Enhanced Photocatalytic Degradation of Tetracycline by Anatase TiO₂ Synthesized over a Broad pH Range

Abstract

Using (Na)₂TiF₆ and CO(NH₂)₂ as raw materials, we proposed a simple one-pot hydrothermal method for synthesizing single-phase anatase TiO₂ across a broad pH range of the precursor solution. The results showed that, irrespective of whether the precursor solution was acidic (pH=1.43, 3.43, 5.37), neutral (pH= 7.23), or alkaline (pH=9.45, 11.18, 13.15) prior to the hydrothermal reaction, the post-reaction solution pH stabilized between 8 and 9, and all resultant TiO₂ materials were identified as single-phase anatase. This finding contrasted with previous reports where phase transformations among anatase, rutile, or brookite were observed under varying pH conditions of the precursor solution. This discrepancy was attributed to the continuous decomposition of urea during the hydrothermal process, which maintained the pH of the reaction solution within a relatively stable range. Comprehensive investigations revealed that anatase TiO₂ synthesized at pH 7.23 exhibited optimal light absorption ability, enhanced charge dynamics, and a larger electrochemically active surface area. As a result, TiO₂ (pH 7.23) showcased the highest photocatalytic activity toward tetracycline (TC), achieving a degradation efficiency of 97.7%. Mechanistic studies indicated that O₂^•− was the predominant reactive species accounting for TC degradation.

Keywords

single-phase anatase TiO₂ / photocatalysis / precursor pH

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