Effects of humic acid on recoverability and fractal structure of alum-kaolin flocs  

作　　者：Runsheng Zhong Xihui Zhang Feng Xiao Xiaoyan Li 

机构地区：[1]esearch Center for Environmental Engineering & Management, Graduate School at Shenzhen Tsinghua Universit) Shenzhen 518055, China. E-mail: [e-mail] [2]Department of Civil Engineering, The University of Hongkong, Hongkong 999077, China

出　　处：《Journal of Environmental Sciences》2011年第5期731-737,共7页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (No. 20721140019, U0773002);the National High Technology Research and Development Program (863) of China (No. 2002AA601120)

摘　　要：Particle surface characteristics, floc recoverability and fractal structure of alum-kaolin flocs were investigated using in situ particle image velocimetry （PIV） and microbalance with or without humic acid. Experimental results indicated that the zeta potential of kaolin particle surface after adsorption of humic acid was related with humic acid concentration and its acid-base buffering capacity. Adsorption of humic acid resulted in more negative electrophoresis on the particle surface. Coagulant dosages for particles to form flocs would increase with increasing humic concentration. PIV was used to evaluate floc structural fragmentation, floc surface erosion as well as recoverability after high shear. It was found that the floc size during the steady phase of growth was small, while the regrowing capability decreased in the presence of humic acid. The recoverability was closely related with floc breakage modes including floc structural fragmentation and floc surface erosion. The fractal dimensions of alum-kaolin flocs by mass-size method based on microbalance would decrease with increasing humic concentration. This study proved that humic acid had adverse influences on the performance of coagulation process.Particle surface characteristics, floc recoverability and fractal structure of alum-kaolin flocs were investigated using in situ particle image velocimetry （PIV） and microbalance with or without humic acid. Experimental results indicated that the zeta potential of kaolin particle surface after adsorption of humic acid was related with humic acid concentration and its acid-base buffering capacity. Adsorption of humic acid resulted in more negative electrophoresis on the particle surface. Coagulant dosages for particles to form flocs would increase with increasing humic concentration. PIV was used to evaluate floc structural fragmentation, floc surface erosion as well as recoverability after high shear. It was found that the floc size during the steady phase of growth was small, while the regrowing capability decreased in the presence of humic acid. The recoverability was closely related with floc breakage modes including floc structural fragmentation and floc surface erosion. The fractal dimensions of alum-kaolin flocs by mass-size method based on microbalance would decrease with increasing humic concentration. This study proved that humic acid had adverse influences on the performance of coagulation process.

关 键 词：humic acid particle image velocimetry floc breakage RECOVERABILITY fractal dimension 

分 类 号：O484.1[理学—固体物理] TP311.13[理学—物理]