Sorption of diethyl phthalate and cadmium by pig carcass and green waste-derived biochars under single and binary systems.

Potentially toxic elements (PTEs) and phthalic acid esters (PAEs) often coexist in contaminated soils. Their co-existence may affect the mutual sorption behavior, and thereby influence their bioavailability and fate in soils. To our best knowledge, the impacts of plant-and animal-derived biochar on the competitive sorption-desorption of PTEs and PAEs in soils with different organic carbon content have not been studied up to date. Therefore, in this study, batch sorption-desorption experiments were conducted to investigate the influence of biochars derived from pig carcass and Platanus orientalis branches on the mono- and competitive sorption of cadmium (Cd) and diethyl phthalate (DEP) in soils with high (HS) and low (LS) organic carbon content. The DEP sorption was well described by Freundlich isotherm model, while Cd sorption fitted better with the Langmuir isotherm model. Application of both biochars enhanced soil sorption of DEP, which increased as the application doses increased. The HS showed a stronger affinity to both DEP and Cd than the LS. In the LS, the pig carcass biochar (PB) addition was more effective to increase the sorption capacity of Cd and DEP and to reduce their desorption than woody biochar (WB) treatments. Moreover, the co-existing of Cd could reduce the sorption of DEP, especially in the LS. The presence of DEP enhanced Cd sorption in LS treated by both biochars, but the sorption of Cd was suppressed with DEP addition in the PB-amended HS. In conclusion, the soil sorption capacity of DEP and Cd was affected by biochar type, application dose and soil organic carbon content. The reciprocal effect between DEP and Cd was also a crucial factor influencing their sorption/desorption by biochar. Therefore, PB and WB, especially PB, can be used for metal/DEP immobilization due to enhanced sorption. This approach is applicable for future remediation of soils contaminated by PTEs and PAEs.