Direct separation and charaterization of lignin from paper black liquor

Abstract

Nowadays, the demand for energy is increasing day by day, but fossil energy, such as oil, is becoming more and more exhausted with people's over-exploitation. The most abundant renewable carbon source on the earth is lignocellulose, which has attracted worldwide attention as a substitute for non-renewable resources such as natural gas. Lignin is one of the three main chemical components of plant fiber, serving as a natural aromatic polymer biomass resource to reserve secondary cellulose, and also a key component of paper black liquor in chemical pulp mills. In this experiment, paper black liquor was prepared, characterized, and various data such as pH were determined. Subsequently, the paper black liquor was separated by methanol, with its pH adjusted to 8~12 before being treated with acid to adjust the pH to 2~5. Following acid and methanol separation, the paper black liquor was further characterized through determination of ultraviolet data for calculating lignin yield, infrared spectrum analysis, molecular weight (Mn) determination for lignin samples, and thermal weight analysis. Ultimately, these methods were compared to identify more effective ways of separating lignin from paper black liquor for better utilization.