Improved thermal properties of lignin via phosphorylation using disodium hydrogen phosphate dodecahydrate salt

This study reports the phosphorylation of lignin using disodium hydrogen phosphate dodecahydrate salt as a phosphate donor and urea as a catalyst. Phosphorylation of lignin was carried out by grafting the salt onto lignin at 80 °C. Weight ratio of lignin and salt was 1:6.25. The phosphorylated lignin was analyzed using EDS which shows that an average of 2,9% of phosphorus element is found in the grafted lignin. This is also confirmed by functional group analysis using FTIR and the result shows that the phosphate group had been successfully grafted onto the lignin. Furthermore, the TGA results show an improve in the thermal stability as seen from the increase of decomposition temperature of the grafted lignin up to 34 °C compared with the pristine one. A slight increase in char residue of grafted lignin as high as 5% compared to pure lignin is also observed.