Purification of biodiesel using natural diatomite and diatomite doped with mno2

Abstract

This research aims to study an adsorption process for purifying biodiesel by using natural diatomite (D) and MnO2-doped diatomite (DDM) as adsorbents. Natural diatomite was firstly used for removal of glycerin from crude biodiesel. The sorption capacity of natural diatomite was further improved by doping diatomite with 0.118 g of manganese oxide per g diatomite, and used for removal of monoglyceride. The surface area of diatomite and MnO2-doped diatomite calculated using BET method were 66 and 138 m2g-1, respectively. The optimum capacity for removal of glycerin could be achieved by using 4% (w/w) of D adsorbent and 20 minutes of contact time at 50oC. In addition, 98% of glycerin was removed by using 1% (w/w) of D adsorbent on the condition that methanol had been removed before treatment. Furthermore, by using 2% (w/w) of DDM 1.5 adsorbent and 10 minutes of contact time at 50oC, 28.92 % of monoglyceride could be removed. According to the adsorption isotherm, these processes are fit to both Fureundlich and Langmuir models. This adsorption process gave the quality of biodiesel as analogous to water washing process and values of acid number, viscosity, flash point and free and total glycerin passed the specification of biodiesel standard. The advantage over conventional water washing process is no wastewater generated from this adsorption process.