Effects of water matrix constituents on micropollutant removal by activated carbon and b-cyclodextrin polymer adsorbents

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The performance of adsorbents for the removal of organic micropollutants from water can be influenced by the presence of water matrix constituents. The objective of this research was to evaluate the influence of water matrix constituents on the performance of coconut-shell activated carbon (CCAC), porous β-cyclodextrin polymer (CDP), and CDP coated on cellulose microcrystal (CDP@CMC) adsorbents [1]. CDP was prepared by crosslinking β-cyclodextrin with tetrafluoroterephthalonitrile [2,3]. CDP@CMC was prepared by polymerizing CDPs in the presence of CMCs, resulting in adsorbents with larger particle sizes amenable for packed bed filtration (PBF) processes[4].

Micropollutants removals were measured in batch experiments for a mixture of 90 MP at 1 mg/L and micropollutants breakthrough was measured in rapid small-scale column test (RSSCT) experiments for a mixture of 15 micropollutants at 500 ng/L. All experiments were performed first with nanopure water, and subsequently with six different water samples collected from two separate groundwater, surface water, and wastewater effluent sources. The results of batch and RSSCT experiments demonstrate more rapid adsorption kinetics and less adsorption inhibition in the presence of matrix constituents for CDP adsorbents relative to CCAC.
Further, the treatment capacity of CDP@CMC in the RSSCT experiments was higher than that of CCAC, particularly in more complex water matrices. Statistical analyses were performed to investigate associations between adsorption inhibition among groups of micropollutants and the concentrations of specific water matrix constituents. For CCAC, adsorption inhibition was observed for all micropollutants and was primarily attributed to the presence of dissolved organic matter with molar weight less than 1000 Da. For CDP adsorbents, adsorption inhibition was primarily observed for cationic micropollutants and was attributed to the screening of the negative surface charge of CDP by inorganic ions in water samples with high ionic strength. These data further demonstrate the value of CDP as an alternative adsorbent to CCAC for the removal of micropollutants during water and wastewater treatment.

References

  1. Ling, Y., Alzate-Sánchez, D. M., Klemes, M. J., Dichtel, W. R., Helbling, D. E. 2020. Evaluating the effects of water matrix constituents on micropollutant removal by activated carbon and β-cyclodextrin polymer adsorbents. Water Research 173 (2020) 115551. https://doi.org/10.1016/j.watres.2020.115551
  2. Alsbaiee, A., Smith, B.J., Xiao, L., Ling, Y., Helbling, D.E., Dichtel, W.R., 2015. Rapid
    removal of organic micropollutants from water by a porous b-cyclodextrin
    polymer. Nature 529, 190e194. https://doi.org/10.1038/nature16185
  3. Ling, Y., Klemes, M.J., Xiao, L., Alsbaiee, A., Dichtel, W.R., Helbling, D.E., 2017.
    Benchmarking micropollutant removal by activated carbon and porous bcyclodextrin polymers under environmentally relevant scenarios. Environ. Sci.
    Technol. 51, 7590e7598. https://doi.org/10.1021/acs.est.7b00906
  4. Alzate-Sanchez, D.M., Ling, Y., Li, C., Frank, B.P., Bleher, R., Fairbrother, D.H.,
    Helbling, D.E., Dichtel, W.R., 2019. b-Cyclodextrin polymers on microcrystalline
    cellulose as a granular media for organic micropollutant removal from water.
    ACS Appl. Mater. Interfaces 11, 8089e8096. https://doi.org/10.1021/acsami.8b22100

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