Abstract
A magnetically modified rice husk biochar (MBC) was successfully prepared by a hydrothermal method from original biochar (BC) and subsequently used to remove phenanthrene (PHE) from aqueous solutions. The porosity, specific surface area and hydrophobicity of BC were significantly improved (approx. two times) after magnetic modification. The adsorption data fitted well to pseudo-second-order kinetic and Langmuir models. Compared with BC, MBC had a faster adsorption rate and higher adsorption capacity of PHE. The adsorption equilibrium for PHE on MBC was achieved within 1.0 h. The maximum adsorption capacity of PHE on MBC was 97.6 mg g−1 based on the analysis of the Sips model, which was significantly higher than that of other sources of BCs. The adsorption mechanism of the two BCs was mainly attributed to the action of surface functional groups and π–π-conjugated reactions. The adsorption of PHE on MBC mainly occurred in the functional groups of C–O and Fe3O4, but that on BC was mainly in the functional groups of –OH, N–H, C=C and C–O.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are fused-ring compounds that contain two or more rings and possess carcinogenic, mutagenic and toxic effects
The BET surface area (SBET), pore volume (Vp), pH, pHpzc, elemental composition and atomic ratio of BC before and after magnetic modification are listed in table 1
During the process of BC magnetic modification, BC and iron oxide were mixed under heating, and a series of reactions of dehydration, dehydrogenation and decarboxylation in the carbon chain of the BC occurred, which resulted in the decrease of the element content such as H and O and the increase of hydrophobicity of magnetic BC (MBC) [23,24]
Summary
Polycyclic aromatic hydrocarbons (PAHs) are fused-ring compounds that contain two or more rings and possess carcinogenic, mutagenic and toxic effects. Wastewater discharges and petroleum spills from industries are the most important sources of PAHs in an aquatic environment [1]. The problem of PAH pollution in an aquatic environment is serious in developing countries such as in some of the surface waters of China [4]. Phenanthrene (PHE), as a typical tricyclic aromatic hydrocarbon possessing high hydrophilicity and certain stability, is often observed with a higher concentration in natural water and wastewater [5,6]. It is necessary to carry out the research of pollution control of PAHs represented by PHE in water
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