不同温度桉树叶生物炭对Cd2+的吸附特性及机制

通过元素分析、BET-N₂、Zeta电位、Boehm滴定，SEM-EDS、FTIR等分析方法对不同热解温度（300、500和700℃）下制备的桉树叶生物炭进行表征，研究了3种生物炭（BC300、BC500和BC700）对Cd²⁺的吸附特性与机制.结果表明，随温度升高，生物炭产率下降，灰分、pH值和Zeta负电荷量上升，比表面积增大.当Cd²⁺浓度为20mg/L时，平衡时间依次为80min（BC700）<360min（BC500）<540min（BC300），均符合准二级动力学模型（R²>0.98），以化学吸附为主.BC300和BC500吸附过程均符合Langmuir和Freundlich模型，BC700更符合Freundlich模型，最大吸附量依次为BC700（94.32mg/g） > BC500（67.07mg/g） > BC300（60.38mg/g）.在Boehm滴定结果分析的基础上，结合FTIR和SEM-EDS，表明生物炭吸附机制主要为静电吸附和官能团络合作用.BC700吸附性能最佳，原因可能是具有较大的比表面积、较多的负电荷量和较为丰富的官能团.

Adsorption characteristics and Mechanism of Cd2+on biochar with different pyrolysis temperatures produced from eucalyptus leaves

Three types of biochar were generated from eucalyptus leaves under different pyrolysis temperatures of 300,500and 700℃(referred as BC300,BC500 and BC700),and their surface characteristics and Cd (Ⅱ) adsorption processes were investigated using element analysis,BET-N₂,Zeta analysis,Boehm titration,SEM-EDS,FTIR and other analytical methods.The results showed that as pyrolysis temperature increased,the yields decreased,but the ash content,pH,specific surface area and Zeta potential increased.The adsorptive capacity followed in the order of BC700(94.32mg/g),BC500(67.07mg/g) and BC300(60.38mg/g),and both Langmuir and Freundlich models were reasonable to describe the adsorption behavior of BC300and BC500,but Freundlich model was more suitable to describe the adsorption processes of BC700.Adsorption kinetic showed the equilibrium time followed by 540min (BC300),360min (BC500) and 80min (BC700),which were better fitted by pseudo-second order model (R²>0.98) indicating the adsorption was mainly chemical.The results of FTIR and Boehm titration indicated that the spectra of BC700incurred more changes than those of other biochars,which suggested more functional groups were involved in the adsorption including -OH、C=O、C=C、C-O groups.BC700biochar are more effective than other biochars to remove Cd²⁺,which was due to larger specific surface,more negative charge amount and functional groups.Based on the studies above,the removal of Cd²⁺ were mainly by surface electrostatic adsorption and chelation.