Snežana Maletic
University of Novi Sad, Republic of Serbia
Title: Removal of divalent heavy-metal ions from aqueous solutions by adsorption process with titanium dioxide nanowires
Biography
Biography: Snežana Maletic
Abstract
The key objective of this work was to investigate kinetics and adsorption capacities of divalent metal ions (Cu2+, Pb2+, Cd2+) from water on TiO2 nanowires at pH 3 and 7. Brunauer-Emmett-Teller (BET) analysis showed that the surface area of the TiO2 nanowires was 115,9 m2g-1. The point of zero charge (pHpzc) was 4.8. Adsorption experiments were performed using the conventional batch technique at room temperature (25±2°C). The background solution was 0.01 M CaCl2 in deionised water. Initial concentrations of heavy metal ions were in the range 0.05–5 mg L-1. The amount of adsorbent corresponded to a sample/solution ratio that resulted in 20-80% uptake of given metal ion. The samples were agitated on horizontal shaker for 30 h. The time to reach adsorption equilibrium was obtained from a kinetic study performed over 72 h. The adsorption kinetics of divalent metal ions on TiO2 nanowires was investigated using pseudo-first order, pseudo-second order and intraparticle diffusion models. Adsorption of metal ions was controlled by chemisorption which was supported by the suitability of the pseudo-second order model. Intraparticle diffusion model data showed that diffusion cannot be considered as the limiting step of adsorption. The equilibrium adsorption data were modeled using Freundlich and Langmuir adsorption isotherms which both showed good agreement with experimental data. The highest removal efficiency of heavy metals was observed at pH=7, except in the case of Pb which has been removed better at pH=3. Adsorption affinities increased in the following order: PbpH3> CdpH7 >PbpH7 > CdpH3> CupH7 > CupH3.