孔结构对活性炭吸附水溶液中铅离子的影响

Effect of Activated Carbon Pore Structure on the Adsorption of Pb(ll) from Aqueous Solution

选取三种表面化学性质相近的活性炭(AC),通过等温吸附实验考察活性炭对水溶液中铅离子的吸附性能,利用扫描电子显微镜(SEM)观察活性炭的表面微观形貌,通过低温(77 K)液氮吸附测定活性炭的比表面积和孔容,并分别以密度泛函理论(DFT)和Barrett-Joyner-Halenda(BJH)法计算微孔和中孔的孔径分布.结果表明:选用的三种活性炭AC1、AC2、AC3在比表面积和总孔容上呈依次下降的趋势,但表面开放孔均匀分布的AC2,具有最高的饱和吸附量,孔结构类似颗粒堆积孔的AC3,具有与表面开放孔分布集中的AC1相近的饱和吸附量;通过对孔结构与吸附量的关联分析可知,在活性炭吸附铅离子的过程中,0.4–0.6 nm的孔是有效吸附孔,10.5–20.6 nm、20.6–55.6 nm、5.2–10.5 nm三个区间的孔则会对吸附产生阻碍作用.

Pb（II） adsorption by three activated carbons（ACs） with similar surface chemistry but different pore distributions was investigated by isothermal adsorption experiments. The ACs were characterized by scanning electron microscopy（SEM） and N2 adsorption at 77 K, while the micropore and mesopore size distributions were obtained from the density functional theory（DFT） and the Barrett-Joyner-Halenda（BJH） method,respectively. The specific surface area and total volume were ranked in order of AC1, AC2, and AC3. The AC2 sample had a uniform distribution of open pores on the surface and the highest saturating adsorption capacity,while the capacity of AC3, which had more aggregated pores, was similar to that of AC1, which had a concentrated distribution of open pores on the surface. A correlation analysis of pore structure and adsorption capacity indicated that pores with diameters in the range of 0.4–0.6 nm were favorable for Pb（II） adsorption,whereas pores with diameters in the ranges of 10.5–20.6 nm, 20.6–55.6 nm, and 5.2–10.5 nm had an adverse effect.