摘要
在通过成功制备2种不同介孔结构的生物质炭AC-1与AC-2的基础上,研究了硝酸氧化改性对不同介孔结构生物质炭铅吸附特性的影响与等温吸附特性。低温氮吸附测试表明,生物质炭AC-1与AC-2的微孔孔容相近,而介孔孔容相差较大,分别为0.319和0.535 cm3·g-1。改性后AC-2-HNO3的介孔孔容与表面含氧酸官能团含量均高于AC-1-HNO3。吸附数据表明,硝酸改性可增强介孔生物质炭对水中铅的吸附去除能力,特别是改性前吸附量较低的AC-2,由于具有较大的介孔孔容和介孔尺寸,经硝酸改性后对铅的吸附性能与去除率均高于微孔孔容相近的生物质炭AC-1,这表明增大介孔孔容与介孔尺寸不仅有利于在介孔炭上接枝活性吸附位,并可缩短被吸附重金属铅离子到吸附活性点的路径,增大硝酸改性生物质炭活性位点对水中铅离子的捕捉机率,从而增大改性生物质炭对铅的吸附性能。Freundlich模型能很好地描述改性前后4种炭对铅的吸附行为,说明上述生物质炭的吸附位主要是非均匀孔隙或表面。
Two mesoporous biochars, AC-1 and AC-2, with different mesopore size distributions were suc- cessfully prepared to study the effect of nitric acid modification on the adsorption of lead on both bioehars, in ad- dition to isothermal adsorption. The N2 adsorption/desorption analysis results show that AC-1 and AC-2 have comparable micropore volumes, while their mesopore volumes differ significantly with values of 0. 319 and 0. 535 3 -1 em · g , respectively. The mesopore volume and oxygen-containing acidic functional groups of AC-2-HNO3 were significantly higher than those of AC-1-HNO3 after modification. The adsorption experiments indicated that both adsorbents exhibited better capacity for lead ion removal after modification. Notably, although the adsorption capacity of pristine AC-2 was lower than that of AC-1, AC-2 modified with nitric acid exhibited a higher Pb2＋ re- moval ratio than modified AC-1 owing to the larger mesopore volume and size of the former. The increased meso- pore volume could shorten the path for Pb2＋ to reach the activated adsorption sites and increase the probability of Pb2 ＋ capture from the solution, thereby improving the adsorption properties of the modified biochars. The experi- mental data fit best to the Freundlich isotherm model, illustrating that nonuniform pores or surfaces are the main adsorption sites.
出处
《环境工程学报》
CAS
CSCD
北大核心
2016年第9期4887-4894,共8页
Chinese Journal of Environmental Engineering
基金
中央高校基本科研业务费专项资金
中国博士后基金(129391)
国家自然科学基金资助项目(51102136)
关键词
生物质炭
硝酸氧化
吸附
吸附等温线
biomass carbon
HNO3 oxidation
adsorption
adsorption isotherm
