Enhanced photocatalysis performance of mechano-synthesized V2O5–TiO2 nanocomposite for wastewater treatment: Correlation of structure with photocatalytic performance

Abstract

The harmful chemical organic dyes used in textile industries and wastewater posses a great threat to human beings due to huge toxicity and enormous health hazards. Consequently, the conversion of these harmful chemicals into harmless substances becomes utmost essential for sustainable development in wastewater research. High-energy ball-milling of orthorhombic V2O5-anatase (a) TiO2 mixture (1:1 M ratio) at room temperature results in the formation of nanocrystalline V2O5–TiO2 solid solution phase. A series of V2O5–TiO2 solid solution is synthesized by varying the milling time from 5min to 20h. The Rietveld X-ray powder structure refinement methodology has been adopted for microstructure characterization of unmilled and all ball-milled nanocomposite samples, in terms of lattice imperfections. From Rietveld analysis, lattice parameters, relative phase abundance of individual phases, crystallite size and r.m.s. lattice strain values are estimated. At the early stage of milling of 30min, a-TiO2 transforms to polymorphic rutile (r)-TiO2 due to high energy impact of mechanical alloying. The final ball-milled powder mixture is composed of V2O5–TiO2 solid solution with a trace amount of r-TiO2 phase. Photocatalytic study through the degradation of Rhodamine B (RhB) in presence of visible light reveals enhanced degradation (~94%) of RhB with 3h ball-milled V2O5–TiO2 nanocomposite, compared to ~74% with 15h milled nanocomposite reported earlier. Optical bandgaps of ball-milled V2O5–TiO2 nanocomposites are within the semiconducting range. FESEM study of ball-milled powder mixture reveals the pineapple flower-like morphology of nanoparticles of V2O5–TiO2 nanocomposites. An enormous number of the leaf (V2O5)/flower (TiO2) semiconducting heterojunctions with small crystallite size and higher surface area are believed to excel the photocatalytic performance of the nanocomposite through electron-hole pair production and easy electron transport mechanism between valance and conduction bands due to low bandgap energy of TiO2 with the addition of V2O5. TEM study further reveals the particle size distribution and confirms the presence of crystalline phases in the ball-milled nanocomposite. FTIR spectrum of 3h ball-milled V2O5–TiO2 in RhB solution corroborates the photocatalytic property of the prepared nanocomposite. Finally, an attempt has been made to establish a correlation between structure/microstructure and photocatalytic performance of the nanocomposites.