Chemical Engineering Journal, Vol.344, 21-33, 2018
Tinidazole degradation assisted by solar radiation and iron-doped silica xerogels
The main objective of this study was to assess the photoactive properties of iron-doped silica xerogels under solar radiation. For this purpose, silica xerogels (XGS) were doped with different doses of Fe(III) by the sol-gel method. Tinidazole (TNZ) was considered as model compound for the degradation study. XGS samples were texturally and chemically characterized by N-2 (77 K), standard test sieves, XRD, FTIR, SEM, HRTEM, PL, XPS, and DRS. The results showed that in aqueous solution of 0.4M Fe(III), XGS was doped with 3.64% iron and contained 33.01% silicon and 63.36% oxygen (XGS-Fe(III)-0.4 M). The addition of Fe(III) modified the textural properties of the xerogels. Thus, XGS-Fe(III)-0.4M had a smaller specific area (587 m(2) g(-1)) than non-doped XGS-BCO (645.92 m(2) g(-1)), with a decrease in pore volume and average pore diameter of 50% and 63.6%, respectively. The band-gap energy (E-g) value was reduced from 3.55 eV (XGS-BCO) to 2.32 eV (XGS-Fe(III)-0.4 M) due to the inclusion of iron zoned in the form of iron oxy-hydroxide. Therefore, this is a photoactive material under solar radiation, with an Eg value < 4 eV. The percentage TNZ degradation was 41% for XGS-BCO and 68% for XGS-Fe (III)-0.4M after 1 h of treatment. Previous irradiation of XGS-Fe(III)-0.4M increased the percentage TNZ degradation to 98%. The radicals generated in the process were quantified. The degradation rate was increased at higher XGS-Fe(III) doses and neutral pH. The low-molecular-weight degradation byproducts obtained are not toxic for HEK-293 cells. Fe(III)-doped xerogels are a good alternative option for drug removal from polluted waters.