Suyanta

Bio: Suyanta is an academic researcher from Gadjah Mada University. The author has contributed to research in topics: Montmorillonite & Colloidal gold. The author has an hindex of 1, co-authored 3 publications receiving 4 citations.

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

Abstract: 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.

Recyclable Clay-Supported Heteropolyacid Catalysts for Complete Glycolysis and Aminolysis of Post-consumer PET Beverage Bottles

Abstract: In this investigation, the use of phosphotungstic acid (PWA) and phosphomolybdic acid (PMA) as well as Zn2+ containing kaolin and bentonite explored for chemical recycling of post-consumer poly(ethyleneterephthalate) (PET) wastes have been explored. The clay supported catalysts containing 5wt% of the metals and heteropolyacids (HPAs) synthesized using wet impregnation method. Nitrogen adsorption and desorption studies, SEM–EDX mapping, powder XRD, FTIR and XPS analysis have evaluated effect of metal ions and HPAs loading on the surface area, pore volume, elemental composition and crystalline nature. Total surface area of BET increased with a loading of 5 wt% of Zn2+, PWA and PMA on kaolin and bentonite, while the pore volume and pore diameter remain unchanged. SEM and EDAX mapping images showed that the heteropolyacids crystals are well dispersed on the surface and occupied interlayer spaces of the clay support. SEM–EDX showed that bentonite showed a better loading of PWA and PMA compared to kaolin. PET waste water bottles collected from the local market used for the chemical recycling process. The aminolysis reaction using Zn2+ and PWA loaded on bentonite showed complete depolymerisation of PET wastes to produce 87–98% of BHETA. The glycolysis reaction using the above catalysts showed complete depolymerisation at 180–210 °C and yielded 78–90% of BHET. When comparing the clay, bentonite performed well in terms of heteropolyacid loading and afforded a higher yield of BHET and BHETA because of higher loading of Zn and HPA, as supported by SEM–EDX and XPS. We also examined reusability of the catalysts for glycolysis.

Removal of Acidic Dye from Aqueous Solution Using Surfactant Modified Bentonite (Organoclay): Batch and Kinetic Study

Abstract: Modified bentonite has been used as effective sorbent material for the removal of acidic dye (methyl orange) from aqueous solution in batch system. The natural bentonite has been modified using cationic surfactant (cetyltrimethyl ammonium bromide) in order to obtain an efficient sorbent through converting the properties of bentonite from hydrophilic to organophilic. The characteristics of the natural and modified bentonite were examined through several analyses such as Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Surface area. The batch study was provided the maximum dye removal efficiency of 88.75 % with a sorption capacity of 555.56 mg/g at specified conditions (150 min, pH= 2, 250 rpm, and 0.5 g/100 ml). The-results-showed that with the Freundlich isotherm model the sorption data was accurately described with (R2≥0.94) in comparison with the Langmuir model under the studied conditions. The kinetic studies were revealed that the sorption follows a pseudo-second-order kinetic model which indicates chemisorption between sorbent and sorbate molecules.