Arsenic removal using hydrous nanostructure iron(III)-titanium(IV) binary mixed oxide from aqueous solution

The synthetic bimetal iron(III)-titanium(IV) oxide (NHITO) used was characterized as hydrous and nanostructured mixed oxide, respectively, by the Föurier transform infra red (FTIR), X-ray diffraction (XRD) pattern and the transmission electron microscopic (TEM) image analyses. Removal of As(III) and As(V) using the NHITO was studied at pH 7.0 (±0.1) with variation of contact time, solute concentration and temperature. The kinetic sorption data, in general, for As(III) described the pseudo-first order while that for As(V) described the pseudo-second order equation. The Langmuir isotherm described the equilibrium data (303 (±1.6) K) of fit was well with the Langmuir model. The Langmuir capacity (qm, mg g−1) value of the material is 85.0 (±4.0) and 14.0 (±0.5), respectively, for the reduced and oxidized species. The sorption reactions on NHITO were found to be endothermic and spontaneous, and took place with increasing entropy. The energy (kJ mol−1) of sorption for As(III) and As(V) estimated, respectively, is 9.09 (±0.01) and 13.51 (±0.04). The sorption percentage reduction of As(V) was significant while that of As(III) was insignificant in presence of phosphate and sulfate. The fixed bed NHITO column (5.1 cm × 1.0 cm) sorption tests gave 3.0, 0.7 and 4.5 L treated water (As content ≤ 0.01 mg L−1) from separate As(III) and As(V) spiked (0.35 ± 0.02 mg L−1) natural water samples and from high arsenic (0.11 ± 0.01 mg L−1) ground water, respectively when inflow rate was (0.06 L h−1).