Synthesis of cellulose graft ionic liquid using silanization reaction

Abstract

Introduction: Ionic liquids (ILs) have attached many attentions due to their interesting physicochemical properties. However, ionic liquids have several disadvantages including high viscosity, difficult to purify, separate and recycle, and expensive. Therefore, supported ionic liquids (SIL) have been developed to overcome these problems. SIL based on cellulose material was conventionally synthesized by silanization reaction between ionic liquid trialkoxyl silane and hydroxyl groups on the surface of cellulose. However, low reactivity of cellulose hydroxyl groups causes the low efficiency of silanization reaction. With the aim to resolve these problems and improve the reactivity of cellulose silanization reaction, cellulose graft ionic liquid was synthesized and characterized.

Methods: Cellulose graft ionic liquid (CL-IL) material was synthesized by silanization reaction. The influence of reaction condition such as IL/CL (w/w) ratio, base catalyst (NH₃) and agent coupling tetraethyl orthosilicate (TEOS) on silanization reaction was investigated. The modified CL-IL materials were characterized using FT-IR, TGA, SEM. The ion exchange properties were evaluated via batch adsorption studies to evidence the efficiency of silanization reaction of cellulose.

Results: The study indicated that adding TEOS with NH₃ catalyst could significantly increase the number of imidazolium groups grafted on cellulose about 75% compared to the conventional approach. CL-IL material is an efficient anion exchange materials displaying fast kinetic adsorption and high capacity adsorption of MO up to 1.4 mmol g^-1.

Conclusion: High-efficiency of cellulose silanization was obtained by using coupling agent TEOS and base catalyst. Therefore, the silanization reaction can be used for synthesis divers of functional cellulose materials. This approach can be aimed for the design of cheaper and high-performance materials for catalysis, polymer composite and adsorption in water treatment and depollution of industrial wastewater.