Experimental Study On Sorption Of PAEs On Biochar: The Effect Of Ash And Ageing

The low volatile,toxic and persistent phthalic acid esters?PAEs?are widely distributed in the environment.It is necessary to manage PAEs by cost-effective approaches.Biochar is attractive for its use in soil and water remediation,carbon fixation and sequestration,soil amendment for promoting crop yields,etc.,However,when biochar is released into the soil and water,the element content,structure and functional groups will change due to the effect of environmental geochemical process.Additionally,the ash is one of the main components of biochar and the presence of has a great influence on biochar to adsorb pollutants.Therefore,it is of great importance to study the effects of ageing and ash content on the adsorption of PAEs on biochar.The following experiments were conducted in this study.?1?We prepared biochar samples and treated biochar using H₂O₂ simulation ageing and de-ashing methods.The properties of biochar samples were compared for the surface morphology,the element distribution,the surface functional groups and the graphitization.?2?We used batch experiments to compare the adsorption of dimethyl phthalate?DMP?and diethyl phthalate?DEP?on fresh,aged and de-ashing biochar.?3?We used the leaching soil column experiments to compare the mobility of DMP and DEP in soil amended with resh,aged and de-ashing biochar.The main results are obtained as follows.?1?In contrast to fresh biochar,the oxygen-containing functional groups on aged biochar increased.The inorganic minerals decreased.The polarity became higher and the aromaticity lower.The hydrophobic effect was enhanced and EDA interaction weakened.The oxidative ageing could break the microscope structure of biochar,decreasing the surface active sites and adsorption capacity.?2?Leaching soil column showed that aged biochar could better immobilize PAEs than fresh biochar.In addition,the effect of the fresh biochar on the buffer capacity of soil is more obvious than aged biochar.?3?The surface morphology and composition of biochar were changed after de-ash treatment.The oxygen content on the surface of biochar decreased but the total oxygen in bulk biochar increased.This indicates that biochar has more hydrophobic parts and fewer polar groups,which could promote the adsorption of PAEs.?4?The mobility of PAEs in soil amended with de-ashing biochar was enhanced due to the combination of ash and organic matter in soil favor to fix PAEs.