Durian peel (Durio zibethinus) utilization as an adsorbent in the purification of acidified crude glycerol

Durian (Durio zibethinus) is highly consumed seasonal fruit that generates abundant waste in the form of peel. Durian peel can serve as an effective adsorbent because it is rich in cellulose–lignin. This waste has potential applications in the chemical industry, such as using durian peel to purify crude glycerol. This research studied durian peel as an adsorbent in the form of activated carbon in the purification of acidified crude glycerol. The purification process begins with the acidification process of crude glycerol using concentrated acid with a mole ratio of phosphoric acid:glycerol (n/n) of 0.5:1, 1:1, 1.5:1, 2:1, and 2.5:1. The adsorption process by carbonization and activated of durian peel using 0.1 N KOH as adsorbent with a mass percentage ratio of adsorbent:crude glycerol (%wt) of 5 %, 10 %, 15 %, 20 %, and 25 %, and stirred using a magnetic stirrer at a speed of 250 rpm for 2 h. The adsorbent utilized has a carbon-rich content of as much as 80.6 % based on Energy Dispersive X-ray analysis. The highest glycerol purity obtained at 96.26 % is achieved at phosphoric acid:glycerol mole ratio of 1:1 and adsorbent:glycerol mass ratio of 25 %. This result also matches the analysis by gas chromatography. Thus, the others test of the purified glycerol, such as density of 1.267 g/cm³, water content of 1.6 %, ash content of 0.2 %, and matter organic non-glycerol of 1.94 %, are in accordance with the glycerol standard BS 2621:1979.