In English

Abstract

The removal of hazardous substances from wastewater is a major problem in the world. The advantages of application of Zn-Al layered double hydroxides (LDHs) and their derivatives for removal of organic contaminants consist in the combination of high adsorption capacity of LDHs and the presence of a photoactive component. Therefore, the present paper focuses on study of the adsorption and photocatalytic capabilities of Zn-Al LDHs to remove cationic dye methylene blue (MB) from aqueous solutions. Zn-Al LDHs with Zn:Al ratio 2 were synthesized by coprecipitation method. Zn-Al LDHs were characterized by XRD, thermogravimetric and spectroscopy analysis. The reconstruction of calcined Zn-Al LDHs in sodium dodecyl sulfate (SDS) solutions in the range of concentrations from 0.012 mol·L –1 to 0.205 mol·L –1 was performed to obtain organo/Zn-Al LDHs. The partial SDS intercalation was clearly evidenced by the appearance of a peak at low 2θ values. SDS-modified LDHs demonstrate the high adsorption capacity to MB. About 90 % of dye was adsorbed with organo/Zn-Al LDHs from 2×10 -4 mol·L –1 MB solution. The study on optical properties of calcined and reconstructed Zn-Al LDHs has detected the presence of ZnO that makes possible the using of Zn-Al LDHs as photocatalysts. About 50 % of dye was destructed by irradiation of MB solution in the presence of Zn-Al LDHs from 2×10 -5 mol·L –1 MB solution in the presence of calcined at 450 °C Zn-Al LDHs. It has been found that the most complete removal of the dye from highly concentrated solutions is achieved by MB adsorption with organo/Zn-Al LDH. The investigation of the irradiation influence on the optical spectra of MB adsorbed on the surface of organo/Zn-Al LDH is needed to clarify the photocatalytic activity of ZnO-contained organo/Zn-Al LDH. The high adsorption capacity of organo/Zn-Al LDHs and the ease of both synthesis and separation processes rendered this adsorbent to be a promising candidate for environmental remediation.