Cellulose nanocrystals: source, production and application as a coagulant for water purification

Abstract

Abstract The coagulation/flocculation technique is an old proven method that utilizes chemical coagulants for water purification but there are health and environmental challenges associated with the long-term application of such coagulants. Cellulose fibre is a renewable, eco-friendly polymer found in many materials. It has been widely researched due to its unique properties, especially when processed in the ‘nano’ form as cellulose nanocrystals (CNCs) but nanocelluloses require surface functionalization in order to improve their suitability for various applications. The aim of this review is to provide an in-depth discussion of the current progress in the synthesis of CNCs with recourse to their source, surface chemistry and extraction procedures. Various techniques used for the conversion of CNCs into coagulants were extensively reviewed while the current development on the potential application of CNCs as a coagulant for water remediation was presented. The results obtained from the potential application of modified CNC-based coagulants demonstrate their remarkable coagulation efficiency for the purification of contaminated water. Therefore, global research into the development of CNC-based coagulants at all levels is crucial in order to generate interest in natural coagulants as a potential replacement for chemical coagulants. Furthermore, potential areas for more research were proposed in this review.