Abstracts Book - IMRC 2018

• SB1-P072
CHLOROPHYLL-SENSITIZED PHENOLIC RESINS FOR
PHOTOCATALYTIC DECOLORIZATION OF METHYLENE BLUE
UNDER VISIBLE LED IRRADIATION: SYNTHESIS,
CHARACTERIZATION AND MECHANISMS
Daniel Simon Olivo Alanis 1 , Elva Melisa Castellanos Escamilla 1 , Alcione Garcia Gonzalez 1 ,
Refugio Bernardo Garcia Reyes 1 , Felipe de Jesús Cerino Córdova 1
1 Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Mexico.
More efficient photocatalysts are required for water treatment, especially those
materials that can be activated under visible irradiation. For instance, it is well
known that plants make photosynthesis possible because chlorophyll absorb
energy sunlight at visible range. Similarly, in the last five years, phenolic resins
(PR) have shown promising results for dyes decolorization when they were
applied as photocatalyst under visible light. In this research, solvent-extracted
chlorophyll spinach was anchored on PR during the stage of curing with
hexamethylenetetramine. FTIR spectra of phenolic resins with chlorophyll (PR-
C) showed a strong band at 1700 cm -1 that is related to carbonyl groups present
on chlorophyll, but this signal was not exhibited on PR. Energy gap of PR-C (2.18
eV) was slightly lower than phenolic resins (2.23 eV), indicating that both
semiconductors are active under visible light. Additionally, an absorption peak
at 670 nm in DRUV-VIS spectrum was observed for PR-C, suggesting
semiconductor activation at low energy due to chlorophyll and subsequent
electron transfer across polymeric matrix until final electron acceptor is reached
(Z-scheme mechanism). Photocatalytic decolorization of methylene blue (MB)
under visible LED irradiation was studied on four different water matrices. PR-C
showed a higher rate than PR for deionized, tap and acidify tap water matrices
(2.64, 1.97 and 3.95-fold, respectively), achieving about 85-95% of decolorization
in 6 h. In contrast, PR achieve a rate 1.39-fold (91% of decolorization) higher than
PR-C for carbonate alkaline water matrix. This unexpected result could be
associated with the release of magnesium that is originally coordinated with
pyrrolic rings on chlorophyll or chlorophyll detachment polymer. Scattering
property of PR-C revealed that recombination activity decreased at wavelength
greater than 610 nm in comparison to PR. Finally, scavenger tests were
conducted to elucidate the photocatalytic mechanisms of PR-C for MB
decolorization under visible LED irradiation. Superoxide radical contributed in a
higher extent in all tested water matrices (49-66%), followed by electron-hole
pair redox processes (20-22% and 2-15%, respectively), and a low contribution