Smart Materials for Advanced Environmental Applications

They range from an introduction to smart materials and their applications (Chapter 1, Zhang and Professor Wang), smart traction solutions in forward osmosis (Chapter 2, Chen and Professor Lu), superwetting materials for oil-water separation (Chapter 3, Gao and Professor Jin), responsive particle-stabilized emulsions (Chapter 4, Kwok and Professor Ngai), self-healing materials (Chapter 5, Professor Zeng et al.), bio-inspired manure collection (Chapter 6, Zhang and Professor Wang), natural inspired "slippery" liquid-infused surfaces (Chapter 7, Professor Zacharia) to challenges and opportunities of superhydrophobic/superamphiphobic coatings in real-world applications (Chapter 8, Paven, Mammen and Professor Vollmer). In my opinion, they are the ones to watch in the coming years in this emerging field of smart materials and their applications to environmental problem solving.

Slippery” Liquid-Infused Surfaces Inspired

Challenges and Opportunities of Superhydrophobic/

3oduction Figure 1.3 (a) a schematic illustration of the piezoelectric effect. b) a hybrid piezoelectric structure for coated nanogenerators. 11oduction Figure 1.7 (a) Synthesis of Mnps functionalized with the thermoresponsive pSSS-pnipaM copolymer. FO process using smart thermo-responsive magnetic nanoparticle drawing solutions and drawing solution regeneration.

Figure 1.1 Oil spill absorbents used in oil leakage incidents. (a) Sorbent booms, sweeps, and snares were used to help aid in the massive cleanup efforts after the Kalamazoo river oil spill, Michigan, US, July 28, 2010

Introduction

Compared to Ro, Fo holds great promise for low energy consumption if a suitable draft-free substance with an economical and efficient regeneration method is available.2,6,23 in addition, Fo has advantages such as low and reversible membrane fouling, robust rejection of various pollutants, high water flux and recovery as well as reduced discharge of concentrated brine.24–28 the ability to also maintain the properties of the feed solution. Smart materials, which can respond to stimuli such as temperature, magnetic field and light, offer opportunities as Fo drag agents to lower the energy consumption of the process with great potential; and recent years have witnessed the growing interest in developing such materials.

Figure 2.1 Schematic illustration of Fo.

Hydrophilic Magnetic Nanoparticles

Current research results revealed that the surfactants, nanoparticle size, concentration and the dissociation extent all have an important impact on the Fo performance. water flood. Kim's group found that the choice and replacement of stainless steel wool played an important role in the complete recovery of nanoparticles.59 after turning off the magnetic field, the stainless steel wool could not be completely demagnetized due to its ferromagnetic characteristic and this residual magnetization prevented the complete removal of the nanoparticles by rinsing with water.

Stimuli-Responsive Magnetic Nanoparticles

Introduction
Thermo-Responsive Magnetic Nanoparticles
Other Stimuli-Responsive Magnetic Nanoparticles as Potential FO Draw Solutes

Light-Responsive Magnetic Nanoparticles
CO 2 -Responsive Magnetic Nanoparticles

Before CO2 scavenging, the primary amine was deionized and the hydrophobic interaction between the alkyl chains of the surfactants tended to cause the nanoparticles to aggregate in aqueous solutions. Future work includes improving the hydrophilicity of the nanoparticles by functionalizing them with polymers bearing more CO2-responsive functional groups and increasing the polymer charge.

Figure 2.8 (a) Size change of pnipam/teg-mnp at different temperatures. (b) Fo performance of recycled pnipam/teg-mnps

Smart Polyelectrolytes and Solvents

Introduction
Thermo-Responsive Polyelectrolytes
CO 2 Switchable Dual Responsive Polymers
Switchable Polarity Solvents

When protonated via Co2 scavenging, the solute became a polyelectrolyte and possessed osmolality high enough for seawater desalination and induced high water flux in the subsequent Fo process. For example, after protonation, the osmolality of the draw solution with a concentration of 0.4 g g-1 increased by two times from 0.6 osm kg-1.

Figure 2.12 polyelectrolyte solution as draw agent in Fo process and the recovery of the water by hot ultrafiltration

Smart Hydrogels

Introduction
Synthetic Methods and FO Performance
Dewatering Method and Performance

When the polymer network is functionalized with specific groups, it can undergo reversible changes in the swelling of the network when exposed to certain external stimuli. For example, the inclusion of the carbon in the pnipam increased the swelling ratio by 93.3%.

Figure 2.18 Synthesis of composite hydrogels consisting of pSa-co-nipam, and carbon particles

Conclusions and Future Perspectives

Introduction

Finally, a summary of this brief review and a perspective for oil/water separation in the future is described in section 3.5.

How to Construct Nanomaterials with Superwetting Surfaces

Theoretical Basis of Wettability of Solid Materials
Theoretical Principle to Construct Superwetting Nanomaterials
Natural and Artificial Examples of Superwetting Nanomaterials

It is assumed that the vapor is trapped in the grooves of the rough surface beneath the liquid, giving a composite surface. 49), copyright 2004. f) and (g) SeM images of porous microspheres and nanofibers of superhydrophobic pS film. 50 (h) water droplet on a superhydrophobic pS film.

Figure 3.2 (a)–(c) digital photograph and SeM images of the superhydrophobic lotus leaf

Superwetting Absorbing Nanomaterials for Separation of Free Oil/Water Mixtures

Sponge- and Foam-Based Superwetting Absorbing Nanomaterials
Textile-Based Superwetting Absorbing Nanomaterials

When hCMp-1 was loaded onto a hydrophilic sponge by the dipping method, the surface wettability of the sponge changed from hydrophilic to superhydrophobic (Figures 3.5e and f). Based on the different behavior of hpS towards oil and water, the authors made a table-top apparatus for collecting oil (Figure 3.6e).

Figure 3.5 Simulation structure (a) (Materials Studio, polymer builder) and teM image (b) of the hCMp-1, scale bar: 200 nm

Superwetting Separation Membranes for Oil/

Water Separation

Mesh- and Textile-Based Superwetting Films for Separation of Oil/Water-Free Mixtures and Emulsions

When an oil/water mixture was poured onto the paM-coated mesh film, water quickly permeated through the film while the oil was retained above the film due to the superwetting property of the film (Figure 3.9f and g). Feng's group reported a double-layer thio2-based mesh film with the multi-functions of oil/water separation and soluble pollutant degradation due to the photo-catalysis of thio2.96, the top layer was fabricated a superhydrophilic thio2-coated mesh film by a hydrothermal approach with micro- and nanostructures.

Polymer-Dominated Superwetting Filtration Membranes for Separation of Oil/Water Emulsions

Due to the robust superwetting Figure 3.14 (a)–(c) SeM images for the membrane surface with scale bar of 200 µm, 20 µm and 2 µm, respectively.87 (d) Wettability of the membrane to water (top) and oil (lower). e) Separation results for oil-in-water and water-in-oil emulsions by the pVdF membrane. f) permeate flux for various oil-in-water and water-in-oil emulsions through the pVdF membrane. Due to the superwetting property, the pMapS-g-pVdF membrane can thoroughly separate oils from oil-in-water emulsions with ultra-high separation efficiency (oil content after one-time separation less than 10 ppm).

Figure 3.13 (a) Schematic illustration of the formation of a superhydrophobic–

Nanomaterial-Based Ultrathin Superwetting Films for Separation of Oil/Water Emulsions

Lu and co-workers reported a mussel-inspired hybrid coating on pVdF MF membranes via the simultaneous polymerization of dopamine and hydrolysis of silane in one step to fabricate superhydrophilic and underwater superoleophilic pVdF MF membranes. with the possibility of separation of oil-in-water emulsions with high water flux and excellent antifouling performance. Due to the inherent hydrophobicity and superoleophilicity of SWCnt film, it is unable to separate oil-in-water emulsions.

Figure 3.15 (a) and (b) digital photograph and teM image of a 70-nm-thick SWCnt film

Summary and Perspective

We believe the realization process of practical and large-scale treatment of real oily water is only at an early stage. Second, submerged superoleophilic membranes, even for high viscosity oils such as crude oil and heavy oil, need to be developed for the separation of emulsified oily water from oil spills.

Introduction

For both of them, the relative wettability of the two liquids is a very important factor in predicting the properties of the resulting emulsion. Compared to small surfactant molecules, individual colloidal particles are adsorbed to the interface with much higher energy, often on the order of 105 kBT.

Particulate Emulsion Stabilizer

The Stabilization of an Emulsion
Special Features About Particulate Emulsion Stabilizers

Particles of colloidal size can also adsorb at interfaces and stabilize emulsions.18 the surface polarity of the particles usually lies between the polarities of liquids. Moreover, if the hydrophilicity of the particle is intermediate, the contact angle of the particle will be very close to 90°.

Figure 4.1 destabilization processes of an emulsion.

Categories of Particles

Inorganic Particles
Biological Particles
Polymeric Particles (Synthetic) and Microgel Dispersions
Janus Particles

Synthetic nanoparticles often require so much effort and resources to increase the monodispersity of the product. In Figure 4.16, it can be discovered that the thermal responsiveness property is also a function of ph if the carboxyl groups are copolymerized.70 In addition to pnipaM microgel particles, there are many more examples of responsive polymer colloidal particles.

Figure 4.10 particle diameter dependence on temperature and water to tetraethyl orthosilicate ratio

Responsiveness of Emulsions

Thermal Stimulation
pH Stimulation
Magnetic Stimulation
Other Stimulations

Moreover, the deprotonation of carboxylic acid groups also suppressed the thermo-responsiveness of the microgel. Besides destabilizing the emulsions, the type of emulsion can be controlled by changing the pH of the system.

Figure 4.20 the thermo-responsiveness of a typical pnipaM microgel dispersion.

Applications

Pharmaceutical Applications
Petroleum Industry
Extraction
Catalysis
Pickering Emulsion Polymerization

In addition, destabilization of responsive pick-up emulsions can be easily initiated after transport. Finally, they successfully demonstrated the temperature-induced destabilization of emulsions.

Figure 4.37 compares the rates of conversion in different conditions. it was Figure 4.35 (a) photos of [p6,6,6,14][dCa] in a water emulsion stabilized by

Concluding Remarks

Colloidal particles can often be used as an antifoam agent.111 Foam reduction is also an advantage of using particle stabilizers. For example, the large industrial production of particle stabilizers with good properties is very important for them to be used in different applications.

Acknowledgements

Introduction

Self-Healing Polymeric Materials via Reversible Bond Formation

Self-Healing Polymeric Materials via Dynamic Covalent Bonding
Self-Healing Polymeric Materials via Supramolecular Chemistry

Hydrogen Bonding
Ionic Interactions
Metal–Ligand Coordination
π–π Stacking

Based on the effect of temperature and ionic content on self-healing efficiency, a healing mechanism was proposed by Kalista et al.72 the heat generated by the friction during the high-energy impact leads to a localized melting of the damage area, and the surfaces fuse together due to interdiffusion of the melt, followed by the reformation of thermally responsive ionic cross-linking as well as hydrogen bonding. Banerjee's group81 discovered a series of self-healing metallo-hydrogels based on the interaction between amphiphilic tyrosine and ni2+, which showed stimuli responses to mechanical shaking, heat, ph and external chemicals.

Figure 5.1 self-healing reactions via dynamic covalent bonding. (a) diel–alder reaction

Mussel-Inspired Self-Healing Polymeric Materials

Catechol-Mediated Interactions

Catechol–Fe 3+ Non-Covalent Coordination
Catechol–B 3+ Dynamic Covalent Coordination
Other Catechol–Metal Coordination
Catechol-Mediated Hydrogen Bonding and Aromatic Interactions

Histidine–Metal Coordination

Catechol–Fe3+ coordination has been the most widely used mechanism to prepare shell-inspired self-healing polymeric materials. Dynamic catechol–B3+ covalent coordination is another catechol–metal coordination that is widely used in the preparation of self-healing hydrogels.

Figure 5.7 Cross-linking mechanism of ph-dependent catechol–Fe 3+ coordination.

Case Studies of Self-Healing Polymeric Materials for Environmental Applications

By simply adding a few drops of acid solutions to the ruptured surfaces and bringing them into contact, the ruptured pieces of hydrogel can heal into an integral part rapidly, due to the reformation of reversible hydrogen bonding between the polar groups of the side chains. of the polymer.

Conclusions and Outlook

Introduction

As more mist droplets are captured, they coalesce to form larger droplets that flow down the mesh material into the gutters and ultimately into the storage tank by gravity.

Desert Beetle-Inspired Surface with Patterned Wettability for Fog Collection

Introduction
Traditional Lithographic Methods for the Fabrication of Biomimetic Patterned Surfaces for Fog Collection
Direct Methods for Creating Patterned Wettability for Fog Harvesting

On the surfaces with star-shaped wetting patterns, mist droplets could be targeted towards more wettable areas (Figure 6.5c). they found that such star-patterned surfaces achieve more efficient water collection compared to other surfaces that are uniformly superhydrophilic, uniformly superhydrophobic, or even circular. The star-shaped pattern's enhanced water collection is because the star's crests generate a Laplace pressure gradient based on the shape gradient, further amplifying this directional movement of water droplets toward the centers of the stars. Optical micrograph of the as printed dopamine droplets (b1) and (b2) on the superhydrophobic surface.

Figure 6.2 Schematic illustration of typical preparation of patterned wetting surfaces by a photolithographic method

Spider Silk-Inspired Fibers for Atmospheric Water Collection

In addition, the authors also analyzed another possible driving force for directional water droplet motion arising from the fusiform geometry of the nodes, which will generate a difference in Laplace pressure. On the other hand, the surface roughness (porous nanostructures) of the spindle nodes was also designed through phase separation.

Figure 6.8 directional water movement inspired by water-collecting spider silk

Desert Plants-Inspired Water Collection

Under an external magnetic field, the Mps in the mixture are arranged along the direction of the magnetic field, resulting in ordered arrays of conical microtips (Figure 6.13). Later, by integrating hydrophobic conical arrays of microtips with a hydrophilic cotton matrix, the authors fabricated a large-scale cactus-like spherical fog collector, as shown in Figure 6.13.

Figure 6.9 In situ optical observation of driving tiny water drops with controlla- controlla-ble direction on artificial spider silks

Summary and Outlook

We believe that in the future, the biomimetic strategy is still one of the most promising resources for the design and fabrication of functional materials and devices to solve the global water crisis, and the challenges and opportunities for practical application are still great. Food and Agriculture Organization of the United Nations, United Nations Convention to Combat Desertification, Mountain Partnership Secretariat, Swiss Agency for Development and Cooperation and Center for Development and Environment.

Figure 6.13 Scheme (a) and optical photographs (b,c) of the prepared micro-tip array

Introduction and Background

Introduction
Background and Biomimetic Inspiration

Nature gives us any number of examples of surfaces from which it is possible to draw inspiration, with special forms of surface wetting such as the well-known lotus leaf, 2 rose petals, 3 butterfly wings, 4 the namib beetle, which is able to collect water from the atmosphere, 5 shark skin ,6 and so on. Water droplets on a lotus leaf surface exist in the Cassie-Baxter state with a layer of air trapped between the water droplet and the lower points of the lotus.