Yayuk Astuti

Synthesis of α-Bismuth oxide using solution combustion method and its photocatalytic properties

The monoclinic bismuth oxide was prepared by the solution combustion method using bismuthyl nitrate as the raw material and citric acid as fuel. The synthesis process consisted of the formation of a clear transparent solution and the formation of white powder after heating the mixture at 250 °C for 2 hours. The yellow pale crystalline materials were obtained after calcination of the white powder at 600 °C for 80 minutes. Furthermore, the photocatalytic activity of the product was also studied using methyl orange as a model pollutant. The result showed that the coral reef-like bismuth oxide was able to degrade 50 mL methyl orange (5 ppm) by 37.8% within 12 hours irradiation using 75-watt tungsten lamp.

Enrichment of Nanodiamond Surfaces with Carboxyl Groups for Doxorubicin Loading and Release

In their pristine state, nanodiamond crystals produced via detonation techniques containing several functional groups present on the surface including amine, amide, alcohol, carbonyl, and carboxyl. These functional groups facilitate nanodiamond to interact drugs so as to nanodiamond is potential for medical application such as drug delivery. Even though research on t he use of nanodiamond for this application has been conducted widely, research on the effect of enrichment of nanodiamond surface with carboxyl functional groups for drug loading and release has not been explored extensively. Therefore, in this paper, the effect of carboxyl-terminated nanodiamond (ND-COOH) on drug loading and release will be presented. The enrichment of nanodiamond with carboxyl groups was undertaken by treating nanodiamond with sulphuric acid and nitric acid. The results show that the doxorubicin (DOX) loading and release efficiencies of ND pristine are higher than that of ND-COOH.

Synthesis of β-Calcium Pyrophosphate by sol-gel method

Beta calcium pyrophosphate [β-CPP, β-CaPO] can be used as bone graft extender in posterolateral lumbar fusion. In this research, β-CPP was synthesized by sol-gel method using phosphorus pentaoxide [PO] and calcium nitrate tetrahydrate [Ca(NO).4HO] as phosphorus and calcium precursors. The reaction was carried out in ethanol medium with Ca/P ratio of 1.67. After 21 hours of reaction and 20 hours of drying at 80°C, white powder of amorphous calcium phosphate (ACP) was produced. Transformation of ACP to β-CPP was undertaken by firring at 400-800°C for 8 hours. Transformations of amorphous to microcrystalline, semicrystalline and crystalline structures occur at 400, 600 and 800°C, respectively. The β-CPP with the crystallite size of 61.71 nm, Ca/P ratio of 0.89 and Ca/O ratio of 0.21 was achieved by firing at 800°C. Morphology changes due to firing in which irregular shape of β-CPP at 400° changed to regular cuboid at 600 °C and above.

Hydrophobicity of silica thin films: The deconvolution and interpretation by Fourier-transform infrared spectroscopy

This work investigated the synthesis of dimethoxydimethylsilane:tetraethoxysilane (DMDMS:TEOS) silica thin films as well as the effect of DMDMS:TEOS molar ratios and calcination temperature on hydrophobic properties of silica thin films and its correlation with the FTIR spectra behaviour. The silica thin films were synthesized by sol-gel method using combination of DMDMS and TEOS as silica precursors, ethanol as solvent and ammonia as catalyst, with DMDMS and TEOS molar ratio of 10:90, 25:75, 50:50, 75:25 and 90:10. The results showed that DMDMS:TEOS molar ratio had significant impact on the hydrophobic properties of silica thin films coated on a glass surface. Furthermore, the correlation between water contact angle (WCA) and DMDMS:TEOS molar ratio was found to be in a parabolic shape. Concurrently, the maximum apex of the parabola obtained was observed on the DMDMS:TEOS molar ratio of 50:50 for all calcination temperature. It was clearly observed that the silica xerogel exhibiting notable change in relative peak intensities showed FTIR peak splitting of υasymmetric Si-O-Si. To uncover what happened at the FTIR peak, the deconvolution was conducted in Gaussian approach. It was established that the changes in the Gaussian peak component were related to DMDMS:TEOS molar ratios and the calcination temperature that allowed us to tailor the DMDMS:TEOS silica polymer structure model based on the peak intensity ratios. With the increase of DMDMS:TEOS molar ratio, the ratio of (cyclic Si-O-Si)/(linear Si-O-Si) decreased, whilst the ratio of (C-H)/(linear Si-O-Si) increased. Both ratios intersected at DMDMS:TEOS molar ratio of 50:50 with contribution factor ratio of 1:16 and 1:50 for silica xerogel calcined at 300°C and 500°C respectively. The importance of this research is the DMDMS:TEOS molar ratio plays an important role in determining the hydrophobic properties of thin films.

Synthesis of Zeolite from Bagasse and Rice Husk Ashes as Surfactant Builder on Detergency Process: Variation of NaOH Concentration for Silica Isolation

Zeolite was successfully synthesised from ash bagasse and from rice husk ash as source of silica and applied to surfactant builder. The removal of silica from bagasse ash and from rice husk ash was influenced by NaOH concentration to obtain sodium silicate. This research aimed to synthesize zeolite, determine the optimum concentration of NaOH to synthetic zeolite, identify the zeolite mineral type, morphology, determine cation exchange rate and detergency by using synthesized zeolite as builder. Synthesis of zeolite was undertaken by sol-gel method followed by hydrothermal process. The stages of this study included the production of bagasse and rice husk ashes, isolation of silicate using a variation of NaOH concentration of 1.67, 3.33, 5.00, 6.67 and 8.30 M in the form of sodium silicate. Synthesis of zeolite was carried out by reacting sodium silicate and sodium aluminate using hydrothermal method. The synthesized zeolites were characterized using XRD and SEM. The results of this research indicated the types of zeolite minerals formed, namely, zeolite A, Na-A, Na-Y and sodalite. The morphology of the synthesized zeolites from both samples was quite homogeneous, NaOH concentration used to produce zeolite from bagasse ash was 1.67 M with value of cation exchange capacity (CEC) and detergency were respectively 121.14 mek/100 gram and 92.09% while synthesis zeolite from rice husk ash was generated using 8.3 M NaOH concentration with value of cation exchange capacity (CEC) and detergency were 65,71 mek / 100 gram and 94,313%, respectively.

Synthesis of Zeolite from Sugar Cane as Detergent Builder: Variation of Si/Al Ratio and Hydrothermal TimeSynthesis of Zeolite from Sugar Cane as Detergent Builder: Variation of Si/Al Ratio and Hydrothermal Time

Synthesis of zeolite from bagasse with variation of Si / Al ratio (1,2,1,4,1,6 and 1,8) with ZS1-ZS5 code and hydrothermal time (160, 190, 250, 340, and 460 minutes) with sample code ZSa - ZSe has been conducted. The synthesized zeolite was then applied to the detergent builder. The detergent builder of synthetic zeolite was used as a substitute for sodium tripolyphosphate, which is not environmentally friendly as it can lead to eutrophication. One of the detergent builder functions is to improve the washing efficiency of the surfactant by inactivating water-absorbing minerals (Ca 2+ and Mg 2+ ions) which may further deter the detergency process. Zeolites were synthesized using a sol-gel method followed by a hydrothermal process. The material used in this synthesis is Na 2 SiO 3 (aq) (derived from bagasse) mixed with NaAl(OH) 4 (aq) , then stirred to form a white gel and continued by heating using autoclave at 100°C. The results obtained are zeolite-A and zeolt-X for variation of Si/Al ratio and hydrothermal time variation, with CEC value and detergency proportional to Si/Al ratio and hydrothermal time.

Sintesis Zeolit dari Abu Sekam Padi menggunakan Metode Hidrotemal :Variasi Waktu dan Temperatur

Telah disintesis zeolit dari abu sekam padi dengan memvariasikan waktu dan temperatur hidrotermal. Hasil yang diperoleh merupakan zeolit Na-A yang mempunyai nilai KTK 53,23 meq/100 gram pada variasi waktu hidrotermal 7 jam dan pada temperatur 100 oC diperoleh zeolit Na-A dengan nilai KTK 132,8 mek/100 gram

Pengaruh CoO dan TiO2 terhadap Warna Glasir Porselen ZnO

Telah dilakukan kajian pengaruh penambahan kobalt dan titanium oksida terhadap warna glasir porselen ZnO yang bertujuan untuk menentukan pengaruh jenis dan konsentrasi oksida logam terhadap warna glasir keramik porselen dengan prinsip pergantian atom pada sisi kristal sehingga menghasilkan warna. Metode yang digunakan dalam percobaan ini adalah pembakaran dan spray. Sampel yang diuji adalah glasir kobalt oksida dan titanium dioksida. Berdasarkan percobaan diketahui bahwa oksida logam yang berbeda akan menghasilkan warna glasir yang berbeda pula. Semakin besar konsentrasi oksida logam yang ditambahkan maka warna glasir yang diperoleh juga semakin gelap atau jelas.

Interlayer free - nickel doped silica membranes for desalination

This work shows for the first time the potential of nickel oxide silica membranes for desalination applications. Nickel oxide silica xerogels were synthesised via a sol-gel method including TEOS, nickel nitrate with and without addition of hydrogen peroxide. The effects of nickel addition (5% - 50 mol %) on the structure-property relationship of the silica materials were systematically studied. The membrane performance were tested as a function of feed salt concentration (0.3-3.5 wt% NaCl) and temperature (27-60 °C). The membranes which were prepared using equal sol-gel conditions to the xerogel samples showed the raised feed temperatures resulted in increased water fluxes, whilst increasing the salt concentration resulted in decreased water fluxes. The membranes with addition of hydrogen peroxide exhibited better performances than their HO absence counterpart. The salt rejection was in excess of 90% and the maximum flux observed was 7.3 kg m h at 60°C for a 0.3 wt% NaCl feed concentration.