Preparation of Titanate Whiskers Starting from Metatitanic Acid and Their Adsorption Performances for Cu(II), Pb(II), and Cr(III) Ions

Titanate whiskers were prepared by hydrothermal method starting from hydrous metatitanic acid and potassium hydroxide. The titanate whiskers were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, and N-2 adsorption/desorption techniques. When the concentrations of potassium hydroxide ranged from 6 to 12 mol L-1, titanate whiskers were formed by bundling layer-structured nanoribbons. The titanate whiskers were certified with the formula of H2-xKxTi3O7 center dot nH(2)O (x=0.6, n=3.8-4.0). After hydrochloric acid treatment, the potassium content and the layer distance decreased due to the replacement of potassium ions by protons. The maximum adsorption capacities of titanate whiskers for Cu(II), Pb(II), and Cr(III) ions were 142.0, 395.7, and 97.0 mg g(-1) when their initial concentrations were 150, 300, and 80 mg L-1, respectively. The adsorption equilibriums were almost established in 30 min. The adsorption of Cu(II), Pb(II), and Cr(III) ions on titanate whiskers followed the pseudo-second-order adsorption kinetics. The Langmuir adsorption isotherms well fitted the adsorption equilibriums of Cu(II) and Pb(II) ions while the Freundlich adsorption isotherm well fitted the adsorption equilibrium of Cr(III) ions.