In this study, humic acid-bound nanosized hydroxyapatite (HA-nHAP) was developed as a novel adsorbent, and the potential of using HA-nHAP for the adsorption of Rhodamine B (RhB) from aqueous solution as functions of pH, adsorbent dosage, contact time, ionic strength and temperature was investigated. The results indicated that the HA binding significantly increased the adsorption of RhB due to the introduction of abundant negatively charged functional groups. The adsorption capacity of HA-nHAP for RhB was found to be pH-dependent, and the optimal pH value was found to be 6.0. The adsorption equilibrium data obeyed Sips and Freundlich isotherms and the kinetic data were well described by the Elovich kinetic model. According to the Sips equation, the maximum adsorption capacity for RhB was 24.12 mg/g. Temperature and ionic strength experiment Downloaded by [University of Sussex Library] at 15:15 18 May 2016 2showed that they both had effect on the adsorption capacity of HA-nHAP. Thermodynamic study confirmed that the adsorption was a spontaneous, endothermic and more random arrangement process. The present investigation showed that HA-nHAP is a promising adsorbent for the removal of RhB from aqueous solution.

Anisotropic single-crystalline gold nanosnakes were synthesised in poly(vinyl pyrrolidone) (PVP)-sodium dodecyl sulphate (SDS) aggregation aqueous solution by reducing HAuCl 4 with PVP without any additional reducing agent. The crystal structures, growth process and the influence of SDS concentrations on the growth of gold nanosnakes have been investigated by X-ray diffraction and transmittance electron microscopy. In this approach, the peculiar structure of PVP-SDS aggregations is indispensable for the asymmetrical formation of gold nanosnakes. Without PVP-SDS aggregations, only long tortuous gold nanobelts were synthesised. When SDS concentration was increased from 3 to 10 mM, gold nanosnakes, nanokites and nanoplates were fabricated. To the best of our knowledge, this is the first report on the SDS-induced shape transformation from snake-like to plate-like at fixed low HAuCl 4 concentration in PVP-SDS aggregation aqueous solutions. Moreover, the gold nanosnakes exhibit excellent electrocatalytic property towards the oxidation of methanol indicating their potential applications in fuel cells, catalysis, biosensing and nanodevices.

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