Steuerung der Bioverfügbarkeit von Chloraromaten durch Tensid-modifizierte Tonminerale : Sorption und biologischer Abbau

To evaluate the influence of surfactant-modified clays (organoclays) on bioavailability and biodegradation of chloroaromates detailed knowledge of the sorption behaviour of these compounds is an essential precondition. Thus the sorption behaviour of 2,4-dichlorophenol (DCP) and monochlorobenzene (MCB) on clay minerals modified with different quaternary ammonium compounds (QAC) were examined. It was observed that the sorption capacity of the organoclays was not only dependent on their hydrophobicity, but that there was a strong influence of the QAC used for modification and the degree of modification. Both factors are responsible for the surfactant arrangement on the clay surface and in the interlayers. Adsorption turned out to be completely reversible. DCP and MCB intercalated in the organoclays´ interlayers led to an enlarged interlayer distance, which could be detected by x-ray diffractometry. The course of the adsorption isothermes differed for DCP (L-type) and MCB (S-type) and referred to different adsorption mechanisms. In addition to equilibrium state, sorption kinetics were investigated for DCP sorption on one type of organoclay. Ad- and desorption were completed within a few minutes, whereby adsorption was faster than desorption. Adsorption measurements on mixtures of organoclay and aquifer material showed no influence of the aquifer material on the sorption behaviour of DCP and MCB. Thus the adsorbed amount of chloroaromates was only dependent on the organoclay ratio in the mixture. Investigations with respect to the influence of organoclay on biodegradation showed, that sorbed DCP was not directly bioavailable. This was proved by carrying out experiments at toxic DCP concentrations: without organoclay no degradation and no cell growth was detected. Addition of organoclay shifted the bioavailable DCP-concentration to non-toxic levels and thus enabled biodegradation to take place. Biodegradation in turn reduced the solved DCP amount and thus induced desorption. As DCP was reversibly sorbed on the organoclay and desorption was fast compared to degradation bit by bit all DCP was desorbed and then degraded. In a second system with MCB as contaminant, all MCB was also degraded in the presence of organoclay, even if it was temporarily bound. Organoclays are obviously suitable for controlling bioavailable contaminant concentrations. This is a very interesting property for their use as supporting material in bioremediation techniques: addition of organoclays can help to set proper degradation conditions and furthermore enable biodegradation in normally toxic concentration ranges.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2002

Author dc:creator

• Witthuhn, Barbara Susanne

Contributors dc:contributor

• Schwuger, M. J.

• info:eu-repo/classification/ddc/540
• Chemie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-118948%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A56871