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All Journal Jurnal Rekayasa Proses Jurnal MEKANIKAL Reaktor International Journal of Science and Engineering (IJSE) TEKNIK Jurnal Kesehatan Lingkungan indonesia JURNAL TEKNOLOGI KIMIA DAN INDUSTRI Prosiding Seminar Nasional Sains Dan Teknologi Fakultas Teknik Bulletin of Chemical Reaction Engineering & Catalysis Majalah Ilmiah MOMENTUM Emerging Science Journal Indonesian Journal of Chemistry JURNAL PANGAN Jurnal Pasopati : Pengabdian Masyarakat dan Inovasi Pengembangan Teknologi Bulletin of Chemical Reaction Engineering & Catalysis

Ratnawati Ratnawati

Department Of Chemical Engineering Faculty Of Engineering Diponegoro University

Author-ID : 2956117

Aerospace Engineering Agriculture, Biological Sciences & Forestry Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Computer Science & IT Control & Systems Engineering Earth & Planetary Sciences Education Electrical & Electronics Engineering Energy Engineering Environmental Science Industrial & Manufacturing Engineering Materials Science & Nanotechnology Mechanical Engineering Public Health Social Sciences

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IMPROVEMENT OF THE REDLICH-KWONG EQUATION OF STATE BY MODIFICATION OF CO-VOLUME PARAMETER Ratnawati Ratnawati
Reaktor Volume 13, Nomor 1, Juni 2010
Publisher : Dept. of Chemical Engineering, Diponegoro University

Cubic equations of state are widely used in phase-equilibrium calculations because of their simplicity and accuracy. Most equations of states are not accurate enough for predicting density of liquid and dense gas. A modification on the Redlich-Kwong (RK) equation of state is developed. Parameter b is modified by introducing a new parameter,b, which is a function of molecular weight and temperature. The modification gives a significant improvement over the original RK equation for predicting density. For 6538 data points of 27 compounds, the proposed equation gives only 2.8% of average absolute deviation (AAD), while the original RK and the Soave-Redlich-Kwong (SRK) equations give 11.4% and 11.7%, respectively. The proposed modification improves the performance of the RK equation for predicting vapor pressure as well. For 2829 data points of 94 compounds, the proposed modification lowers the AAD of the RK equation from 1460% down to 30.8%. It is comparable to the famous SRK equation, which give 5.8% of AAD. The advantage of the proposed equation is that it uses only critical pressure and temperature as other equations of states do, and molecular weight, which is easily calculated. Another advantage is that the proposed equation simpler than the SRK equation of state.

PADDY DRYING IN MIXED ADSORPTION DRYER WITH ZEOLITE: DRYING RATE AND TIME ESTIMATION Mochammad Djaeni; Dewi Ayuningtyas; Nurul Asiah; Hargono Hargono; Ratnawati Ratnawati; Wiratno Wiratno; Jumali Jumali
Reaktor Volume 14, No. 3, APRIL 2013
Publisher : Dept. of Chemical Engineering, Diponegoro University

Recently, the main problem of the rice stock and distribution in Indonesia is the quality degradation as indicated in unpleasant odor (smelly), stained, yellowness, and high percentage of broken rice. This is due to the low of paddy quality dried by from either direct sunlight or conventional fluidized bed dryer. As a result, the paddy cracks and breaks easily during milling in which causes the storage life being shorter as the enzymatic degradation by germ or fungi occurs. Air dehumidified with zeolite at drying medium temperature is potential to improve the quality of paddy. Zeolite is a material having high affinity to water vapor. In this case, the paddy and zeolite was mixed and fluidized with the air. The air will evaporate water from paddy, and at same time, the zeolite will adsorb water from air. Hence, the humidity of dryer can be kept low in which improves the driving force for drying. This work discusses the effect of presence of zeolite in the dryer, operational drying temperature, air velocity and relative humidity on drying rate of paddy. The results showed that increasing of zeolite as well as operational temperature increased the drying rate. In addition, using the model, the air dehumidification with zeolite and increase of air velocity can speed up drying time significantly at operational temperature below 80oC. This condition is very suitable for paddy drying since the quality degradation can be avoided.

AKUMULASI LISTRIK STATIS PADA GELAS PLASTIK PRODUKSI MESIN INJECTION MOLDING: PENGARUH KELEMBABAN UDARA, TEMPERATUR, DAN BAHAN ADITIF Ratnawati Ratnawati; Aprilina Purbasari; Yustina Linasari
Reaktor Volume 14, No. 4, OKTOBER 2013
Publisher : Dept. of Chemical Engineering, Diponegoro University

Akumulasi listrik statis pada gelas polipropilena hasil produksi mesin injection molding dapat menyebabkan gelas memiliki gaya elektrostatik dan tidak dapat turun secara gravitasi. Masalah ini menghambat aplikasi gelas pada mesin pengisian air minum dalam kemasan (AMDK). Penelitian ini bertujuan untuk mengetahui pengaruh kelembaban udara, temperatur, dan penambahan bahan aditif TiO2 terhadap potensial listrik permukaan gelas polipropilena. Hasil penelitian menunjukkan bahwa potensial listrik permukaan dipengaruhi oleh kelembaban udara ruang produksi, temperatur, dan penambahan TiO2. Potensial listrik permukaan semakin kecil dengan naiknya kelembaban udara. Setelah kelembaban mencapai 68% potensial listrik permukaan cenderung konstan. Ditinjau dari beda potensial (DV) antara permukaan dua gelas, kelembaban optimum adalah 67-68%, yang ditandai dengan beda potensial yang paling rendah. Beda potensial ≤ 5,2 kV menyebabkan gelas cepat turun, beda potensial 5,2 kV < DV ≤ 6,7 kV menyebabkan gelas turun dengan lambat, dan DV ≥ 6,7 kV menyebabkan gelas sangat lambat turun atau menempel. Potensial listrik turun dengan naiknya temperatur. Potensial listrik statis permukaan hanya sedikit turun akibat penambahan 0,75% berat TiO2. Hasil penelitian ini juga menunjukkan bahwa penggunaan gelas dengan potensial listrik permukaan rendah dapat menaikkan kecepatan mesin pengisian AMDK menjadi 220-250 rpm dan 140-160 rpm, masing-masing untuk mesin pengisian gelas 180 ml dan 225 ml.

Effect of pH and Gas Flow Rate on Ozone Mass Transfer of Κ-Carrageenan Solution in Bubble Column Reactor Aji Prasetyaningrum; Dyah Arum Kusumaningtyas; Purbo Suseno; Ratnawati Ratnawati
Reaktor Volume 18 No. 4 December 2018
Publisher : Dept. of Chemical Engineering, Diponegoro University

This research was conducted to calculate the mass transfer coefficient value for ozonation reaction of κ-carrageenan solution in the bubble column reactor. Ozone gas was produced using ozone generator type corona discharge. In this study, operating conditions were regulated at ozone gas flow rate 2- 5 L min-1, pH 4-10, and temperature 29 ± 1 oC. Samples were tested every 5 minutes to determine the dissolved ozone concentration. The results showed that dissolved ozone concentrations increased with increasing ozonation time and ozone gas flow rate. However, a very high gas flow rate can increase turbulence so that the mass transfer coefficient (kLa) value decreased. In alkaline conditions, the formation of free radicals (HO*) increases so that the amount of dissolved ozone decreases. The kLa value of ozone gas in κ-carrageenan solution is slightly lower than the kLa value of the ozone gas in the water. The results of this study indicate that (kLa) ozone gas in water is 0.131 / minute while the value (kLa) in κ-carrageenan solution is 0.128 / minute.Keywords: ozone; mass transfer; pH; flowrate

Encapsulation of Lemongrass Extract (Cymbopogon citratus) Coated Alginate/Chitosan Using Gelation Method Aji Prasetyaningrum; Sadam Arrois; Fitri Lafifa; Aat Zaki Mubarok; Fadlillah Fani; Noer Abyor Handayani; Ratnawati Ratnawati; Bakti Jos
Reaktor Volume 21 No. 3 September 2021
Publisher : Dept. of Chemical Engineering, Diponegoro University

Lemongrass (Cymbopogon citratus) is a medicinal plant with various biological activities such as antibacterial, antifungal, antiprotozoal, anti-inflammatory, and antioxidant. This study aimed to encapsulate lemongrass bioactive in alginate/chitosan complex by enhancing the properties of CaCl2 crosslinked incorporated with tween 80 by ionic gelation method. The hydrogel was prepared by mixing alginate solution (2% w/v) and chitosan solution (1% w/v) with a ratio (1:1 v/v). Tween 80 (2% v/v) was added as a dissolution enhancer and CaCl2 as a crosslinker agent. The formulation varying by concentration of CaCl2 (0.1M to 0.3M) and lemongrass extract (2% to 12%). Encapsulation lemongrass with alginate-chitosan beads is characterized to determine encapsulation efficiency, swelling study, morphology, functional groups, and release study. The results showed that encapsulation efficiency ranged from 74.81% to 83.07%. Encapsulation efficiency increased with the addition of CaCl2 and lemongrass extract concentration. The swelling ratio ranged from 27.29 to 37.81, it will decrease with the addition of CaCl2 and lemongrass extract concentration. The Scanning Electron Microscopy (SEM) analysis of hydrogel beads shows a polyhedral shape, porous, and rough surface which indicates bioactive of lemongrass trapped on the beads. The Fourier Transform Infrared Spectroscopy (FTIR) results show new peaks at 1734 cm-1 as carbonyl stretch vibrations in ketones, aldehydes, and carboxylic acids, indicating the addition of lemongrass extract. Bioactive of lemongrass extract loaded alginate-chitosan beads was successfully released as much as 87.12% at pH 6.8. This study suggested the strong potential alginate-chitosan beads as an encapsulating agent for lemongrass extract using the ionic gelation method, and it has potential as a drug delivery system.Keywords: encapsulation; lemongrass; alginate; chitosan; CaCl2

Optimasi Proses Ozonasi pada Depolimerisasi κ-Karagenan dengan Metode Respon Permukaan Aji Prasetyaningrum; Ratnawati Ratnawati; Bakti Jos
Reaktor Volume 17 No.1 Maret 2017
Publisher : Dept. of Chemical Engineering, Diponegoro University

Abstract OPTIMIZATION OF OZONATION PROCESS FOR κ-CARRAGEENAN DEPOLYMERIZATION USING RESPONSE SURFACE METHODOLOGY. The objective of this research is to optimize the operating parameters in depolymerization of κ-carrageenan by ozone treatment. The optimization is done by using Box-Bhenken Design (BBD) model with ozonation time (5-15 minute), pH (3-11) and temperature (20-40oC) as the independent variables.The response of ozonation process is the degree of depolymerization of κ-carrageenan (DP). The initial molecular weight of refined κ-karagenan was 271 kDa. The κ-carrageenans powder was completely dissolved in distilled water to form 1% (weight/volume). The experiments were carried out in a 2000 ml of a glass reactor with an ozone gas sparger. The inlet ozone concentration was 80±2 ppm. The result shows that ozonation time, pH and temperature have significant effects during ozonation process (p< 0.05). Analysis of variance shows that the experimental data fit the model very well with the R2 value of 0.98. The optimum conditions during ozonation process are achieved at the reaction time of 15 min, ozonation pH of 3 and reaction temperature of 25oC. Under these optimum conditions the DP of κ-carrageenan is 91.513%. Keywords: depolymerization; κ-carrageenan;optimization; ozonation process Abstrak Tujuan penelitian ini adalah menentukan kondisi optimum parameter operasi depolimerisasi κ-karagenan dengan perlakuan ozonasi. Optimasi dilakukan dengan menggunakan model statistika Box-Bhenken Design (BBD) dengan variabel yang digunakan yaitu waktu ozonasi (5-15 menit), pH (3-11), dan suhu (20-40oC). Respon dari proses ozonasi adalah derajat depolimerisasi κ-karagenan (DP). Berat molekul awal refined κ-karagenan adalah 271 kDa. Sampel κ-karagenan dilarutkan secara sempurna dalam air distilasi dan konsentrasi diatur 1% (berat/volume). Percobaan dilakukan dalam reaktor gelas volume 2000 ml yang dilengkapi dengan sparger gas ozon. Konsentrasi gas ozon yang masuk adalah 80±2 ppm. Hasil penelitian menunjukkan bahwa waktu ozonasi, pH, dan suhu berpengaruh secara signifikan terhadap proses ozonasi (p<0,05). Analisis varian menghasilkan ketelitian yang tinggi antara data eksperimen dan prediksi, dengan nilai koefisien R2 = 0,98. Kondisi optimum diperoleh pada waktu ozonasi 15 menit, pH ozonasi 3 dan temperatur reaksi 25oC. Pada kondisi optimum ini diperoleh DP κ-karagenan sebesar 91,513%. Kata kunci:depolimerisasi; κ-carrageenan;optimasi; proses ozonasi

VAN DER WAALS MIXING RULES FOR THE REDLICH-KWONG EQUATION OF STATE. APPLICATION FOR SUPERCRITICAL SOLUBILITY MODELING Ratnawati Ratnawati
Reaktor Volume 10, Nomor 2, Desember 2006
Publisher : Dept. of Chemical Engineering, Diponegoro University

A solid-supercritical fluid system is highly asymmetric in terms of the size and energy differences of the components. The key point in extending a cubic equation of state to such system is on the choice of proper mixing rules. New mixing rules for the Redlich-Kwong equation of state are developed. The developement is based on the statistical-mechanical theory of the van der Waals mixing rules. The Redlich Kwong equation of state with the proposed mixing rules along with the original ones is used to predict solubilities of solids in supercritical fluid. The prediction is done with kij equal zero, as well as with optimized kij. The results show superiority of the proposed mixing rules over the original ones. For most of the systems considered, the proposed mixing rules with the kij equal zero are closer to the experimental data than the original ones do. For 28 systems with 521 data points taken from various sources, the original and the proposed mixing rules give the overall AAD of 13.4%, while the original mixing rules give 45.9%.

The Impact of Combination of Ozonation and Ultrasonication Process on Morphological and Chemical Properties of κ-Carrageenan Nurfiningsih Nurfiningsih; Ratnawati Ratnawati; Aji Prasetyaningrum
Reaktor Volume 19 No. 2 June 2019
Publisher : Dept. of Chemical Engineering, Diponegoro University

Carrageenan application in the biomedical field is influenced by the size of molecular weight. Depolymerization process is needed for changing the high molecular weight (HMW) fraction of κ- carrageenan into low molecular weight fraction (LMW) of κ- carrageenan. Ozone is a powerful oxidant and considered for depolymerization of κ- carrageenan. This research was conducted as an investigation on the influence of the combination of ozonation and ultrasonication (OZ/US) on the chemical and morphological characteristics of κ-carrageenan. FTIR and Scanning electron microscopy (SEM) was used to determine the change of chemical and morphological characteristics of κ-carrageenan. The result of this study showed that there was no change of chemical properties of κ-carrageenan during OZ/US treatment. The sulfate content was obtained after OZ/US treatment tends to be stable. Nevertheless, the result of SEM analysis showed that there were changes on morphological characteristics of κ-carrageenan after OZ/US treatment. Keywords: ultrasonication, κ-carrageenan, ozonation, morphological, chemical

Prediction Of Solubility Of Solid N-Paraffins In Supercritical Fluids Using Modified Redlich-Kwong Equation Of State Ratnawati Ratnawati
Reaktor Volume 08 No.1 Juni 2004
Publisher : Dept. of Chemical Engineering, Diponegoro University

Three equation of state are used to predict solubilities of solid n-pafaffins in supercritical fluids. The equations are the Redlich-Kwong, the Soave-Redlich-Kwong, and equation proposed by Hartono et.al. (2003; 2004). Both the last two equations were formed by modificating the Redlich-Kwong equqtion of state. With the binary interactions parameter, kif , equals zero, the equations proposed by Hartono et.al. is better than both the Redlich-Kwong and the Soave-Redlich-Kwong equations of state are. Upon optimization with kif as the adjustable parameter, the equation of state proposed by Hartono et.al. is closer to the experimental data than the other equqtions are. For 142 data points of 12 systems the equation proposed by Hartono et. Al. gives the average deviation of 36.6%, while the Redlich-Kwong and the Soave-Redlich-Kwong give 66.7% and 65.8%, respectively.Keywords : equation of state, solubility, supercritical

Nutritional Characteristics and Potential Applications of Flour Prepared from Indonesian Wild White Yam (Dioscorea esculenta L.) Diah Susetyo Retnowati; Ratnawati Ratnawati; Andri Cahyo Kumoro
Reaktor Volume 19 No. 2 June 2019
Publisher : Dept. of Chemical Engineering, Diponegoro University

Gembili or wild white yam (Dioscorea esculenta L.) is one of underutilized tubers that can be found during dry season in Indonesia and other Southeast Asian countries. Although it has been consumed as staple food by people for centuries during famine, no further studies have been conducted to explore its potentials in food applications. This work aims to study the preparation, characterization and potential analysis of Gembili flour for use as raw material in novel foods development. Creamy white flour was obtained from white yam tuber from milling and sieving of dried tuber chips. The flour has water content about 12.08%, which is acceptable for storage. No lipid was detected. In addition, the protein, ash, and fiber content of the flour were respectively 3.00%, 1.27%, and 9.04%. The carbohydrate and amylose contents of the flour were 86.69% and 29.92% indicating its suitability for energy source. As expected, the cyanide content is very low of about 1.688 ppm suggesting that it is safe for consumption. Refer to those properties, Gembili flour can be a promising raw material for the preparation of bakery, cookies, noodle and confectioneries.Keywords: proximate composition, flour, white yam, food, preparation

Co-Authors . Widayat A. Nugroho A. Nugroho Aat Zaki Mubarok Affian Widjanarko Affian Widjanarko Aji Prasetyaningrum Amin Nugroho Andri C. Kumoro Andri Cahyo Kumoro anggoro D.D. Anggoro Anita Pinalia Aprilina Purbasari Bakti Jos Bayu Prianto Catarina S. Budiyati Catarina Sri Budiyati Cindi Yasintasia Dewi Ayuningtyas Diah S. Retnowati Diah Susetyo Retnowati Djoko Mulyono Dyah Arum Kusumaningtyas Dyah Hesti Wardhani Fadlillah Fani Fitri Lafifa G.A. Mansoori G.A. Mansoori Gian Restu Prinanda H Hadiyanto Hargono Hargono Hartono, Damin Henny Setyaningsih Jefri Chandra Runanda Johannes Leonard Jumali Jumali L. Buchori Lestari, Novi Dian Luqman Buchori M. Djaeni Maharani Ratridewi Maria Augustine Graciafernandy Nafiah Amalia Nita Indriyani Nita Indriyani Noer Abyor Handayani Noor Hidayati Nur Rokhati Nurfiningsih Nurfiningsih Nurkhikmah, Eli Nurul Asiah Nurul Asiah Prawita Dhewi Purbo Suseno R Ridwan R. Ridwan Retno Wulandari Rizky Adi N Sadam Arrois Siti Thomas Zulaikhah Suherman Suherman Sulastri, Neng Sumarno . Teguh Riyanto Utami Diah P. Wiratno Wiratno Yudhy Dharmawan Yustina Linasari

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