The removal of tris(2-chloroethyl)phosphate by a composite biosorbent: Preparation, performance and mechanism

Organophosphate flame retardants (OPFRs), as one kind of emerging organic pollutants, were discovered in various environment, among which chlorinated OPFRs (Cl-OPFRs) were the most abundant. In this study, a novel composite biosorbent (AC-Y4) was developed by a functional bacterial strain and activated carbon, to remove tris(2-chloroethyl)phosphate (TCEP) that was one of the Cl-OPFRs with high detection rate and biotoxicity in surroundings. The results showed that TCEP of 3 mg/L could be efficiently removed by AC-Y4 with an adsorption capacity of 0.0667 mg/g, of which 87.3 % was degraded. And its adsorption of 5 mg/L TCEP was 0.0997 mg/g, which higher than using the activated carbon or TCEP degrading strain only. The removal process was in accordance with pseudo-second-order kinetic and Langmuir isotherm, indicating that the adsorption of TCEP by this composite biosorbent was chemical adsorption. In addition, pH, and heavy metal ions were proved to play an important role in the TCEP removal, especially during the first 12 h of the reaction. The removal rate of TCEP by the composite adsorbent AC-Y4 was the highest when solution pH = 7. Besides, both Cu²⁺ and Cd²⁺ had less effect on the TCEP removal while Cr⁶⁺ inhibited this process, and the AC-Y4 was found that it could remove TCEP/heavy metals combined pollutants simultaneously. Furthermore, the determination of degradation intermediates and Cl⁻ ions induced that the AC-Y4 not only could efficiently adsorb TCEP but also could decompose it, and the main degradation pathways of TCEP by AC-Y4 were dechlorination and bio-hydrolysis.