Cellulose particles on micro and nanoscales used as adsorbents for water purification have been an area of great interest in materials science research in recent years.1 The current report focuses on a deeper fundamental understanding of the adsorption behavior of metal ions on cellulosic material from micro to nano to molecular scale. Atomic force microscopy (AFM) is a powerful tool and has made possible the in situ examination of the morphological and mechanical properties of materials in both dry and wet conditions. We employed two AFM based methods to evaluate the surface interaction and adsorption behavior between cellulosic materials and metal ions; Ag(I), Cu(II) (See TOC Figure). In the first approach, three types of cellulose microsphere (native cellulose and its derivatives with sulfate and phosphate groups) were used to functionalize the AFM probe cantilever.2 The interactions (adhesion and repulsion forces) between the functionalized probes and substrate was measured and compared in AgNO3 solution under different pHs. In the second approach, single TEMPO cellulose nanofiber (TOCNF) was anchored on the substrate and PF-QNM mode was applied to measure the topography, adhesion force and stiffness of the fiber at the same position by comparing before and after adsorption in CuSO4 solution. The AFM, SEM-EDS and XPS results agreed with each other and were further supported by the extensive spectroscopic characterization (FTIR and Raman) and Density functional theory (DFT) simulations. All the results indicate that metal ions were first adsorbed by the functional groups grafted on cellulose chains in aqueous medium and followed by metal nano-layer/ nanocluster formation process during drying in air. This study is of great assistance for understanding the mechanisms associated with water purification and other forms of interfacial interaction domains.

Investigation of surface interactions of micro/nano-cellulose with metal ions at micro-nano-molecular scale

253rd National Meeting (2017)

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