ZnCr-LDHs with dual adsorption and photocatalysis capability for the removal of acid orange 7 dye in aqueous solution

International audienceThis study aims to explore the potential of layered double hydroxides (LDHs) materials for the treatment of contaminated waters by organic pollutants, using a combined dual process, namely adsorption-photocatalysis. A series of LDHs of ZnCr-X where (X = Cl, SO4 and CO3) were synthesized and characterized by several techniques such as DRX, FTIR, BET, TEM, and UV-Visible spectrophotometry. The pollutant acid orange 7 (AO7) is efficiently adsorbed on the surface of the three LDHs. The adsorption depends on the nature of the intercalated anion. The adsorption percentage of AO7 achieved for the intercalated anions , and Cl−, was 25, 32 and 49.5% respectively. We find that ZnCr–SO4 LHD is the most effective photocatalyst for AO7 dye decomposition in the UV and visible range and its photocatalytic activity is preserved during three cycles of photocatalytic tests. Such remarkable properties allow considering ZnCrSO4-LDH as a promising photocatalyst with high activity, long-term durability and excellent applicability

Enhanced photocatalytic activity of hydrozincite-TiO2 nanocomposite by copper for removal of pharmaceutical pollutant mefenamic acid in aqueous solution

International audienceNanocomposites based on Hydrozincite-TiO 2 and copper-doped HZ-xCu-TiO 2 (x= 0.1; 0.25; 0.35) were synthesized in a single step using the urea method. The samples were characterized by XRD, FTIR, SEM/TEM and DRS. The study of adsorption capacity and photocatalytic efficiency of these nanocomposites have been tested on a pharmaceutical pollutant, mefenamic acid (MFA). Kinetic study of removal of MFA, indicates that this pollutant was adsorbed on the surface of the synthesized phases, according to Langmuir's model. Such adsorption proved to be well adapted in a kinetic pseudo-second order model with capacity of 13.08 mg/g for HZ-0.25Cu-TiO 2. Subsequently, the kinetics of photocatalytic degradation under UV-visible irradiation was studied according to several parameters, which allowed us to optimize our experimental conditions. The nanocomposite HZ-0.25Cu-TiO 2 showed significant removal efficiency of MFA. Elimination rate reached 100% after 20 min under UV-vis irradiation, and 77% after 7h under visible light irradiation. Repeatability tests have shown that this nanocomposite is extremely stable after six photocatalytic cycles. By-products of MFA were detected by LC/MS. These photoproducts produced by three types of reactions of hydroxylation; cyclization and cleavage of the aromatic ring. MFA underwent complete mineralization after 22 h of irradiation in the presence of the HZ-0.25Cu-TiO 2