Nanocomposites of immobilized nano-zirconia on low-cost activated carbon derived from hazelnut shell for enhanced removal of 3-Nitro-4-Hydroxy-Phenylarsonic acid from water.

3-Nitro-4-hydroxy-phenylarsonic acid (NHPA) as a veterinary drug can degraded into highly toxic inorganic arsenic and will be harmful to environment and food safety. Nanocomposites for the uptake of NHPA were obtained by efficiently immobilizing the nano-sized zirconium oxide onto hazelnut shell-based activated carbon using pyrolysis method. We found that the pyrolysis temperature played a crucial role in the adsorptive performances of the nanocomposites. The prepared nanocomposite at pyrolysis temperature of 600 °C with a mass ratio of ZrOCl2/activated carbon of 1:3 exhibited a fast adsorption equilibrium for NHPA within 5 min, excellent adsorption capacity of 825.7 mg g-1 and the higher adsorption capacity with the increase in temperature from 20 to 45 °C across a pH range of 4-6. 90% of the NHPA uptake was sustained in the NaNO3 solution of 0.7 mol L-1. The adsorption data were well simulated by the Langmuir and pseudo-second order equations. Thermodynamic parameters suggested that the uptake of the NHPA occurred spontaneously (ΔG0<0) with an endothermic characteristic (ΔH0>0). A synergetic effect of electrostatic attraction, As-O-Zr surface coordination and π-π interaction is the main adsorption mechanism of the nanocomposites for the removal of the NHPA.

Nanocomposites of graphene and zirconia for adsorption of organic-arsenic drugs: Performances comparison and analysis of adsorption behavior.

3-Nitro-4-hydroxy-phenylarsonic acid (3-NHPAA), an organic-arsenic compound, as one of widely used antibacterial veterinary drug, has greatly attracted the attention due to its potential threats on ecological environment. A series of the nanocomposites of zirconia nanoparticles with crystal phases (pure monoclinic, pure tetragonal and mixed phase (monoclinic + tetragonal)) anchored on reduced graphene oxide were produced through managing the concentration of triethanolamine solution and the reaction time. The effects of the crystal phases of the zirconia in the structure of the nanocomposites were played a key role in the adsorption performances of the 3-NHPAA. Experiment data identified the nanocomposites with monoclinic phase of zirconia excelled at the adsorption of the 3-NHPAA with a higher adsorption capacity up to 207.2 mg g-1. The uptake of the 3-NHPAA by the three nanocomposites was implemented within 60 min and highly pH-dependent which illustrated electrostatic attraction between them as a main mechanism during the adsorption process. A wider pH range (3.8-8.8) for the uptake of the 3-NHPAA by the nanocomposites with the monoclinic phase of zirconia was obtained compared with the nanocomposites containing tetragonal phase (3.8-5.9) or the mixed phase (3.8-7.1) of zirconia. The adsorption of the 3-NHPAA was well described by the pseudo-second order kinetic and Langmuir equations. The thermodynamic parameters suggested that the adsorption of the 3-NHPAA over the three nanocomposites was endothermic and spontaneous in nature. In summary, the nanocomposites of reduced graphene oxide and monoclinic phase of zirconia nanoparticles as an adsorbent were better to the adsorption of the 3-NHPAA.