 45 minutes. The resulting solution was then refluxed for 24 hours. The zeolite formation was confirmed by FTIR and XRD analysis. The zeolite was then activated by 20% HCl for 2 hours. Fly ash, zeolites and activated zeolite were characterized for their adsorptive properties using a cationic dye via batch experiment. The maximum adsorption capacity (Qm) of fly ash, zeolite, and acid activated zeolite were 0.0003 mg g, 51 mg/g, and 101 mg/g, respectively. BET analyses indicated that the surface area of fly ash was 7 m2/g, while that for zeolite and acid activated zeolite were 82.4 m2g and 82.6 m2/g, respectively. The FTIR showed the Si-OH groups were significantly enhanced upon acid activation indicated by absorption peak at 960-1100 cm-1. It can be concluded that the chemisorption via cation-exchange or monolayer interaction played a major role in the adsorption mechanism of zeolite, supported by the allignment of the adsorption data plots to Langmuir isoterm adsorption model.

Abstract: Arsenic contaminants in drinking water pose a threat to human health. In this study, we report the use of nanotechnology to enhance the efficiency of arsenic removal. In here, zinc oxide (ZnO) has been selected for this application due to its environmentally friendly to human being. One-dimensional ZnO nanorods were grown on porous ceramic substrate by hydrothermal technique. The monolith nano-adsorbents were investigated using field emission scanning electron microscope (FESEM, Hitachi, SE-8030), while phase compositions and specific surface area were examined by x-ray diffractometer (XRD, PAnalitical, X’Pert PRO). Experiments of arsenic adsorption were conducted by using 200 ppb arsenic concentration solution with a continuously stirring system. After the adsorption, each water sample was then measured the arsenic content by inductively coupled plasma-optical emission spectroscope (ICP-OES) as compare to the original water sample to calculate the percentage of arsenic removal. We found that morphology of nano-adsorbent on using the growth solution concentration of 20mM of growth solution concentration and 20 hours of growth time showed the highest density of ZnO hexagonal nanorods with about 100 nm in diameter. The optimization studies obtained 30 minute of adsorption time, pH as 7. This nano-adsorbent exhibited about 98% of arsenic removal. For the comparison with commercial adsorbent (As600), ZnO nano-adsorbent has a better efficiency. The strong competitive ion on the arsenic removal was PO₄^3-. Moreover, the real groundwater after treatment doesn’t have any toxic residue. Therefore, ZnO nanorods coated on porous ceramic can be the candidate material for arsenic removal from groundwater.