Sri Juari Santosa

Automated continuous-flow hydride generation with inductively coupled plasma mass spectrometric detection for the determination of trace amounts of selenium(IV), and total antimony, arsenic and germanium in sea-water

An automated continuous-flow hydride generation system was developed for the determination of trace amounts of Se IV and total Sb, As and Ge in sea-water using ICP-MS detection. Since the same responses can be obtained between the Sb species Sb V and Sb III , among the As species As V , As III , monomethylarsonic acid and dimethylarsinic acid, and between the Ge species Ge IV and monomethylgermanium, a single Sb, As and Ge species can be used for calibration. A sensitivity enhancement was observed when methanol was used for matrix modification. Matrix modification was also useful for achieving recoveries close to 100% in recovery tests performed on a sea-water sample. Detection limits of 2.2 ng l -1 for Sb as Sb III , 6.5 ng l -1 for As as As V , 2.4 ng l -1 for Ge as Ge IV and 0.5 ng l -1 for Se IV were obtained. For replicate determinations in both a standard solution and a real sea-water sample, the repeatabilities were within 7% (as RSD). The proposed method is rapid (15 samples can be analysed per hour) and sufficiently sensitive to allow trace amounts of Se IV and total Sb, As and Ge to be directly determined in surface sea-water samples taken at a high latitude of the North Pacific Ocean from Japan to Canada.

A study on the concentration, distribution, and behavior of metals in atmospheric particulate matter over the North Pacific Ocean by using inductively coupled plasma mass spectrometry equipped with laser ablation

The concentrations and distribution of 11 metal elements (Al, Ti, V, Mn, Ni, Zn, As, Se, Cd, Sb, and Pb) in marine atmospheric particulate matter collected daily over the North Pacific Ocean during the 14 separate cruises of M/V Skaugran from Japan to the west coast of the American continent and back to Japan from March 1995 to October 1996 have been investigated in order to clarify their behavior. A total of 223 samples were collected and analyzed by laser ablation inductively coupled plasma mass spectrometry (LA/ICP-MS). For crustal elements such as Al and Mn, their concentrations decreased from the western to central and then only slightly increased in the eastern North Pacific Ocean. The concentrations of anthropogenically derived elements such as Zn and Pb were also significantly higher in the western than in the central and eastern North Pacific Ocean. Both crustal and anthropogenic elements displayed high concentrations in the commonly known dust season (March to May) and low concentrations in the summer (June to August). In winter (November to December), however, only anthropogenic elements showed significantly high concentrations. The high concentrations for crustal elements in the dust season are suggested as resulting from the input of mineral particulate matter transported from the Asian continent by westerly winds. This input does not occur in winter because the land surface is frozen. The westerly winds also distribute anthropogenic elements to the North Pacific Ocean. However, in summer the westerly wind is replaced by the oceanic wind that dilutes both crustal and anthropogenic elements in the marine atmosphere, and therefore their concentrations were significantly lower in summer.

The Effect of Alkaline Ratios of NaOH to NH3 on the Formation of Nanostructured Titania

The effect of alkaline solvent of NaOH and NH3 in the synthesis of nanostructured titania (TiO2) has been studied. Powder of anatase titania as the precursor was mixed with various volume ratios of 10 M of NaOH and 15 M of NH3. The mixture was heated in Teflon-lined autoclave at 150 °C for 24 h. The as-synthesized TiO2 powders were then washed with 0.1 M HCl and calcined at 300 °C. The calcined samples were characterized using TEM (transmission electron microscope), and XRD (X-Ray diffraction). Raman spectroscopy was further used to determine the contributing crystalline phases for the synthesized TiO2. It is shown that varying the solvent ratios of NOH to NH3 resulted in nanotubes, nanosheets, and nanoparticle morphology of TiO2. The TEM images showed the formation of nanotube structure in alkaline ratio NaOH:NH3 of 1:0 and 3:1, with diameter of about 10 nm. At volume ratio of 1:1, the nanosheets and nanotubes both were formed and at volume ratio of NaOH:NH3 of 1:3, nanosheets contributed as its main morphology. While, at fully NH3 solvent, the nanospheres with anatase domain were produced. Raman spectra confirmed that the major contributor for hydrothermal synthesis employing less NaOH for volume ratio of NaOH:NH3 of 3:1 was predominantly anatase with slight presence of titanate. For volume ratio at higher NH3 the presence of titanate is not prominent, but the morphology has already changed into more nanosheet and then nanospheres. The crystallinity of TiO2 anatase crystalline phase was enhanced as more NH3 utilized.

Adsorption of Crystal Violet Dye Using Zeolite A Synthesized From Coal Fly Ash

Adsorption of Crystal Violet (CV) dye using zeolite A synthesized from coal fly ash (ZA) has been done. Effect of pH, contact time, and the initial concentration of dye adsorption was studied in this adsorption. Model experimental of adsorption isotherms and adsorption kinetics were also studied. The adsorption is done in a batch reactor at room temperature. A total of 0.01 g of zeolite A was added to the Erlenmeyer flask 50 mL containing 20 mL of the dye solution of Crystal Violet in a variety of conditions of pH, contact time and initial concentration. Furthermore, Erlenmeyer flask and its contents were shaken using an orbital shaker at a speed of 200 rpm. After a specified period of adsorption, the solution was centrifuged for 2 minutes so that the solids separated from the solution. The concentration of the dye after adsorption determined using Genesis-20 Spectrophotometer. The results showed that the Zeolite A synthesized from coal fly ash could be used as an effective adsorbent for Crystal Violet dye. The optimum adsorption occurs at pH 6, and contact time 45 minutes. At the initial concentration of 2 to 6 mg/L, adsorption is reduced from 79 to 62.8%. Crystal Violet dye adsorption in zeolite A fulfilled kinetic model of pseudo-order 2 and model of Freundlich adsorption isotherm.

Mechanism of the Removal of AuCl-4 Ions from Aqueous Solution by Means of Peat Soil Humin

Peat soil humin, obtained after the removal of fulvic and humic acid fractions according to the recommended procedure of the International Humic Substances Society (IHSS), has the ability to remove AuCl−4 ions from aqueous solution. The removal was greatest at medium acidity, which was equivalent to pH 2.0, and it was governed by two different processes, i.e. attachment onto un-ionized –COOH groups through hydrogen bonding and reduction to Au metal by the action of the –OH group. Purification of humin through repeated immersion and shaking in a mixed solution consisting of 0.1 M HCl and 0.05 M HF led to the abrupt increase in the –COOH contents from 386 mmol/kg to 2510 mmol/kg, while the content of total –OH functional groups remained relatively constant at values slightly higher than 3000 mmol/kg. The increase in –COOH content improved the removal of AuCl−4 ions from 23 mg/g to 27 mg/g, but it was unfortunately accompanied by a diminished reduction ability to Au metal. Hence, the role of the –COOH functional group in removing AuCl−4 ions through hydrogen bonding was more significant for the purified humin, while that of the –OH group in removing AuCl−4 ions through reduction to Au metal was better for the crude (unpurified) humin.

Chitosan succinate/PVA-PEG Membrane: Preparation, Characterization and Permeation Ability Test on Creatinine

Evaluation character of chitosan membrane-succinate / poly vinyl alcohol-poly ethylene glycol (PVA-PEG) were prepared in acetic acid solvent through a phase inversion method has been performed. The study began with the preparation of crosslinked chitosan compounds with succinic acid, followed by preparation into membrane by combining PVA-PEG. Character analysis of the resulting material using FTIR, EDX, TGA, water absorption test, tensile strength, membrane hydrophilicity. The ability of membrane permeation was tested against creatinine. The results showed that the succinate had reacted with chitosan. Chitosan modification through cross link and polymer alloys increases tensile strength and membrane strain of 1.7-2.5 x of pure chitosan membrane. In addition, the modified membrane also has higher water absorption and hydrophilicity values than the unmodified membrane, and this implies the ability of membrane-induced creatinine permeation. Permeable permeation values were 13.8% in chitosan, 24.84% on chitosan-succinate and 25% in chitosan-succinate / PVA-PEG. Chitosan-succinate membranes have the ability to use more than 4x repeated use.

Adsorption of Congo Red Dye on HDTMA Surfactant-Modified Zeolite A Synthesized from Fly Ash

Adsorption of anionic dyes Congo Red (CR) on HDTMA surfactant-modified zeolite A has been studied. The zeolite A, which is synthesized from coal fly ash, was modified with surfactant hexdeciltrimethylammonium bromide (HDTMA-Br) as much as 200% cation exchange capacity (CEC) of the zeolite. The effect of pH, contact time and initial concentration on the CR adsorption has been evaluated.The adsorption was carried out in a batch reactor at various pH, contact time and initial concentration on the given temperature. The amount CR adsorption varies as a function of pH, contact time and initial concentration of solution. Adsorption model of Langmuir and Freundlich from empirical data is used for this experiment. The Langmuir isotherm is more suitable for this adsorption. The experimental data fulfilled pseudo second-order kinetic models. The surfactant-modified zeolite A is more effective than zeolite A without modified on the adsorption of CR in aqueous solution.

The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g−1, equilibrium constant (K) was 5.651 (mol/L)−1, and multilayer sorption capacity was 2.646 × 10−2 mol g−1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. ...

Synthesis of Silver Nanoparticles Using o-Hydroxybenzoic, p-Hydroxybenzoic, and o,p-Dihydroxybenzoic Acids as Reducing Agents

Synthesis of silver nanoparticles (AgNPs) by reduction of AgNO3 with o-hydroxybenzoic, p-hydroxybenzoic and o,p-dihydroxybenzoic acids as reducing agents was investigated. This research was conducted to determine the effect of the position and number of hydroxyl groups towards the size, shape and stability of the resulted AgNPs. Surface Plasmon Resonance (SPR) of AgNPs was characterized by UV/Vis spectrophotometer, the shape and size of AgNPs was determined by Transmission Electron Microscope (TEM). The results showed that the reducing agent that has substituents in the para position (p-hydroxybenzoic acid) has the higher reduction ability than the others. AgNPs were yielded by all types of reducing agents in alkaline system. Reducing agents which have greater number of substituents (o,p-dihydroxybenzoic acid) could produce AgNPs with smaller concentration of AgNO3 than the others. AgNPs that was produced by reducing agent having substituents on the para position (p-hydroxybenzoic acid) was more stable and smaller particle size, i.e. 34 ± 1.78 nm than reducing agent that has substituent on the ortho para positions (with particle size 45 + 3.67 nm) and ortho positions (with particle size 70 ± 4.96 nm).

Synthesis of Gold Nanoparticle from Adsorbed Au on Hydrotalcite Using SDS and Sodium Citrate as Capping Agent and its Recovery into Pure Gold

Gold nanoparticles (AuNPs) have been synthesised from adsorbed Au on hydrotalcite (Mg/Al HT-AA-Au) using SDS (sodium dodecyl sulfate) and sodium citrate as capping agent. Then, the nanoparticles were recovered into pure gold by centrifugation. It is shown that sodium citrate has better activity compared to SDS as the capping agent. The electronic spectra of the resulted AuNPs showed that the optimum pH, sodium citrate concentration and time of sonication were 5, 70 mM, and 2 h, respectively. The results showed that the average size of AuNPs was 32 nm at SPR 531 nm. By centrifugation at 13000 rpm for 8 min, gold dust of Au(0) can be obtained from the gold nanoparticles capped sodium citrate. Based on infrared spectra and XRD, it is proven that the gold dust still contains citric and Mg/Al HT.