Plasma‐Enabled Simultaneous Synthesis and Nano‐Anchoring of TiO _{2− x} Nanolayers on Mesoporous Bio‐Silica for Effectiv

ABSTRACT

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) (TiO _{2− x} ) and hydroxyl groups, which were synthesized and nano‐anchored via a rapid, low‐temperature (<60°C) atmospheric pressure plasma process in an aqueous medium, resulting in homogeneous deposition of a TiO _{2− x} nanolayer within the mesopores of bio‐silica. The resultant TiO _{2− 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 TiO ₂ ‐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 TiO ₂ ‐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.