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Adsorption characteristics of selected pharmaceuticals and an endocrine disrupting compound-Naproxen, carbamazepine and nonylphenol-on activated carbon. | LitMetric

Adsorption characteristics of selected pharmaceuticals and an endocrine disrupting compound-Naproxen, carbamazepine and nonylphenol-on activated carbon.

Water Res

Department of Civil and Environmental Engineering, University of Waterloo, 200 University Ave. W., Waterloo, Ontario, Canada N2L 3G1.

Published: June 2008

AI Article Synopsis

  • The study examined how well activated carbon adsorbs two pharmaceuticals (naproxen and carbamazepine) and one endocrine disruptor (nonylphenol) at low environmental concentrations, finding unexpected results based on the compounds' hydrophobicity.
  • Nonylphenol was the least adsorbed compound despite having a high hydrophobicity factor, whereas carbamazepine was most effectively adsorbed, highlighting the limitations of using high concentration isotherms to predict behavior at lower concentrations.
  • The research indicated that standard carbon dosage used for removing other micropollutants could also effectively remove these pharmaceuticals at low levels, proposing that carbon usage rates for achieving significant removal of these compounds remain efficient even under 500 ng/L

Article Abstract

The adsorption of two representative pharmaceutically active compounds (PhACs) (naproxen and carbamazepine) and one endocrine disrupting compound (nonylphenol) were evaluated on two types of activated carbon. When determining their isotherms at environmentally relevant concentration levels, it was found that at this low concentration range (10-800 ng/L), removals of the target compounds were contrary to expectations based on their hydrophobicity. Nonylphenol (log K(ow) 5.8) was most poorly adsorbed, whereas carbamazepine (log K(ow) 2.45) was most adsorbable. Nonylphenol Freundlich isotherms at this very low concentration range had a much higher 1/n compared to isotherms at much higher concentrations. This indicates that extrapolation from an isotherm obtained at a high concentration range to predict the adsorption of nonylphenol at a concentration well below the range of the original isotherm, leads to a substantial overestimation of its removals. Comparison of isotherms for the target compounds to those for other conventional micropollutants suggested that naproxen and carbamazepine could be effectively removed by applying the same dosage utilized to remove odorous compounds (geosmin and MIB) at very low concentrations. The impact of competitive adsorption by background natural organic matter (NOM) on the adsorption of the target compounds was quantified by using the ideal adsorbed solution theory (IAST) in combination with the equivalent background compound (EBC) approach. The fulfilment of the requirements for applying the simplified IAST-EBC model, which leads to the conclusion that the percentage removal of the target compounds at a given carbon dosage is independent of the initial contaminant concentration, was confirmed for the situation examined in the paper. On this basis it is suggested that the estimated minimum carbon usage rates (CURs) to achieve 90% removal of these emerging contaminants would be valid at concentrations of less than 500 ng/L in natural water.

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Source
http://dx.doi.org/10.1016/j.watres.2008.02.020DOI Listing

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