TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation

A TiO2 pillared montmorillonite (TiO2/MMT) adsorbent was used to remove As(III) and As(V) from aqueous solution with or without UV irradiation. The adsorption kinetics, role of pH, effect of UV, and column experiments are discussed herein. The Ti-polyoxocations in pillared montmorillonite (MMT) were crystallised to anatase in the interlayer and on the external surface with hydrothermal treatment. The anatase TiO2 exhibited not only an improved arsenic adsorption capacity, but also enhanced photocatalytic efficiency. The TiO2/MMT adsorbent was characterised by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photo-electron spectroscopy (XPS) and nitrogen adsorption–desorption techniques. The interlayer d-spacing and BET-specific surface area increased after intercalation of TiO2 in montmorillonite. Without UV irradiation, the adsorption capacities of As(III) and As(V) were 4.58 and 4.86 mg g−1. With UV irradiation, the adsorption capacities of As(III) and As(V) were 5.19 and 5.16 mg g−1, respectively, and the equilibrium concentrations of both As(III) and As(V) were below 10 μg L−1. In addition, column experiments of arsenic-contaminated groundwater removal were conducted using granular TiO2/MMT packed in a 10-cm-ID column with initial arsenic concentrations of 120, 220 and 410 μg L−1. The results indicated that TiO2/MMT is a promising adsorbent for As(III) and As(V) removal from arsenic-contaminated water.

► A TiO2 pillared montmorillonite (TiO2/MMT) has been successful synthesised. ► The TiO2/MMT contained anatase TiO2 in the interlayer and on the external surface. ► These anatase TiO2 nanoparticles were responsible for arsenic photoactive sorption. ► With UV light, 5.19 mg of As(III) and 5.16 mg As(V) were removed by TiO2/MMT. ► The TiO2/MMT is a promising adsorbent in arsenic-contaminated groundwater.