(487c) Removal of Tcep From Aqueous Solutions by Adsorption with Zeolites

Emerging contaminants (ECs) and micropollutants are becoming a global environmental problem as there is increasing information linking them to environmental and human health hazards. One micropollutant of interest is tris-2-chloroethyl phosphate (TCEP), an organo-phosphate ester used as a plasticizer and flame retardant.  The European Union (EU) classifies TCEP as dangerous to the environment, toxic to aquatic organisms, because it may cause long-term adverse health effects in the aquatic environment. The EU report also suggests that TCEP is potentially carcinogenic and may cause impaired fertility in humans. Canada concluded that there may be a probability of harm to humans at any exposure level.  Within the US, Minnesota considers TCEP a chemical of “emerging concern”, California has included TCEP on the “Chemicals known to the State to Cause Cancer or Reproductive Toxicity”, and New York has recently instated a law to prohibit the sale of any child care product containing TCEP.

Recent studies have focused on the presence of TCEP in environmental and drinking waters, and several other previous studies indicated that TCEP was the most frequently detected compound of the ECs investigated. Transport of TCEP from wastewater effluents to raw water sources is supported by research that identifies the presence of TCEP in surface waters at concentrations (0.1 mg/L to 0.6 mg/L) similar to those detected in wastewater effluents.  This supports the premise that the TCEP is not being removed from the water cycle. 

TCEP is one of the more recalcitrant compounds to remove with available wastewater technologies. Activated sludge processes studied in Europe achieved up to 20% removal of TCEP. Oxidation processes that include chlorination, ozonation, and UV radiation and UV/hydrogen peroxide each achieved less than 40% removal of TCEP.  The published data for removal with activated carbon suggest less than 50% removal.

Therefore, TCEP is of special interest not only due to its potential toxicity and prevalence in the environment but it presents a difficulty in removal through conventional wastewater treatment operations. There are limited studies available to support removal of TCEP using adsorption.  This paper presents a novel approach of using microporous zeolite adsorbants to remove TCEP from aqueous solutions.  Equilibrium adsorption isotherms of TCEP on the selected zeolites were obtained experimentally.  Surface hydrophbicity measurements and NMR analysis of the zeolite-TCEP system were conducted and provide valuable insight to the adsorption mechanism. 

The results show excellent TCEP removal (>99%) as well as provide a foundation to extrapolate the zeolite adsorption application to other difficult to remove polar hydrophilic ECs from water and wastewater sources.