Flocculation and magnetically-assisted sedimentation of size-sorted beidellite platelets mixed with maghemite nanopartic
- PDF / 2,400,297 Bytes
- 11 Pages / 612 x 808 pts Page_size
- 0 Downloads / 126 Views
Flocculation and magnetically-assisted sedimentation of size-sorted beidellite platelets mixed with maghemite nanoparticles Sofia Housni1, Sébastien Abramson1 (), Jean-Michel Guigner2, Pierre Levitz1, and Laurent Michot1 1
Laboratoire de PHysico-chimie des Electrolytes et Nanosystèmes InterfaciauX (PHENIX UMR 8234, Sorbonne Université – CNRS), Sorbonne Université, Paris 75252, France 2 Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC UMR 7590, Sorbonne Université – IRD – CNRS – MNHN), Sorbonne Université, Paris 75252, France © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 23 April 2020 / Revised: 29 June 2020 / Accepted: 30 June 2020
ABSTRACT In this study, the flocculation and the subsequent decantation step of mixed suspensions of 10 nm-sized γ-Fe2O3 magnetic nanoparticles and 500 nm-sized beidellite clay platelets was investigated. This work may find application in the field of water treatment, specifically the flocculation processes with magnetically assisted sedimentation. After a short description of the preparation and characterization of the raw materials (nanoparticles and clays), the influence of several parameters (pH, concentrations of nanoparticles and clays etc.) on the amount of flocculated materials was examined, which gave information on the concentration ranges allowing a complete flocculation, together with a better understanding on the interactions between nanoparticles and clays responsible for flocculation. The optimal conditions for magnetically assisted settling were then determined by comparing for each sample sedimentation velocities under gravity and in the presence of a Nd-Fe-B magnet. Finally, the complex multiscale structure of the flocs in water was explored, through the measurement of several bulk properties (zeta-potential and volume measurements, laser granulometry), while the organization of the materials at a microscopic scale was investigated by cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS).
KEYWORDS magnetic separation, nanoparticles, clay, flocculation, decantation, characterization
1
Introduction
Flocculation is a physicochemical process during which colloidal particles in suspensions agglomerate and form bigger particles called flocs. Usually, a flocculating agent, such as an inorganic salt (Al2(SO4)3, FeSO4, FeCl3, etc.) and/or an organic polymer (polydiallyl-dimethylammonium chloride, polyacrylic acid, polyacrylamide…) is added to trigger agglomeration. This method is used in many applications, especially in water treatment [1]. In this field, flocculation is frequently employed in drinking water plants. It aims at eliminating most of the colloidal fraction originally present in raw water under the form of natural organic matter, bacteria, clays or other inorganic particles. In such a process, as floc density is low, floc sedimentation under gravity is rather slow. This major drawback increases the costs and reduces the efficiency of the process
Data Loading...
