CHAPTER 1CHEMISTRY, GREEN CHEMISTRY, AND

ENVIRONMENTAL CHEMISTRY

From Green Chemistry and the Ten Commandments of Sustainability, Stanley E. Manahan, ChemChar Research,

Inc., 2006manahans@missouri.edu

• All matter is chemical; we are chemical

• The human body is a complex chemical factory

• Green Chemistry seeks to present a body of chemical knowledge from the most fundamental level within a framework of the relationship of chemical science to human beings, their surroundings, and their environment.

• Green chemistry is the practice of chemistry in a manner that maximizes its benefits while eliminating or at least greatly reducing its adverse impacts

1.1. Chemistry is Good

• Pharmaceuticals that have improved health and extended life

• Fertilizers that have greatly increased food productivity

• Semiconductors that have made possible computers and other modern electronic devices

Good Things from Chemistry

The Downside of Chemistry

• Pollutants

• Toxic substances

• Nonbiodegradable plastic containers

These have resulted in harm to the environment

• Inorganic chemistry deals with materials composed of most elements other than carbon (and includes a few carbon compounds)

• Organic chemistry deals with carbon-containing materials, most having carbon-carbon bonds

• Physical chemistry involves the underlying theory and physical phenomena that explain chemical processes

• Biochemistry is the chemistry of living processes

• Analytical chemistry is the identification and quantification of chemical species, often at very low levels

Major Categories of Chemistry

Into theriverOut the door

Up the stack“By sensible definition any by-product of a chemical operation for which there is no profitable use is a waste. The most convenient, least expensive way of disposing of said waste—up the chimney or down the river—is best.”

From American Chemical Industry—A History, W. Haynes Van Nostrand Publishers, 1954

The Old Attitude:

• Chemistry is required to deal with environmental problems and challenges to sustainability

• Of all professionals, chemists are the best qualified to understand environmental problems from the misuse of chemistry

• The practice of environmentally beneficial chemistry is not a burden, but rather an opportunity that challenges human imagination and ingenuity

Chemists and Chemistry are Part of the Solution

1.2. THE ENVIRONMENT AND THE FIVE ENVIRONMENTAL SPHERES

• Very thin, most within several kilometers of Earth’s surface

• Provides oxygen for animals and other organisms, carbon dioxide and nitrogen for plants

• Vital protective function

• Stratospheric ozone protects against harmful ultraviolet

• Stabilizes Earth’s temperature by re-absorbing outgoing heat as infrared radiation

• Conduit for fresh water by way of the hydrologic cycle

The Atmosphere

• More than 97% in oceans

• Most of the remaining fresh water is ice and snow in polar ice caps and glaciers

• Small fraction of water in atmospheric water vapor

• Fresh water on the surface in lakes, reservoirs, and streams and as groundwater in underground aquifers

The Hydrosphere

• Includes all rocks and minerals

The Geosphere

Soil, where present

Crust, several km or less

Lithosphere, 50-100 km

Molten rock

• The crust is the part of the geosphere that is available to interact with the other environmental spheres and that is accessible to humans

• All living organisms

• Most found in a very thin layer at the interface of the geosphere and atmosphere and in the hydrosphere

• Involved with the geosphere, hydrosphere, atmosphere and even anthrosphere through biogeochemical cycles

• Biogeochemical cycles involve important life elements including carbon, nitrogen, and phosphorus

The Biosphere

• Strong interactions with other environmental spheres

• Cultivation of land modifies the geosphere

• Diversion and use of water affects the hydrosphere

• Emission of particles, acid gases, organics, greenhouse warming carbon dioxide

• Perturbation of biogeochemical cycles

• Entering anthropocene era

The Anthrosphere

S(coal) + O2 SO2SO2SO2 + 1/2O2 + H2O H2SO4H2SO4H2SO4, sulfates

Environmental ChemistryEnvironmental chemistry is the study of the sources, reactions, transport, and fates of chemical species involving all environmental spheres

2HCO3 + hν-Photosynthesis{CH2 } + O O2(g) + CO32-CO3 + H2O -Acid baseHCO3 + OH-- + Ca CO3 CaCO3(s)Precipitation2{CH2 } + O SO4 + 2H+MicrobialactionH2 (Sg) + 2H2O + 2CO2(g)UptakeLeachingGr -oundwaterCd2+NH+4NO3-CO2O2

Sediment2-2+2-2-Colloids

ChelationGas exchange with the atmosphere

Aquatic Chemistry

*H3CCOH+ hν →H3CCOHH3C.+CHO.H3C. + O2 → H3COO.NOH3CO. + NO2

- Gas phase molecules can absorb photons to produce excited species That can dissociate topr oduce reactive radicals

Radicals in turn participate in .a number of chain reactionsSO2, O2H2SO4 Reactions also occur inside water droplets And on particle.surfaces

Atmospheric Chemistry

Chemistry of the Geosphere and Soil

ToxicantOrganismToxiceffect. . . + . . .ToxicologyToxicologicalchemistry

Chemistry of the Biosphere and Toxicological Chemistry

Materialsprocessing andmanufactureConsumer

WasteprocessorEnergyPrimarymaterialsproducer

Chemistry of the Anthrosphere within a Framework of Industrial Ecology

Awareness from

• Silent Spring, Rachel Carson, 1962

• Approximately 10,000 deformed children from thalidomide

• Visible air pollution

• “Dead” bodies of water

• Love Canal around 1970

1.4. Environmental Pollution

WastewatertreatmentRemediation

Stack controls

Command and Control Approach Emphasizing End-of-Pipe Treatment

Measures

1.5. What is Green Chemistry?

RenewablefeedstocksProduct

No waste

Recycle

Degradability

Reactionconditions,catalystsControl

Green chemistry is the sustainable practice of chemical science and manufacturing within a framework of industrial ecology in a manner that is sustainable, safe, and non-polluting, consuming minimum amounts of energy and material resources while producing virtually no wastes.

• Economic: At a high level of sophistication, green chemistry normally costs less in conventional economic terms (as well as environmental costs) than chemistry as it is traditionally practiced

• Materials: By efficiently using materials, maximum recycling, and minimum use of virgin raw materials, green chemistry is sustainable with respect to materials

• Waste: By reducing insofar as possible, or even totally eliminating their production, green chemistry is sustainable with respect to wastes

Green Chemistry is Sustainable

Synthetic chemistry involves finding ways to make new chemicals and new ways to make known chemicals

1.6. Green Chemistry and Synthetic Chemistry

• Use existing feedstocks, but make them by more environmentally benign processes

• Use other feedstocks made by environmental benign processes

Chemicalsynthesis processExisting chemicalsEnvironmentally benignsynthesis of existingfeedstocks

Subsitute chemicals madeby environmentally benignprocessesProducts

Yield and Atom Economy (1)

Typical reaction with less than 100% yield and with byproducts

Yield and Atom Economy (2)

• Reduced exposure: The hazard remains, but exposure to it is reduced, such as by wearing safety goggles around an eye hazard (a command and control approach)

• Reduced hazard: The hazard is diminished or eliminated at its source; measures still may be taken to reduce exposure to remaining hazard

• Hazard exposure is less costly because costs of protective measures may be reduced

1.7. Reduction of Risk: Hazard and Exposure

Risk = F{hazard exposure}

• Refusal to take any risks can cause scientific and economic progress to stagnate

• Example: Refusal to take the risks of thermally treating wastes (hazardous waste incineration) can lead to waste accumulation, or important industrial processes making the waste may be ceased

• Example: Unwillingness to take risks involved with nuclear energy can lead to greenhouse warming from using fossil fuels or to economic stagnation from energy shortages

1.8. The Risks of No Risks

• Costs of engineering controls, regulatory compliance, personnel protection, wastewater treatment, and safe disposal of hazardous solid wastes have become high costs of doing business

• Waste prevention applying the principles of green chemistry and industrial ecology is a much better approach

1.9. Waste Prevention

1.It is better to prevent waste than to treat or clean up waste after it is formed

2.Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product

3.Synthetic processes should avoid use and generation of toxic and environmentally damaging substances

4.Chemical products should be as effective as possible but with minimum toxicity

5.Auxiliary substances, such as solvents and separation agents should be avoided or should be as innocuous as possible

6.Energy requirements should be low; extreme temperatures and pressures should be avoided

1.10. Twelve Principles of Green Chemistry (1)

Twelve Principles of Green Chemistry (2)7. Raw materials should be from renewable sources8. Derivatization for blocking groups protection and

property modification should be avoided9. Catalytic reagents should be used when possible

because of their specificity and minimum amounts required

10.Chemical products should be designed so that at the end of their lifetime they readily break down to harmless products

11.The best analytical and monitoring capabilities should be employed to allow real-time, in-process monitoring that prevents formation of hazardous substances

12.Substances and forms of them used should be chosen to avoid potentially harmful releases, fires, and explosions

1.11. Some Things to Know About Chemistry Before You Even Start

• Fewer than 100 naturally occurring elements, about 30 made by humans

• All elements composed of chemically identical atoms

• Each atom of a particular element has the same number of positively charged protons in its nucleus equal to the atomic number of the element.

• Electrons are in motion around the nucleus; a neutral atom has equal numbers of electrons and protons

• Each element has a chemical symbol (nitrogen, N, sodium, Na, for Latin name natrium

• The average mass of all atoms of an element is its atomic mass

• Two or more uncharged atoms bonded together by chemical bonds compose a molecule

• A covalent chemical bond is composed of two or more shared electrons

1.12. Combining Atoms to Make Molecules and Compounds

H HHH2HThe H atoms in elemental hydrogen

are held together by chemical bonds in molecules

That have the chemical formula H2

• A chemical compound is a substance consisting of atoms of two or more elements joined together by chemical bonds

CHEMICAL COMPOUNDS

H H2OH HHO OHydrogen atoms and oxygen atoms bond together

To form molecules in which 2 H atoms are attached to 1 O atom

The chemical formula of the resulting compound, water is H2O

• Ions are electrically charged atoms or groups of atoms

• Cations are positively charged ions and anions are negatively charged ions

• An ionic compound consists of cations and anions held together by their opposite charges—ionic bonds—in a crystalline lattice.

Ionic Bonds

NaCl Na+Cl --The transfer of a negatively charged electron from a neutral sodium atom to a neutral chlorine atom produces positively charged Na+ cations and negatively charged Cl- ions held together by ionic bonds in the ionic compound sodium chloride

• A chemical reaction occurs when chemical bonds are broken and formed and atoms are exchanged to produce chemically different species.

1.13. Chemical Reactions

CH4 + 2O2 2H2O + CO2 Reactants Products

Yields

Above is a chemical equation for the reaction of methane with oxygen. It is balanced because it has the same number of each kind of atom (1 C, 4H, 4O) among both the reactants and products.

• Most matter consists of mixtures composed of two or more chemically distinct substances

• A homogeneous mixture, such as air, consists of substances mixed at the molecular level that cannot be separated by mechanical means.

• A heterogeneous mixture is composed of two or more substances that are visibly distinct and can be separated by mechanical means.

• Mixtures are important in green chemistry; the separation of components of wastes and byproducts is often a significant expense in recycling

1.14. The Nature of Matter and States of Matter

A solid has a definite shape and volume regardless of the container into which it is placed.

States of Matter

A quantity of liquid has a definite volume, but takes on the shape of its container.

A quantity of gas has the shape and volume of the container it occupies.