Abstract: Cellulose, the most prevalent natural polymer, has greatly impacted the world and society in broad reaching areas. Advanced processing, allowed researchers to discover the nanoscale cellulose structures that exhibit extraordinary properties. These nanostructures are naturally occurring and have sizes ranging from a few nanometers to microns with high strength, properties comparable to Kevlar. Generally, CNs can be categorized as cellulose nanocrystals (CNCs) or cellulose nanofibrils (CNFs). CNCs are highly crystalline with fewer amorphous regions compared to CNFs.
Recently, there has been interest in water treatment applications of CNCs owing to their properties of controlled size and morphology, surface chemistry, high specific surface area, nanometric dispersity, good colloidal stability and high mechanical properties 2. Two different applications of CNCs for water treatment will be presented (Figure 1), the first use of CNCs to stabilize Nano Zero-valent iron nanoparticles (nano-ZVI) for ground water remediation and CNCs incorporation in membrane for water filtration.
Nano-ZVI have been widely studied for in-situ remediation of groundwater and other environmental matrices for his ability to degrade large spectrum of contaminants, such as halogenated hydrocarbons, azo dyes, hexavalent chromium and various heavy metal ions. Nano-ZVI particle mobility and reactivity are the main concern to achieve efficient in-situ groundwater remediation 3. In comparison to nano-ZVI “coating” strategy, the nano-ZVI stabilization on supporting material allows a direct contact with the pollutant, reduces the electron path from nano-ZVI to the target contaminant and increases nano-ZVI reactivity 4. However, even if the nano-ZVI dispersion at the support surface is efficient, the mobility of supported nano-ZVI is limited by the support material itself. We use CNCs as a support to stabilized nano-ZVI. The nano-ZVI-CNCs nanocomposites appear to be highly mobile with no affinity to the porous surface, the CNC also improve the nano-ZVI reactivity toward the contaminant.
In membrane application, nanomaterials and particularly carbon nanotubes (CNTs), have been incorporated to improve membrane permeability and selectivity as well as to increase the durability of the membranes. CNCs present the advantage in comparison to CNTs to have a lower manufacturing cost and low ecotoxicity. In addition, the inherent properties (i.e. hydrophilicity and mechanical strength) of environmental friendly CNCs make them a possible alternative to CNTs 5. We prepare different membrane incorporating CNCs and CNTs and compare the membrane permeability and durability. The hydrophilicity of the CNC-Membrane was greater than the CNT-Membrane. In addition, the Young’s modulus and tensile strength were enhanced for both the CNC-Membrane and CNT-Membrane. While smaller concentrations of CNTs were required to achieve an equal increase in Young’s modulus compared with the CNCs, the elasticity of the CNC-composite membranes was greater.
These two applications reveal that it is achievable to widely utilize CNC in environmental engineering applications.