Preparation of lignin-based silica composite submicron particles from alkali lignin and sodium silicate in aqueous solution using a direct precipitation method

A novel and practical co-precipitation process in an aqueous medium was developed to prepare lignin-based silica composite submicron particles from chemical modified alkali lignin and sodium silicate by a high-value-added application strategy of lignin. The alkali lignin was first modified by phosphorylation reaction using sodium 3-chloro-2-hydroxypropyl phosphate as a modifier. The phosphorylated alkali lignin named sodium lignin phosphate (SLP) was added to silica matrix as a co-precipitant and dispersant to prepare lignin-based silica composite particles (SLP-SiO2) via the hydrogen bonding interaction between the hydroxyl groups in lignin and silica. The weight ratio of lignin to silica reached 1.33. SEM, BET and XPS analyses indicated that lignin mainly deposited on the surface and pores of silica to increase the surface hydrophobicity. The average diameter of the SLP-SiO2 was about 300 ∼ 400 nm. With the increase of lignin incorporated onto the silica matrix, the BET surface area decreased from 385.6 to 54.8 m2 g−1. Results of the study were of practical importance in high-value-added application of lignin.