Issue 22, 2018, Issue in Progress

Novel pathway to produce high molecular weight kraft lignin–acrylic acid polymers in acidic suspension systems

Abstract

Kraft lignin (KL) produced in kraft pulping process has a low molecular weight and solubility, which limits its application in industry. For the first time, KL was polymerized with acrylic acid (AA) in an acidic aqueous suspension system to produce a water soluble lignin–AA polymer with a high molecular weight in this work. The polymerization reaction was carried out using K2S2O8 as an initiator, and the influence of reaction conditions on the carboxylate group content and molecular weight of resultant lignin polymers was systematically investigated. The mechanism of polymerization of KL and AA was discussed fundamentally. The resulting lignin–AA polymer was characterized by Fourier Transform Infrared spectrophotometry (FTIR), proton nuclear magnetic resonance (1H-NMR) and elemental analyses. The results showed that the phenolic hydroxyl group (Ph-OH) content of KL promoted the polymerization under an acidic environment. Under the conditions of 1.5 wt% of initiator, 3.5 of pH, 10.0 of AA/lignin molar ratio, 0.15 mol L−1 of lignin concentration, 3 h and 80 °C, the carboxylate group content and the molecular weight of the polymer were 7.37 mmol g−1 and 7.4 × 105 g mol−1, respectively. The lignin–AA polymer was water soluble at a 10 g L−1 concentration and a pH higher than 4.5. Furthermore, the flocculation performance of lignin–AA polymer in an aluminium oxide suspension was evaluated. Compared with polyAA, the lignin–AA polymer was a more efficient flocculant for aluminium oxide suspension, which shows its potential to be used as a green flocculant in industry.

Graphical abstract: Novel pathway to produce high molecular weight kraft lignin–acrylic acid polymers in acidic suspension systems

Supplementary files

Article information

Article type
Paper
Submitted
01 Dec 2017
Accepted
22 Mar 2018
First published
29 Mar 2018
This article is Open Access
Creative Commons BY license

RSC Adv., 2018,8, 12322-12336

Novel pathway to produce high molecular weight kraft lignin–acrylic acid polymers in acidic suspension systems

F. Kong, S. Wang, W. Gao and P. Fatehi, RSC Adv., 2018, 8, 12322 DOI: 10.1039/C7RA12971H

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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