- Degradation of tri(2-chloroisopropyl) phosphate by the UV/H2O2 system: Kinetics, mechanisms and toxicity evaluation
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A photodegradation technology based on the combination of ultraviolet radiation with H2O2 (UV/H2O2) for degrading tri(chloroisopropyl) phosphate (TCPP) was developed. In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.0035 min?1 (R2 = 0.9871) for 5 mg L?1 TCPP using 250 W UV light irradiation with 50 mg L?1 H2O2. In detail, the yield rates of Cl? and PO43? reached 0.19 mg L?1 and 0.58 mg L?1, respectively. The total organic carbon (TOC) removal rate was 43.02%. The pH value of the TCPP solution after the reaction was 3.46. The mass spectrometric detection data showed a partial transformation of TCPP into a series of hydroxylated and dechlorinated products. Based on the luminescent bacteria experimental data, the toxicity of TCPP products increased obviously as the reaction proceeded. In conclusion, degradation of high concentration TCPP in UV/H2O2 systems may result in more toxic substances, but its potential application for real wastewater is promising in the future after appropriate optimization, domestication and evaluation.
- He, Huan,Ji, Qiuyi,Gao, Zhanqi,Yang, Shaogui,Sun, Cheng,Li, Shiyin,Zhang, Limin
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- A Mechanistic Characterization of the Spontaneous Ring Opening Process of Epoxides In Aqueous Solution: Kinetic and Product Studies
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A careful determination of the extent of rearrangement during epoxide hydration was carried out in conjunction with nuclear magnetic resonance kinetic studies for both propylene and isobutylene oxides.The complete pH-rate profile was mapped at ionic strength 2.0, and solvent kinetic isotope effects were determined for several limbs.Spectrophotometric analysis of the quantity of aldehyde formed by rearrangement in both the acidic and spontaneous limbs reveals that ionic strength has a profound effect.At ionic strength zero, more rearrangement product is generated in the acidic limb, whereas at ionic strength 2.0, larger amounts of aldehyde are formed in both regions.These results support the conclusion that a different carbocationic intermediate exists in the reaction mechanism for the acidic and spontaneous regions.The experimental observations of the spontaneous region can be explained by the existence of zwitterionic intermediate III.Observed solvent kinetic isotope effects, kH3O+/kD3O+, kHspon/kDspon, of 0.33+/-0.02, 1.78+/-0.25 and 0.35+/-0.03, 1.48+/-0.27 for propylene and isobutylene oxides, respectively, were dissected into components on the basis of classical product studies.At high ionic strength, isolation of compound I, an isobutyraldehyde isobutylene glycol acetal, supports the existence of intermediate III.Apparent partitioning ratios for both the β-hydroxy carbocation, II, and the zwitterion, III, are examined and contrasted.Detailed mechanistic proposals are advanced, and their congruence with a variety of observations described previously in this journal is outlined.
- Pocker, Y.,Ronald, B. P.,Anderson, K. W.
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p. 6492 - 6497
(2007/10/02)
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