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Prudent Practices in the Laboratory:Handling and Management of Chemical Hazards, Updated Version MANAGEMENT OF WASTE 209 8.13 PROCEDURES FOR THE LABORATORY 8.D.1 Treatment of Acids and Bases SCALE TREATMENT OF SURPLUS Neutralization of acids and bases (corrosives) is AND WASTE CHEMICALS generally exempt from a RCRA treatment permit. As described above in section 8.B.5,there are many However,because the products of the reaction are of- good reasons to perform in-laboratory-scale hazard ten disposed of in the sanitary sewer,it is important to reduction procedures.The pros and cons of many other ensure that hazardous waste such as toxic metal ions waste management methods are discussed earlier in is not a part of the effluent. this book (see Chapter 5, section 5.13, and Chapter 6, In most laboratories, both waste acids and waste section 6.13). The small-scale treatment,hazard reduc- bases are generated,and so it is most economical to col- tion procedures, and deactivation of products (and lect them separately and then neutralize one with the byproducts)as part of the experiment plan make sense other.If additional acid or base is required,sulfuric or for certain wastes and certain situations at the level of hydrochloric acid and sodium or magnesium hydrox- the actual generator,the trained laboratory personnel. ide,respectively,can be used. Beware that unless there is a significant reduction in Safety must be carefully considered before beginning risk by such action,there may be little benefit in carry- any work.If the acid or base is highly concentrated,it ing out a procedure that will simply produce another is prudent to first dilute it with cold water(adding the kind of waste with similar risks and challenges for acid or base to the water)to a concentration below 10%. disposal. Section 8.B.6 describes when federal law al- Then the acid and base are mixed, and the additional lows treatment of hazardous waste without permit.To water is slowly added when necessary to cool and recap,they are dilute the neutralized product. The concentration of neutral salts disposed of in the sanitary sewer should • In certain states small-scale treatment is allowed generally be below 1%. within a laboratory,sometimes as part of a permit- by-rule allowance. Be sure to check with your 8.D.2 Treatment of Other Chemicals state regulators. • Treatment in an accumulation container is al- The procedures listed below are for general use at lowed. the laboratory scale. Additional procedures can be • Elementary neutralization(see 8.D.1,below);the found in the earlier editions of this book' and other mixing of acidic and alkaline waste to form a salt books listed on the accompanying CD. See Tables solution, has long been encouraged as long as 8.2 and 8.3 for a list of types of chemicals that have safety considerations are addressed.In particular, known treatment methods. Specific procedures for dilute solutions should be used to avoid rapid laboratory treatment are increasingly being included heat generation. in the experimental sections of chemical journals and • Treatment is allowed as part of an experiment(or in publications such as Organic Syntheses and Inorganic the last step)before it becomes a waste.Treatment Syntheses. of experimental byproducts assumes the material Safety must be the first consideration before under- has not been declared a waste or handled in a taking any of the procedures suggested. Procedures wastelike manner. Such treatment cannot be per- presented in this book are intended to be carried out formed anywhere other than the location where only by,or under the direct supervision of,a trained sci- the byproduct was generated. entist or technologist who understands the chemistry and hazards involved.Appropriate personal protection An explanation of the federal allowance to treat should be used.(See Chapter 7,section 7.F,for informa- waste in an accumulation container has been pub- tion on protective equipment and Chapter 6 for more lished in the Federal Register(1986).For this allowance, information about working with chemicals.) With the the container must be kept closed except when adding exception of neutralization, procedures are generally or removing waste, and all standard time limits for intended for application only in small quantities, that accumulation and container management apply. De- is, not more than a few hundred grams. Because risks pending on the final disposition of treatment byprod- tend to increase exponentially with scale, larger quantities ucts, federal Land Disposal Restrictions (40 CFR 268) should be treated only in small batches unless a qualified treatability standards may apply. chemist has demonstrated that the procedure can be scaled To ensure compliance,be sure to check local and state regulations that may apply,and seek a legal review if 'Prudent Practices for Disposal of Chemicals from Laboratories(NRC, any clarification is needed. 1983); Prudent Practices in the Laboratory: Handling and Disposal of Chemicals(NRC,1995). Copyright National Academy of Sciences. All rights reserved.