Extraction and Use of Potassium Hydroxide from Ripe Plantain Peels Ash for Biodiesel Production

Abstract

The extraction of the ash of ripe plantain peels to obtain potassium hydroxide (KOH) and its application in the trans-esterification of refined rapeseed and crude jatropha oils have been investigated. At 30 �C, extraction time 1 hr and volume of 5, 7.5 and 10 ml/g ash, the percentage recovery of KOH progressively increased in the first stage, from 26.05 to 26.20 and then to 30.75% respectively, but decreased in the second stage (extraction of the spent ash from stage 1), from 2.20 to 2.10 and to 1.90% respectively. Same trend was also observed at 40 and 50 �C but cumulatively, KOH values recovered increased relatively with increasing extraction time and temperature. The percentage cumulative recovery of KOH was 40.10% at extracting temperature of 50 �C, extracting volumes 10 ml/g ash and extraction time of 3 hrs while it was 40.00% at 50 �C, 10 ml/g ash and 2 hrs extraction time. The least percentage cumulative recovery of KOH was 28.25% at 30 �C with 5 ml extracting volume/g ash and 1 hr extraction time. The percentage purity of the extracted KOH gave 80.0%. The trans-esterification of the two vegetable oils showed the percentage conversion obtained with rapeseed oil was 71.01% using 1 g of KOH extract from ripe plantain peels ash at reaction temperature and time of 75 �C and 4 hours respectively. Under the same reaction conditions, 1 g of commercial caustic potash recorded 70.06% conversion of the rapeseed oil. From the optimized batch process, 97.15% conversion was achieved with crude jatropha oil using 1 g caustic potash extract from ripe plantain peels ash; at reaction temperature and time of 83 �C and 4 hours respectively.