The Effects of Lignin Purification on the Performance of Iron Complex Drilling Mud Thinner

Soda lignin was extracted from black liquor of oil palm empty fruit bunch (EFB) fibers by 20% (v/v) sulfuric acid. The yield of lignin, which is 3.016 grams from every 200 mL of black liquor, was then purified by n-pentane using soxhlet apparatus for six hours. A comparison study between purified lignin and standard lignin was then performed through physico-chemical properties and structural features using a Fourier transform infrared spectroscopy (FTIR), ultraviolet spectrometry (UV), gel permeation chromatography (GPC), high performance liquid chromatography (HPLC), and ash contain test. The FTIR and HPLC results showed that there was no significant difference between the purified sample and the standard lignin. However, the UV result revealed that purified lignin gave slightly higher absorbance value than the standard lignin. The purified and unpurified samples of lignin comprised 0.345% and 5.75% ash respectively. From the GPC results, the poly-dispersity (Mw/Mn) values for the purified lignin and the standard lignin were 1.23 and 1.25, respectively. The lignin was then reacted with ferrous ion to form ferrumtannin- lignin (FTL) complex at 105°C in the presence of formaldehyde to initiate cross-linking reaction. The rheological properties of the pure FTL (FTLpurified) was compared with the unpure FTL (FTLunpurified) and a commercial thinner, lignosulfonate (LS). Generally, the FTLpurified gave comparable results with the FTLunpurified, which suggests that purification process is not required to increase the performance of chelated ferrous ion drilling mud thinner