Highly efficient ZnO nanoflowers for the removal of highly toxic aqueous Pb(II) and Cr(VI).

In this work, flower-like zinc oxide (ZnO) nanostructures were synthesized using hydrothermal synthesis. The fabricated nanoflowers were used as adsorbents for the removal of heavy metal ions such as lead and chrome. Morphological assessments and chemical investigations of the ZnO nanoflowers were conducted by using X-ray diffraction, field emission electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy techniques. To optimize the heavy metal recovery process optimum parameters like pH, eluent type, adsorbent amount, solution volume, and adsorption time were studied; flame atomic absorption spectrometry was used in the optimization process. The optimum conditions for Cr(VI) and Pb(II) were determined as 3 M HNO3, pH 6.5, 20 mL, 30 min. But the amount of ZnO nanoflowers for Cr(VI) and Pb(II) was determined as 200 and 50 mg, respectively. Outstanding heavy metal ion removal performance of the ZnO nanoflowers was achieved on spinach (NIST-SRM1570a), and apple leaf (NIST-SRM 1515) for the method validation where the solid phase extraction technique was used as the main enrichment method. The flame AAS method was applied to determine for Cr(VI) and Pb(II) metal ions in real samples (spinach, rocket leaf, collard leaf, parsley, bottled drinking water and hardaliye), after and before enrichment on the present ZnO. Relative standard deviation (%RSD) was found in the range of 0.2–5.3. [ABSTRACT FROM AUTHOR]