A Comparison of Sodium Lignosulfonate (SLS) Synthesis from Black Liquor Lignin and Commercial Lignin

Abstract

Sulphonation of lignin has been considered as a promising step to produce lignosulfonate which may serve as dispersant, flocculant, and surfactant. The aim of present study was to compare the synthesis of sodium lignosulfonate (SLS) from different lignin feedstocks namely commercial lignin and lignin isolated from black liquor (BL) of pulp and paper industry. A novel technique to isolate lignin from BL was introduced with the aid of CO2 and coagulant of alumunium sulfate. The FTIR spectra of BL lignin showed similarity with commercial lignin which indicates that the isolation of BL lignin with the present technique did not alter the chemical structure of lignin. Furthermore, sulphonation of commercial and BL lignin with NaHSO3 solution has been conducted to obtain SLS powder. In general, the FTIR spectra of SLS from commercial and BL lignin were similar to their parent lignin. However, absorption peak which corresponds to SO3 vibration was lightly detected on both samples which indicated the insertion of SO3 functional group into the lignin structure. The ability of SLS to increase the oil mobility for Enhanced Oil Recovery (EOR) was measured from the interfacial tension (IFT). Our results showed that the IFT values of SLS solution from commercial lignin and BL lignin were 0.3759 mN/m and 0.2675 mN/m, respectively. Further formulation of SLS from BL lignin with octanol and PFAD solution may lower the IFT value to 0.0186 mN/m.