摘要
以农田生态系统废弃农作物秸秆资源化利用为前提,以生物炭去除水体重金属镉(Cd)污染及其回收利用为目的,该文以500℃裂解的原始玉米秸秆生物炭(MSB,maize straw biochar)和磁性玉米秸秆生物炭(MMSB,magnetic maize straw biochar)试验材料,在2种生物炭的表面性状进行表征的基础上,探究了不同吸附条件下生物炭对污染水体中Cd(Ⅱ)的吸附去除作用及其回收利用的可能性。结果表明:MSB和MMSB对Cd(Ⅱ)的吸附量在pH值为5时达到最大,其最大吸附量分别为27.52和33.45 mg/g;当MSB和MMSB添加量为1.4和0.8 g/L时,对Cd(Ⅱ)的去除率分别可达85.15%和95.48%;Langmuir方程能更好地模拟等温吸附行为,MSB和MMSB达到平衡时的最大吸附容量分别为26.03和43.45 mg/g,趋近实际值;动力学数据与二级动力学方程拟合度更高,MSB和MMSB的平衡吸附量Qe理论值分别为13.42和24.31 mg/g;MMSB对其表面吸附Cd(Ⅱ)的解吸率均显著低于MSB。磁性生物炭对Cd(Ⅱ)的吸附效率和固着能力增强可能与其较高的pH值、更大的比表面积、更多的极性含氧官能团有关。此外,在外部存在磁场的情况下,磁性生物炭可以通过磁力作用加以回收再利用。研究成果对促进农业废弃物的资源化利用以及水体环境中重金属净化技术的进步均有重要意义。
China is a large agricultural country whose output of crop straw is more than 800 million tons,but the effective resource utilization technology of straw is still lacking.Heavy metal pollution in water is also one of the major environmental problems at present.Adsorption methods are widely used in removing heavy metals from water environment due to the simple operation,no need to add a large amount of chemical agents,and low energy consumption.The preparation of biochar from maize straw provides a resource utilization approach for agricultural waste.Besides,maize straw biochar can be used as a new type of environmentally friendly material for the treatment and repair of polluted water.Based on the premise of resource utilization of crop straw wastes in farmland ecosystems,the objective of this study was to remove the heavy metal cadmium(Cd)from water using biochar and realize the recycling of biochar.The original maize straw biochar(MSB)and magnetic maize straw biochar(MMSB)that cracked at 500℃were used as experimental materials for this purpose.Based on the characterization of the original biochar and the magnetic biochar,the adsorption and removal effects of the 2 kinds of biochar on Cd(II)in polluted water and the possibility of recycling biochar were explored.The results showed that the adsorption of Cd(II)by biochar increased first and then decreased with the increase of the pH value of the solution,and the adsorption of Cd(II)by MSB and MMSB reached the maximum at the pH value of 5.The maximum adsorption capacities were 27.52 and 33.45 mg/g,respectively.When MSB and MMSB were added at 1.4 and 0.8 g/L,the removal rates of Cd(II)were up to 85.15%and 95.48%respectively,and the difference was significant(P<0.05).Langmuir equation could better simulate the isothermal adsorption behavior,the fitting coefficients of MSB and MMSB were both over 0.970 0,and the maximum adsorption capacities at equilibrium reached 26.03 and 43.45 mg/g respectively,which approached the actual values.The kinetic data had a higher fitting degree with the second-order kinetics equation.The theoretical values of equilibrium adsorption capacity of MSB and MMSB were 13.42 and 24.31 mg/g respectively,which had only differences of 2.26%and 3.84%with the actual values respectively.The maximum desorption rates of MSB and MMSB were 41.10%and 29.88%,respectively,and the desorption rates of MMSB were significantly lower than that of MSB.The adsorption process of Cd(II)by biochar was a combination of various mechanisms,mainly chemical mechanism,and the adsorption mechanism mainly includes electrostatic adsorption,ion exchange,surface complexation and cation-πaction.The enhancement of adsorption efficiency and fixation ability of magnetic biochar on Cd(II)might be related to its higher pH value,larger specific surface area,and more polar oxygen-containing functional groups.In addition,in the case of external magnetic fields,magnetic biochar could be recovered and reused by magnetic action.The research results are of great significance to promote the resource utilization of agricultural waste and the advancement of heavy metal purification technology in the water environment.
作者
胡学玉
陈窈君
张沙沙
王向前
李成成
郭晓
Hu Xueyu;Chen Yaojun;Zhang Shasha;Wang Xiangqian;Li Chengcheng;Guo Xiao(School of Environment,China University of Geosciences(Wuhan),Wuhan 430074,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2018年第19期208-218,共11页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(41371485)
湖北省自然科学基金重点项目(2014CFA116)
中央高校基本科研业务费专项资金资助项目(CUG170103)
关键词
生物量
吸附
重金属
生物炭
磁性生物炭
重金属去除
水环境
biomass
adsorption
heavy mental
biochar
magnetism biochar
heavy mental removal
aqueous solutions