Crude glycerol is a valuable by-product obtained from biomass-to-biodiesel conversion processes1. High-purity glycerol has been widely used in various industries as shown in Fig. 12. In contrast, crude glycerol derived from biodiesel production is of low value and has very limited application because of impurities.
The major impurities in crude glycerol are esters, fatty acids, and mineral ions. Thus, purification of crude glycerol is necessary, and can directly add value and economic benefits to glycerol. Normally, refining of glycerol is a sequential procedure which includes saponification, acidification, neutralization, solvent extraction, and decolourization. Most of these processes require activated carbon (AC). To the best of our knowledge, adsorptive removal of impurities in glycerol by AC is mainly used in the finishing step of glycerol purification. It was found that ACs from different sources exhibit different adsorption behaviors. Thus, it is important to understand the characteristics and properties of AC, which plays an important role for this state of the art. To gain insight into the physicochemical properties of ACs obtained from various sources, we (NANOTEC and Patum Vegetable Oil) used many advanced characterization techniques such as a synchrotron X-ray photoelectron spectroscopy (PES) and soft X-ray absorption spectroscopy to study the features of ACs. The results showed that the coal-based AC has essential functionalities for adsorbing the pigments and trace mineral ions, especially transition metal ions, while AC prepared from coconut shells is not suitable for this application due to a lack of some functionalities. However, when comparing the prices of ACs obtained from these two sources, the coconut shell-based AC is incredibly cheaper, and it is also abundant in Thailand. Thus, developing ACs produced in the local areas by adding some key functionalities to meet the standard requirements of glycerol purification would significantly reduce the operational cost for the glycerol-producing companies in Thailand.
National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand
Synchrotron Light Research Institute (
1 Energies 2017, 10, 1817; doi:10.3390/en10111817
2 Renewable and Sustainable Energy Reviews 42 (2015) 1164–1173