Plasma-Enabled Simultaneous Synthesis and Nano-Anchoring of TiO2-x Nanolayers on Mesoporous Bio-Silica for Effective Photodegradation of Tetramethylammonium Hydroxide

초록

Organic pollutants from semiconductor manufacturing pose significant threats to aquatic ecosystems and remain challenging to treat. To address these issues, mesoporous bio-silica (diatomite) was employed as a platform material to accommodate titanium dioxide nanoparticles with oxygen vacancies (OVs) (TiO2-x) and hydroxyl groups, which were synthesized and nano-anchored via a rapid, low-temperature (<60 degrees C) atmospheric pressure plasma process in an aqueous medium, resulting in homogeneous deposition of a TiO2-x nanolayer within the mesopores of bio-silica. The resultant TiO2-x nanolayer/bio-silica composite (DE 700), with a low bandgap (2.68 eV) and a mixed anatase-rutile composition, achieved exceptional photocatalytic performance under a 300 W commercial solar lamp, degrading 20 ppm of tetramethylammonium hydroxide (TMAH), a highly toxic semiconductor wastewater pollutant, using a catalyst loading of 0.5 g/L. The catalyst achieved 62% TMAH conversion into ammonium ions with trace amine intermediates and complete TMAH degradation after 12 h of solar lamp exposure. It degraded 20 ppm methylene blue (MB) by 90% in 30 min and 100% in 120 min, significantly outperforming commercial TiO2-P25, which achieved 29.22% TMAH removal and 14.11% ammonium ion conversion under same condition. Electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence (TRPL) analyses indicated improved interfacial charge-transfer kinetics and suppressed charge-carrier recombination in DE 700 compared to TiO2-P25. Additionally, the catalyst maintained 91%-97% degradation efficiency over four reused cycles, and a preliminary plant-based sprouting assay indicated no observable phytotoxicity of the treated effluent, highlighting its potential as a cost-effective solution for treating challenging feedwater streams.

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