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Effects of nonionic surfactants on the solubilization and mineralization of phenanthrene in soil–water systems
Author(s) -
Laha Shonali,
Luthy Richard G.
Publication year - 1992
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260401111
Subject(s) - phenanthrene , pulmonary surfactant , chemistry , critical micelle concentration , sorbitan , mineralization (soil science) , micelle , triton x 100 , alkylphenol , nonionic surfactant , chromatography , surface tension , dilution , environmental chemistry , organic chemistry , alkyl , aqueous solution , biochemistry , fatty acid , nitrogen , fatty acid ester , physics , quantum mechanics , thermodynamics
The solubilization and mineralization of 14 C‐phenanthrene in soil–water systems was examined with several commercially available surface‐active agents, viz., an alkyl ethoxylate C 12 E 4 ; two alkylphenol ethoxylate surfactants: C 8 PE 9.5 and C 9 PE 10.5 ; two sorbitan ethoxylate surfactants: the sorbitan monolaurate (Tween 20) and the sorbitan monooleate (Tween 80); two pairs of nonionic ethoxylate surfactant mixtures: C 12 E 4 /C 12 E 23 at a 1:1 ratio, and C 12–15 E 3 /C 12–15 E 9 at a 1:3 ratio; and two surfactants possessing relatively high critical micelle concentration (CMC) values and low aggregation numbers: CHAPS and octyglucoside. Surface tension experiments were performed to evaluate surfactant sorption onto soil and the surfactant doses required to attain the CMC in the soil–water systems. Surfactant solubilization of 14 C‐phenanthrene commenced with the onset of micellization. The addition of surface‐active agents was observed not to be beneficial to the microbial mineralization of phenanthrene in the soil–water systems and, for supra‐CMC surfactant doses, phenanthrene mineralization was completely inhibited for all the surfactants tested. A comparison of solubilization, surface tension, and mineralization data confirms that the inhibitory effect on microbial degradation of phenanthrene is related to the CMC of the surfactant in the presence of soil. Additional tests demonstrated the recovery of mineralization upon dilution of surfactant concentration to sub‐CMC levels, and a relatively high exit rate for phenanthrene from micelles. These tests suggest that the inhibitory effect is probably related to a reversible physiological surfactant micelle–bacteria interaction, possibly through partial complexing or release of membrane material with disrupting membrane lamellar structure. This study indicates that nonionic surfactant solubilization of sorbed hydrophobic organic compounds from soil may not be beneficial for the concomitant enhancement of soil bioremediation. Additional work is needed to address physicochemical processes for bioavailability enhancement, and effects of solubilizing agents on microorganisms for remediation and treatment of hydrophobic organic compounds and nonaqueous phase liquids. © 1992 John Wiley & Sons Inc.