Removal of Ni(II) and Cr(VI) with Titanium(IV) Oxide Nanoparticle Agglomerates in Fixed-Bed Columns

Removal performances of Ni(II) and Cr(VI) from water were investigated using a packed fixed bed of agglomerated nanoparticles of hydrous titanium(IV) oxide (NHTO). The parameters varied were the (i) bed depth, (ii) flow rate, and (iii) feed solution concentrations. Comparison of breakthrough volumes indicated that the removal performance of Ni(II) (at pH 5.0 +/- 0.1) was better than that of Cr(VI) (at pH 2.0 +/- 0.1) by the NHTO fixed-bed columns. The breakthrough data were described better by the Thomas (R-2 = 0.983-0.999) and bed-depth service time (BDST) (R-2 = 0.992-0.998) models than by the Adams-Bohart model (R-2 = 0.844-0.982). The Thomas model column capacity (q(0)) for Ni(II) was greater than that for Cr(VI) at any conditions. The breakthrough time (t(b)) of the BDST model increased with increasing bed depth of the NHTO columns, and the increase in t(b) was greater than the increase in bed depth. NHTO fixed-bed columns were able to treat Ni(II)- and Cr(VI)-contaminated industrial wastewater successfully.