Judul: Adsorpsi asam lemak bebas dan zat warna menggunakan campuran kaolin-limbah padat tapioka
Abstrak: Adsorption of free fatty acids in used cooking oil and methylene blue dye is studied. The results showed that the mixture of kaolin and tapioca solid waste is a potential adsorbent for the adsorption free fatty acids and dyes. The effect of kaolin activation treatment, such as heating temperature and the use of acid is also studied. The best activation results for the kaolin activation used in the free fatty acid adsorption was heating treatment at 750 °C followed by treatment with H2SO4 30%, whereas for methylene blue adsorption by acid treatment only. Activation of tapioca solid waste was using 30% H3PO4 treatment. Optimum conditions for adsorption, adsorption capacity, and adsorption efficiency of a mixture of kaolin and tapioca solid waste showed different results and specific for each type of sample used. For the same amount of adsorbent, free fatty acid adsorption was reached in 90 minutes using the ratio of activated kaolin and tapioca solid waste of 25:75 (1:3). Meanwhile, methylene blue adsorption was achieved at 30 minutes with the ratio of activated kaolin and tapioca solid waste of 75:25 (3:1). The results showed that the type of adsorption isotherm for free fatty acids was Freundlich isotherm, whereas for methylene blue adsorption was Langmuir isotherm.
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Judul: Adsorpsi Asam Lemak Bebas dan Zat Warna Biru Metilena Menggunakan Campuran Selulosa Kayu Sengon-Zeolit
Abstrak: Limbah minyak goreng bekas dan zat warna dari berbagai macam industri merupakan penyebab pencemaran di Indonesia. Tujuan penelitian ini adalah melakukan adsorpsi asam lemak bebas dari minyak goreng bekas dan zat warna biru metilena menggunakan selulosa hasil isolasi kayu sengon dan zeolit yang diaktivasi secara asam, menentukan kondisi optimum adsorpsi, serta menentukan isoterm adsorpsi dan kinetika adsorpsi. Percobaan yang digunakan adalah metode tumpak. Kondisi yang dioptimisasi meliputi bobot, waktu, dan nisbah dari kedua adsorben. Kondisi optimum adsorpsi asam lemak bebas didapatkan pada bobot 1 gram, dengan nisbah adsorben 3:1 pada selulosa:zeolit, dan waktu adsorpsi selama 60 menit. Kondisi optimum zat warna biru metilena didapatkan pada nisbah adsorben 1:3 untuk selulosa:zeolit pada waktu 10 menit. Adsorpsi asam lemak bebas dan biru metilena mengikuti isoterm Freundlich. Adsorpsi asam lemak bebas dan biru metilena mengikuti kinetika reaksi orde dua semu.
Keyword: adsorption, adsorption kinetics, cellulose, free fatty acid, methylene blue, zeolite

Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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