Using Sulfobutylated and Sulfomethylated Lignin as Dispersant for Kaolin Suspension.

Derya Yesim Hopa,Pedram Fatehi

doi:10.3390/polym12092046

Abstract

Kraft lignin is an abundant natural resource, but it is underutilized. In this study, sulfoalkylated lignin derivatives with similar charge densities but with different alkyl chain length were produced via sulfobutylation and sulfomethylation reactions. The contact angle studies revealed that sulfobutylated lignin (SBL) with longer alkyl chains had a higher hydrophobicity than sulfomethylated lignin (SML) did. The adsorption behavior of sulfoalkylated lignins was studied using a Quartz crystal microbalance with dissipation (QCM-D) on Al2O3 coated surface as representative of positively charged sites of kaolin particles. The results of adsorption studies showed that SBL deposited more greatly than SML did on the Al2O3 surface, and it generated a thicker but less viscoelastic adlayer on the surface. The adlayer thickness and configuration of molecules on the surface were also related to the zeta potential and stabilization performance of the polymers in the kaolin suspension system. The results also confirmed that both lignin derivatives were very effective in dispersing kaolin particles at neutral pH, and their effectiveness was hampered under alkaline or acidic pH.

Highlights

The properties of kaolin, such as particle size, chemical stability, non-abrasiveness, and its whiteness [1], make it a widely used industrial mineral with a variety of uses in paint, ceramic, and paper industries [2,3,4]
Under alkaline conditions, kaolin suspension did not need a dispersant. These results reveal that the effect of the dispersant is switchable with pH, which implies that the dispersion of kaolin suspension can be interrupted by acidifying the suspension
Two sulfoalkylated lignin derivatives with different alkyl chain lengths were prepared via sulfobutylation and sulfomethylation routes

Summary

Introduction

The properties of kaolin, such as particle size, chemical stability, non-abrasiveness, and its whiteness [1], make it a widely used industrial mineral with a variety of uses in paint, ceramic, and paper industries [2,3,4]. Kaolin particles that are platelet in shape with negative basal surface charges and positive edge charges have heterogeneous structures [7]. The heterogeneous structure of kaolin promotes its aggregation in concentrated aqueous suspensions [8]. Synthetic polymers containing long alkyl chains such as alkylammonium surfactants [10], and poly-electrodes, such as poly-acrylamides, poly-acrylic acrylates, polycarboxylates, and their derivatives are widely used as dispersants for stabilizing kaolin particles in suspensions [6,9,11,12,13,14]. As synthetic dispersants are oil-based, and they cause serious environmental and health-related issues arising from their poor biodegradability and their degradation intermediate products, there is a great demand for developing sustainable and biodegradable dispersants [15,16,17]

Methods

Results

Conclusion