tailieunhanh - Flocculation In Natural And Engineered Environmental Systems - Chapter 7

Một tỷ lệ lớn các hợp chất vi lượng (điển hình là 40% đến 90%) được hấp phụ chất keo thủy sản thông qua kết cộng hóa trị, tĩnh điện, hay kỵ nước, 2 Dựa trên kích thước và mật độ cân nhắc, chất keo sẽ còn lơ lửng trong cột nước và được vận chuyển trên một khoảng cách dài. Mặt khác, đông máu hoặc keo tụ có thể tạo điều kiện thuận lợi cho việc loại bỏ các chất keo từ cột nước bằng cách sản xuất cốt liệu có đủ lớn để , 4 Trong các hệ thống phức tạp chẳng. | 7 Contrasting Roles of Natural Organic Matter on Colloidal Stabilization and Flocculation in Freshwaters Kevin J. Wilkinson and Alain Reinhardt CONTENTS Introduction. 143 Characterization of the Major Aquatic Colloids . 144 Inorganic Colloids. 145 Allochthonous Macromolecules Humic Substances. 148 Autochthonous Macromolecules Proteins Lipids and Polysaccharides . 149 Principal Mechanisms of Colloidal Stabilization and Destabilization. 150 Charge Modification. 152 Bridging Flocculation. 152 Depletion Flocculation. 153 Steric Stabilization. 154 Primary Colloidal Interactions in Freshwaters. 154 Homocoagulation . 154 Heterocoagulation Role of HS. 156 Heterocoagulation Role of Rigid Polysaccharides and Peptidoglycans . 157 Heterocoagulation Contributions of Other Types of Organic Matter . 159 Summary and Future Perspectives. 162 Acknowledgments . 164 References . 164 INTRODUCTION A large proportion of trace compounds typically 40 to 90 are adsorbed to aquatic colloids via covalent electrostatic or hydrophobic 2 Based 1-56670-615-7 05 2005 by CRC Press 143 Copyright 2005 by CRC Press 144 Flocculation in Natural and Engineered Environmental Systems upon size and density considerations colloids will generally remain suspended in the water column and be transported over long distances. On the other hand coagulation or flocculation can facilitate the elimination of colloids from the water column by producing aggregates that are large enough to 4 In complex systems such as natural waters colloidal aggregation is ubiquitous due to the large number of colloid types and reactive sites. Indeed size fractionation analysis has often demonstrated that each colloid type may be found in all size This suggests that it is at least as important to understand interactions among the colloids as it is to determine the binding energies of trace compounds