Investigation into the feasibility of black carbon for remediation of nonylphenol polluted sediment through desorption kinetics after different order spiking

Abstract

The binding order of sorbent, sediment and organic compounds, as well as binding time is important factors determining the potential success of sorbent amendment, which should be considered when the practicability of sorbents was assessed. But until now, relevant research was rare. In this study, desorption in three practical conditions were simulated, by three mixing spiking orders among nonylphenol (NP), rice straw black carbon (RC) and sediment (the order of mixing spiking is (RC+Sediment)+NP, (Sediment+NP)+RC and (RC+NP)+Sediment, for situation I, II and III, respectively), to discuss the feasibility of using RC to remedy NP pollution. Results demonstrated that amendment of RC into sediment decreased desorption fractions of NP, and increased the resistant desorption fraction (Fr), implying strong affinity of NP to RC and efficient sequestration by RC. No significant differences were observed for desorption among the three fresh situations, meaning NP may be adsorbed on RC exterior surface sites and inter-phase diffusion is faster than desorption. However, Fr for three aged situations was in the order: situation I<II<III, due to NP diffusion into the inter-pores or irreversible sorption sites of RC, reducing the releasing risk of NP. Regardless of time, Fr of three situations were all>0.5, suggesting RC is an effective sorbent for remedying NP pollution in the aquatic environment. Overall, we proposed a practical and analytical method for properly assessing the validity of a sorbent.