Document Detail

Passivation of bimetallic catalysts used in water treatment: Prevention and reactivation.
MedLine Citation:
PMID:  23030387     Owner:  NLM     Status:  In-Data-Review    
With respect to degradation rates and the range in contaminants treated, bimetals such as Ni-Fe or Pd-Fe generally outperform unamended granular iron. However, the catalytic enhancement is generally short-lived, lasting from a few days to months. To take advantage of the significant benefits of bimetals, this study aims at developing an effective method for the rejuvenation of passivated bimetals and alternatively, the prevention of rapid reactivity loss of bimetals. Because the most likely cause of Ni-Fe and Pd-Fe passivation is the deposition of iron oxide films over the catalyst sites, it is hypothesized that removal of the iron oxide films will restore the lost reactivity or avoiding the deposition of iron oxide films will prevent passivation. Two organic ligands (ethylenediaminetetraacetic acid (EDTA), and [s,s]-ethylenediaminedisuccinate acid ([s,s]-EDDS)) and two acids (citric acid and sulphuric acid) were tested as possible chemical reagents for both passivation rejuvenation and prevention. Trichloroethene (TCE) and Ni-Fe were chosen as probes for chlorinated solvents and bimetals respectively. The test was carried out using small glass columns packed with Ni-Fe. TCE solution containing a single reagent at various concentrations was pumped through the Ni-Fe columns with a residence time in the Ni-Fe of about 6.6 min. TCE concentrations in the influent and effluent were measured to evaluate the performance of each chemical reagent. The results show that (i) for passivated Ni-Fe, flushing with a low concentration of acid or ligand solution without mechanical mixing can fully restore the lost reactivity; and (ii) for passivation prevention, adding a small amount of a ligand or an acid to the feed solution can successfully prevent or at least substantially reduce Ni-Fe passivation. All four chemicals tested are effective in both rejuvenation and prevention, but sulphuric acid and citric acid are considered to be the most practical reagents due to their relatively low costs and environmentally friendly nature. This study suggests that the use of bimetals in above-groundwater treatment applications could become practical with appropriate engineering design.
Jianming Chen; Robert W Gillham; Lai Gui
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering     Volume:  48     ISSN:  1532-4117     ISO Abbreviation:  J Environ Sci Health A Tox Hazard Subst Environ Eng     Publication Date:  2013  
Date Detail:
Created Date:  2012-10-03     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9812551     Medline TA:  J Environ Sci Health A Tox Hazard Subst Environ Eng     Country:  England    
Other Details:
Languages:  eng     Pagination:  48-56     Citation Subset:  IM    
a Department of Earth and Environmental Sciences , University of Waterloo , Waterloo , Ontario , Canada.
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