Adsorption molybdate ions using nanoscale zero valent iron-incorporated mesoporous carbons

There were three methods for the preparation of iron nanoparticles incorporating ordered mesoporous carbons (OMCs): the incipient wetness impregnation technique (OMC-Fe(imp)), iron contained precursor (OMC-Fe) method, and citric acid chelated iron precursor (OMC-Fe-(citric)) method. The incorporated iron was reduced to nanoscale zero-valent iron (nZVI) by hydrogen at 673 K. The synthesized nZVI-incorporated OMCs were then used as an adsorbent to remove trace amount of molybdate ions from aqueous solutions. The texture characterization of OMCs was determined by nitrogen adsorption analysis. The morphology was observed by X-ray diffraction and transmission electron microscopy, and the surface functional groups were determined by X-ray photoelectron spectroscopy. The bulk iron contents were determined by thermal gravimetric analysis. The adsorption capacities of molybdate ions on the nZVI-incorporated OMCs were determined by using a batch reactor. Experimental results showed that the adsorption capacity of the OMC-Fe-(citric) is superior to that of OMC-Fe(imp) and OMC-Fe. At pH = 3 and initial concentration of 200 mg/L, the equilibrium adsorption capacities were 119 and 278 mg/g on OMC and OMC-Fe-(citric) containing 5 wt.% iron, respectively. The isotherm data and adsorption kinetics data were adequately fitted by the Langmuir equation and the pseudo-second-order adsorption kinetic model, respectively.