Proper disposal of chemicals
Most chemicals used by the amateur chemist come from every day use and do not require special treatment before being discarded in the usual way. However there are many chemicals, such as heavy metal compounds or organic solvents, that require special disposal techniques. In the interest of keeping lab costs low, though, it may be a good idea to look into ways to recycle and recover chemicals such as solvents, which can be reclaimed by distillation.
Contents
Standard procedures
Acids
Acids should be neutralized with a base, such as carbonate/bicarbonate, hydroxide (calcium hydroxide e.g.) usually as a solution. The soluble salts of halogen acids and oxoacids (except perchloric and chloric acids) can be safely poured down the drain. Special acids and their salts, such as hydrazoic acid and azides must not be poured directly down the drain, they must be treated with nitrous acid to destroy them.
Oxidizing mixtures, such as Aqua regia, piranha solution or mixed acid must also never be poured down the drain, as they're much more dangerous than simple acids, and can wreak havoc on your plumbing. Instead, they must be neutralized first.
Bases
Alkali hydroxides can be left in open air to absorb carbon dioxide as well as corrosive and unpleasant gases, forming carbonates and salts. For quicker results, alkali bases can be neutralized with any acid, though for practical and economical purposes, acetic acid or citric acid are sufficient. Bases may be reused to absorb acidic vapors in a desiccator, which mitigates their dangers. Care must be taken to avoid excess heating with strong bases.
Cyanides
Waste containing cyanide, either from gold refining or from organic extractions of alkaloids from cyanide containing plants, must be neutralized with bleach or hydrogen peroxide, to turn them into less harmful cyanates. Cyanates can be further neutralized to nitrogen and carbon dioxide.
Cyanides must never be poured down the drain.
Heavy metals
Since the biggest hazard comes from the volatile and soluble heavy metal compounds, it's best to convert them into insoluble compounds, which are less toxic.
Heavy metals, such as mercury, can often be neutralized with sulfur, generating mercury(II) sulfide, which is generally insoluble in water and has little reactivity.
Very dangerous heavy metals such as cadmium and arsenic should always be properly disposed of at designated facilities, as their effects on human life and the environment is sometimes catastrophic.
Inorganic anions
Inorganic anions, based on halogens, sulfur, phosphorus, nitrogen, carbon and silicon can be flushed down the drain with lots of water. Examples of these are sulfide, sulfate, chloride, chlorate, nitrate, nitrite, thiocyanate.[1]
Metal ions
A good rule of thumb for transition metals is to convert solutions of their ions to the insoluble carbonate or oxide, often one of the most stable and nontoxic forms of these elements, prior to disposal. Another simple solution is to reduce the ions back to the metal.
Copper salts are dangerous to the environment and should be reduced with iron to elemental copper, that can be reused, and the iron salts produced are less toxic.
Nickel-containing compounds, especially organonickel compounds, are carcinogens, and are also dangerous to many other forms of life. It is a good idea to take these to a proper waste disposal facility.
Cobalt salts may be carcinogenic and should be taken to a proper waste disposal facility.
Aluminium compounds should not be disposed in the sewage. They can, however, be converted to aluminium sulfate, which is safe to dispose of in soil, though it will cause a decrease in pH(it is used as a fertilizer for this purpose). It is a good idea to dispose of aluminium sulfate and a safe basic compound (such as calcium carbonate) at the same time.
Many compounds of chromium, especially chromium(VI), are poisonous and carcinogenic. These should be converted to the +3 oxidation state; hydrogen peroxide as well as sulfites or thiosulfate will do this, which is typically the least harmful, preferably to chromium(III) oxide. Chromium dioxide may be another feasible option, as it is found in cassette tapes and can be recycled with them.
Zinc compounds can be refined to zinc metal using electrowinning. It's not recommended to use zinc compounds as zinc supplemements for soil or livestock, as it may contain traces of cadmium.
Some MSDS sheets recommend that rare earths be converted to their oxalates or carbonates and disposed of in the trash.
Alkali metals are minimally toxic as their salts and may be dumped down the drain.
Organic compounds
Organic solvents should be dumped in labeled waste tanks, such as: halogenated, non-halogenated solvents. Flammable organic solvents that safe in low exposures such as ethanol, methanol, and acetone can often simply be burned outside for disposal, as most often their combustion products are simply carbon dioxide and water. It may be a better idea just to recover them by distillation, though.
A good way to destroy halogentated and aromatic compounds is with Fenton's reagent, which breaks them down to simpler non-toxic compounds. It's best however, to avoid dumping large quantities of waste, as the reaction in exothermic and may splash or volatilize some of the waste, so it's best to perform the neutralization in small steps.
Organic salts, such as acetates and oxalates can be pyrolyzed to carbonates and water vapors.
Recycling
Sometimes it is an option to purify waste products into chemicals that are pure enough to be used again. While this can sometimes be time consuming, it can often be more environmentally and economically friendly than discarding the waste in one manner or another is. Before discarding waste, think about what all it contains, and if there is some way that it could be used.
Down the drain vs. into the soil
The availability of these disposal methods varies depending on where you live. If you live in an apartment block, you only have the drain. If you live in a suburban house, you have both. If you live in some quaint rustic shithole like the author of this edit, you only have the "into the soil" option.
Generally, the soil option is safer, because there is no plumbing you should worry about, but some chemicals shouldn't be released into the soil, either. In general, your designated place for pouring chemicals into the soil should be far from any gardens, horticulture or any other agricultural objects. But chemicals marked as "Oh yes!" in the table are harmless and even useful in agriculture as fertilizers. These you can pour down in your garden.
Lists of various chemical compounds that can be safely released in the ground or down the drain can be found here, here or here.
Other
Heavy metal salts or solutions can be mixed with cement, and trapped in the resulted concrete block. The resulting block can also be covered in another layer of cement, to reduce the diffusion of the heavy metals. Unless the resulting concrete is damaged, broken and dissolved in acid, the heavy metal ions will not be released. However, this merely is a method to prevent the heavy metals from being released in the environment, and is not a permanent way of disposal.
Chemical disposal table
| Substance | Neutralization | Heat treatment | Down the drain | Into the soil | Environmental considerations |
|---|---|---|---|---|---|
| 1,2-Dichloroethane | |||||
| 1,4-Dioxane | |||||
| 2,2,4-Trimethylpentane | |||||
| 2,4-Dinitrobromobenzene | |||||
| Acetaldehyde | |||||
| Acetic acid | Bicarbonates, carbonates, bases, oxides | Flammable (high concentrations), no dangerous combustion products | Yes | Yes | Safe, biodegradable; avoid dumping large amounts, acidifies soil |
| Acetic anhydride | Bicarbonates, carbonates, bases, oxides | Flammable, no dangerous combustion products | Yes | Yes | Biodegradable; avoid dumping large amounts, acidifies soil |
| Acetone | Oxidation, reducing, photolysis | Flammable, no dangerous combustion products | Not advised | Yes | Biodegradable; not advised |
| Acetone peroxide | Photolysis, detonation in safe area | Explosive, not recommended | Not advised | Not advised | Biodegradable; not advised |
| Acetonitrile | |||||
| Acetylene | Oxidation, photolysis | Dangerously flammable | Not possible | Not possible | Biodegradable |
| Acetylsalicylic acid | Any base | Not particularly helpful | Yes | Yes | Biodegradable |
| Alpha-pinene | |||||
| Aluminium chloride | Treatment with water, precipitation with a base | No effect; Water solutions however will give off hydrogen chloride vapors | Not advised | Yes | |
| Aluminium nitrate | |||||
| Aluminium sulfide | Hydrogen peroxide, bleach | No | NO | NO | Releases hydrogen sulfide on contact with water, which is toxic to organisms |
| Ammonia | Oxidation, neutralization with acids | At high concentrations | Not possible (gaseous), safe to pour (as solution) | Not possible (gaseous), safe to pour (as solution) | Biodegradable |
| Ammonium acetate | Unnecessary | -- | Yes | Yes | Safe, biodegradable |
| Ammonium bicarbonate | Pyrolysis, hydroxides, acids | Decomposes on heating | Yes | Oh yes! | Safe, good fertilizer (nitrogen source) |
| Ammonium nitrate | Pyrolysis, Hydroxides, carbonates | Emits nitrous oxide, may explode if the temperature is too high | Yes | Oh yes! | Safe, good fertilizer (nitrogen source) |
| Anthocyanin | |||||
| Asbestos | |||||
| Ascorbic acid | Unnecessary | Yes | Yes | Safe, biodegradable | |
| Barium ferrate | |||||
| Barium manganate | Sulfuric acid | Not advised | Yes | ||
| Basic lead chromate | |||||
| Benzene | Oxidation with Fenton's reagent | Generates dangerous combustion products | DO NOT DUMP | No | Avoid releasing in environment |
| Bis(ethylenediamine)copper(II) perchlorate | Crystallize and ignite safely | Detonates | DO NOT DUMP | No | Copper kills aquatic life and plant roots |
| Bismuth trioxide | Reduced to bismuth metal | Will oxidize anything (yes, platinum too) when molten | |||
| Boric acid | |||||
| Boron trioxide | |||||
| Butane | |||||
| Butanol | |||||
| Butyl acetate | |||||
| Caesium hydroxide | |||||
| Calcium acetate | Pyrolysis | Decomposes to calcium carbonate and acetone at high temperature | Yes | Yes | Biodegradable |
| Calcium carbide | |||||
| Calcium carbonate | |||||
| Calcium chloride | |||||
| Calcium fluoride | |||||
| Calcium hydroxide | |||||
| Calcium hypochlorite | |||||
| Calcium nitrate | |||||
| Calcium oxide | |||||
| Calcium perchlorate | |||||
| Calcium sulfate | |||||
| Carbon dioxide | |||||
| Carbon disulfide | |||||
| Carbon monoxide | |||||
| Carbon tetrachloride | |||||
| Carbonic acid | |||||
| Charcoal | |||||
| Chevreul's salt | |||||
| Chloric acid | |||||
| Chloroauric acid | |||||
| Chlorobutanol | |||||
| Chloroform | Destruction with aqueous sodium hydroxide, which can be aided by methanol or acetone; Oxidation with Fenton's reagent | Boils to form vapor, should not be attempted indoors | DO NOT DUMP | DO NOT DUMP | May cause ozone depletion, dangerous to aquatic life |
| Chromium(III) oxide | |||||
| Chromium(III) sulfate | |||||
| Citric acid | |||||
| Cobalt(II) chloride | |||||
| Cobalt (III) oxide | |||||
| Copper(I) chloride | |||||
| Copper(II) acetylsalicylate | |||||
| Copper(II) carbonate | |||||
| Copper(II) chloride | Precipitate as carbonate or reduce to copper metal using aluminum | Loses water, turns brown | DO NOT DUMP | Yes but far from any agricultural plants | Kills aquatic life and plant roots |
| Copper(II) hydroxide | |||||
| Copper(II) nitrate | |||||
| Copper(II) oxide | |||||
| Copper oxychloride | |||||
| Copper(II) phosphate | |||||
| Copper(II) sulfate | |||||
| Copper chromite | |||||
| Curcumin | |||||
| Cyclohexane | |||||
| Dichloromethane | Destruction with aqueous sodium hydroxide, iron can also be used; Oxidation with Fenton's reagent | Boils to form vapor; pyrolysis at high temperatures yielding chlorine, hydrochloric acid and carbon monoxide | DO NOT DUMP | No | May cause ozone depletion, dangerous to aquatic life |
| Diethyl ether | |||||
| Diisopropyl ether | |||||
| Dimethyl sulfoxide | |||||
| Dimethylformamide | |||||
| Dipicolinic acid | |||||
| Disulfur dichloride | |||||
| Erythritol | Not required | Yields carbon oxides, water vapor | Yes | Yes | Low toxicity |
| Ethane | |||||
| Ethanol | Not required | Yields carbon oxides, water vapor | Yes | Not recommended | Deadly to small animals on direct contact, dangerous to aquatic and soil life |
| Ethyl acetate | |||||
| Ethylene glycol | |||||
| Ethylene glycol dinitrate | |||||
| Ethylenediamine | |||||
| Formaldehyde | |||||
| Formic acid | |||||
| Glycerol | |||||
| Hematein | |||||
| Heptane | |||||
| Hexamethylene triperoxide diamine | |||||
| Hexamine | Burning in an oxygen atmosphere yields carbon oxides, water vapor, nitrogen; Pyrolysis generates formaldehyde, carbon oxides, ammonia and nitrogen fumes; at temperatures >800°C also yields hydrogen cyanide | Yes | Yes | ||
| Hexane | |||||
| Holmium citrate | |||||
| Hydrazine | |||||
| Hydrazine sulfate | |||||
| Hydrazoic acid | |||||
| Hydrobromic acid | |||||
| Hydrochloric acid | Any alkali or alkaline-earth carbonate, bicarbonate | DON'T! Results in acidic vapors, extremely dangerous and corrosive | NO! Neutralize first | NO! | Toxic to wildlife and corrosive to minerals |
| Hydrofluoric acid | |||||
| Hydrogen chloride | |||||
| Hydrogen iodide | |||||
| Hydrogen peroxide | |||||
| Hydrogen sulfide | |||||
| Hydroiodic acid | |||||
| Iron(II) sulfate | |||||
| Iron(II,III) oxide | |||||
| Iron(III) chloride | |||||
| Iron(III) oxide | |||||
| Iron(III) sulfate | |||||
| Isobutanol | |||||
| Isopropanol | |||||
| Isopropyl nitrite | |||||
| Lead(II) acetate | Alkali carbonate or hydroxide; Lead precipitate should be taken to disposal facilities | Results in lead oxides; Yields carbon oxides, water vapors | DO NOT DUMP! | DO NOT DUMP! | |
| Lead(II) chromate | |||||
| Lead(II) nitrate | |||||
| Lead(II) oxide | |||||
| Lead(II,IV) oxide | |||||
| Lead(IV) acetate | |||||
| Limonene | |||||
| Lithium aluminium hydride | |||||
| Lithium chloride | |||||
| Lithium hydroxide | |||||
| Magnesium chloride | Not required | Hydrated form gives the oxychloride salt | Yes | Yes | May increase the magnesium and chloride content in the soil significantly |
| Magnesium sulfate | |||||
| Manganese dioxide | |||||
| Manganese heptoxide | |||||
| Methane | |||||
| Methanol | |||||
| Methyl ethyl ketone | |||||
| Methyl formate | |||||
| Methyl nitrate | Alkali solution, recommended to be cooled | Will lead to explosion | No | No | Dangerous to wildlife |
| Methyl salicylate | |||||
| Methyl tert-butyl ether | |||||
| Mineral oil | Will burn at high temperatures, releasing carbon oxides, water vapors and soot | No | No | Oils float on water bodies and inhibit the cellular breathing of many organisms | |
| Naphthalene | |||||
| Neodymium oxalate | |||||
| Nicotine | |||||
| Nitric acid | |||||
| Nitrocellulose | |||||
| Nitrogen dioxide | Bubbling through an alkali solution, peroxide solution | Not useful | Not possible | No | Will react with atmospheric moisture to generate nitric acid and contributes to the acid rain; extremely toxic to animals and plants |
| Nitrogen trichloride | |||||
| Nitrogen triiodide | |||||
| Nitroglycerin | |||||
| Nitromethane | |||||
| Nitrous oxide | |||||
| Octyl acetate | |||||
| Oxalic acid | |||||
| Ozone | Any compound easily oxidizable that does not ignite, such as carbon monoxide, activated charcoal | Aceelerates the decomposition of ozone, but not enough | Not possible | No | Dangerous to wildlife, may oxidize various gaseous compounds, contributing to the acid rain |
| Pentaerythritol | |||||
| Pentane | |||||
| Perchloric acid | |||||
| Permanganic acid | |||||
| Peroxymonosulfuric acid | |||||
| Petroleum ether | |||||
| Phenol | |||||
| Phosgene | |||||
| Phosphoric acid | |||||
| Phosphorus pentoxide | Alkaline solution, lots of water | Will volatilize at very high temperatures | No, reaction with water is highly exothermic and may generate acidic steam | Neutralize first | Corrosive and dangerous on direct contact with wilflife; Reaction with water will lead to phosphoric acid, highly corrosive and dangerous. |
| Picric acid | |||||
| Polytetrafluoroethylene | Not required; Can simply be dumped in trash | Generates toxic fluorine, hydrogen fluoride, fluorocarbons and carbon oxide vapors | DO NOT DUMP | DO NOT DUMP | Resistent to most corrosive chemicals, cannot be digested by wildlife |
| Potassium antimony tartrate | |||||
| Potassium bromide | |||||
| Potassium carbonate | |||||
| Potassium chlorate | |||||
| Potassium chloride | |||||
| Potassium dichromate | |||||
| Potassium ferrate | |||||
| Potassium hydroxide | |||||
| Potassium iodide | |||||
| Potassium manganate | |||||
| Potassium metabisulfite | |||||
| Potassium nitrate | Not required | Gives off nitrogen oxides at very high temperatures; burns in presence of organic compounds, releasing carbon oxides, nitrogen and leaving behind alkaline slag | Yes | OH YES | Excellent fertilizer, though may lead to uncontrolled algae growth if dumped in water bodies |
| Potassium perchlorate | |||||
| Potassium permanganate | |||||
| Potassium peroxymonosulfate | Alkaline solution, sodium carbonate | Decomposes, releasing oxygen | Recommended be neutralized first | Must be neutralized first | Dangerous to the environment in short term |
| Potassium sulfate | |||||
| Propane | |||||
| Propylene carbonate | |||||
| Propylene glycol | Not required | Generates carbon oxides and water vapor, as well as other toxic pyrolysis compounds | Yes | Yes | Little toxic effect on aquatic wildlife |
| Prussian blue | |||||
| Pyranine | |||||
| Pyridine | |||||
| Rosocyanine | |||||
| Safrole | |||||
| Salicylic acid | |||||
| Schweizer's reagent | |||||
| Silicon dioxide | Not required | At high temperatures results in melting; Can be used to indurate crystalline silica | Not recommended, may clog the plumbing | Yes | Finely divided silica is dangerous for fauna |
| Silver nitrate | |||||
| Sodium acetate | |||||
| Sodium acetylsalicylate | |||||
| Sodium azide | |||||
| Sodium benzoate | |||||
| Sodium bicarbonate | |||||
| Sodium bisulfate | |||||
| Sodium carbonate | |||||
| Sodium chloride | |||||
| Sodium ferrate | Diluted organic solutions will reduce it to its constituent oxides | Breaks down to its constituent oxides, both dry and as solution | Yes | Not recommended due to its sodium content | Dangerous to organisms due to its strong oxidizing properties |
| Sodium hydroxide | |||||
| Sodium hypochlorite | |||||
| Sodium metabisulfite | |||||
| Sodium nitrate | |||||
| Sodium perchlorate | |||||
| Sodium peroxide | |||||
| Sodium silicate | |||||
| Sodium sulfate | |||||
| Sodium thiosulfate | Bleach | No | Yes | Yes | Breaks down rapidly in the environment due to air and microorganisms, yielding sulfides and sulfates. |
| Sorbitol | Not needed | Releases carbon dioxide and water vapor | Yes | Yes | None |
| Strontium carbonate | |||||
| Strontium oxide | |||||
| Sucrose | |||||
| Sulfur dichloride | |||||
| Sulfur dioxide | |||||
| Sulfur trioxide | |||||
| Sulfur hexafluoride | Not required | May lead to sulfur dioxides and fluorine at very high temperatures | Not possible | Yes | Strong greenhouse effect |
| Sulfuric acid | |||||
| Terbium(III) oxide | Unnecessary, simply dump in trash | Releases absorbed water or carbon dioxide | Unnecessary | Effects unknown, may stimulate plant growth | |
| Terbium sulfate | |||||
| Tetraamine copper(II) complex | |||||
| Tetraaminecopper(II) persulphate | |||||
| Tetrachlorocupric acid | |||||
| Tetrahydrofuran | |||||
| Tin(IV) chloride | |||||
| Titanium dioxide | Not required; Can be dumped in trash | Leads to fusing in the presence of alkaline and alkaline-earth oxides and hydroxides | Yes, but not recommended | Yes, but recommended | May lead to staining water bodies and soil in a white color |
| Toluene | |||||
| Trichloroethylene | |||||
| Trichloroisocyanuric acid | |||||
| Trimethyl borate | |||||
| Tris(ethylenediamine)nickel perchlorate | |||||
| Tungsten carbide | |||||
| Urea | Not required | Generates carbon oxides, nitrogen fumes; May corrode metal container, if done in one | Yes | OH YES | May cause uncontrolled algae growth in water bodies |
| Vanadium pentoxide | |||||
| Water | Not required | Leads to steam | YES | YES | It's...water |
| Xylene | |||||
| Xylitol | |||||
| Zinc carbonate | |||||
| Zinc chloride | |||||
| Zinc chromate | |||||
| Zinc oxide | Not required; Weak acids can be used to dissolve zinc oxide stains to soluble zinc compounds | Turns the oxide yellow at high temperatures; process is reversible | Not recommended | Yes, but not recommended | May pose a threat to aquatic life |
| Zinc peroxide | |||||
| Zinc phosphate | |||||
| Zinc sulfate | |||||
| Zinc sulfide |
