Judul: Delignification of Oil Palm Empty Fruit Bunches using Ozone Microbubble Technique
Abstrak: Proses delignifikasi biomassa berlignoselulosa umumnya masih banyak menggunakan bahan kimia seperti klorin yang limbahnya berbahaya bagi lingkungan. Mikrogelembung ozon merupakan salah satu metode yang ramah lingkungan untuk mengurangi kadar lignin dalam biomassa. Penelitian ini bertujuan menetapkan kondisi terbaik berdasarkan parameter selektivitas delignifikasi (nisbah selulosa/lignin) pada proses ozonolisis dan mencirikan serat berdasarkan kriteria serat untuk pulp dan kertas. Serat tandan kosong kelapa sawit (TKKS) didelignifikasi pada pH 3 (larutan asam oksalat), pH netral (akuades), dan pH 10 (larutan NaOH) selama 30, 45 dan 60 menit dengan laju alir ozon 3 L menit-1. Perlakuan ozonolisis terbaik diperoleh pada kondisi pH asam selama 60 menit yang berhasil mendegradasi lignin dari 11,4% menjadi 7,0% dengan selektivitas delignifikasi 8,86. Serat TKKS termasuk serat kelas III untuk pulp kertas dan proses ozonolisis tidak mengubah kelasnya. Ozonolisis serat TKKS memberikan proses delignifikasi yang lebih hemat waktu dan energi serta ramah lingkungan., The delignification process of lignocellulosic biomass generally still uses many chemicals, such as chlorine, which produces hazardous waste for the environment. Ozone microbubbles are an environmentally friendly method for reducing lignin content in biomass. This study aims to determine the best conditions based on delignification selectivity (cellulose/lignin ratio) in the ozonolysis process and characterize the fiber characteristics based on fiber criteria for pulp and paper. The oil palm empty fruit bunch (OPEFB) fibers were delignified at pH 3 (oxalic acid solution), neutral pH (distilled water), and pH 10 (NaOH solution) for 30, 45 and 60 minutes with an ozone flow rate of 3 L min-1. The best ozonolysis treatment was obtained under acidic pH conditions for 60 minutes which succeeded in degrading the lignin content from 11,4% to 7,0% with a delignification selectivity value of 8,86. OPEFB fiber was classified as class III fiber for paper pulp, and the ozonolysis process does not change its class. The OPEFB fiber ozonolysis process provide a delignification process that saves time and energy as well as is environmentally friendly.
Keyword: delignification, delignification selectivity, microbubble, oil palm empty fruit bunches, ozone

Judul: Delignifikasi Biomassa Accacia mangium melalui Teknik Mikrogelembung Oksigen dan Ozon
Abstrak: Delignifikasi pulp masih banyak menggunakan bahan kimia yang limbahnya membahayakan lingkungan. Teknik ozonolisis dan mikrogelembung merupakan salah satu teknologi prospektif dalam menjaga kebersihan lingkungan dan mengurangi biaya operasional. Penelitian ini bertujuan menentukan selektivitas delignifikasi (nisbah selulosa/lignin yang tersisa dalam biomassa), menetapkan parameter terbaik dalam delignifikasi biomassa Acacia mangium, serta mendeskripsikan seratnya. Sampel diozonolisis dalam 3 kondisi tingkat keasaman: larutan asam oksalat dengan pH 3, dalam air dengan pH 7, dan dalam larutan NaOH dengan pH 10. Ozon dialirkan melalui reaktor dalam bentuk mikrogelembung dengan laju 3 L/menit selama 30, 45, atau 60 menit. Nilai selektivitas delignifikasi terbaik ialah pada perlakuan asam selama 45 menit, yaitu 4,23. Ozonolisis memberikan delignifikasi yang lebih baik daripada menggunakan alkali aktif dan tetap unggul dalam segi ramah lingkungan, hemat energi, dan durasi reaksi. Dimensi serat tidak banyak berkurang dibandingkan kontrol sehingga tidak menurunkan kualitasnya untuk dijadikan bahan baku kertas kelas II., Pulp delignification still use many chemicals, which is harmful to the environment. Ozonolysis and microbubble techniques are one of the prospective technologies in maintaining environmental cleanliness and reducing operational costs. This study aims to determine delignification selectivity (cellulose/lignin ratio remaining in biomass), determine the best parameters in the delignification of biomass Acacia mangium, and describe the fiber quality as paper pulp. Ozonolysis was emploted under 3 acidity conditions: oxalic acid solution at pH 3, in water at pH 7, and in NaOH solution at pH 10. Ozon was flowed through the reactor in the form of microbubbles at a rate of 3 L/min for 30, 45, or 60 minutes. The best value of selectivity of delignification is in acid treatment for 45 minutes, which is 4.23. Ozonolysis provides better delignification than using active alkalis and still excels in terms of environmental friendliness, energy savin, and reaction duration. The dimensions of the fiber are not much reduced compared to the control, meaning that it does not reduce its quality to be used as raw material for paper, as class II.
Keyword: Acacia mangium, delignification, microbubbles, ozonolysis, delignification  selectivity

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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