铁基秸秆源和牛粪源生物炭对镉砷的吸附特征及机制

Adsorption characteristics and mechanism of cadmium and arsenic by iron-based straw and cow manure biochar

为提高生物炭对镉(Cd)和砷(As)的吸附能力,分别对小麦秸秆生物炭(WBC)和牛粪生物炭(MBC)进行铁改性,得到两种铁基生物炭(Goe@WBC和Goe@MBC).对4种生物炭进行表征分析,并通过批实验考察其对Cd(II)和As(III)的吸附性能.结果表明,铁改性后生物炭铁(Fe)元素含量增加,表面出现大量Fe‒O、‒OH/Fe‒OH官能团.与WBC和MBC相比,Goe@WBC和Goe@MBC对Cd(II)的吸附能力分别提高了47%和27%,对As(III)的吸附能力分别提高了903%和940%.与Goe@WBC相比,Goe@MBC表现出对Cd(II)更强、对As(III)更弱的吸附能力,这是因为牛粪富磷,PO_(4)^(3-)可与Cd(II)结合为沉淀,而与As(III)存在竞争吸附.综上,通过在生物炭表面生成铁基,可同时提高其对正电重金属镉(Cd)和负电重金属砷(As)的吸附能力,为修复重金属复合污染提供新途径.

To improve the adsorption capacity of biochar for cadmium(Cd)and arsenic(As),wheat straw biochar(WBC)and cow manure biochar(MBC)were modified with iron to obtain two iron-based biochars(Goe@WBC and Goe@MBC),respectively.Characterization and analysis of four biochars and investigation of their adsorption performance for Cd(II)and As(III)by batch experiments.The results showed that the content of the iron(Fe)element increased and a large number of Fe‒O and‒OH/Fe‒OH functional groups appeared on the surface of the biochar after iron modification.Compared with WBC and MBC,the adsorption capacity of Goe@WBC and Goe@MBC increased by 47%and 27%for Cd(II),and 903%and 940%for As(III),respectively.Goe@MBC showed stronger adsorption capacity for Cd(II)and weaker adsorption capacity for As(III)compared to Goe@WBC because cow manure is rich in phosphorus and PO_(4)^(3-)can bind to Cd(II)as a precipitate.At the same time,there is competition for adsorption with As(III).In conclusion,modifying biochar with iron can improve the adsorption capacity of biochar for both positively charged heavy metal cadmium(Cd)and negatively charged heavy metal arsenic(As),providing a new way to remediate heavy metal complex pollution.