Defect evolution on the activity of samarium doped Na2TinO2n+1 with different sodium/titanium ratio for photocatalytic degradation of fluoroquinolones drugs, toxicity assessments and eco-toxicity prediction

Abstract

In this study, samarium (Sm) doped sodium titanate (Na2TinO2n+1) with different Na/Ti molar ratios {n: 3, 6, and 9} were synthesized by using sol-gel method. The prepared nanostructures were characterized by XRD, SEM, EDS, BET, UV–vis, EIS and photoluminescence analysis. XRD analysis depicts the Na2Ti6O13 was the main substance, while Sm–Na2Ti9O19 contained a minor proportion of Na2Ti6O13, and rutile phase TiO2. The pore size distribution for all samples is between 2 nm and 20 nm, indicating that most of the pores are in the range of meso porosity. The adsorption-desorption isotherms shows the mesoporous properties of the prepared samples. The band gap energies for samarium doped sodium titanate were lower than the sodium titanate nanostructures. The productivity of hydroxyl radicals on the samarium doped sodium titanates was in the sequence Sm–Na2Ti9O19 > Sm–Na2Ti6O13 > Sm–Na2Ti3O7. The different samarium doped sodium titanates samples were utilized for degradation ofloxacin and ciprofloxacin under UV light irradiation. The results showed that the complete degradation ofloxacin (94.2 %) and ciprofloxacin (99.7 %) were obtained by using Sm–Na2Ti9O19 within 70 min, while the degradation efficiency of Sm–Na2Ti6O13 and Sm–Na2Ti3O7 were lower than Sm–Na2Ti9O19 nanostructures. Also, the marine microalgaes growth rate and biotoxicity of the Sm-doped sodium titanates were investigated on Chaetoceros calcitrans, and Nannochloropsis oculata. The results showed that high concentration of the samarium doped sodium titanates were inhibited the algae growth rate.