Hazardous Materials

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Course Learning Outcomes for Unit III

Upon completion of this unit, students should be able to:

4. Evaluate chemical interactions as they relate to control of potential hazards. 4.1 Determine the chemical reactions and products formed when certain alkali metals and other

metallic substances react with water as related to potential or actual emergency response incidents.

4.2 Determine the chemical reactions of common acids or bases as related to potential or actual emergency response incidents.

5. Classify hazardous materials according to Department of Transportation (DOT) classification and warning systems. 5.1 Identify the hazard class, descriptions, labels, markings, or placards that DOT requires when

transporting corrosive, water reactive and pyrophoric materials. 5.2 Identify the response actions that are applicable to incidents involving water and air-reactive

materials.

6. Determine strategies for dealing with chemical properties of specific types of hazardous substances. 6.1 Identify the chemical properties, uses, and associated unique hazards of common acids and

bases as related to the tasks and safety of an EHS & FS professional.

Course/Unit Learning Outcomes

Learning Activity

4.1 Unit III Lesson Chapter 9 Reading Unit III Quiz

4.2 Unit III Lesson Chapter 8 Reading Unit III Essay

5.1 Unit III Lesson Chapter 9 Reading Unit III Quiz

5.2 Unit III Lesson Chapter 9 Reading Unit III Quiz

6.1 Unit III Lesson Chapter 8 Reading Unit III Essay

6.2 Unit III Lesson Chapter 9 Reading Unit III Quiz

Reading Assignment

Chapter 8: Chemistry of Some Corrosive Materials, pp. 270-304

Chapter 9: Chemistry of Some Water- and Air-Reactive Substances, pp. 308-342

UNIT III STUDY GUIDE

Chemistry of Acids/Bases and Water/Air-Reactive Materials

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Unit Lesson

In this unit, we will study the chemistry of corrosive materials (acids and bases) and water-reactive and air- reactive (pyrophoric) materials. These are covered in Chapters 8 and 9 of our textbook.

Chapter 8 discusses the nature and properties of acids/bases and differentiates between strong versus weak acids/bases; concentrated versus diluted acids; and oxidizing versus non-oxidizing acids. The concept of the pH scale is re-introduced, including the values of some various aqueous solutions. Specific information regarding the uses, properties, and chemical reactions associated with commonly encountered acids and bases is provided. The chapter concludes with a discussion of Department of Transportation (DOT), Environmental Protection Agency (EPA), and Occupational Safety and Health Administration (OSHA) regulatory requirements regarding these materials. This includes recommended emergency response actions to incidents involving their unplanned release.

Chapter 9 identifies and discusses the properties and reactions associated with commonly encountered water-reactive and air-reactive materials. Similar to Chapter 8, DOT and OSHA requirements applicable to the handling and transportation of these materials are discussed.

Corrosive Materials

When we hear or think of corrosion, we normally associate it with some metals in a deteriorating condition (rusting, pitting, and breaking). That association is correct as corrosion is defined as the degradation of a material, which includes metals, plastic, or concrete, due to its reaction with the environment. Visit NASA’s Corrosion Technology Laboratory website for additional information, http://corrosion.ksc.nasa.gov/corr_fundamentals.htm. This brings us to the substances or materials that cause this corrosion phenomenon. Acids and bases are the best examples of corrosive materials.

An acid generates hydrogen ions (H+) when dissolved in water, while a base produces hydroxide ions (OH-) when dissolved in water. An ion is, “an atom (or group of atoms bound together) with a net electric charge due to the loss or gain of electrons” (Meyer, 2014, p. 117). Those acids and bases that yield a relatively high concentration of hydrated hydrogen and hydroxide ions are called strong acids and bases, respectively (Meyer, 2014). In contrast, acids and bases that do not ionize (break apart) or give up the hydrogen or hydroxide ions are called weak acids and bases. The ability of the acids and bases to form ions in water is what makes them corrosive.

An acid participates in a chemical reaction as either an oxidizing acid or a non-oxidizing acid. An oxidizing acid acts as an oxidizing agent, while a non-oxidizing acid cannot act as an oxidizing agent. Oxidizing acids include sulfuric, nitric, and perchloric acids; non-oxidizing acids include hydrochloric, hydrofluoric, and phosphoric acids (Meyer, 2014). Concentrated acid is when it is at its strongest concentration. It can get diluted with the addition of water.

pH scale: This indicates if an aqueous solution is acidic (pH of 0 to <7.0) or basic (>7 to 14). The pH of an aqueous solution or mixture can be measured with a meter or with a pH paper. In a chemical laboratory, one can also measure the pH of a solid (soil/residue samples) by adding deionized water to the solid sample. Note that the pH of a solution changes with temperature, which is why there are usually differences between on- site and laboratory pH measurements. Acids act as corrosive materials by reacting with metals, metallic oxides, metallic carbonates, and skin tissue (see Sections 8.6-A through D in your textbook). Bases act as corrosive materials by reacting also with metals and skin tissue (see Sections 8.6-E and F in your textbook).

The textbook provides specific information on the acids and bases that are encountered in practice by EHS and FS professionals. Please note that there are workplace regulations involving acids/bases as well as DOT requirements when they are being transported.

Regarding incidents involving a release of a corrosive material (after the material has been identified as a corrosive material), emergency responders should consider the following actions: dilute the material if appropriate, or neutralize with a solid material. The ERG recommends initial isolation and protective action zone distances. Incidents that may also come up involving corrosive materials are acid or alkali poisoning incidents. Poisoning incidents may include corrosive materials that inadvertently get splashed into or on an individual’s eyes/skin or may even be ingested.

http://corrosion.ksc.nasa.gov/corr_fundamentals.htm

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Additional note: A corrosivity characteristic is one of the criteria used by the federal EPA and some states to determine if a waste is considered a hazardous waste. It is usually determined by measuring the pH such that an aqueous liquid with a pH of less than or equal to 2.0, or equal or greater than 12.5 is considered a hazardous waste (EPA, 2013). Visit the following EPA website for additional information: http://www.epa.gov/epawaste/hazard/wastetypes/characteristic.htm.

Water-Reactive and Air-Reactive Materials

We often assume that the use of water is the best way to mitigate incidents involving hazardous materials because of its diluting and/or cooling effect, not to mention its availability. However, this is not always the case since there are certain materials that react with water to produce flammable gases that ignite spontaneously. In some cases, toxic or corrosive products are produced that could endanger lives. When water reacts with another substance, the process is called hydrolysis (Meyer, 2014).

There are also materials that ignite spontaneously upon exposure to ambient air, typically posing the risk of fire and explosion (Meyer, 2014). These are known as pyrophoric or air-reactive materials. The inherent hazard may be initiated by their reactions with the moisture in the air as they are released from containment. Pyrophoric materials are sometimes stored and processed under oil within enclosed, oxygen free, or dry atmosphere to avoid hazardous reactions. OSHA requires manufacturers, distributors, and importers to post GHS flame pictograms on the labels of pyrophoric liquids or solids (Meyer, 2014). In addition, flame and explosive pictograms must be included on labels of substances or mixtures that upon contact with water form flammable gases. Many of these compounds are recognizable to us, such as aluminum powder, which is a component of solid rocket fuels. Pyrophoric characteristics are also exhibited by dust containing titanium, magnesium, or aluminum.

Alkali Metals: In this unit, the properties of the alkali metals—lithium, sodium, and potassium—are discussed. If you recall from the periodic table, these metals belong to the same family. In reaction to water, sodium and potassium produce hydrogen, which bursts spontaneously into flame. Lithium is less reactive, so the hydrogen generated does not immediately ignite.

Combustible Metals: Other metals that include magnesium, titanium, aluminum, zirconium, and zinc are typically difficult to ignite when in bulk pieces, but may self-ignite in their divided form without an ignition source. These metals represent the fuels of Class D fires (Meyer, 2014). The finely divided forms of combustible metals are regarded as both water-reactive and pyrophoric to varying degrees.

Combustible Dust: A category of material that poses fire or explosion hazard is combustible dust. Although it is not specifically discussed in the textbook, we need to be aware that incidents involving combustible dust explosions are more common than we think. Combustible dust is defined by the NFPA as, “any finely divided solid material that is 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air" (as cited in OSHA, 2014, para. 15). The conditions necessary for a dust explosion include a sufficiently dense dust cloud, adequate oxygen or air to support combustion, and an ignition source (Plog, 1988).

Materials that can pose an explosive hazard in dust form can be found in many industries that include, “food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil-fuel power generation” (OSHA, n.d., para. 3). For information on regulations, training, prevention, and mitigation of combustible dust related fires/explosions, check the OSHA website at https://www.osha.gov/dsg/combustibledust/index.html .

Other Water and/or Air Reactive Materials: These other materials that are discussed in the textbook are aluminum alkyl compounds and their derivatives, ionic hydrides, metallic phosphides, and metallic carbides. Certain substances react with water to produce hydrogen chloride vapor or hydrochloric acid, such as aluminum chloride and phosphorus trichloride. Some substances such as acetic anhydride and acetyl chloride also produce acetic acid when they react with water.

http://www.epa.gov/epawaste/hazard/wastetypes/characteristic.htm

https://www.osha.gov/dsg/combustibledust/index.html

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Title When handling, storing, or transporting these water-reactive and pyrophoric materials, caution must be taken to avoid their contact with water. OSHA and DOT requirements must be followed to avoid hazardous incidents involving these materials.

References

Environmental Protection Agency. (2013). Characteristic wastes. Retrieved from http://www.epa.gov/epawaste/hazard/wastetypes/characteristic.htm

Meyer, E. (2014). Chemistry of hazardous materials (6th ed.). Upper Saddle River, NJ: Pearson.

Occupational Safety and Health Administration. (n.d.). Combustible dust: An explosion hazard. Retrieved from https://www.osha.gov/dsg/combustibledust/index.html

Occupational Safety and Health Administration. (2014). Combustible dust in industry: Preventing and mitigating the effects of fire and explosions. Retrieved from https://www.osha.gov/dts/shib/shib073105.html

Plog, B. (1988) Fundamentals of industrial hygiene (3rd ed.). Chicago, IL: National Safety Council.