Nano-selenium functionalized zinc oxide nanorods: A superadsorbent for mercury (II) removal from waters

In this study, nano selenium functionalized zinc oxide nanorods, NanoSe@ZnO-NR, was prepared, characterized and investigated for Hg(II) removal from waters of different types. The study results revealed that the material showed a superior adsorption capacity (q_m, 1110 mg g^-1) and excellent distribution coefficient (K_d, 9.11 × 10⁸ mL g^-1) which is two or more orders above most of the adsorbents reported in the literature. It should be also known that, 30 mg of the adsorbent can quickly reduce 10 mg L^-1 Hg(II) to undetectable level from 10 mL of sample solution. The adsorption data were well explained with the pseudo-second order kinetic model and Langmuir adsorption isotherm model. Besides, the capturing capability of the material is independent on the pH change (2-12), selective against interfering cations, and exhibited fast kinetics (equilibrium time, ∼1 min). The NanoSe@ZnO-NR performance was also tested on real samples from different origin, surface waters (tap, lake and river) and wastewaters (effluent and influent), and complete removal and ≥99.2% removal efficiency was observed at 0.01 and 10 mg L^-1 spiking levels, respectively. Therefore, NanoSe@ZnO-NR can be considered as a potential adsorbent in advancing the wastewater treatment technology.