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Bittern (pl. bitterns), or nigari, is the
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...
formed when
halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...
(table salt)
precipitates In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
from
seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...
or
brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for br ...
s. Bitterns contain
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
, and
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
ions as well as
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
,
sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...
,
iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
, and other ions. Bittern is commonly formed in salt ponds where the
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
of water prompts the precipitation of halite. These salt ponds can be part of a salt-producing industrial facility, or they can be used as a waste storage location for brines produced in
desalination Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in Soil salinity control, soil desalination, which is an issue f ...
processes. Bittern is a source of many useful salts. It is used as a natural source of Mg2+, and it can be used as a coagulant both in the production of
tofu Tofu (), also known as bean curd in English, is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness; it can be ''silken'', ''soft'', ''firm'', ''extra firm'' or ''super firm ...
and in the treatment of
industrial wastewater Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reused or released to a sa ...
.


History

Bittern has been extracted for a long time, at least several centuries. The Dutch chemist
Petrus Jacobus Kipp Petrus Jacobus Kipp (Utrecht, 5 March 1808 – Delft, 3 February 1864) was a Dutch apothecary, chemist and instrument maker. He became known as the inventor of the Kipp apparatus, chemistry equipment for the development of gases. Biograph ...
(1808–1864) experimented with saturated solutions of bittern. The term for the solution is a modification of "bitter".


Uses


Salt derivation

Bittern is a source of many salts including
magnesium sulfate Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, ...
(epsom salt). Multiple methods exist for removing these salts from the bittern, and the method ultimately used depends on the target product. Products that would naturally precipitate from the bitterns
crystallize Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...
as
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
proceeds. Products that do not preferentially precipitate from bitterns may precipitate through the addition of another
compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struct ...
or through
ion exchange Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
. Potassium-magnesium sulfate
double salt A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula ) and Tutton's salts (with the general formula ). Other examples include potassium sodium tartrate, ammo ...
, a good
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
, is a salt that precipitates from bitterns upon addition of
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
.
Ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
is also used, but it exhibits a preference for
potassium sulfate Potassium sulfate (US) or potassium sulphate (UK), also called sulphate of potash (SOP), arcanite, or archaically potash of sulfur, is the inorganic compound with formula K2SO4, a white water-soluble solid. It is commonly used in fertilizers, pro ...
precipitation. The solution can furthermore be used in the production of
potash Potash () includes various mined and manufactured salts that contain potassium in water-soluble form.
and potassium salts.
Tartaric acid Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally i ...
is one compound that can facilitate the precipitation of these salts.
Magnesium hydroxide Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...
(Mg(OH)2) can be derived from bittern. Adding an
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
ne
solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...
such as
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...
(NaOH) or
lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...
will cause magnesium hydroxide to precipitate, although lime is not as effective. Slower addition of the alkaline solution results in the precipitation of larger particles that are easier to remove from solution.


Coagulation


Tofu

Bittern (nigari) was the first coagulant used to make
tofu Tofu (), also known as bean curd in English, is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness; it can be ''silken'', ''soft'', ''firm'', ''extra firm'' or ''super firm ...
. It is still used today because tofu made using bittern preserves the original flavor of the
soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...
s used to make it. Although bittern causes too-rapid coagulation of tofu that decreases the overall quality of the tofu, different methods of tofu production utilizing bittern have been developed to work around this issue.


Wastewater treatment

Bittern can be used instead of
aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
-based coagulants in the treatment of wastewater produced during the fabric-
dyeing Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. Dyeing is normally done in a special solution containing dyes and particular ...
process. The wastewater pH is
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
, which is favorable for the use of bittern. After the addition of bittern, precipitated magnesium hydroxide works as the coagulant to collect
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
, solids,
organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
, and
heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...
from the wastewater before settling out of solution. The
sludge Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. For example, it can be produced as a settled suspension obtained from conventiona ...
produced from this wastewater treatment is also easier to dispose of than sludge produced by aluminum-based coagulants because there are less restrictions surrounding the disposal of magnesium, and it may be possible to recycle the sludge as fertilizer. Bittern can also be used as a source of magnesium ions (Mg2+) for the precipitation of
struvite Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft m ...
, a useful fertilizer, from wastewater containing
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
. One source of useful wastewater is
landfill A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...
leachate A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed. Leachate is a widely used term in the environmental sciences wher ...
. Bittern is just as good as other sources of magnesium ions at removing phosphorus from wastewater streams, but it lags behind other magnesium ion sources in terms of the removal of
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
(a nitrogen compound).


Other uses

Bittern can be used to culture ''
Haloquadratum ''Haloquadratum'' (common abbreviation: ''Hqr.'') is a genus of archaean, belonging to the family Haloferacaceae. The first species to be identified in this group, ''Haloquadratum walsbyi'', is unusual in that its cells are shaped like square, f ...
''
archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
. ''Haloquadratum'' are distinctly square-shaped and are abundant in hypersaline environments such as salt ponds. Their cultivation is necessary for understanding both their
ecological Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
function in those environments as well as their unique
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
. The presence of ''Haloquadratum'' in an environment deemed inhospitable for most life has prompted closer study of these archaea. A study has been performed exploring the use of bittern as a natural magnesium supplement used to decrease cholesterol spikes after a meal (postprandial
hyperlipidemia Hyperlipidemia is abnormally elevated levels of any or all lipids (fats, cholesterol, or triglycerides) or lipoproteins in the blood. citing: and The term ''hyperlipidemia'' refers to the laboratory finding itself and is also used as an umbre ...
). Due to its high salinity, bittern can also be used as a draw solution for an osmotic process that concentrates
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...
in
sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...
juice. Because
forward osmosis Forward osmosis (FO) is an osmotic process that, like reverse osmosis (RO), uses a semi-permeable membrane to effect separation of water from dissolved solutes. The driving force for this separation is an osmotic pressure gradient, such that a "d ...
is being used, the process is relatively energy-efficient. Epsom salt can also be taken from the bittern draw solution once it is used. This method is particularly useful in areas where sugarcane and salt production are in close proximity to avoid costs associated with movement of either the sugarcane juice or the bittern.


Environmental impact

In some jurisdictions, most bitterns are used for other production instead of being directly discarded. In other jurisdictions each tonne of salt produced can create 3+ tonnes of waste bitterns. Although bittern generally contains the same compounds as seawater, it is much more concentrated than seawater. If bittern is released directly into seawater, the ensuing
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
increase may harm
marine life Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. M ...
around the point of release. Even small increases in salinity can disrupt marine species' osmotic balances, which may result in the death of the
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
in some cases. In December 1997, 94 corpses of green sea turtles, ''
Chelonia mydas The green sea turtle (''Chelonia mydas''), also known as the green turtle, black (sea) turtle or Pacific green turtle, is a species of large sea turtle of the Family (biology), family Cheloniidae. It is the only species in the genus ''Chelonia' ...
'', were found at the
Ojo de Liebre Lagoon Ojo de Liebre Lagoon (also known as Scammon's Lagoon), translated into English as "hare eye lagoon", is a coastal lagoon located in Mulegé Municipality near the town of Guerrero Negro in the northwestern Baja California Sur state of Mexico. I ...
(OLL) in Mexico, adjacent to the industrial operation of
Exportadora de Sal S.A. Exportadora de Sal S.A. (abbreviated as ESSA) is a company dedicated to salt production through solar evaporation of sea water in the Ojo de Liebre Lagoon, Baja California Sur, Mexico. Founded in 1954 by American shipping businessman Daniel K. ...
(ESSA), the largest saltworks in the world. The Fluoride Ion F- content in bitterns was 60.5-fold more than that in seawater. The bitterns osmolality was 11000 mosm/kg of water, whereas the turtle's plasma osmolality was about 400 mosm/kg of water. Researchers concluded that the dumping of bitterns into the ocean should be avoided. The lack of adequate disposal methods for bitterns and concerns of local commercial and recreational fishing associations about bitterns’ deleterious impacts upon local fish and prawn hatchery areas led the Western Australian EPA in 2008 to recommend against the proposed 4.2 million tonne per annum Straits Salt project in The Pilbara region of WA. The EPA concluded that:


References

{{Salt topics Salts Chemistry Evaporite