flinnsci.com SAFETY REFERENCE CHEMICAL DISPOSAL PROCEDURES
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Review of Chemical
Disposal Procedures
Responsible management of the chemical resources of school science labs
encompasses best practices for the purchase, storage, use and disposal of
chemicals. It is a shared responsibility of the administration, faculty and staff.
Chemical disposal procedures require compliance with a variety of federal, state
and local laws and regulations and are therefore a particular challenge for many
science departments.
The Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act (RCRA) is the key law dealing with
the identification, management and disposal of hazardous waste. All institutions
are required to have a policy for identifying hazardous waste and complying with
the requirements of RCRA, which was enacted in 1976. The overarching goals of
the law are to reduce the amount and toxicity of hazardous waste and thus protect
human health and the environment. In writing the regulations to ensure that the
goals of RCRA are achieved, the Environmental Protection Agency (EPA) also has
the mandate to promote methods to minimize the amount of hazardous waste and
reduce its environmental impact. These methods include source reduction, reuse
and recycling of wastes and chemical treatment that will eliminate hazardous waste
characteristics.
Knowing Your RCRA Status and Requirements
In most cases, authority for implementing and enforcing the law has been delegated
to individual states that have adopted the RCRA guidelines. Some states may be
more restrictive or impose additional conditions than federal guidelines require.
The Federal EPA recognizes three classes of hazardous waste generators based
on the amount and kinds of hazardous waste generated in one month. The storage
and reporting regulations become increasingly more stringent as the amount of
hazardous waste increases. Schools that generate less than 100 kg (220 lbs) of
hazardous waste per month—and no more than 1 kg of acutely hazardous waste in
any month—would fall into the least regulated “conditionally exempt small quantity
generator” class. The EPA defines hazardous waste as a subset of solid waste, where
solid waste is anything that will be discarded or may enter the environment—by
burning, for example. (It’s confusing, but the term solid waste thus includes solids,
liquids or gases!) Obviously, all schools and other institutions produce solid waste.
Regardless of their RCRA status, all schools are required to determine which types of
solid waste must be classified as hazardous waste. (The definitions for these types
of waste are summarized in the following sections.)
Identifying Hazardous Waste
The first step in managing chemical disposal is identifying which discarded
chemicals, as well as chemical reaction mixtures or byproducts that will not be
reused, must be considered hazardous waste. There are two broad categories of
hazardous waste—characteristic wastes and listed wastes. Characteristic wastes
have one or more of the following properties:
• Ignitable wastes include flammable or combustible liquids (flash point <140 °F)
as well as flammable compressed gases and solid oxidizers. Organic solvents,
such as acetone or toluene, compressed gases, such as hydrogen, and solid
ammonium nitrate are examples of ignitable wastes.
• Corrosive wastes are acidic or basic solutions that have a pH <2 or >12.5,
respectively.
• Reactive wastes are substances that react violently with air or water, are capable
of detonation or can generate toxic gases under relatively neutral conditions.
Examples include the alkali metals sodium and potassium, diethyl ether and other
peroxide-forming organic compounds and cyanides or sulfides.
• Toxic chemical wastes are substances that, if disposed in a landfill, are capable
of leaching threshold amounts of specific chemicals into groundwater. There are
40 substances in this category (also known as toxicity characteristic wastes).
Although many of the substances on this list are pesticides, the list includes
common heavy metals, including lead, barium and silver.
There are four categories of listed wastes. Two categories include chemical
byproducts from manufacturing processes and do not generally apply to schools.
The other two categories, designated by the codes P and U, identify by name
specific discarded commercial chemical products. All academic institutions
should be aware of the chemicals on the P- (acutely toxic) and U- (toxic) lists.
The P-listed, or acutely toxic, wastes are especially important because any school
generating more than 1 kg (2.2 pounds or approximately one quart of liquid) of
acutely hazardous waste per month will be subject to the most stringent generator
requirements for listing, storing and reporting all their hazardous waste. Most
institutions do not use many P-list chemicals. The exceptions, which some schools
might use, are sodium cyanide, potassium cyanide, arsenic trioxide, sodium
azide, ammonium vanadate and carbon disulfide. Recall that listed wastes refer
to discarded or unused commercial chemical products where the chemical is the
sole active ingredient. Make sure your school has effective chemical purchasing
and inventory controls in place if you use P-listed chemicals in your science labs.
This will prevent the school from accumulating excess chemicals that must be
discarded.
Treating Chemicals in the Lab
The EPA encourages all waste generators, including academic institutions and
laboratories, to minimize the amount of hazardous waste. Treating materials in
the lab to reduce or eliminate chemical and physical hazards is one strategy for
accomplishing this goal. Chemicals or chemical byproducts that are stored in the
lab or remain in the lab after a lab activity is finished are not generally regulated
as solid waste. The treatment of hazardous waste without a permit is generally not
allowed. To avoid restrictions on treating hazardous waste, always incorporate
treatment or disposal of excess reagents or chemical byproducts from a
chemical reaction into the lab procedure itself. The Flinn Suggested Disposal
Methods described on pages 736–753 frequently may be used to treat chemicals
and eliminate potential hazards. Before undertaking any of these methods, it is
important to read, review and understand the general principles and guidelines
governing the disposal of laboratory chemicals:
• Check all federal, state and local guidelines that may apply.
• All procedures should be carried out by skilled and trained personnel who
are familiar with the physical and chemical properties of the chemicals and
understand the procedure.
• Observe all safety precautions, including the requirements for personal protective
equipment.
• Carry out all reactions that may generate gases in the hood.
• Provide secondary containment to protect against spills.
• Consult current Safety Data Sheets for storage, handling and disposal information.
• Wear chemical splash goggles, chemical-resistant gloves and a lab coat or
chemical-resistant apron.
Examples of generally allowed chemical treatment methods include
neutralization of acids and bases (Flinn Suggested Disposal Methods #24a, #24b
and #10, respectively); redox reactions for oxidizing agents and reducing agents
(Flinn Suggested Disposal Methods #12a and #12b); and precipitation reactions for
metals (Flinn Suggested Disposal Methods #11 and #27h).
As an example of this strategy, some experiments or demonstrations, such as
the iodine clock reaction, may produce small amounts of iodine as a byproduct.
Incorporate reduction of the iodine, an oxidizer, at the conclusion of the experiment.
(Halogens may be reduced with sodium thiosulfate according to Flinn Suggested
Disposal Method #12a.) In reviewing this treatment method, make sure you know the
balanced chemical equation so the appropriate molar excess of reducing agent, as
well as any acid or base needed for the reaction, will be used.
REVIEW OF CHEMICAL DISPOSAL PROCEDURES continued on next page.
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