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General Guidance on Absorbents

Here are some situations to watch out for when using absorbentsProduct that can be used to contain or clean up a chemical spill. Some absorbents can react with particular chemicals (that is, they are incompatible), so caution should be used in selecting the correct absorbent for your situation.鈥攁nd steps to minimize potential problems:

• Contaminants from Spill CleanupContaminants from Spill Cleanup

  If contaminants (such as dirt and rust) become mixed in with a spilled chemical and the absorbent used on the spill, it听may cause runaway exothermicA chemical reaction that generates heat. Opposite of endothermic, in which heat is taken in from the surroundings. reactions during spill clean-up and in the waste absorbent in its disposal packaging.

  Steps to Minimize the Problem:

  • Be aware of contaminants in the spill area that could mix with the spilled chemical and absorbent during cleanup.
  • Quickly dispose of and incinerate disposal packs.
  • Monitor the temperature of used disposal packs鈥攅specially if (a) potentially reactiveReadily reacts with other chemicals. contaminants were mixed in or (b) the packs must be stored for an extended time.
• Flammable Atmosphere Above Used AbsorbentsFlammable Atmosphere Above Used Absorbents

  A flammableEasy to ignite and burns readily. atmosphere can develop above absorbents wetted with a chemical that is above its flash pointThe lowest temperature at which a liquid gives off enough vapor to be ignited at its surface.. A chemical that has a high heat of absorption with a given absorbent will increase in temperature when mixed with that absorbent. If its flash point is just above ambient temperature, that increase in temperature may be enough to warm the chemical above its flash point and generate a flammable atmosphere. For example, amines have a high heat of absorption when they are absorbed onto Mineral-Based or Clay-Based Absorbents.

  Steps to Minimize the Problem:

  • Avoid creating a chemical/absorbent mixture known to have a high heat of absorption.
  • Ensure good ventilation when applying an absorbent to a spilled chemical.
  • Consider diluting the spilled chemical before using absorbents鈥攁s long as the spilled chemical is not water-reactiveCan react vigorously when mixed with water or steam or when spilled into water; the reaction may generate hazardous gas or overpressurize a container..
  • Reduce the amount of oxygen in the headspaceVolume remaining at the top of a filled container before it is sealed. of the disposal pack by filling it with water鈥攁s long as the spilled chemical is not water-reactive.
• Heat Buildup in Used AbsorbentsHeat Buildup in Used Absorbents

  Even small amounts of heat generated from a chemical reactionThe change that takes place when two or more substances interact to form new substances. on an absorbent can cause a thermal runaway. Since heat loss occurs at the surfaces of materials, heat loss is less efficient when the surface area of the used absorbent is decreased. This could happen when used absorbents have been collected into a large pile or placed in a disposal container. Particulate or granular solids lose heat at slower rates than liquid systems.

  Steps to Minimize the Problem:

  • Don't absorb chemicals that are incompatibleSubstances that react together, if mixed. with the absorbent. This avoids heat generation in the first place.
  • Allow used absorbent to cool to ambient temperature before collecting it into a disposal pack.
  • If air oxidationA chemical reaction in which oxygen bonds to an element or compound. By extension, a reaction in which one element or compound rises to a higher oxidation state while another drops to a lower oxidation state (the term is used in this sense even when no oxygen whatever is present). of the absorbed chemical is an issue, minimize air in the disposal pack containing the waste absorbent by filling it with water or purging with nitrogen; also ensure that containers are fully sealed from air intrusion (rather than loosely capped).
  • Quickly dispose of and incinerate all wastes.
  • If you must store disposal packs for long periods of time, or if the packs contain questionable mixtures of chemicals and absorbents, monitor the packs for increases in temperature or internal pressure.
• Moisture in AbsorbentsMoisture in Absorbents

  Water in any absorbent can react with water-sensitive compounds, potentially causing gas generation and a thermal runaway. Example water-sensitive compounds include acyl chlorides, anhydrous ferric chloride, and isocyanates.

  Steps to Minimize the Problem:

  • Carefully monitor moisture content in absorbents that are intended for use with water-sensitive compounds, both in new lots of absorbent material and in stored (or opened) packages of absorbent especially if stored in humid areas or for long periods of time.
  • Consult with experts for ways to reduce the moisture content of absorbents.
• Oxidizable Organics on AbsorbentsOxidizable Organics on Absorbents

  Liquids have more surface area in contact with air once they have been absorbed by high-surface-area solids. This is a problem when the liquids are organics that are susceptible to exothermicA chemical reaction that generates heat. Opposite of endothermic, in which heat is taken in from the surroundings.听oxidation by air, because the amount of liquid available to react with air is much greater than if the liquid were in a puddle or in container by itself. The amount of heat generated by the exothermic oxidationA chemical reaction in which oxygen bonds to an element or compound. By extension, a reaction in which one element or compound rises to a higher oxidation state while another drops to a lower oxidation state (the term is used in this sense even when no oxygen whatever is present). reaction can lead to a thermal runaway in used absorbents鈥攑ossibly resulting in a fire or explosionA chemical or physical process in which the rate at which energy is being generated exceeds its ability to escape to its surrounding environment. The hazards of an explosion can include a shock wave (especially near the point of explosion) and projectiles generated by the shock wave..

  Steps to Minimize the Problem:

  • Allow used absorbent to cool to ambient temperature before collecting it in a disposal pack.
  • Use airtight, sealed disposal packs to exclude entrance of additional air.
  • Minimize air in disposal packs by filling the packs with water or purging with nitrogen.
  • Incinerate disposal packs as soon as possible.
  • If you must store disposal packs for long periods of time, monitor the packs for increases in temperature or internal pressure.
• Source of Absorbent and Lot-to-Lot ConsistencySource of Absorbent and Lot-to-Lot Consistency

  Dirt, Clay-Based and Mineral-Based Absorbents mined from different locations can have varying levels of acidity and trace impurities (such as heavy metals). ExothermicA chemical reaction that generates heat. Opposite of endothermic, in which heat is taken in from the surroundings.听polymerizationChemical reaction in which small molecules join to form larger molecules; polymerization reactions typically release heat, and can cause containers to overpressurize. of many reactive monomersOne of the molecules that link together to make a polymer. For example, the monomer of natural rubber is isoprene. Monomers may be naturally occurring or synthetic.听can be initiated by acidic sites or impurities within these absorbents. The varying composition of absorbents from different sources can result in unanticipated reactivityThe tendency of a substance to undergo chemical change. The reactivity of most substances depends on the temperature and pressure of the surroundings, and on the chemicals with which it comes in contact. Under ordinary conditions, innately reactive substances are those that react rapidly with water, air, and other common components of the environment, as well as substances that self-react (decompose or polymerize). with reactive monomers.

  Steps to Minimize the Problem:

  • Avoid using dirt, clay-based, and mineral-based absorbents with reactive monomers.

  The moisture content of different lots of the same kind of absorbent (for example, sawdust) can be quite different. The higher moisture content of some lots can result in unanticipated reactivity of wet absorbent with water-sensitive compounds鈥攁 situation that can lead to thermal runaway.

  Steps to Minimize the Problem:

  • Monitor moisture content in new and opened containers of absorbents鈥攅specially in the case of absorbents that could be used on water-sensitive compounds.
• Spills of Concentrated 365bet娱乐Spills of Concentrated 365bet娱乐

  Spills of concentrated strong oxidizersOr oxidizing agent. A material that can cause or enhance the combustion of other materials, usually by providing oxygen., monomersOne of the molecules that link together to make a polymer. For example, the monomer of natural rubber is isoprene. Monomers may be naturally occurring or synthetic., and other high-energy compounds pose response, handling, and disposal concerns because of the high reactivityThe tendency of a substance to undergo chemical change. The reactivity of most substances depends on the temperature and pressure of the surroundings, and on the chemicals with which it comes in contact. Under ordinary conditions, innately reactive substances are those that react rapidly with water, air, and other common components of the environment, as well as substances that self-react (decompose or polymerize). of these chemicals.

  Steps to Minimize the Problem:

  • Follow the manufacturer's spill clean-up recommendations.
  • Consult experts for guidance on the safe disposal of concentrated reactive chemicals.
  • If the spilled chemical is water-soluble and not water-reactiveCan react vigorously when mixed with water or steam or when spilled into water; the reaction may generate hazardous gas or overpressurize a container., consider diluting it with water before using absorbents.
• Spills of Concentrated PeroxidesSpills of Concentrated Peroxides

  The absorption of concentrated peroxides onto high-surface-area solids can result in rapid peroxide decomposition, a reaction which is highly exothermicA chemical reaction that generates heat. Opposite of endothermic, in which heat is taken in from the surroundings. and generates oxygen gas. Oxygen gas can support the combustionAlso burning. A chemical reaction between oxygen and another element or compound that is rapid and exothermic enough to generate heat and light. of other materials, including combustible absorbents (such as sawdust), and this overall situation can easily result in a fire or explosionA chemical or physical process in which the rate at which energy is being generated exceeds its ability to escape to its surrounding environment. The hazards of an explosion can include a shock wave (especially near the point of explosion) and projectiles generated by the shock wave..

  Steps to Minimize the Problem:

  • Pure peroxides must be diluted with water prior to disposal and should never be disposed of directly.
  • Do not mix peroxide-containing waste with other chemical waste.
  • Consult with experts for further information.

  Recommendations from Clark, D. E. 2001. "Peroxides and Peroxide-Forming Compounds." Journal of Chemical Health and Safety. 8(5): 12-21.

Other Absorbent Topics

• Cellulose-Based Absorbents
• Dirt/Earth
• Expanded Polymeric Absorbents
• Mineral-Based and Clay-Based Absorbents
• Sand