Role of primary reaction initiated by 254 nm UV light in the degradation of p-nitrophenol attacked by hydroxyl radicals.
The degradation kinetics of p-nitrophenol (p-NP) exposed to 254/185 nm UV light were studied in two modes, i.e., 254 nm UV light intensity enhanced mode and normal mode. It was observed that the extra 254 nm UV light source accelerated the degradation process both in the presence and the absence of oxygen. Considering that hydroxyl radical (*OH) is the dominant factor that causes the degradation of p-NP, the enhanced degradation that occurred in the presence of the extra light source was attributed to the synergistic effect between *OH attack and the primary reactions initiated by 254 nm UV light. The synergistic effect has been confirmed by 266 nm laser flash photolysis (LFP) experiments. It is demonstrated that the phenoxy radical generated from the photoionization of p-NP is capable of reacting with *OH. On the basis of these results, it should be noted that UV light could cause more severe damage to p-NP attacked by *OH in aqueous solution.
Self-assembled material of palladium nanoparticles and a thiacalix[4]arene Cd(II) complex as an efficient catalyst for nitro-phenol reduction
A new material based on the self-assembly of palladium nanoparticles by a thiacalix[4]arene (TCA) based Cd(II) complex is synthesized. Hydrophobic interactions between tert-butyl groups on either ends of the TCA–cadmium complex and palladium nanoparticles generate self-assembled material 5. The material shows its potential application as a heterogeneous recyclable catalyst for the reduction of 4-nitrophenol (4-NP). The rate constants for catalyst 5 observed in 1st and 5th catalytic cycles were 0.117 min−1 and 0.109 min−1, respectively, revealing the efficiency of the catalyst.
489. The radiation and photochemistry of aqueous solutions of benzene
Saturated aqueous solutions of benzene, when irradiated with x rays in the presence of oxygen, yield as major primary products phenol (G 1.8) as well as mucondialdehyde STAG 1.5 (acid solutions), 0.8 (neutral solutions)!. Another primary product is probably pyrocatechol STAG = 0.3!. It is shown that both phenol and mucondialdehyde may be formed by way of free-radical intermediate. The yields of phenol and of mucondialdehyde depend on the dose rate. A mechanism accounting for the aromatic ring-opening is discussed. The photochemistry of saturated aqueous solutions of benzene was investigated in the presence and absence of oxygen. In the presence of oxygen at neutral pH, the main photochemical product is mucondialdehyde, and phenol is not formed in signiflcant amounts. At acid pH values in the presence of oxygen, mucondialdehyde is not formed and acid-catalyzed addition of water to benzene appears to prevail. With evacuated solutions the latter process appears to predominate at all pH's. (auth)