Removal of tartrazine, ponceau 4R and patent blue V hazardous food dyes from aqueous solutions with ZnAl-LDH/PVA nanocomposite

Zinc-aluminum-based layered double hydroxide-polyvinyl alcohol (ZnAl-LDH/PVA) nanocomposite has been synthesized by one-pot co-formation method. An intercalation approach was realized using (ZnAl LDH/PVA) nanocomposite as adsorbent and photocatalyst for adsorption and solar photodegradation of hazardous food dyes-tartrazine, ponceau 4R and patent blue V. The characterization of synthesized nanocomposite was carried out by XDR, SEM, FTIR and UV-Vis. The adsorption of dyes onto the synthesized adsorbent was carried out under different initial dye concentrations, pH, adsorbent weight and three different temperatures. The optimal pH for tartrazine, ponceau 4R and patent blue V was determined as 2.0, 7.0 and 2.0, respectively. The optimal temperature at optimal pH was 303K after 40 min. Pseudo-first-order kinetic model, Langmuir and Temkin isotherm models were represented well for the definition of the adsorption mechanism of tartrazine. The adsorption of ponceau 4R and patent blue V on the ZnAl-LDH/PVA nanocomposite follows the Freundlich isotherm. The value of the slope of 1/n for ponceau 4R and patent blue V is more close to the unit (1/n = 0.668 and 0.768, respectively), which indicates the possibility of the adsorption process according to the Freundlich model. Because the adsorbent shows a photocatalytic property, after high effective sorption, the cyclic reusability of the sorbent was ensured by keeping the sample in its dye solution at 308K in bright sunlight for 5hours. The completely decolorized sorbent has shown high efficiency in subsequent sorption experiments. [GRAPHICS] HIGHLIGHTS The prepared ZnAlLDH/PVA nanocomposite exhibited high effectivity in adsorption and photocatalytic experiment. The effect of pH condition, tartrazine concentration and temperature on adsorbance and photocatalysis performance was studied by XRD, FTIR and UV-Vis technics in detail. Using ZnAl-LDH/PVA nanocomposite, the sorption time of tartrazine was reached to 40 min. Cyclic reusability of adsorbent was achieved by the photodegradation of adsorbed dye compound from the nanocomposite. Most importantly, the photodegradable nanocomposite after sorption showed higher efficiency in the subsequent sorption process. This is explained by the layered structure of the nanoparticles and the anion exchange intercalation of the high molecular weight dye compounds.