老化作用促进生物炭已吸附Cd(Ⅱ)的进一步稳定化研究

Study of aging effect on the stability of biochar initially adsorbed Cd(Ⅱ)

环境变化是否会导致已被生物炭吸附Cd(Ⅱ)的活化?本文通过人工加速模拟老化实验研究老化作用对生物炭已吸附Cd(Ⅱ)稳定性的影响.首先进行2种生物炭对Cd(Ⅱ)的饱和吸附实验,再将饱和吸附Cd(Ⅱ)的秸秆生物炭(RS+Cd)和浮萍生物炭(LM+Cd)分别进行化学老化、物理老化和自然老化,通过TCLP(Toxicity characteristic leaching procedure)提取实验研究生物炭吸附Cd(Ⅱ)的稳定性并探究可能存在的稳定机理.结果显示,老化56 d时,RS+Cd的3种老化处理的TCLP提取态Cd(TCLP-Cd)较老化初期降低了18.58%~49.23%,而LM+Cd降低了15.10%~26.16%,老化作用提高了生物炭对Cd(Ⅱ)的吸附稳定性,稳定化效果依次为化学老化>物理老化>自然老化.进一步稳定化机理为老化作用提高了生物炭表面氧化性,增加含氧官能团,并且老化后生物炭发生破碎,有利于生物炭内部的P、Fe、Ca等元素的溶解释放,为Cd(Ⅱ)提供更多的吸附点位.浮萍生物炭对Cd(Ⅱ)的吸附较秸秆生物炭有更强的稳定性.

Could the initially adsorbed Cd on biochar be remobilized when environment changes？ This study explored the aging effect on the absorption stability of Cd（ Ⅱ） by rice strawderived biochar（ RS） and Lemna minor derived biochar（ LM） via lab-based experiment. First of all,a Cd adsorption batch experiment was conducted to determined the Cd adsorption capability by RS and LM,and then a mixture of biochar and Cd（ RS＋Cd,LM＋Cd） was aging by chemical aging（ CHEM）,physical ageing（ PHY） and spontaneous aging（ SPON）. Finally,the Cd stability was evaluated by Toxicity Characteristic Leaching Procedure（ TCLP）,and the possible immobilization mechanism was deduced. The results showed as followed： Compared with the beginning of aging,the TCLP-Cd of RS＋Cd samples with three aging methods were declined by 18.58% ~ 49.23% after 56 days of aging,while the LM＋Cd samples declined by 15.10% ~ 26. 16%. Aging further increased the stability of initially adsorbed Cd on biochar instead of re-mobilizing,with the stability effect by three aging methods followed by chemical aging physical aging spontaneous aging. Aging could increase the oxidability of biochar surface,as well as the amountof oxygen-containing functional groups. In addition,elements such as P,Fe and Ca could be more easily released from aged biochar because of fragmentation,which could create more adsorption points for Cd. Compared with the two biochar,the Cd stability by LM was stronger than RS.