Judul: Pemanfaatan Sekam Padi sebagai Adsorben Logam Timbal dalam Kerang darah
Abstrak: Water pollution by lead affects one of potential food, such as blood cockles. The aim of this research is to compare rice husk and rice husk charcoalinreducinglead concentration in the blood cockles. The rice husk and rice husk charcoalwere activated by NaOH 1 M, then theiradsorption toward lead solution and lead in blood cockles were determined.The result showed that the maximum capacity of the activated rice husk and rice husk charcoal were29 mg/g and 52 mg/g,respectively,at optimum condition of adsorption. The optimumadsorption condition in 100 mL Pb solution by the activatedrice husk was 0.32 g, pH 5, and 4 hours, whileby theactivatedrice husk charcoalwas 0.20 g, pH 5, and 2 hours. Lead content in blood cockles was 2 mg/kg, which washigher thanthe threshold. Lead adsorption bythe activatedrice husk reduced lead concentration in blood cockles of 40% better than the activatedrice husk charcoal, which was 32%.
Keyword: rice husk, lead adsorption, charcoal of rice husk, blood cockle

Judul: Penjerapan zat warna rreaktif cibacron red menggunakan adsorben sekam padi
Abstrak: Textile wastewater containing dyes can pollute aquatic environment. This study utilized rice husk as adsorbent for Cibacron Red reactive dyes which are widely used in textile industries. Husks were made into adsorbent without modification (ATM) and acid modified adsorbent (AMA). The optimum condition was obtained under adsorption time of 30 minutes, 1.0 g of adsorbent, and initial concentration of dye solution was 150 ppm. The optimum condition for AMA was obtained under adsorption time of 60 minutes, 2.0 g of adsorbent, and 150 ppm initial concentration of dye solution. The optimum condition of activated charcoal (AA) as a comparison was 30 minute time of adsorption, 3.0 g of adsorbent, and 150 ppm initial concentration dye solution. Adsorption capacity of ATM, AMA, and AA at the optimum conditions was 2879.00, 6898.30, and 2470.00 μg/g, respectively. Adsorption efficiency of ATM, AMA, and AA at the optimum conditions was 19.86, 91.71, and 40.51%, respectively. All three types of adsorbent followed the Freundlich isotherm. Application of the adsorbent on waste of textile manufacture showed a decrease in colour after adsorption by ATM, AMA, and AA, up to 52.05, 98.86 and 48.69%, respectively, with the initial colour intensity of 1485 Pt-Co. Starting with COD of the wastewater which was 7372.0 mg/L, the values decreased after the adsorption with ATM, AMA, and AA were 43.30, 98.56 and 52.58%, respectively. Starting with BOD of 149.09 mg/L, the values decreased after adsorption by ATM, AMA, and AA were 63.41, 76.09, and 72.46%, respectively. Based on these results, rice husk is potentially used as an adsorbent of dyes, thereby reducing the level of pollution of aquatic environment.
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Judul: Best Difference Equation Aproximation to Duffing 's Equation
Abstrak: Persamaan Duffing merupakan persamaan yang sering muncul sebagai model masalah sistem ayun mekanis atau pada masalah rangkaian listrik. Umumnya penyelesaian persamaan ini secara numerik memberikan hampiran dengan gala! yang tinggi, seperti dengan metode Runge-Kutta. Tulisan ini mengkonstruksi suatu persamaan beda untuk menghampiri persamaan Duffing tersebut. Penyelesaian dari persamaan beda ini melibatkan fungsi-fungsi eliptik Jacobi. Berdasarkan penyelesaian ini diperoleh basil bahwa penyelesaian hampirannya persis sama dengan penyelesaian analitiknya. Penyelesaian analitik yang diperolehjuga melibalkan fungsi-fungsi eliptik Jacobi.
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