Fast removal of polybrominated diphenyl ethers from aqueous solutions by using low-cost adsorbents

Abstract

4-Dibromodiphenyl ether (BDE-3) and 4,40-dibromodiphenyl ether (BDE-15) are two of the major polybrominated diphenyl ethers used as flame-retardant additives in computer main boards and in fireproof building materials. In this study, we evaluated the potential of three low-cost adsorbents, black tea, green tea, and coconut palm leaf powders, to adsorb BDE-3 and BDE-15 from aqueous solutions. The results showed that pressure steam washing of the adsorbents increased their capacities to adsorb BDE-3 and BDE-15. The maximum adsorption capacities of pressure steam-washed black tea, green tea, and coconut palm leaf powders were 21.85 mg·L-1, 14.56 mg·L-1 and 22.47 mg·L-1, respectively. The results also showed that the adsorption equilibrium (qe) was achieved at 4 min. Moreover, 97.8% of BDE-3 and 98.5% of BDE-15 could be removed by adsorbents pretreated with pressure steam washing. The kinetic data fitted well with a pseudo-second-order equation. The adsorption rate constants (k2) of all pressure steam-washed adsorbents ranged from 8.16 × 10-3 to 6.61 × 10-2 g·(mg·L-1)-1·s-1, and the amount adsorbed at qe by all pressure steam-washed adsorbents ranged from 4.21 to 4.78 mg·L-1. Green alga Chlorella vulgaris was used as the test organism and the median effective concentration values of BDE-3 and BDE-15 were 7.24 and 3.88 mg·L-1, respectively. After BDE-3 and BDE-15 were removed from the solution, their biotoxicities markedly decreased. These findings indicate that these low-cost adsorbents can be used to remove BDE-3 and BDE-15 from aqueous solutions and wastewater.