Wyniki wyszukiwania - Biblioteka Nauki

1

Degradation and detoxifi cation of 2-chlorophenol aqueous solutions using ionizing gamma radiation

100%

Basfar A. A. , Muneer M. , Alsager O. A.

|

tom Vol. 62, No. 1

61--68

EN

Chlorophenols are compounds with high toxicity, poor biodegradability, and carcinogenic and recalcitrant properties. This work studies, for the first time, the destruction and detoxification of 2-chlorophenol (2-CP) in water using 60Co gamma radiation under different conditions including varied radiation doses, addition of hydrogen peroxide (H2O2), and varied pH values. High-performance liquid chromatography (HPLC) and ion chromatography (IC) confirmed a successful degradation of 2-CP to primarily yield phenol molecules and chloride anions. A radiation dose as low as 25 kGy achieved approximately 90% removal of 50–150 ppm of 2-CP in neutral water. However, the addition of a strong oxidizer such as H2O2 to 2-CP solutions reduced the required dose to achieve 90% removal to at least 1.3-fold. The reduction in radiation doses was also observed in acidic and alkaline media, reducing the required doses of 90% removal to at least 0.4-fold. It was imperative to study the toxicity levels of the oxidation by-products to provide directions for the potential applicability of this technology in water treatment. Toxicology Microtox® bioassay indicated a significant reduction in the toxicity of the degradation by-products and the detoxification was further enhanced by the addition of H2O2 and changing the pH to more acidic or alkaline conditions. These findings will contribute to the knowledge of the removal and detoxification of such challenging environmental contaminant and could be potentially applied to other biologically resistant compounds.

2

Photosensitized oxidation as a tool for degradation of harmful substances in water solutions

58%

Gryglik D. , Miller J. S.

|

tom Vol. 12, nr 9

977-987

EN

The applicability of photochemical process involving singlet molecular oxygen (102) in the field of environmental protection was considered. 102 was generated via energy transfer from dye sensitizer excited by visible light to ground stale oxygen (302). The photosensitized oxidation was applied for degradation of 2-chlorophenol (2-CP), a common model organic pollutant, and ingredient of many pesticides. The 2-CP decomposition in, an aqueous solution was studied using various sensitizers in two types of reactions: in the homogeneous system with a solubilized sensitizer and in the heterogeneous system with a sensitizer immobilized in silane gel covering the glass reactor walls. In both systems the influence of various experimental conditions (light intensity, the amount of sensitizer, oxygen concentration) on the rate of 2-CP degradation was investigated. Finally, the possibility of using sunlight for decomposition of 2-CP in aqueous solutions both in homo- and heterogeneous system was demonstrated.

PL

Badano sensybilizowane fotoutleniania, pod kątem rozpoznania możliwości jego zastosowania do degradacji szkodliwych zanieczyszczeń w środowisku wodnym. W procesie zastosowano różne sensybilizatory w postaci roztworu oraz immobilizowane w żelu silanowym na szklanym podłożu. Efektywność procesu określano przez szybkość rozkładu 2-chlorofenolu w różnych warunkach natlenienia i naświetlania roztworu reakcyjnego. Sprawdzono również możliwość degradacji 2-chlorofenolu w procesie sensybilizowanego utleniania pod działaniem promieniowania słonecznego.

3

Rozklad chlorofenoli w srodowisku wodnym

51%

Bogacka T. , Makowski Z. , Ceglarski R.

|

1996

|

tom 47

|

nr 2

181-195

PL

Wyznaczono dynamikę i kinetykę rozkładu chlorofenoli (2,4-DCF; 2, 6-DCF; 2,4,5-TCF; 2,3,6-TCF, 2,4,6-TCF; 2,3,4,6-TeCF i PCF) w warunkach modelowanych, symulujących środowisko wody rzecznej i destylowanej oraz ekosystemu wodnego. Szybkość rozkładu badano w zależności od stężenia początkowego chlorofenoli, temperatury, zdolności adaptacyjnych mikroflory do środowiska tych związków oraz właściwości kumulacyjnych.

EN

The purpose of this study was to establish the distribution of the selected chlorophenols of point (2,4-DCF, 2,6-DCF, 2,4,5-TCF and 2,3,6-TCF) and nonpoint origin (2,4,6-TCF,2,3,4,6-TeCF and PCF) under conditions simulating the environment of river and distilled water and laboratory water ecosystem. The distribution process developed in accordance with the kinetic equation of 1st order, the average degradation half-time at 20°C amounted: model of river - 23, 58,-76, 92 days, and model of distilled water - 36, 53-47, 25 days. The rate degradation in river and distilled water indicates that the river water microoraganisms have no influence on the degradation of determined compounds. When the microflora had been adapted to the presence of chlorophenols the process of degradation was as rule more rapid both investigated temperatures (20°C and 7°C). This process was slowed down by temperature fall to about 7°C. The mixture of chlorophenols at concentration of 10 and 50µg/l when exposed for 20 days to water ecosystem under dynamic conditions, was found to be reduced up 13%. Chlorophenols were not absorbed by Elodea canadensis and Physa fortinalis and weakly by Lebistes reticulatus (cumulation coefficients - 0,42-30,27). In the case residual DCP and TCP -weakly (4,71 -46,23 µg/kg). The investigated concentrations of chlorophenols didn't exert positive effect on the aquatic biocenosis (except Lebistes reticulatus), settled in the ecosystem.