Comparative sorption and desorption of benzo[α]pyrene and 1,2,3-trichlorobenzene by biochar in the presence of dissolved organic matter

Abstract

Sorption and desorption of benzo[α]pyrene (BaP) and 1,2,3-trichlorobenzene (TrCB) on biochar prepared from maple wood shavings heated at 500°C were studied in the presence of dissolved organic matter (DOM), including citric acid, l-phenylalanine (L-PH), and peptone. Compared to TrCB, BaP exhibited more nonlinear and stronger sorption on biochar. Nonlinearity of the sorption isotherms increased in the presence of DOM. The presence of citric acid enhanced the sorption capacity and desorption hysteresis of BaP and TrCB on biochar mainly due to the strong sorption of citric acid on the biochar surface. Moreover, there were positive relations between the concentration dependent sorption capacity coefficient (K_d) values of BaP and TrCB and the citric acid concentration (P < 0.01). In contrast, peptone reduced the sorption capacity and increased the sorption reversibility because of the partition of BaP and TrCB in the peptone solution. L-PH at 50–200 mg/l also leads to a decrease in the sorption capacity and irreversibility attributed to solubilization, although the sorbed L-PH on the biochar surface can slightly increase the BaP and TrCB sorption. At the same concentration, peptone leads to a higher decrease in the BaP and TrCB sorption than L-PH. Also, negative correlations were found between the K_d values of BaP and TrCB, and the L-PH and peptone concentration (P < 0.05). Our results may help understand the different impacts of DOM on the transport and fate of halogenated aromatic hydrocarbons in aquatic environments polluted with biochars.