title: Swelling induced regeneration of TiO2-impregnated chitosan adsorbents under visible light.
abstract: Since only the molecules that are in direct contact with the TiO2 surface undergo photosensitization, it is challenging to regenerate the TiO2-impregnated chitosan (TIC) adsorbent beads under visible light. This study focused on the role of chitosan swelling properties. It was found that dye-loaded TIC adsorbent exhibited a pH-dependent swelling owing to protonation/deprotonation of free amino groups on chitosan chains. In the acidic medium (pH<6.0), the adsorbent underwent a 'smart' phase transition from a dry contracted state to a hydrated swollen state, and its physicochemical properties were also significantly changed, which eventually enabled the photosensitized oxidation of dye. This swelling induced regeneration was further confirmed by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The involvement of oxygen radical species (O2(-)/HOO and OH) was also confirmed with electron spin resonance (ESR) spectroscopy. Moreover, the adsorption effectiveness of TIC adsorbent was mostly recovered after six regeneration cycles.
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Limin
authors.initials: L
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China. Electronic address: leijiang@upc.edu.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Di
authors.initials: D
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Sisi
authors.initials: S
authors.lastname: Li
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, PR China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xue
mesh_terms: D000327:Adsorption; D048271:Chitosan / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry; D005240:Feasibility Studies; D008027:Light; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; C009495:titanium dioxide; D048271:Chitosan; D014025:Titanium
keywords: Chitosan; Photosensitized oxidation; Regeneration; Swelling; TiO(2)