Dalam kajian ini, daun kering Khaya senegalensis telah ditukar kepada hidrochar oleh hidroterma karbonisasi pada suhu yang berbeza, iaitu, 200 ºC, 225 ºC dan 250ºC dengan menggunakan tiga masa yang berbeza; 24 jam, 48 jam dan 72 jam. Objektif utama kajian ini adalah untuk mengkaji kesan suhu dan masa dalam menghasilkan hidrochar. Objektif yang seterusnya adalah untuk menganalisis sifat-sifat fizikokimia dalam hidrochar. Berdasarkan keputusan, terdapat peningkatan yang ketara dalam kandungan tenaga dan tenaga hasil manakala penurunan dalam hasil hidrochar diperolehi apabila suhu meningkat. Kandungan tenaga tertinggi sebanyak 28813 J/g diperolehi apabila daun tersebut dibakar pada 250 ºC selama 72 jam. Peningkatan sebanyak 62.72% dalam kandungan tenaga hidrochar tersebut berbanding dengan kandungan tenaga daun tanpa dibakar, iaitu 0.668 m2/g. Di samping itu, nilai pH hidrochar yang terhasil adalah dalam julat 5.0-6.8, membuktikan ianya sedikit berasid. Selain daripada itu, keputusan mikroskop electron pengimbas menunjukkan bahawa hidrochar mempunyai keliangan dan permukaan kawasan yang tinggi berbanding dengan daun kering. Luas permukaan hidrochar adalah paling tinggi selepas dirawat pada suhu 250 ºC selama 24 jam, iaitu 13.922 m2/g. Berdasarkan keputusan ini, boleh disimpulkan bahawa sifat-sifat hidrochar berubah mengikut suhu dan masa. Oleh itu, suhu dan masa mempunyai kesan yang besar dalam menghasilkan hidrochar dan ia bergantung kepada tujuan penggunaannya.
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In this study, dried leaves of Khaya senegalensis were converted into hydrochar by hydrothermal carbonization (HTC) at different temperatures of 200 ºC, 225 ºC and 250ºC under three residence times; 24 hours, 48 hours and 72 hours. The main objective of this study was to study the effect of temperature and residence time on the production of the hydrochar. The secondary objective was to analyze the physiochemical properties of hydrochar. Based on the results, there was a significant increase in the energy content and energy yield while decrease in yield of hydrochar with increase in temperature. The highest energy content of 28813 J/g was obtained when the feedstock was heated at 250 ºC for 72 hours which showed 62.72 % increase in energy content compared to that of raw feedstock, which was 0.668 m2/g. Besides, the pH values of the hydrochar formed were in the range of 5.0-6.8, which were slightly acidic. Other than that, scanning electron microscopy (SEM) results showed that hydrochar had a high porosity and surface area compared to raw dried leaves. 13.922 m2/g was the highest surface area of hydrochar obtained under Brunauer-Emmett-Teller (BET) method after being treated at 250 ºC for 24 hours. Based on these results, properties of hydrochar varied according to temperatures and residence time. Therefore, the temperature and residence time had a significant effect in producing the hydrochar and it depends on the purpose of its application.
Conversion of dried leaves into hydrochar through hydrothermal carbonization / Thineswaren V.Subramaniam