Response of tenuous clay-polysaccharide flocs to hydrodynamic shearing  

作　　者：Li He Hang Yin Yongkang Wu Wei Sun Guoping Zhang 

机构地区：[1]Institute of Fundamental and Frontier Sciences,University of Electronic Science and Technology of China,Chengdu,610054,China [2]Department of Civil and Environmental Engineering,University of Massachusetts Amherst,Amherst,MA 01003,USA [3]Department of Civil and Environmental Engineering,Southern University,Baton Rouge,LA 70807,USA [4]School of Civil Engineering,Beijing Jiaotong University,Beijing,100044,China

出　　处：《International Journal of Sediment Research》2024年第6期984-997,共14页国际泥沙研究(英文版)

基　　金：Louisiana Board of Regents'Economic Development Assistantship Program and Louisiana State University Graduate School Supplement Award,and at the later phase partially by Beijing Natural Science Foundation(Grant No.8222028);National Natural Science Foundation of China(Grant No.52209119).

摘　　要：The response of suspended tenuous clay-polysaccharide flocs to hydrodynamic shearing was investigated in the laboratory via particle size analyses to understand the molecular-scale interactions between clay minerals and polysaccharides and their hydrodynamic behavior such as size kinetics, re-flocculation/breakdown, and shear strengths of the hybrid flocs. While the studied suspensions had a fixed clay concentration of 0.4 g/L, an array of other parameters was varied to reflect the complexity of clay-polysaccharide systems, including four types of clay minerals with varying layer charges and swellability (i.e., kaolinite, illite, and sodium- (Na-) and calcium- (Ca-) montmorillonites), two exopolymers of dissimilar polarities (i.e., xanthan and guar), six polysaccharide (P) to clay (C) weight ratios (i.e., P/C = 0, 1, 2, 5, 10, and 20 wt%), and three hydrodynamic shearing rates of 187, 429, and 1,100 1/s (i.e., corresponding to laminar, transitional, and turbulent flows, respectively). Results show that the clay-polysaccharide floc sizes are sensitive to the shear stress and also vary with different clay-polysaccharide systems. Four discrete particle groups were identified by statistical analyses, consisting of primary particle (PP), flocculi (FL), microfloc (MiF), and macrofloc (MaF), which exhibit distinct stabilities to shearing. The MaF is much weaker than MiF and can easily breakdown, as indicated by the decrease in MaF fraction with increasing shearing, while the MiF is the dominant particle group in transitional and turbulent flows. The fractions of PP and FL generally increase with shearing rate. Based on floc survivability in different flow conditions, the MaF's upper and lower bound shear strengths were estimated to be 0.95 and 0.17 Pa, respectively. The strongest MaF with a maximum shear strength of 0.95 Pa is formed in the clay-guar suspensions at a P/C of 10 wt%. Anionic xanthan only forms flocs with kaolinite with little surface charges, but cannot induce clay-polysaccharide flocs for illite and Ca/N

关 键 词：Clay-polysaccharide interactions Flocculation Floc strength Hydrodynamic shearing Particle size distribution MULTIMODALITY 

分 类 号：TV14[水利工程—水力学及河流动力学]