Abstract
Urea is an important nitrogen source for plant but the price of urea fertilizer is relatively high. Urea uptake from urea manufacture waste water and its application as fertilizer is of high interest. The purpose of this study is to find out desorption ability of urea adsorbed porous carbon to be applied as fertilizer. Theoritically, urea released from porous carbon to environment has slower rate of mass transfer compare to conventional urea fertilizer because urea molecules in porous carbon has to pass through pores of carbon during its movement out of carbon. The porous carbon as adsorbent was made from coconut shell by pyrolysis, followed by sulfuric acid oxidation treatment Oxidation treatment carried out to extent adsorption capacity as well as to give additional sulfur nutrient when applied as fertilizer. Oxidation of carbon surface was performed using sulfuric acid (50%w) to soak porous carbon followed by heating at 90oC temperature for 2 hours. Desorption was conducted by placing porous carbon into beaker contain water and the raising of urea concentration in water recorded after 3,5,10, 30, and 60 minutes. Results reveal that the value of mass transfer coefficient (kc) and effective diffusivity (De) of urea desorption from porous carbon are 0,0293 – 0,0743 cm/s and 8 x 10-10 – 5 x 10-9 cm2/s with initial concentration of urea 1000, 2000, and 4000 mg/L. Release rate of urea from porous carbon and urea prill are 0,07 ppm/s and 1,23 ppm/s. Slower release rate of urea off porous carbon than urea prill shows the promising of urea recovery using porous carbon as slow release fertilizer.
Highlights
S carbon and urea prill are 0,07 ppm/s and 1,23 ppm/s
Slower release rate of urea off porous carbon than urea prill shows the promising of urea recovery using porous carbon as slow release fertilizer
Australian Journal of Soil Research, 48, 569-576
Summary
Urea pada permukaan tanah sangat mudah mengalami penguapan dalam bentuk amonia. potensi hilangnya nitrogen menjadi amonia akan meningkat dengan meningkatnya suhu, pH tanah, kelembapan, dan kecepatan pemupukan (Savoy, 2007). Konsumsi pupuk secara global menunjukkan peningkatan tajam dalam kurun waktu 50 tahun terakhir, diperkirakan 30 -70 % nutrient hilang disumbangkan oleh pupuk komersial yang dipengaruhi cara pemupukan dan kondisi tanah (Niu dkk, 2012). Penggunaan biochar dalam tanah menunjukkan adanya peningkatan penyimpanan N, meningkatkan efisiensi pemakaian pupuk N (Zwieten dkk, 2010), dan mengurangi hilangnya N karena leaching (Guerena dkk, 2013). Dari penelusuran pustaka yang telah dilakukan, keaslian atau kebaruan penelitian ini terletak pada penggunaan karbon berpori yang dioksidasi asam sulfat untuk adsorpsi urea dalam aqueous solution dan diaplikasikan sebagai pupuk lepas lambat, yang dibuktikan dari kecepatan pelepasan urea dari karbon berpori. Tujuan dari penelitian ini adalah menentukan nilai koefisien transfer massa (kc) dan nilai difusivitas efektif (De) yang merupakan parameter kinetika desorpsi urea dari karbon berpori, serta menentukan perbandingan kecepatan pelepasan antara urea dari karbon berpori dengan urea prill. Nilai difusivitas efektif (De), koefisien transfer massa (kc), dan konstanta kesetimbangan (H) dapat ditentukan dengan cara memasukkan data konsentrasi urea (CAf) dan waktu (t)
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