The Chemistry of Environmental Engineering

Johannes Karl Fink

• Publisher: Wiley-Scrivener
• Year: 2020
• ISBN:
  9781119707837
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

The focus of this book is the chemistry of environmental engineering and its applications, with a special emphasis on the use of polymers in this field. It explores the creation and use of polymers with special properties such as viscoelasticity and interpenetrating networks; examples of which include the creation of polymer-modified asphalt as well as polymers with bacterial adhesion properties. The text contains the issues of polymerization methods, recycling methods, wastewater treatment, types of contaminants, such as microplastics, organic dyes, and pharmaceutical residues.

After a detailed overview of polymers in Chapter 1, their special properties are discussed in the following chapter. Among the topics is the importance of polymers to water purification procedures, since their use in the formation of reverse osmosis membranes do not show biofouling. Chapter 3 details special processing methods, such as atom transfer radical polymerization, enzymatic polymerization, plasma treatment, and several other methods, can be used to meet the urgent demands of industrial applications. Chapter 4 addresses the important environmental issue of recycling methods as they relate to several types of materials such as PET bottles, tire rubbers, asphalt compositions, and other engineering resins. And wastewater treatment is detailed in Chapter 5, in which the types of contaminants, such as microplastics, organic dyes and pharmaceutical residues, are described and special methods for their proper removal are detailed along with types of adsorbents, including biosorbents. Still another important issue for environmental engineering chemistry is pesticides. Chapter 6 is a thorough description of the development and fabrication of special sensors for the detection of certain pesticides. A detailed presentation of the electrical uses of polymer-based composites is given in Chapter 7, which include photovoltaic materials, solar cells, energy storage and dielectric applications, light-emitting polymers, and fast-charging batteries. And recent issues relating to food engineering, such as food ingredient tracing, protein engineering, biosensors and electronic tongues, are presented in Chapter 8. Finally, polymers used for medical applications are described in Chapter 9. These applications include drug delivery, tissue engineering, porous coatings and also the special methods used to fabricate such materials.

1
Special Polymers

The properties of some base resins with very few additives other than stabilizers have been discussed in a monograph (1).

Typically, high-performance resins will be used in tough metal replacement applications or replacement of ceramic materials. Thermoset resins are generally highly filled with mineral fillers and glass fibers. Elastomers are polymers that can be stretched substantially beyond their original length and can retract rapidly and forcibly to essentially their original dimensions. Specialty rubbers offer higher performance over general-purpose rubbers and find use in more demanding applications (1).

1.1 Poly(ethylene)

Depending on the temperature, pressure, catalyst, and the use of a comonomer, three basic types of poly(ethylene) (PE) can be produced: high density poly(ethylene), low density poly(ethylene), and linear low density poly(ethylene) (LLDPE) (1).

1.1.1 Metallocene Poly(ethylene)

Unsymmetrical permethylindenyl bent metallocene complexes have been synthesized and reacted with inorganic solid supports to afford catalysts for the slurry phase polymerization of ethylene. Those products, supported on solid polymethylaluminoxane were both highly active catalysts and afforded polymers with a desirable, low aggregation (2).

1.1.1.1 Film Applications

Metallocene catalyzed PE with high and medium densities are known to have good optical properties (3). However, for film applications, they have mechanical properties which can still be improved, in particular dart impact, tear strength and slow puncture resistance. On the other hand, PE prepared with dual site catalysts in the gas phase or with Ziegler-Natta catalysts have good mechanical properties, but poorer optical properties. Nucleating agents are required to improve the gloss and haze. However, nucleating agents are not particularly effective for PE resins. For example, for a haze of 30%, a nucleating agent cannot improve haze to less than 25%.

The preparation of a metallocene-catalyzed PE resin has been reported (3, 4). The metallocene is preferably a bridged unsubstituted bis(tetrahydroindenyl), such as ethylene-bis(tetrahydroindenyl) zirconium dichloride, c.f. Figure 1.1. Triisobutylaluminium can be used as activating agent.

Figure 1.1 Ethylene-bis(tetrahydroindenyl) zirconium dichloride.

The polymer has a multimodal molecular weight and composition distribution from 45% to 75% of a low density fraction. This fraction has a density below or equal to 918 g cm⁻³ as measured by the the standard test ISO 1183 (5), at a temperature of 23°C., wherein the density of the polyethylene resin is from 0.920 to 0.945 g cm⁻³. The M_w/M_n of the polyethylene is of from 2.8 to 6 and the melt index MI2 of the PE resin ranges from 0.1 to 5 g/10min.

The described PE resin composition is particularly suitable for film applications i.e. to prepare films. In particular, it shows a good balance in both mechanical and optical properties. In comparison to commercial grades, the mechanical properties are just as good, if not better, with the added advantage that the films obtained using this metallocene-catalyzed PE are particularly transparent i.e. have low haze (3).

1.1.1.2 Brominated Poly(ethylene)

A metallocene-catalyzed copolymerization of ethylene and 11-bromo-1-undecene was carried out to synthesize a brominated PE (6). A modified methylaluminoxane (Methanolato dimethyl aluminium) solution was used as a cocatalyst and ethylene-bis(tetrahydroindenyl) zirconium dichloride, c.f. Figure 1.1, was used as catalyst.

The copolymerization showed a high activity and afforded the copolymer with a 11-bromo-1-undecene incorporation ranging from 1.0 to 4.3 mol-%. When using a dried methylaluminoxane as cocatalyst, the incorporation ratio of 11-bromo-1-undecene increased remarkably to 25.2 mol-%. It was demonstrated that the type of methylaluminoxane used as a cocatalyst can affect the composition of the ethylene 11-bromo-1-undecene copolymer without changing the structure of the catalytic complex (6).

1.1.1.3 Comb-Shaped Materials

Comb-branched ethylene/1-octene copolymer elastomers were synthesized, and their properties were investigated (7).

The polymers had crystalline PE long chain branches attached to amorphous ethylene/1-octene random copolymer backbones. The unique structure was generated through a tandem catalyst system consisting of a Zr ligated with phenoxycycloalkylimine and a constrained geometry catalyst (CGC-Ti). Linear PE macromonomers, with more than 88% of the chains terminally unsaturated, were synthesized with the phenoxycycloalkylimine containing catalyst, while the constrained geometry catalyst catalyst was used in the copolymerization of ethylene, 1-octene, and the PE macromonome...

Table of contents

• Cover
• Table of Contents
• Preface
• 1 Special Polymers
• 2 Special Properties of Polymers
• 3 Processing Methods
• 4 Recycling
• 5 Wastewater Treatment
• 6 Pesticides
• 7 Electrical Uses
• 8 Food Engineering
• 9 Medical Uses
• Index
• Also of Interest
• End User License Agreement