Abstract
In the study, a facile one-step method for synthesizing magnetic-TiO2-nanophotocatalysts was developed. With the same composing ratio of 0.5 and 0.35 (Fe:Ti, mole:mole), we prepared two types of magnetic-TiO2-nanocomposites as one-step synthesized FexOy-composed TiO2 (FexOy/TiO2-0.5 and FexOy/TiO2-0.35) and two-step synthesized core-shell FexOy@TiO2 (FexOy@TiO2-0.5 and FexOy@TiO2-0.35), and tested their performance in rhodamine 6G (R6G) photodegradation. X-ray diffraction (XRD) analysis showed that FexOy@TiO2-0.5 has the smallest crystallite size (16.8 nm), followed by FexOy@TiO2-0.5 (18.4 nm), FexOy/TiO2-0.35 (21.0 nm) and FexOy/TiO2-0.5 (19.0 nm), and X-ray photoelectron spectroscopy (XPS) suggested the decreasing percentage of Fe3O4 from 52.1% to 36.7%-47.2% after Ti-deposition treatment. The saturated magnetisms followed the order: FexOy@TiO2-0.5 > FexOy@TiO2-0.35 > FexOy/TiO2-0.5 > FexOy/TiO2-0.35. R6G photodegradation followed the first order kinetics and was slightly influenced by pH but significantly affected by initial photocatalyst concentration. FexOy/TiO2-0.35 achieved the highest removal efficiency for R6G (92.5%), followed by FexOy@TiO2-0.35 (88.97%), FexOy@TiO2-0.5 (60.49%) and FexOy/TiO2-0.5 (48.06%). Additionally, all these magnetic-TiO2-nanocomposites had satisfied magnetic recoverability and exhibited laudable reusability after 5-times reuse, even achieving higher R6G removal efficiencies from 97.30% to 98.47%. Our one-step method took only 75 min for nanocomposite synthesis, 90 min less than conventional two-step method, showing its feasibility as a practical method for magnetic-TiO2-nanocomposite synthesis in industrial application.
Highlights
The main advantages of this method are: 1) simplified synthesis procedure without the need of pre-synthesizing magnetic nanoparticulates (MNPs) or TiO2 precursor; 2) 55% less synthesis time comparing to two-step method; 3) cost-saving for fewer reagents in synthesis process
The elemental composition of the synthesized MNPs and magnetic-TiO2-nanocomposites was analysed by X-ray photoelectron spectroscopy (XPS) (Fig 2A)
Fe3O4 accounted for 52.1% of the total iron oxides in MNPs, decreasing to 36.7%-47.2% in magnetic-TiO2-nanocomposites
Summary
Photocatalysis is one of most popular advanced oxidation processes (AOPs) in water treatment owning to its promising features of environment-friendly, generally non-selectivity and less. Most TiO2 catalysts are used in nano-scale [8,9], challenging the separation and recovery of these ultrafine particles after photocatalytic reaction Considering their risks to the environment [10], recovering and reusing these TiO2 nano-photocatalysts is of great urgency. MagneticTiO2-nanophotocatalysts with different silver composing ratios could degrade 83.9% of methylene blue within 6 hours and the degradation efficiency remained 79% after 5-cycle reuse [23]. These magnetic-TiO2-nanophotocatalysts achieved satisfied photodegradation efficiencies and magnetic recoveries, they all require a complicated multiple-step synthesis and time-consuming pre-synthesis of MNPs or TiO2 precursor [5]. The main advantages of this method are: 1) simplified synthesis procedure without the need of pre-synthesizing MNPs or TiO2 precursor; 2) 55% less synthesis time comparing to two-step method; 3) cost-saving for fewer reagents in synthesis process
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