1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Oil spills and industrial organic pollutants have induced severe water pollution and threatened every species in the ecological system. To deal with oily water, special wettability stimulated materials have been developed over the past decade to separate oil-and-water mixtures. Basically, synergy between the surface chemical composition and surface topography are commonly known as the key factors to realize the opposite wettability to oils and water and dominate the selective wetting or absorption of oils/water. In this review, we mainly focus on the development of materials with either super-lyophobicity or super-lyophilicity properties in oil/water separation applications where they can be classified into four kinds as follows (in terms of the surface wettability of water and oils): (i) superhydrophobic and superoleophilic materials, (ii) superhydrophilic and under water superoleophobic materials, (iii) superhydrophilic and superoleophobic materials, and (iv) smart oil/water separation materials with switchable wettability. These materials have already been applied to the separation of oil-and-water mixtures: from simple oil/water layered mixtures to oil/water emulsions (including oil-in-water emulsions and water-in-oil emulsions), and from non-intelligent materials to intelligent materials. Moreover, they also exhibit high absorption capacity or separation efficiency and selectivity, simple and fast separation/absorption ability, excellent recyclability, economical efficiency and outstanding durability under harsh conditions. Then, related theories are proposed to understand the physical mechanisms that occur during the oil/water separation process. Finally, some challenges and promising breakthroughs in this field are also discussed. It is expected that special wettability stimulated oil/water separation materials can achieve industrial scale production and be put into use for oil spills and industrial oily wastewater treatment in the near future.

Biomimetic super-lyophobic and super-lyophilic materials applied for oil/water separation: a new strategy beyond nature

This chapter highlights a variety of techniques that are commonly used to measure contact angles, including the conventional telescope-goniometer method, the Wilhelmy balance method, and the more recently developed drop-shape analysis methods. The various applications and limitations of these techniques are described. Notably, studies of ultrasmall droplets on solid surfaces allow wetting theories to be tested down to the nanometer scale, bringing new insight to contact angle phenomena and wetting behavior.

https://www.springer.com/cda/content/document/cda_downloaddocument/9783642342424-c1.pdf?SGWID=0-0-45-1368817-p174704744

Contact Angle and Wetting Properties

Design, and Applications Shutao Wang,†,‡ Kesong Liu, Xi Yao, and Lei Jiang*,†,‡,§ †Laboratory of Bio-inspired Smart Interface Science, Technical Institute of Physics and Chemistry, and ‡Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, BeiHang University, Beijing 100191, People’s Republic of China Department of Biomedical Sciences, City University of Hong Kong, Hong Kong P6903, People’s Republic of China

Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications

Field-flow fractionation (FFF) is a family of flexible elution techniques capable of simultaneous separation and measurement. Its sample domain extends across a broad macromolecular-colloidal-particulate continuum from about 1 nanometer to more than 100 micrometers and incorporates both simple and complex macromaterials of biological, biomedical, industrial, and environmental relevance. Complex materials are separated into components to simplify measurement. Component properties measurable by FFF include mass, size, density, charge, diffusivity, and thickness of adsorbed layers. When characterization by these properties is inadequate, other measurement tools can be readily coupled to FFF, either off-line or on-line, by virtue of its flow-elution operation. This article describes the principles and major subtechniques of the FFF family along with application of its measurement and separative capabilities.

https://science.sciencemag.org/content/sci/260/5113/1456.full.pdf

Field-flow fractionation: analysis of macromolecular, colloidal, and particulate materials

The term superhydrophilicity is only 11–12 years old and was introduced just after the explosion of research on superhydrophobic surfaces, in response to the demand for surfaces and coatings with exceptionally strong affinity to water. The definition of superhydrophilic substrates has not been clarified yet, and unrestricted use of this term to hydrophilic surfaces has stirred controversy in the last few years in the surface chemistry community. In this review, we take a close look into major definitions of hydrophilic surfaces used in the past, before we review the physics behind the superhydrophilic phenomenon and make recommendation on defining superhydrophilic surfaces and coatings. We also review chemical and physical methods used in the fabrication of substrates on surfaces of which water spreads completely. Several applications of superhydrophilic surfaces, including examples from the authors' own research, conclude this review.

Hydrophilic and superhydrophilic surfaces and materials

Synthesis of hydroxyapatite for biomedical applications

The term superhydrophobicity was introduced in 1996 to describe water-repellent fractal surfaces, made of a hydrophobic material, on which water drops remain as almost perfect spheres and roll off such surfaces leaving no residue. Today, superhydrophobic surfaces are defined as textured materials (and coatings) on (nonsmooth) surfaces on which water forms contact angles 150° and larger, with only a few degrees of contact angle hysteresis (or sliding angle). The terms superhydrophilicity and superwetting were introduced a few years after the term superhydrophobicity to describe the complete spreading of water or liquid on substrates. The definition of superhydrophilic and superwetting substrates has not been clarified yet, and unrestricted use of these terms sometimes stirs controversy. This Letter briefly reviews the superwetting phenomenon and offers a suggestion on defining superhydrophilic and superwetting substrates and surfaces.

Emil Chibowski

Papers

Hydrophilic and superhydrophilic surfaces and materials

Synthesis of hydroxyapatite for biomedical applications

Superhydrophilic and Superwetting Surfaces: Definition and Mechanisms of Control

Surface free energy of a solid from contact angle hysteresis

Aqueous suspension of fumed oxides, particle size distribution and zeta potential