The multiple roles of ethylenediamine modification at TiO2/activated carbon in determining adsorption and visible-light-driven photoreduction of aqueous Cr(VI)

• Modification of AC and TiO2 were synchronously acquired by ethylenediamine treatment.
• The forming of interfacial heterojunctions between AC and TiO2 was promoted.
• Enhanced adsorption capability for Cr(VI) on modified TiO2/AC was obtained.
• Improved performance of modified TiO2/AC for reduction of Cr(VI) was achieved.

The surface NH2-grafting on activated carbon (AC), N-doping into TiO2 and dense interfacial heterojunctions between AC and TiO2 were achieved synchronously by treating of TiO2/AC with ethylenediamine. The obtained materials were characterized and applied for the removal of aqueous Cr(VI) through their adsorption and visible-light-driven photoreduction. Results obtained showed that ethylenediamine was grafted covalently onto AC through amide linkage, and simultaneously, served as the precursor of nitrogen doped into TiO2. Improved performance of modified TiO2/AC for Cr(VI) removal was acquired, which can be attributed to the multiple roles of ethylenediamine modification at TiO2/AC as: to enhance the adsorption capability of AC for Cr(VI) through electrostatic, coordinative and hydrogen bonding; to extend and intensify the optical absorption on TiO2; to promote the forming of dense heterojunctions between TiO2 and AC through Ti–O–C linkages, facilitating the intimate contact and fast interfacial mass transfer of Cr(VI) and photo-generated electrons between AC and TiO2.

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