Transformation of Phenol in Solid Mixtures with Humic Acids During Electron Beam Irradiation
摘要
The pulsed cathodoluminescence spectra of solid phenol; humic acids isolated from oxidized brown coal (Mongolia, China), including those subjected to mechanical activation; and mixtures of humic acids with 10, 30, 50, 70, and 90 wt.% of phenol were recorded. The spectra were recorded in the range from 350 to 850 nm with irradiation by an electron beam of 2 ns duration with an average energy of 170 keV. The number of irradiation pulses at a repetition rate of 1 Hz varied from 20 to 4000, while the absorbed dose from one pulse was ~1.4 kGy. It was shown that humic acids did not luminesce, although phenol emission did appear in the mixtures. The degree of phenol transformation in the mixtures under the action of the electron beam was determined by analyzing pulsed cathodoluminescence spectra. An intense band at 375 nm was due to a transition from the phenol T1 triplet state to the S0 ground state. Two bands at 395 and 475 nm were formed by transitions from the T1 state to the first and fourth vibrational levels of the S0 ground state. A long-wavelength band at 740 nm corresponded to a Ti → T1 transition. The behavior of the intensities of all four phenol luminescence bands became extreme, indicative of its transformation, with an increase in the number of irradiation pulses. The interaction of humic acids with phenol occurred through physical adsorption. The presence of humic acids in most samples inhibited the transformation of phenol molecules. The relative positions of the carboxyl functional group and the phenol molecule in the mixtures had an effect.