Dwi Siswanta

In vitro hemocompatibility of PVA-alginate ester as a candidate for hemodialysis membrane.

Alginate based biopolymer with improved physical and chemical properties after esterification using polyvinyl alcohol (PVA) has been studied for possible application as a hemodialysis membrane. The alginic acid to vinyl alcohol molar ratio was predetermined at 0, 0.1, 0.5 and 1. Mechanical strength, hydrophilicity and Ca(2+) adsorption of the membrane before and after modification were evaluated. The obtained PVA-alginate (PVA-Alg) ester membrane was also confirmed using FTIR and SEM. It shows that the PVA-Alg membrane tensile strength is higher than that of native alginate. The water contact angle of the membrane was found to be around 33-50°. The Ca(2+) adsorption capacity tends to decrease with the increase in molar ratio. Furthermore, the modified PVA-Alg ester membrane achieves better protein adsorption and platelet adhesion than the unmodified one. It also exhibits a dialysis performance of 47.1-50.0% for clearance of urea and 42.2-44.6% for clearance of creatinine, respectively. It is expected that this PVA-Alg ester may challenge cellulose acetate for potential application as hemodialysis membranes.

Sensitivity Improvement of Ammonia Gas Sensor Based on Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) by Employing Doping of Bromocresol Green

The aim of this research is to improve the sensitivity of ammonia gas sensor (hereafter referred to as sensor) based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) by employing the doping dye of bromocresol green (BCG). The doping process was carried out by mixing the BCG and the PEDOT:PSS in a solution with an optimum ratio of 1 : 1 in volume. The sensor was fabricated by using spin-coating technique followed by annealing process. For comparison, the BCG thin film and the PEDOT:PSS thin film were also deposited with the same method on glass substrates. For optical characterization, a red-light laser diode with a 650 nm wavelength was used as light source. Under illumination with the laser diode, the bare glass substrate and BCG film showed no absorption. The sensor exhibited linear response to ammonia gas for the range of 200 ppm to 800 ppm. It increased the sensitivity of sensor based on PEDOT:PSS with BCG doping being about twofold higher compared to that of without BCG doping. Furthermore, the response time and the recovery time of the sensor were found very fast. It suggests that the optical sensor based on BCG-doped PEDOT:PSS is promising for application as ammonia gas sensor.

Adsorption of gold(III) on ionic imprinted amino‑silica hybrid prepared from rice hull ash

In this research, the adsorption of Au(III) ion on ionic imprinted amino-silica hybrid (Im-ASH) in aqueous solution has been studied. Im-ASH was synthesized via sol-gel technique using a solution of sodium silicate (Na2SiO3) from rice hull ash (RHA) as the precursor and Au(III) ion as the template. Adsorption was carried out in a batch system with variation of pH, contact time, and Au(III) ion concentration. The selectivity of adsorbent toward Au(III) was examined in the presence of Cu(II) ion. The result of the kinetic study demonstrated that the adsorption of Au(III) ion followed pseudo-second order. The optimum adsorption of Au(III) on Im-ASH and non-Im-ASH was obtained at pH of 3.0. Im-ASH was twice as selective toward Au(III) ion than ASH was.

Dairy products discrimination according to the milk type using an electrochemical multisensor device coupled with chemometric tools

This study shows the potential application of a potentiometric electronic tongue coupled with a lab-made DataLogger device for the classification of dairy products according to the type of milk used in their production, i.e., natural, fermented and UHT milk. The electronic tongue device merged a commercial pH electrode and 15 lipid/polymeric membranes, which were obtained by a drop-by-drop technique. The potentiometric signal profiles gathered from the 16 sensors, during the analysis of the 11 dairy products (with ten replicate samples), together with principal component analysis showed that dairy samples could be naturally grouped according to the three types of milk evaluated. To further investigate and verify this capability, a linear discriminant analysis together with a simulated annealing variable selection algorithm was also applied to the electrochemical data, which were randomly split into two datasets, one used for model training and internal-validation using a repeated K-fold cross-validation procedure (with 64% of the data); and the other for external validation purposes (containing the remaining 36% of the data). The multivariate supervised strategy used allowed establishing a classification model, based on the potentiometric information of four sensor lipid membranes, which enabled achieving a successful discrimination rate of 100% for both internal- and external-validation processes. The demonstrated versatility of the built electronic tongue for discriminating dairy products according to the type of milk used in their production combined with its simplicity, low-cost and fast time analysis may envisage a possible future application in dairy industry.

A novel Arduino Mega 2560 microcontroller-based electronic tongue for dairy product classification

An electronic tongue (e-tongue) consisted of a sensor array of the ion-selective electrode based on lipid/polymer membranes has been developed. The e-tongue consisted of 8 sensors with gold electrodes and equipped with an Arduino Mega 2560 Microcontroller-based data acquisition system. The lipid/polymer membranes were fabricated by combining polyvinyl chloride (PVC) as a matrix, 4 different kinds of plasticiser material (2-NPOE, bis(2-ethylhexyl) sebacate, bis(2-ethylhexyl) phosphate, and cis(1-butyl pentyl) adipate), and 4 different kinds of lipids (octadecyl amine, oleoyl alcohol, methyl trioctylammonium chloride, and oleic acid) for an active material. Potentiometric measurements were carried out with a reference electrode Ag/AgCl. Data logger was equipped with a moving average filter for reducing the noise. From the score plot of principal component analysis (PCA), the first and second PCs contribute 90.5% of the total variance. It indicates that the developed e-tongue is able to classify dairy products according to the types and brands.

Preparation of crosslinked carboxymethyl chitosan with epichlorohydrin and its use for Pb(II) removal

A modified pectin has been synthesized by reacting/combining -OH group among pectin and chitosan with ECH (Epichlorohydrin) croslinker agent. Chitosan was grafted with acetate to form carboxymetyl chitosan (CMC). The result of this study was Pectin-CMC-ECH film could be greater adsorp Pb(II) ion than chitosan without modified. The structure of Pectin-CMC-ECH film was characterized by Fourier transform infrared (FTIR) spectroscopy. Adsorption experiment were performed in batch processes; Result of the study showed that optimum conditions for the adsorption of Pb(II) on the adsorbent were found at pH 5 with with 93 % of adsorption and adsorption capacity was 42.77 mg/g, contact time 12 hour with 91 % of adsorption and adsorption capacity was 39.74 mg/g. Pectin-CMC-ECH film demonstrate the ability to absorb Pb (II) metal ions was higher than chitosan without modified.

THE INFLUENCE OF PVA.cl.CITRIC ACID/CHITOSAN MEMBRANE HYDROPHICILITY ON THE TRANSPORT OF CREATININE AND UREA

The influence of cross-linking and membrane hydrophilicity on the transport rate had been studied using a membrane prepared from a mixture of chitosan/PVA cross-linked citric acid (PVA.cl.CA) for creatinine and urea transport. The optimum mole ratio of PVA:citric acid as well as the best composition of chitosan:PVA.cl.CA were determined using creatinine transport study. Using the optimum compositions, further study was done using different thickness of the membrane in transporting creatinine, urea and a mixture of 3 species (creatinine, urea and vitamin B12). Membrane characterization was done using FT-IR spectrophotometer, water absorption test, TG/DTG and SEM. The results showed that the optimum composition PVA:citric acid was obtained to be 90:1, having % WU of 113.74% and creatinine transport percentage of 18.16%. Meanwhile, the optimum composition of chitosan:PVA.cl.CA was found at 4:6 ratio having % WU and % transport of 136.67% and 24.26%, respectively. The optimum transport capacity was found for membrane thickness of 50 μm with WU% at 139.61% and the percent transport of creatinine and urea each was 38.93% and 60.36%. The presence vitamin B12 in the solution of is proved to disturb the transport of creatinine and urea through the membrane. Finally, hydrophilicity seemed to give substantial contribution in the transport process as well as the mechanical strength of the membrane.

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.

Preparation and Characterization of Composite Membrane Chitosan-Silica-Polyethylene Glycol

Chitosan membrane (Ch) has mechanical stability, physical, and chemical low thus limiting their application to a variety of purposes. Therefore in this study examined the effect of adding silica and polyethylene glycol (PEG) on the mechanical properties, physical, and chemical chitosan-based membranes. A source of silica used is tetraethyl orthosilicate (TEOS). Composite membrane Chitosan-silica-PEG (Ch/Si/P) was prepared using the sol-gel process and characterized morphology, crystallinity, and changes in functional groups. In general, the addition of silica in the preparation of composite membrane Ch/Si, increases tensile strength, Youngs Modulus, pore size distribution, as well as lower percent Elongation but does not affect the crystallinity and the change of functional groups on the membrane. The addition of PEG on manufacture composite membrane Ch/Si/P, increases the percent Elongation, Youngs Modulus decrease and decreased pore size distribution, but does not affect the crystallinity, as well as to changes in the functional groups on the membrane. The results showed that membrane with a mass ratio of chitosan/silica/PEG of 1:0.7:0.5 have a maximum percent Elongation and the minimum Youngs Modulus.

The preparation of polyelectrolyte complexes carboxymethyl chitosan(CMC)-pectin by reflux method as a Pb (II) metal ion adsorbent

Aim of this research is to synthesized a chemically stable polyelectrolyte complexs carboxymetyl chitosan CMC-pectin as Pb(II) ion adsorbent by reflux method. During synthesis process, the optimum mass ratio of CMC and pectin was pre-determined and the active groups of the CMC-pectin complex was characterized by using IR spectrofotometer. Finally, adsorption capacity of the adsorbent material for Pb (II) ions was studied under optimum condition, i.e. adsorbent mass, contact time, and pH. Result shows that CMC could be succesfully combined with pectin to produce CMC-pectin complex. The optimum mass ratio CMC: pectin to form the polyelectrolyte complexs CMC-pectin was 70% : 30%. The active groups identified in the CMC-pectin complex was a hydroxyl (OH) and carboxylate (-COOH) groups. The optimum conditions for Pb (II) ion absoprtion was 10 mg of the adsorbent mass, 75 min of contact time, and pH 5. This material can be effectively used as adsorbents for Pb (II) ions, where up to 91% Pb (II) metal ions was a...