Efficient Removal of Heavy Metal Ions with Biopolymer Template Synthesized Mesoporous Titania Beads of Hundreds of Micrometers Size

摘要

We demonstrated that mesoporous titania beads of uniform size (about 450 μm) and high surface area could be synthesized via an alginate biopolyrner template method. These mesoporous titania beads could efficiently remove Cr(Ⅵ), Cd(Ⅱ), Cr(Ⅲ), Cu(Ⅱ), and Co(H) ions from simulated wastewater with a facile subsequent solid-liquid separation because of their large sizes. We chose Cr(Ⅵ) removal as the case study and found that each gram of these titania beads could remove 6.7 mg of Cr(Vl) from simulated wastewater containing 8.0 mg·L~(-1) of Cr(Ⅵ) at pH = 2.0. The Cr(Ⅵ) removal process was found to obey the Langmuir adsorption model and its kinetics followed pseudo-second-order rate equation. The Cr(Ⅵ) removal mechanism of titania beads might be attributed to the electrostatic adsorption of Cr(Ⅵ) ions in the form of negatively charged HCrO_4~- by positively charged TiO_2 beads, accompanying partial reduction of Cr(Ⅵ) to Cr(Ⅲ) by the reductive surface hydroiyl groups on the titania beads. The used titania beads could be recovered with 0.1 mol·L~(-1) of NaOH solution. This study provides a promising microanostructured adsorbent with easy solid-liquid separation property for heavy metal ions removal.