Arsenate and arsenite removal by Fe-modified activated carbon supported nano-TiO2: influence factors and adsorption effect

In this paper, the preparation of Fe-modified activated carbon supported nano-TiO2 (Fe-TiO2/AC) particles and the test results of the properties of the synthesized material, including crystallinity structure, surface morphology, functional groups, and surface texture, obtained using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy, are presented. The removal rates of arsenic were evaluated using batch tests under several simulated conditions, including pH, ionic strength, material dosage, and initial arsenic concentration. The results indicated that arsenic removal was effective in weak alkaline conditions, and the maximum adsorption for arsenic was observed at pH = 8. The arsenic removal rate was improved by increasing the ionic strength and the adsorbent dosage. The adsorption of As(III) and As(V) reached equilibrium within 3 h and 1.14 h, respectively. The pseudo-second-order model satisfactorily described the adsorption processes. Isotherm data were fitted using the Freundlich equation. The isotherm results showed that the maximum adsorption capacities of Fe-TiO2/AC were 28.66 mg.g(-1) for As(III) and 35.22 mg.g(-1) for As(V). In the adsorption process, nano-TiO2 and Fe2O3 played key roles in increasing the adsorption efficiency and converting As(III) to As(V). Moreover, the presence of Fe(III) accelerated the oxidation of arsenic.