学术讲座丨【岩土工程新进展】第6次线上讲座

《The frontier of geotechnical engineering》 – BJTU Series Online Academic Open Lectures

Electrical Double Layer on Clay Surfaces: Origins, Concepts, and Phenomena

●Date：Oct 16, 2022 (Sun). 09:00 – 12:00AM (GMT+8, Beijing Time).

●Webinar ID：

●Organize Institute: Key Laboratory of Urban Underground Engineering, Beijing Jiaotong University.
●Lecture Organizer:

Professor LI Xu (xuli@bjtu.edu.cn),

Dr. DU Saizhao (dusz@bjtu.edu.cn),

Dr. WU Yongkang (ykwu@bjtu.edu.cn),

School of Civil Engineering, Beijing Jiaotong University.

●Contact Person: Dr. DU Saizhao（dusz@bjtu.edu.cn）

Speaker

ZHANG Guoping
(Prof.)

University of Massachusetts Amherst.
Department of Civil & Environmental Engineering.

01.

Speaker Introduction

Dr. ZHANG Guoping is currently a professor in the Dept. of Civil & Environmental Eng. at the University of Massachusetts Amherst, and had prior appointments at Louisiana State University and the University of Nottingham (UK). He obtained a Ph.D. from Massachusetts Institute of Technology in 2002, and an M.Eng. and dual B.Eng. degrees from Tsinghua Univ. (China) in 1994 and 1991 respectively. His research interests are divided into four major areas: green geopolymers and alkaline-activation for sustainability, nanomechanical and microscale characterization of clay-based geomaterials, hydrophobicity and surface modifications of minerals, and clay-biopolymer interactions. He has published more than 100 articles in a variety of journals and more than 50 conference proceeding papers.

02.

Lecture Outline

The electrical double layer (EDL), adopted by a plethora of disciplines (e.g., clay science, soil mechanics, electrochemistry, interface science, materials science, colloid chemistry), describes a nanoscale layer of electrolyte solutions (usually with water as the solvent) adjacent to a charged electrode (e.g., anode, cathode) surface, where the oppositely charged counter ions balance the net charges of the electrode. A unique feature is that the concentration of the counter ions decreases nonlinearly with the distance from the charged electrode surface, and hence EDL is often also termed “diffuse double layer (DDL)”, which has been used interchangeably with EDL. The word “double” means that the EDL consists of two distinct or distinguishable layers: (1) a so-called Stern or Helmholtz layer, where “the counter ions are bound, usually transiently (i.e., as exchangeable ions, such as cation exchange)”, and (2) a real diffusive layer where the counter ions diffuse away from the electrode surface, as indicated by the concentration of counterions decreases asymptotically to that of the bulk solution. Because clay minerals possess negative permanent charges on face surfaces and variable charges on edge surfaces, which can be treated as a microscale electrode, the original concepts and theories of electrode-based EDL can be applied to clay particles.
This webinar aims to report a summary review of the origins, concepts, and recent validations on the EDL on clay surfaces. In particular, the effects of clay mineral surfaces’ diversity, heterogeneity, and nanostructure (e.g., cavities in the tetrahedral sheet, broken bonds on edge surface) on the EDL behavior and structure are discussed, such as “inner sphere complexes”, “outer sphere complexes”, spillover of double layer, differences between interlayer complexes and EDL, and hidden EDL. Finally, interpretation of exemplary engineering phenomena is highlighted to reflect the essence and importance of understanding the EDL concepts and theories as well as the underlying sciences.

03.

Course Introduction

《Frontier of geotechnical engineering》 is an all English online course for foreign students from the Civil Engineering School of BJTU. Based on this course, a series of online academic public lectures are specially held. This course is also opened to the public. All interested students or researchers are welcome to attend FREE without any registration.

●Please refer to link below for more information regarding BJTU Series Online Academic Open Lectures:
https://mp.weixin.qq.com/s/yq7QzTz028ZoeI6jT783gQ

You are welcomed to follow our official wechat account for more info. (Geotechnical Department, Beijing Jiaotong University. “北交岩土”)

【岩土工程新进展】
线上开放课程第六讲

Electrical Double Layer on Clay Surfaces: Origins, Concepts, and Phenomena

●主办单位:北京交通大学土建学院城市地下工程教育部重点实验室
●讲座组织者:

李旭教授(xuli@bjtu.edu.cn),

杜赛朝(dusz@bjtu.edu.cn),

吴永康(ykwu@bjtu.edu.cn),

北京交通大学土木工程学院。

●联系人:杜赛朝(dusz@bjtu.edu.cn)

报告人

张国平教授

马萨诸塞大学阿默斯特分校，土木与环境工程系

01.

报告人简介

张教授现任马萨诸塞大学阿默斯特分校土木与环境工程系教授，曾在路易斯安那州立大学和英国诺丁汉大学任职。他于2002年获得麻省理工学院博士学位，并于1994年和1991年分别获得清华大学硕士和双学士学位。他有4个主要的研究领域：绿色地质聚合物和碱性活化可持续性、黏土基岩土材料的纳米机械和微尺度表征、矿物的疏水性和表面改性以及黏土-生物聚合物相互作用。他在各种期刊上发表了100多篇文章，并发表了50多篇会议论文。

02.

报告内容简介

许多学科(如黏土科学、土壤力学、电化学、界面科学、材料科学、胶体化学)都采用了双电层(EDL)的概念，它描述了与带电电极（如阳极、阴极)表面相邻的纳米级电解质溶液层（通常以水为溶剂)，其中相反带电的反离子平衡电极的净电荷。一个独特的特征是，反离子的浓度随距离带电电极表面的距离而非线性降低，因此EDL通常也称为“扩散双层(DDL)”，它与EDL互换使用。单词“double”表示EDL由两个不同或可区分的层组成：(1)所谓的Stern或Helmholtz层，其中“反离子通常是瞬间结合的(即交换离子，如阳离子交换)”，以及(2)真正的扩散层，其中反离子从电极表面扩散开，如图所示，反离子的浓度逐渐降低到体溶液的浓度。由于黏土矿物在表面具有负永久电荷，在边缘表面具有可变电荷，可以作为微型电极处理，因此基于电极的EDL的原始概念和理论可以应用于黏土颗粒。
本次讲座旨在总结黏土表面EDL的起源、概念和最近验证。特别是讨论了黏土矿物表面的多样性、异质性和纳米结构(如四面体板中的空洞、边缘表面的断裂键)对EDL行为和结构的影响，如“内层复合物”、“外层复合物”，双层溢出，层间复合物和EDL之间的差异，以及隐藏的EDL。最后，强调对典型工程现象的解释，以反映理解EDL概念和理论以及基础科学的本质和重要性。

03.

课程介绍

《岩土工程新进展》是一门北京交通大学针对土建学院外籍留学生开设的全英文博士研究生线上课程。依托这个课程，特举办系列在线学术公开讲座。此次系列讲座面向校内外师生及社会专业人士免费开放，师生可通过进入腾讯会议直接收看课程并参与互动，欢迎各位老师、同学、专业人士转发和参

矿业人|20221016直播预告【岩土工程新进展No.6】ZHANG Guoping——Electrical Double Layer on Clay Surfaces: Origins, Concepts, and Phenomena

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