College of Architecture and Civil engineering, Beijing University of Technology, No. 100 Xi Da Wang Road, Chao Yang District, Beijing, 100124, People's Republic of China.
Environ Sci Pollut Res Int. 2019 Mar;26(9):9161-9173. doi: 10.1007/s11356-019-04392-y. Epub 2019 Feb 4.
Ultrasound-assisted regeneration of powdered activated carbon (PAC) saturated with 4-chlorophenol (4-CP) was investigated in this work. The variables, i.e., acoustic frequency, density levels, regenerating solution species, spent PAC mass, and the number of repeated cycle, were optimized. The UV-Vis spectra, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and pore structure analysis were used to characterize the regenerated PAC as compared to the virgin and spent PAC. The adsorption experiments indicated that the adsorption kinetics of 4-CP fitted well with the pseudo-second-order model, and the main chemisorption process was nonlinear and heterogeneous. The desorption results showed that the optimized regenerated conditions were identified as 40 kHz of frequency, 0.18 W/mL of sonication intensity, 0.1 M NaOH and 50% (v/v) ethyl alcohol mixture of regeneration solution, and 1 g/L of saturated PAC mass. Under this condition, the regeneration efficiency reached up to 86.81%. Hydroxylated oxidation products especially benzoquinone and hydroquinone were formed during ultrasound regeneration. Ultrasound mainly acted on surface functionalities, mesopores, and macropores of PAC through the hydroxyl radical oxidization resulted from the cavitation effect.
本工作研究了超声辅助再生粉末活性炭（PAC）对 4-氯苯酚（4-CP）的吸附。优化了超声频率、密度水平、再生溶液种类、废 PAC 质量和重复循环次数等变量。通过紫外-可见光谱、热重分析（TGA）、傅里叶变换红外光谱（FT-IR）、扫描电子显微镜（SEM）、BET 和孔径结构分析对再生 PAC 进行了表征，并与原 PAC 和废 PAC 进行了比较。吸附实验表明，4-CP 的吸附动力学符合准二级模型，主要的化学吸附过程是非线性和非均相的。解吸结果表明，优化的再生条件为 40 kHz 的频率、0.18 W/mL 的超声强度、0.1 M NaOH 和 50%（v/v）乙醇混合再生溶液，以及 1 g/L 的饱和 PAC 质量。在此条件下，再生效率达到 86.81%。超声再生过程中形成了羟基化氧化产物，特别是邻苯醌和对苯二酚。超声主要通过空化效应产生的羟基自由基氧化作用对 PAC 的表面官能团、中孔和大孔进行作用。
