Judul: Pengaruh Tekanan terhadap Adsorpsi CO2 pada Biogas Menggunakan Zeolit 13X untuk Meningkatkan Kemurnian Metana
Abstrak: Karbon dioksida yang terkandung dalam biogas dapat mempengaruhi nilai kalor biogas sehingga perlu dipisahkan. Salah satu metode yang digunakan untuk menghilangkan karbon dioksida pada biogas dapat melalui proses adsorpsi. Peningkatan tekanan pada proses adsorpsi diduga akan meningkatkan tumbukan antar partikel gas pada kolom adsorpsi sehingga kontak antara molekul CO2 dengan adsorben semakin besar. Penelitian ini bertujuan mengkaji pengaruh tekanan adsorpsi terhadap performansi penjerapan gas CO2 oleh Zeolit 13X untuk meningkatkan kemurnian metana. Hasil penelitian menunjukkan peningkatan tekanan terhadap proses adsorpsi akan meningkatkan kapasitas adsorpsinya. Hal ini mengindikasikan proses adsorpsi berlangsung secara fisika akibat gaya Van der Waals. Melalui keseimbangan adsorpsi Langmuir, diperoleh kapasitas adsorpsi maksimum sebesar 24,51 mg/g dan konstanta Langmuir sebesar 0,63 bar-1. Nilai ARE pada penelitian ini lebih kecil dari 5% menunjukkan model isotermal Langmuir dapat digunakan untuk menduga mekanisme adsorpsi pada Zeolit 13X, meskipun model tersebut menggunakan asumsi bahwa molekul adsorbat membentuk lapisan monolayer. Disamping menjerap gas CO2, Zeolit 13X juga menjerap gas CH4 meski dalam jumlah yang lebih sedikit. Peningkatan tekanan hingga 2 bar berdampak positif terhadap penjerapan CO2 pada Zeolit 13X karena memiliki selisih dengan kapasitas adsorpsi CH4 yang paling besar., Carbon dioxide contained in biogas can affect the calorific value of biogas, thereby has to be removed. One of the methods used to remove carbon dioxide in biogas is the adsorption process. Increasing pressure in the adsorption process is expected to increase the collision between gas particles in the adsorption column so that the contact between CO2 molecules and the adsorbent is also increasing. This study aims to examine the effect of adsorption pressure on the performance of CO2 adsorption by Zeolite 13X in order to increase the purity of methane. The results showed that increasing the pressure in the adsorption process would increase the adsorption capacity. This indicates that the adsorption process takes place physically due to the Van der Waals force. Through the Langmuir adsorption equilibrium, the maximum adsorption capacity was 24,51 mg/g and the Langmuir constant was 0,63 bar-1. The ARE value in this research was less than 5% indicates the Langmuir isotherm model is valid with the experimental results, even though the model assuming that the adsorbate molecules form a monolayer. Besides adsorbing CO2, Zeolite 13X also adsorb CH4 with smaller capacity. Increasing pressure up to 2 bar gives positive impact to CO2 adsorption since it gives larger difference with adsorption capacity of CH4.
Keyword: adsorpsi, biogas, karbon dioksida, metana, Zeolit 13X

Judul: The Effects of Temperature to Adsorption Rate Constant of Carbondioxide (CO2) by Zeolite 13X in Purification of Bio-Methane
Abstrak: Pemisahan komponen CO2 dari biogas merupakan salah satu bentuk upaya peningkatan kualitas biogas. Salah satu proses pemisahan dilakukan dengan adsorpsi. Tujuan dari penelitian ini adalah untuk mempelajari kinetika adsorpsi CO2 dan pengaruhnya terhadap variasi suhu terhadap nilai konstanta kinetika adsorpsi dan untuk menentukan model kinetika yang sesuai antara pseudo first order (PFO) atau pseudo second order (PSO) dalam menduga parameter laju adsorpsi serta energi aktivasi. Penelitian ini dilakukan secara eksperimental, menggunakan Zeolit 13X sebagai adsorben. Proses adsorpsi dijaga pada tekanan konstan 2 bar, sedangkan suhu divariasikan pada 30°C (303 K), 50°C (323 K), 75°C (348 K), dan 100°C (373 K). Hasil penelitian menunjukkan bahwa kenaikan suhu menyebabkan kenaikan konstanta kinetika adsorpsi CO2 karena adanya peningkatan interaksi adsorbat-adsorben seiring dengan kenaikan suhu. Model yang sesuai dalam merepresentasikan data eksperimen adalah model PSO dengan koefisien korelasi (R^2) pada kisaran 0,98-0,99 dan nilai ARE pada kisaran 5,53%-8,49%. Hasil juga menunjukkan bahwa seiring dengan adsorpsi CO2 yang terjadi, gas CH4 juga teradsorpsi, namun karena selektivitas Zeolit yang unik, CO2 akan cenderung lebih banyak teradsorpsi. Penelitian ini menunjukkan bahwa variasi kenaikan suhu akan berpengaruh negatif terhadap pemisahan CO2 dari biogas karena selisih kapasitas yang dijerap dengan CH4 semakin kecil seiring dengan kenaikan suhu., Separation of CO2 from biogas is indispensable in order to improve the energy density of biogas. One of the separation methods is adsorption. The objective of this research is to study the kinetics of CO2 adsorption as affected by temperature and to determine the appropriate kinetic model between PFO or PSO and the value of activation parameters. This research was conducted experimentally using Zeolite 13X as adsorbent. The adsorption process controlled at a constant pressure of 2 bar, while the temperature was varied at 30°C (303 K), 50°C (323 K), 75°C (348 K), and 100°C (373 K). The results showed that the increase in temperature caused an increase in kinetic constant of CO2 adsorption because of the adsorbate-adsorbent interaction as the temperature increase. The appropriate model (that is suitable in representing the experimental data is the PSO model with the correlation coefficient (R^2) in the range of 0.98-0.99 and the ARE value in the range of 5.53%-8.49%. The results also showed as the adsorption that as CO2 adsorption occurred, Zeolite 13X also adsorb CH4 gas, but with lower capacity due to the unique selectivity of the adsorbent (Zeolite). This study shows that temperature rising gives negative effect on the separation of CO2 from biogas because the difference in capacity that is absorbed with CH4 is getting smaller as the temperature rises.
Keyword: Adsorption rate, Biogas, Kinetics, Zeolite

Judul: Posisi Filogenetik Kura-Kura Carettochelys Insculpta  (Reptillia: Testudinata)
Abstrak: Carettochelys insculpta is an endemic freshwater turtle of southern Papua and northern Australia. Phylogenetic position of this turtle is remain unresolved until now. Most of the research conducted show close relationships of C. insculpta and members of Trionychidae family. However, some of the research show distance between C. insculpta and members of Trionychidae family. This research is conducted to analyze phylogenetic relationship between C. insculpta and other members of Testudinata using 12S rRNA, 16S rRNA, and both gene as markers. DNA samples were obtained from three different organisms of C. insculpta. Two species used as outgroups were Alligator mississippiensis and Iguana iguana. Phylogenetic analysis was carried out using Neighbor-Joining method with Felsenstein 1981 (F81) modeltest. A polytomy tree of Testudinata was produced by using 12S rRNA gene. However, analysis using 16S rRNA and both genes as markers confirmed that C. insculpta was located between the Chelonidae and the Trionychidae family.
Keyword: