S-incorporated TiO2 coatings grown by plasma electrolytic oxidation for reduction of Cr(VI)-EDTA with sunlight

Abstract

The plasma electrolytic oxidation (PEO) technique was used to prepare photocatalytic S-TiO coatings on Ti sheets; the incorporation of the S ions was possible from the electrolyte for modifying the structural and optics characteristics of the material. In this work, substrates of Ti (ASME SB-265 of 20 × 20 × 1 mm) were used in a PEO process in 10 min, using constant voltage pulses of 340 V with frequency of 1 kHz and duty cycles of 10% and of 30%. Solutions with HSO (0.1 M) and CHNS (52 and 79 mM) were used as electrolytes. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS) were utilized to analyze the surface morphology, crystalline phase, and chemical composition of the samples. According to the results, the catalyst coatings had microporous structure and contained anatase-rutile TiO nanocrystalline mixture, until 73.2% rutile and 26.8% anatase in the samples grown with 30% duty cycle and the lowest concentration of CHNS. From the EDS measurements, the incorporation of sulfur ions to the coatings was 0.08 wt%. 99.5% reduction efficiency of Cr(VI)-EDTA with sunlight was observed after 2 h; it was determined by diphenyl carbazide spectrophotometric method. These coatings have potential for effective sunlight heterogeneous photoreduction of this toxic, cumulative, and non-biodegradable heavy metal that contaminates the soil and water and is a serious risk to sustainability, ecosystems, and human health.

In Vitro Biological Characterization of Silver-Doped Anodic Oxide Coating on Titanium

“…It should be noted that AgNP incorporation via PEO can prevent the release of Ag ions into the bloodstream due to immobilization of AgNPs deep inside the oxide layer and can prevent expected toxic effects [ 29 ]. With the aim of obtaining functional coatings, different organic and inorganic chelating agents, such as ethylenediaminetetraacetic acid (EDTA), could be used for the PEO process [ 30 ]. Nitrilotriacetic acid (NTA) is a widely used chelating agent utilized for fluorescent agent development [ 31 ] and drug encapsulation [ 32 ].…”