Reaksi Hidrolisis Minyak Zaitun Menggunakan Lipase Rhizopus oryzae yang di Imobilisasi Melalui Metode Adsorpsi

Reaksi Hidrolisis Minyak Zaitun Menggunakan Lipase Rhizopus oryzae yang di Imobilisasi Melalui Metode Adsorpsi 

Abstrak 

Immobilisasi merupakan teknik  recovery enzim yang menjadi perhatian dalam beberapa tahun belakangan, dilakukan dengan bantuan  support sebagai media yang dapat mencegah terlarutnya enzim. Metode immobilisasi yang digunakan pada penelitian ini adalah metode adsorpsi, dengan menggunakan lipase Rhizopus oryzae. Reaksi yang diamati adalah reaksi hidrolisis minyak zaitun dalam sistem emulsi minyak-air. Beberapa macam support seperti kitin, silika gel, Al2O3, CaCO3, dan latex diseleksi berdasarkan kemampuannya  dalam mengadsorb lipase. Reaksi hidrolisis dengan  free lipase pada jam ke-8 memperlihatkan konversi hidrolisis mencapai 29.46 %. Kitin dan silika gel memiliki enzim  loading masing-masing 68.67 %, 56.62 %, lebih besar dibandingkan Al2O3  (50.60 %), CaCO3 (46.98 %), dan  latex (43.37 %). Silika gel dan kitin disimpulkan sebagai support terbaik untuk immobilisasi adsorpsi. Waktu adsorpsi optimal kitin dan silika gel dalam meng-immobilisasi lipase adalah selama 3 jam. Lipase pada  support kitin memiliki konversi hidrolisis 24.7 %, lebih tinggi dibanding lipase silika gel sebesar 19.9 %. Lipase bekerja optimal pada pH 7 dan temperatur 37oC. Hal ini berlaku untuk free lipase maupun lipase ter-immobilisasi. Lipase ter-immobilisasi dalam uji stabilitas dapat dioperasikan sampai pada penggunaan ke-3 kali, reaksi selanjutnya menghasilkan konversi hidrolisis dibawah 5 % yang dianggap sudah tidak ekonomis untuk dilanjutkan. 

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A comparative study of hydrothermal and sol–gel methods in the synthesis of MnO2 nanostructures

A comparative study of hydrothermal and sol–gel methods in the synthesis of MnO2 nanostructures

Abstract 

In this work, MnO2 nanostructure powders with different crystalline phases have been successfully prepared by hydrothermal and sol–gel methods. The obtained products were characterized by XRD and SEM techniques and their crystallographic phases and morphological properties compared. Results showed that a-MnO2, b-MnO2, and d-MnO2 nanorods were synthesized by hydrothermal method and c-MnO2 polymorph was obtained by sol–gel method.

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Novel Synthesis and Characterization of Thiosemicarbazone Compounds Containing 4-Acyl-2-pyrazolin-5-ones

Novel Synthesis and Characterization of Thiosemicarbazone Compounds Containing 4-Acyl-2-pyrazolin-5-ones

Abstract:  

A novel synthesis of 4-acylthiosemicarbazone-3-methyl-1-(4`-methylphenyl)-2-pyrazolin-5-one by condensation  of  4-acyl-3-methyl-1-(4`-methylphenyl)-2-pyrazolin-5-one  with  thiosemicarbazide  is  carried  out.  The compounds were characterized on the basis of elemental analysis, IR, 1H NMR, Mass, DSC  and 

13C NMR  spectral  data.  The  structures were  investigated  for  their  antibacterial  and  antifungal  activity.  They  are  very  essential  to  study  on cerebral infarction (Free radical scavenger). A single crystal X-ray study of this thiosemicarbazones and their metal complexes is in progress. 

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Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

Abstract:

A tangential filtration process was implemented in this study using porous ceramic tubes made of -alumina produced by the slip-casting technique. These tubes were sintered at 1450 ◦C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 m. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 ◦C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600◦C showed the best demulsification performance, with the concentration on permeate smaller than 10mg/L. The impregnated tube sintered once at 900 ◦C presented low carbon concentration (smaller than 20mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube.

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Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA

Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA

Abstract:

Lithium manganese oxide (LiMn2O4) powder with spinel structure has been synthesized by a sol-gel method using an aqueous solution of metal nitrates containing polyvinyl alcohol (PVA). The role of PVA and the calcination conditions for the formation of LiMn2O4 have been studied. Homogeneity and reactivity of the precursor powder are enhanced with an increase in the amount of PVA in the starting solution. When the amount of PVA is low, an impurity phase-Mn2O3 is formed at low temperature. On the other hand, when the vinyl alcohol monomer unit of PVA to metal ion ratio is 2 : 1 in the starting solution, only spinel phase is formed at 180± C and organic-free LiMn2O4 powder is obtained at as low as 400± C. Nanosized LiMn2O4 particles with a narrow size distribution have been successfully prepared by this technique. This method with proper amount of PVA results in much lower calcination temperature and shorter calcination time for producing the single spinel phase in comparison with the conventional solid state reaction and other solution techniques.

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Synthesis and Characterization of Manganese Oxide Catalysts for the Total Oxidation of Ethyl Acetate

Synthesis and Characterization of Manganese Oxide Catalysts for the Total Oxidation of Ethyl Acetate

Abstract:

Manganese oxide catalysts were synthesized by direct reaction between manganese acetate and permanganate ions, under acidic and reflux conditions. Parameters such as pH (2.0–4.5) and template cation (Na?,K? and Cs?) were studied. A pure cryptomelane-type manganese oxide was synthesized under specific conditions, and it was found that the template cation plays an important role on the formation of this kind of structure. Cryptomelane was found to be a very active oxidation catalyst, converting ethyl acetate into CO2 at low temperatures (220 C). This catalyst is very stable at least during 90 h of reaction and its performance is not significantly affected by the presence of water vapour or CO2 in the feed stream. The catalyst performance can be improved by the presence of small amounts of Mn3O4.

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Characterisation of K, Na, and Li birnessites prepared by oxidation with H2O2 in a basic medium. Ion exchange properties and study of the calcined products

Characterisation of K, Na, and Li birnessites prepared by oxidation with H2O2 in a basic medium. Ion exchange properties and study of the calcined products

Abstract:

Birnessites containing Na, K or Li in the interlayer have been prepared by oxidation of Mn(II) cations with H2O2 in a basic medium with different alkaline cation/Mn molar ratios. The solids prepared have been characterised by elemental chemical analysis, powder X-ray diffraction, thermal analyses (differential thermal analysis and thermogravimetric analysis), FT-IR spectroscopy and surface texture assessment by adsorption of N2 at −196◦C. Crystalline birnessites are obtained for A/Mn ratios (A = K, Li) larger than 3.4, but MnO(OH) has been also identificed when such a ratio is smaller than 3.4. Ion exchange is topotactic, but is not complete for exchanging Na, K, or Mg for pre-existing Li. The solids are stable up to 400◦ C, and formation of spinels and solids with tunnel structures is observed at this temperature. Li-containing birnessites are transformed to LiMn2O4 spinel at 400◦C, and co-crystallization of bixbyte (Mn2O3) is observed at higher temperatures. Bixbyte and cryptomelane are formed at 500◦C for the K-containing birnessites.

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Chalcones, Pyrazolines and Aminopyrimidines as Antibacterial Agents

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