Adsorption of PAHs in water by polydimethylsiloxane modified biochar:performance and mechanism
Straw biochar was prepared by phosphoric acid activation method.Polydimethicone(PDMS)was used to modify the surface hydrophobic property of biochar.The biochar before and after PDMS modi-fication was characterized by means of BET,FTIR and contact angle measuring instruments.This study in-vestigated the adsorption efficiency of biochar on typical polycyclic aromatic hydrocarbons(PAHs)(phe-nanthrene,acenaphthe and naphthalene)in water.Under the role of PDMS modification,the maximum ad-sorption capacity of phenanthrene,acenaphthe and naphthalene were increased by 23%,33%and 14%,respectively.The adsorption kinetics of PDMS modified biochar was more consistent with the quasi-sec-ond-order kinetic model,indicating that chemisorption was the main mechanism.In terms of isotherm mod-el fitting results,the experimental results are more consistent with Freundlich model,indicating multimo-lecular layer adsorption.FTIR spectra showed that a new Si—O—Si bond was detected on the surface of biochar after hydrophobic modification,indicating that PDMS coating modified biochar surface,and PDMS coating increased the water contact angle of biochar surface by about 10°.PDMS hydrophobic coating can improve the hydrophobic performance of biochar,and thus improve its adsorption performance.The PDMS hydrophobic coating provides a new technique for enhancing the adsorption of PAHs from water by bio-char.
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