The present study aimed to investigate biodegradation mechanisms of black carbon (BC)-bound contaminants in BC-amended sediment when BC was applied to control organic pollution. The single-point Tenax desorption technique was applied to track the species changes of nonylphenol (NP) during biodegradation process in the rice straw carbon (RC)-amended sediment. And the correlation between the biodegradation and desorption of NP was analyzed. Results showed that microorganisms firstly degraded the rapid-desorbing NP (6 h Tenax desorption) in RC-amended sediment. The biodegradation facilitated the desorption of slow-desorbing NP, which was subsequently degraded as well (192 h Tenax desorption). Notably, the final amount of NP degradation was greater than that of NP desorption, indicating that absorbed NP by RC amendment can be degraded by microorganisms. Finally, the residual NP amount in RC-amended sediment was decided by RC content and its physicochemical property . Moreover, the presence of the biofilm was observed by the confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) so that microorganisms were able to overcome the mass transfer resistance and directly utilized the absorbed NP. Therefore, single-point Tenax desorption alone may not be an adequate basis for the prediction of the bioaccessibility of contaminants to microorganisms or bioremediation potential in BC-amended sediment.
Black carbon (BC) is considered to be a promising novel material for controlling organic contaminants due to its strong adsorption property, low production cost, and less secondary pollution. However, seldom systemic research was conducted to investigate adsorption-desorption characteristics and interaction mechanism between BC and nonylphenol (NP), one kind of endocrine-disrupting contaminants (EDCs) and persistent organic pollutants (POPs). Therefore, in the present study, adsorption characteristics of NP on two BCs (rice straw black carbon (RC) and fly ash carbon (FC)) involving adsorption isotherm, kinetics, effect of pH, as well as desorption kinetics, were investigated to explore the feasibility of BC for remediation of NP pollution in a water environment. Adsorption isotherm data showed that Q
max was 61,889.21 ± 2777.68 and 6538.99 ± 606.72 mg/kg and n was 0.39 ± 0.037 and 0.55 ± 0.043 for RC and FC, respectively, suggesting the sorption capacity and nonlinearity of RC to NP is far higher than FC and indicating BC was an effective sorbent for NP pollution control, especially RC. The pH affected BC sorption capacity to NP by influencing the surface properties of BC and the NP speciation together. Desorption kinetics data indicated that more than 80% NP could not be released from both BCs, suggesting that BC could reduce NP releasing risk in a water environment evidently when BC is applied for NP pollution remediation.
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