Key Engineering Materials Vol. 811

Abstract: Metal oxide semiconducting compounds have potential application as photocatalyst materials to decompose many types of dyes and pollutants in the water. Zn₂SnO₄ and SnO₂ are semiconducting materials that have photocatalytic properties and the properties of those two semiconducting materials in the composite form have been studied. Metal oxide compounds of Zn₂SnO₄ and SnO₂ have been prepared through sonochemical methods using ZnCl₂ and SnCl₄.5H₂O as precursors. After sonication and heat treatment at 1000 °C, we could obtain Zn₂SnO₄ and SnO₂ compound in the sample as confirmed by x-ray diffraction measurement. The volume fraction of Zn₂SnO₄ and SnO₂ phases in the sample were found to be at 60 % and 40 %, respectively. The absorption spectra revealed that the band gap of the composite materials is 3.7 eV. This material could degrade all of the methylene blue with concentration of 6.0 x 10^-6 M in 120 minutes. The band structure calculation revealed that the comparable band gap values are found for Zn₂SnO₄ and SnO₂ compounds. However, the absorption edges for those compounds are slightly different, with absorption edge at 3.2 eV for SnO₂ and 3.6 eV for Zn₂SnO₄, respectively.

Abstract: Water pollution is one of the most common problem in industrialized society owing to increase in manufacturing process. Phenol is one of the water pollutant subsequently released into the waste water in manufacturing papers, paints, textile and plastics. Phenol caused serious health effect if in contact with human hence removal of this substance from waste water is crucial. Using bio sorbent in adsorption of phenol offered a green and cheap method for phenol removal particularly in Bandung area where supply of bio sorbent from agricultural waste are abundant. Biomass from Chinese cabbage (Brassica Pekinensis L.) contains cellulose, hemicellulose and lignin, among other substances that present in smaller amount. Dried stems were blended and filtered through 140 mesh and washed with ethanol to provide biosorbent. Modification was carried out by treatment with epichlorohydrin and HCl. Biosorbents were characterized using FTIR, SEM and BET analysis. Adsorption study was carried out according to the following parameters: pH range 5-9, contact time 10-80 minutes, mass of biosorbent 0.2-1.1 g and initial concentration of phenol is 10-50 mg/L. Upon adsorption, the concentration of phenol was measured by HPLC analysis at the following parameter: eluent methanol: water 7:3 v/v, flowrate 0.8 mL/minute at 273 nm. Untreated biosorbent showed adsorption capacity 0.097 mg/g whilst treatment with epichlorohydrine and HCl showed a decrease in adsorption capacity of 0.057 mg/g and 0.059 mg/g respectively. The optimum adsorption capacity was obtained at pH 8, 20 minutes contact time, 0.8 g mass of biosorbent and initial phenol concentration of 10 mg/L.

Abstract: Mercury (II) extraction from acidic solution with benzoyl-acetone as a cation carrier by liquid membrane emulsion (LME) technique was researched. The liquid membrane emulsion was made by mixing 15 mL the membrane phase solution (containing 2% mixed surfactant of span-80 & span-20, 0.020 M of Benzoyl-acetone in kerosene) and 15 mL the internal phase solution (containing nitric acid) with emulsification rate of 2000 rpm. The optimum condition for mercury (II) extraction were found as follows : extraction time with 300 rpm rate is 10 minutes, pH of the external phase is 2, concentration of HNO₃ in the internal phase is 2 M. Determination of mercury (II) in the external phase after extraction was done by Viscible Spectrophotometer (490 nm) with dithizone as a complexing agent. By using these optimum conditions, 30 ml of LME can extract 30 ppm of mercury (II) within 150 ml of the external phase with extraction percentage of 96.8.

Abstract: Ionic liquids (ILs) are organic salts that have a liquid phase under 100°C. Due to its ionic nature, it has affinity with water as well as organic compounds that make it potential to be developed as solvents with tuneable property. One class of material that possess this property is imidazolium compound which serves as organic cation. Variations of substituents (alkyl or aryl groups) in the parent cation provide several compounds that can be used as medium in various reactions. In this research, the synthesis of several imidazolium based ionic liquids had been performed utilizing Microwave Assisted Organic Synthesis (MAOS) method namely: butyl-methyl imidazolium chloride (BMIM-Cl), Decyl-methyl imidazolium bromide (DMIM-Br), Dodecyl-methyl imidazolium bromide (DDMIM-Br). The ILs were subsequently used as medium in cyclization reactions of diketone to provide an alternative route to flavanon. The structure of the synthesized ILs and the cyclization product were characterized by FT-IR and ¹H-NMR spectroscopy. The yield of the synthesized ILs were moderate (24-87%) while the yield of cyclization reactions was high (99%). The formation of the cyclization product, was clearly indicated by the ¹H-NMR spectrum with the peaks that appear at 6.81 ppm as singlet which corresponded to the proton at the pyranone ring.

Abstract: The aim of this study is to investigate the effect of natural zeolites characteristics on the adsorption capacity of Pb²⁺ from an aqueous environment. The used natural zeolites were originated from 3 regions in Indonesia. i.e. Bayah, Banten (coded as ZB) and two samples from South Lampung (coded as ZL-1 and ZL-2) and Nanggung, Bogor (ZN). The characteristics of each natural zeolite were evaluated through a series of detailed analysis including XRD, FTIR, XRF, SEM and N₂ physisorption. It was revealed that ZB, ZL-1 and ZL-2 were dominated by clinoptilolite (HEU) frameworks while the major phase of ZN was mordenite (MOR) type. From XRF data, the three natural zeolites (ZB, ZL-1 and ZN) possessed a comparable Si/Al ratio (ca. 5.5 to 6) whereas ZL-2 had slightly lower Si/Al ratio (ca. 4). We found that, at comparable Si/Al ratio, clinoptilolite frameworks has a higher adsorption capacity of Pb²⁺ compared to that of mordenite due to the compatibility of Pb²⁺ inside the pores of clinoptilolite. Lower Si/Al ratio of natural zeolite tended to show higher adsorption capacity of Pb²⁺ since the net charge of zeolite frameworks became more negative. These two factors, the framework type and the Si/Al ratio, are significant for the adsorption capacity. Another factor, i.e. surface area, had no certain effect on the adsorption capacity in this case.

Abstract: The potential of polyacrylic acid (PAA) nanofiber prepared by the electrospinning technique for the humic acid (HA) adsorption from aqueous solution was investigated. In this study, the adsorption experiments were carried out to investigate the effect of temperatures in a batch system. From experiment it can be seen that the HA adsorption using PAA nanofiber increased with increasing temperature. Thermodynamic parameters data indicated that the HA adsorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (∆G^o) in the range of 1.721-0.980 kJ mol^-1, enthalpy (∆H^o) and entropy (∆S^o) of 7.24 kJ mol^-1 and 18.52 J mol^-1 K^-1, respectively.

Abstract: In this study, voltammetry method for RhB determination was developed using tartrazine as sensitivity enhancement compound. The working electrode used was a molecularly imprinted poly (3-aminophenol) modified carbon paste electrodes. Measurements were conducted in 0.1 M PBS pH 7 as supporting electrolyte. RhB : tartrazine ratio of 1:10 was the best ratio for RhB determination that gave linear curve in the concentration range of 1 nM - 10 μM with a detection limit of 1.17 pM. RhB had been determined with this method in two real sample namely sekoteng and crackers. The results were similar to those found with spectrophotometry method but voltammetry method was more sensitive than spectrophotometry method.

Abstract: Methanol is a simple alcohol compound which is known very volatile and to be toxic inside of human’s body. Therefore, it is necessary to develop a sensor that is capable to detect the methanol vapor in indoor air. Zn-based MOF is a polymeric coordination compound made up of Zn_xO_yC_z inorganic cluster as the secondary building unit (SBU) and benzene dicarboxylate as the bridging ligand and formed bulky and porous material. In this research, composites of manganese oxide (MnO₂) and Zn-based MOF are synthesized and characterized as material sensor for its capability towards sensing of methanol gas. Diffractogram of PXRD reveals that the synthesized Zn-MOF is crystalline and become more amorphous due to MnO₂ addition. The composite was made into pellets and measured of its resistivity. The addition of MnO₂ to the Zn-MOF lowered the resistivity of the Zn-MOF and the composite was found to be sensitive towards methanol vapor.

Abstract: Polymer electrolyte membranes of cellulose acetate-LiClO₄ were prepared from the cellulose acetate with various ratios of lithium perchlorate in tetrahydrofuran (THF) as solvent. The properties of polymer electrolyte membranes with various ratios of lithium perchlorate were studied by Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The obtained TGA curves showed that these membranes were degraded thermally in three steps, which were attributed to dehydration, the main thermal degradation of the cellulose acetate chains, and the carbonization of the product to form ash. The thermal stability of the membrane decreased with the increase in LiClO₄ content. The initial temperatures of the main degradation process decreased gradually from 330 °C in pure cellulose acetate membrane to 258 °C in cellulose acetate membrane containing 25% lithium perchlorate. The morphology of the membranes transformed from dense to the more porous membrane along with the increase in lithium perchlorate ratios on membranes.

Abstract: Nowadays some types of polymer are being developed as Polymer Light Emitting Diode (PLED) materials because they have some advantages compared to small molecule organic light emitting diode (SM-OLED). Polymers which have numerous conjugated double bonds can be used as PLED materials, such as the polyethersulfone (PES) and its derivatives. Therefore, further research on the synthesis of PES and its derivatives is needed to explore their potential as PLED materials. In this research, the synthesis of polyethersulfone has been performed utilizing Microwave Assisted Organic Synthesis (MAOS) method and subsequently the synthesized PES was being transformed into the nitrated PES (PES-NO₂) and the aminated PES (PES-NH₂) utilizing the conventional method (reflux). Polymer structure is elucidated through FT-IR and ¹H-NMR spectrum. Polymer application as PLED material is characterized by fluorescence emission spectrum. The maximum wavelengths in the fluorecence emission spectra of polymer in NMP were 444 nm for PES, 356 nm and 444 nm for PES-NO₂, also 440 nm for PES-NH₂.Based on the various analyses of data, the synthesis of PES, PES-NO₂, and PES-NH₂ has been successfully performed and all of polymers have the potent to be used as PLED materials because of its ability to emit light (blue) in the visible area.