Short-cut synthesis of tri-titanate nanotubes using nano-anatase: Mechanism and application as an excellent adsorbent

• Short-cut hydrothermal synthesis of TNTs by nano-anatase and NaOH was achieved.
• Similar crystal array of anatase and tri-titanate greatly reduced reaction time.
• Longer Ti–O–Ti bond in anatase than in rutile lead to easier breakage of the bond.
• Over 90% reaction time was saved for TNTs synthesis as an excellent adsorbent.
• Abundant –ONa sites on TNTs guaranteed excellent adsorption performance.

Conventional hydrothermal synthesis of titanate nanotubes (TNTs) by P25 TiO2 and NaOH has been blamed for its long reaction time (continuous heating for three days). This paper presented a short-cut hydrothermal synthesis of TNTs by nano-anatase and NaOH, which significantly reduced the reaction time from 72 to 6 h while the other experimental conditions were same. Essential interpretation of such a surprising reduction of reaction time was given in terms of TEM, XRD and FTIR analysis. It indicates that the transformation from anatase to sodium tri-titanate nanotubes includes the following three steps: (1) aggregation of spherical anatase particles (0–1 h), (2) morphologic transformation to titanate nanosheets with fewer visible anatase crystal arrays (1–3 h), and (3) crimping of tri-titanate nanosheets and a final generation of TNTs (3–6 h). Further comparison with TNTs synthesis process from P25 TiO2 (ca. 80% of anatase and 20% of rutile) indicates that the rate-limiting step for breakage of Ti–O–Ti bond is largely controlled by crystal array of the concerned nanomaterials. The as-prepared TNTs are proved to exhibit similar Cd adsorption capacity compared with conventional TNTs based on batch adsorption experiments. The widely distributed anatase in nature as well as its over 90% reaction time saving in TNTs preparation process under facile conditions makes the proposed short-cut synthesis of great potential in engineering applications.

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