Kinetics and Thermodynamics of Sorption for As(V) on the Porous Biomorph-Genetic Composite of α-Fe2O3/Fe3O4/C with Eucalyptus Wood Hierarchical Microstructure

A novel porous biomorph-genetic composite of alpha-Fe2O3/Fe3O4/C (PBGC-Fe/C) with eucalyptus wood template was prepared, characterized and tested for its sorption capacity of As(V) from aqueous solution. The result indicated that the PBGC-Fe/C material retained the hierarchical porous structure of eucalyptus wood with three different types of pores (widths 70 similar to 120, 4.1 similar to 6.4 and 0.1 similar to 1.3 mu m) originating from vessels, fibres and pits of the wood, respectively. Its surface area was measured to be 59.2 m(2)/g. With increasing initial As(V) concentration from 5 to 100 mg/L, the amounts of As(V) sorbed on the pulverized PBGC-Fe/C sorbent (<0.149 mm) increased from 0.50 to 4.01 mg/g at 25 degrees C, from 0.50 to 4.83 mg/g at 35 degrees C and from 0.50 to 4.19 mg/g at 45 degrees C, and the corresponding removal rates decreased from 99.97 to 40.10 % at 25 degrees C, 99.95 to 48.40 % at 35 degrees C and 99.92 to 42.05 % at 45 degrees C. At the initial concentrations of 5, 10 and 50 mg/L, the sorption capacities for the unpulverized PBGC-Fe/C sorbent (>3 mm) were determined to be 0.50, 0.99 and 2.49 mg/g, respectively, which exhibited a similar average value to those of fine particles or nanoparticles of iron oxides. The sorption could well be described by the pseudo-second-order kinetic equation. The equilibrium data were found to follow Freundlich as well as Langmuir isotherms.