Judul: Carbonization of Palm Oil Shell Waste via Plasma Pyrolysis Technique
Abstrak: Cangkang kelapa sawit merupakan limbah biomassa yang dapat digunakan sebagai sumber karbon. Metode yang dapat digunakan untuk mensintesis karbon yaitu pirolisis plasma menggunakan Arc Plasma Sintering (APS) dengan variasi arus (40 A, 50 A, 60 A, 70 A, dan 80 A). Sampel karbon kemudian dikarakterisasi menggunakan Raman Spectroscopy, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), dan Fourier Transform Infrared Spectroscopy (FTIR). Hasil analisis dengan Raman Spectroscopy menunjukkan rasio IG/ID pada sampel dengan perlakukan arus 40 A, 50 A, 60 A, 70 A, dan 80 A masing-masing sebesar 0,4300, 0,4615, 0,5271, 0,6963, dan 0,4466. Rasio IG/ID cenderung meningkat seiring dengan peningkatan arus plasma hingga 70 A. Hasil data XRD menunjukkan difraktogram yang menyerupai amorf dan menunjukkan bahwa sampel karbon memiliki struktur turbostratik. Hasil gambar TEM kelima sampel menunjukkan fasa amorf dan kristal. Sampel karbon hasil plasma mengalami transformasi fasa amorf menuju kristal yang melewati fasa turbostratik. Hasil perhitungan parameter kisi dari pola SAED (Selected Area Electron Diffraction) TEM diperoleh nilai parameter kisi yang mendekati nilai parameter kisi untuk struktur kristal grafit. Hasil FTIR menunjukkan keberadaan gugus fungsi yang sama pada semua sampel karbon dengan variasi arus., Palm oil shells are biomass waste that can be used as a carbon source. The method that can be used to synthesize carbon is plasma pyrolysis using Arc Plasma Sintering (APS) with varying currents (40 A, 50 A, 60 A, 70 A, and 80 A). The carbon samples were then characterized using Raman Spectroscopy, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). The results of analysis using Raman Spectroscopy show that the IG/ID ratio in samples treated with currents of 40 A, 50 A, 60 A, 70 A, and 80 A is 0,4300, 0,4615, 0,5271, 0,6963, and 0,4466, respectively. The IG/ID ratio tends to increase as the plasma current increases up to 70 A. The results of the XRD data show a diffractogram that resembles amorphous and indicates that the carbon sample has a turbostratic structure. The TEM image results of the five samples show amorphous and crystalline phases. The carbon sample produced by plasma undergoes an amorphous phase transformation to crystalline which passes through the turbostratic phase. The results of lattice parameter calculations from the SAED (Selected Area Electron Diffraction) TEM pattern show lattice parameter values that are close to the lattice parameter values for the graphite crystal structure. FTIR results show the presence of the same functional groups in all carbon samples with varying currents.
Keyword: cangkang kelapa sawit, karbon, pirolisis plasma

Judul: Production and Characterization of Biochar from Torrefaction of Palm Oil Solid Waste
Abstrak: Limbah padat kelapa sawit yang semakin melimpah masih belum dimanfaatkan dengan baik dan dapat menyebabkan masalah lingkungan. Penelitian ini bertujuan memanfaatkan limbah padat kelapa sawit menjadi bioarang. Percobaan diawali dengan preparasi sampel, torefaksi, dan karakterisasi bioarang sesuai dengan parameter standar mutu bioarang berdasarkan SNI 01−6235−2000. Limbah padat kelapa sawit diantaranya cangkang, pelepah, dan tandan kosong kelapa sawit (TKKS) diolah kembali menjadi bioarang melalui proses torefaksi pada suhu 200–300 ℃. Parameter uji ialah kadar air, kadar abu, zat terbang, karbon terikat, daya serap iodin, dan kadar logam dengan spektroskopi serapan atom. Bioarang yang diperoleh dari cangkang, pelepah, dan TKKS terbukti memenuhi standar nasional Indonesia. Bioarang dari cangkang kelapa sawit memiliki kualitas terbaik dengan rendemen tertinggi 45,7%, kadar air dan abu yang rendah masing−masing 2,5% dan 1,9%, kadar zat terbang dan karbon terikat tertinggi masing−masing 12% dan 82%. Bioarang yang dihasilkan terbukti mengandung logam Cu, Mg, K, Ca yang bermanfaat sebagai bahan pembenah tanah., Palm oil solid waste which was increasing in number weren’t optimally utilized and can cause environmental problems. This study aims to use palm oil solid waste into biochar. The method, was carried out by sample preparation, torrefaction, and biochar characterization by the parameters of the biochar quality standard based on SNI 01−6235−2000. Palm oil solid waste, including shells, fronds, and empty fruit bunches (EFB), is reprocessed into biochar through a torrefaction process with a temperature of 200−300 ℃. The results showed data on several parameters, namely, water content, ash content, volatile matter, bound carbon, absorption of iodine, and metal content using Atomic Absorption Spectroscopy (AAS). Biochar obtained from the shell, fronds, and EFB is proven meets Indonesian national standards. Biochar from oil palm shells has the best quality with highest yield of 45,7%, low moisture and ash content of 2,5% and 1,9%, respectively, volatile matter, and highest bound carbon content of 12% and 82%. It's shown that metal content Cu, Mg, K, and Ca are good for soil enhancers.
Keyword: Bioarang, limbah padat kelapa sawit, pembenah tanah, torefaksi, Biochar, palm oil solid waste, soil repairer, torrefaction

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model