Abstract
Calcined and organo-modified Zn-Al layered double hydroxides (LDHs) were studied as adsorbents and photocatalysts for removal of cationic dye, as namely methylene blue (MB). Zn-Al LDHs with a cationic ratio of 2:4 were obtained by the coprecipitation method. As-synthesized samples were calcined at different temperatures and the phase transformations were investigated by XRD, TG/DTG, and UV–vis-DR methods. The activity of as-synthesized and calcined Zn-Al LDHs under UV light was attributed to the presence of ZnO phase. The amount of ZnO in LDHs can be regulated by varying of Zn/Al ratio and heating temperature. The impact of Zn/Al ratio on photocatalytic activity of LDHs was observed predominant. The calcined Zn-Al LDHs demonstrated low adsorption of MB. The modification of ZnAl LDHs by sodium dodecyl sulfate was performed using a reconstruction method. The organo/LDH nanohybrids demonstrated high adsorption capacity to MB. The removal of MB from solutions with organo/Zn-Al LDHs was enhanced by using UV light due to MB photodestruction.
Highlights
The removal of hazardous organic dyes from wastewater and remediation of contaminants in surface water, groundwater is a major problem in the world
Characterization The XRD pattern for the as-synthesized Zn-Al LDHs (Zn)–Al layered hydroxides (LDHs) with the different Zn2+/Al3+ cationic ratio are presented at Fig. 1a
An additional ZnO phase was present in the ZnAl41 LDH as indicated by the XRD patterns
Summary
The removal of hazardous organic dyes from wastewater and remediation of contaminants in surface water, groundwater is a major problem in the world. Several traditional methods including adsorption, coagulation, flocculation, ozonation, membrane-filtration, ion-exchange, oxidation, and chemical precipitation are known for the treatment of dye-containing effluents [1, 2]. The use of layered double layered hydroxides (LDHs) as alternative materials for the removal organic dyes from aqueous media has been explored [6,7,8]. LDHs are known as anionic clays and hydrotalcite-like materials. Their basic structure resembles that of brucite, Mg(OH), when a fraction x of divalent cations is isomorphously replaced by trivalent cations, rendering positively charged layers.
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