硫改性牛粪生物炭对Hg^(2+)的高效吸附及其机理

HIGH EFFICIENCY ADSORPTION OF Hg^(2+)BY SULFUR-MODIFIED COW MANURE BIOCHAR AND ITS MECHANISM

以牛粪为原料在400,500,600℃条件下限氧热解制备牛粪生物炭(BC),然后以不同质量比将升华硫和BC混合共热解制备硫改性牛粪生物炭(BCS)。使用元素分析仪、SEM、FTIR、XPS和BET对制得的BC和BCS进行了表征,并研究了各BC和BCS对Hg^(2+)的吸附特性。结果表明:热解过程使BC和BCS变得粗糙多孔,Hg^(2+)被吸附到生物炭表面和孔道内;BC和BCS的吸附过程符合准二级动力学模型,BCS对Hg^(2+)的吸附平衡时间仅为30 min,且吸附过程不受pH影响;Langmuir模型可较好地描述BC吸附过程,吸附量随热解温度的升高而降低,BCS吸附过程符合Freundlich模型,吸附能力较BC显著提升,最大拟合吸附量达到407.81 mg/g;BCS的吸附稳定性较高,在各解吸剂中的解吸率均低于5%;BC主要吸附机理为官能团络合,BCS主要吸附机理为Hg^(2+)S沉淀。因此BCS是一种高效稳定的Hg^(2+)吸附材料。

Cow manure biochar(BC)were prepared by low-limit oxygen pyrolysis of cow manure at 400℃,500℃and 600℃,and then sulfur-modified cow manure biochar(BCS)were prepared by co-pyrolysis of sublimated sulfur and BC at different mass ratios.The BC and BCS were characterized by elemental analyzer,SEM,FTIR,XPS and BET,and the adsorption characteristics of each BC and BCS sample for Hg^(2+)were studied.The results showed that with the increase of pyrolysis temperature,BC and BCS became coarse and porous,and Hg^(2+)was adsorbed on the surface and pore of biochar.Kinetic experiments showed that the adsorption process of BC and BCS could be better described by the pseudo-second-order model than the pseudo-first-order model.The equilibrium time of BCS for Hg^(2+)adsorption was only 30 min,and the adsorption process was not affected by pH.The results of isothermal experiments showed that Langmuir model could better describe the adsorption process of BC,and the adsorption capacity decreased when increasing pyrolysis temperature.The isothermal adsorption of BCS to Hg^(2+)conformed to the Freundlich equation,the adsorption capacity of BCS was significantly higher than BC,and the maximum adsorption capacity was 407.81 mg/g.The desorption experiments showed that the adsorption stability of BCS was higher than BC,and the desorption rate was lower than 5%in each desorption agent.The results of FTIR and XPS showed that the main adsorption mechanisms of BC and BCS were functional group complexation and Hg^(2+)S precipitation,respectively.Therefore,BCS is a highly efficient and stable mercury adsorption material.