Adsorptive properties of Fe3O4/Ni/NixB nanocomposite coated nutshell for the removal of arsenic(iii) and arsenic(V) from waters

A novel adsorbent Fe3O4/Ni/NixB-nanocomposite coated nutshell was synthesized and used for the identification of the adsorption characteristics for both As(III) and As(V). The point of zero charge of pH of the adsorbent was determined as 8.0. The adsorption of arsenic on the adsorbent was optimum at pH 7.5. The Langmuir isotherm well fitted to the equilibrium data with a maximum adsorption capacity of 3.6 and 2.6 mg/g for As(III) and As(V), respectively. The separation factor, RL, calculated from the Langmuir isotherm and the parameter, n, calculated from the Freundlich isotherm showed that the adsorption of both As(III) and As(V) on Fe3O4/Ni/NixB nanocomposite coated nutshell was favorable. The D–R isotherm showed that the adsorption was chemical in nature. The kinetic data followed the pseudo-second-order model which supported that the adsorption mechanism was chemical. The adsorption method was applied to real samples with a column. The removal efficiencies were about 100%. The adsorbent effectively reduced the concentration of arsenic species in water sample from 100 μg/L to the level below 10 μg/L (the recommended limit of arsenic in drinking water). The regeneration of the spent adsorbent was successfully done with 3% NaCl + 2% NaOH solution. The adsorption and the regeneration cycle were repeated for three times without loss efficiency.