Document Detail

Causes and implications of colloid and microorganism retention hysteresis.
MedLine Citation:
PMID:  22820488     Owner:  NLM     Status:  Publisher    
Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1μm) and microorganisms (coliphage φX174 and E. coli D21g) under various transient solution chemistry conditions, and 360μm Ottawa sand that was subject to different levels of cleaning, namely, a salt cleaning procedure that removed clay particles, and a salt+acid cleaning procedure that removed clay and reduced microscopic heterogeneities due to metal oxides and surface roughness. Comparison of results from the salt and salt+acid treated sand indicated that microscopic heterogeneity was a major contributor to colloid retention hysteresis. The influence of this heterogeneity increased with IS and decreasing colloid/microbe size on salt treated sand. These trends were not consistent with calculated mean interaction energies (the secondary minima), but could be explained by the size of the electrostatic zone of influence (ZOI) near microscopic heterogeneities. In particular, the depth of local minima in the interaction energy has been predicted to increase with a decrease in the ZOI when the colloid size and/or the Debye length decreased (IS increased). The adhesive interaction was therefore largely irreversible for smaller sized 0.1μm CML colloids, whereas it was reversible for larger 1.1μm CML colloids. Similarly, the larger E. coli D21g exhibited greater reversibility in retention than φX174. However, direct comparison of CML colloids and microbes was not possible due to differences in size, shape, and surface properties. Retention and release behavior of CML colloids on salt+acid treated sand was much more consistent with mean interaction energies due to reduction in microscopic heterogeneities.
Scott A Bradford; Hyunjung Kim
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-7
Journal Detail:
Title:  Journal of contaminant hydrology     Volume:  138-139C     ISSN:  1873-6009     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8805644     Medline TA:  J Contam Hydrol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  83-92     Citation Subset:  -    
Copyright Information:
Copyright © 2012. Published by Elsevier B.V.
US Salinity Laboratory, USDA, ARS, Riverside, CA, USA.
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