The copper adsorption on to CNTs is attributed to the formation of an inner-sphere complex between copper and CNT surface functional groups. At pH values exceeding the PZC (point of zero charge), oxygen functional groups give rise to a net negative surface charge promoting metal cation adsorption. CNT hybrids were obtained by recovering CNTs with copper from isotherm adsorption bottles after equilibrium. The solution pH dropped after equilibrium by release of H+ from CNT surface. Zeta potential experiments show that the electronegativity decreased (less negative surface charge) with increasing pH. Kinetic studies demonstrate the copper adsorption rate on OH functionalized CNTs, exceeded that of COOH functionalized CNT surfaces. Network forces within acid and alcohol functionalized CNTs bundles suggest formation of different mesopore structures, leading to the conclusion of different diffusivity driving forces. Kinetic modeling is proposed for the diffusion rate of copper. FTIR spectra compare vibration peaks of hybrids and as-received CNTs. XRD and SEM/EDX experiments confirm the presence of solid copper species at pH 4.7. ICP-AES analysis measures the amount of copper and other metals leaching from hybrids and as-received CNTs after different rinse cycles.

Adsorption mechanisms of copper species on multiwall carbon nanotubes (CNTs): Study of chemical structures and regeneration of hybrids and as-received CNTs

243rd National Meeting (2012)

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