Aluminum sulfate –more familiarly, alum- has been known to mankind since the beginning of
recorded time. As early as 2000 B.C. naturally occurring alum was in use by the Egyptians as a
mordant to speed dyeing,to fix the dyes and to improve their color…takes which later assumed even
greater importance and which still consume limited quantities of this salt. Pliny mentions alum
in his comprehensive “Natural History” and its use as an agent for the softening of hides was
recorded during the early years of the Christian era. For even longer man has known aluminum
sulfate improves the durability of parchment and its receptivity to pen and ink. Modern paper
makes add it during processing for similar purposes, an important, that it requires two-thirds of all
In this country, aluminum sulfate was among the first of the heavy chemicals to be produced… With
records showing the colonists using domestic material as early as 1635. Exactly two hundred and fifty
years later, Stauffer Chemical Company was established to supply chemicals for industry and
agriculture, and the company has been for many years a primary source for aluminum sulfate.
Alum no longer is a product of varying composition derived by crude production methods.
In modern chemical plants, it is manufactured under carefully controlled conditions and carefully
assayed. Commercial alum is available in two physical forms; as a dry material ground from partially
dehydrated slabs and in aqueous solution commonly known as “alum liquor”.
Chemically speaking, “alum” denotes the hydrated double sulfates of aluminum with univalent metals
or radicals such as potassium, sodium or ammonium. It is erroneous to speak of aluminum
sulfate as “alum” but it is the nature of people to shorten long words or terms in frequent use,
so that “alum” for “aluminum sulfate” prevails among speakers in industrial and water purification
activities. It refers both to the single salt, also known as commercial alum, paper makes’ alum or filter
alum or to the double salts known as crystal alum, ammonium alum, potassium alum or sodium alum.
Water treatment: Surely, one of the most important processes in our complex economy is the
maintenance of a pure water supply. So it is the second largest consumer of aluminum sulfate is
the water treating industry.
For human consumption, water should be clear, colorless, odorless, tasteless and free from harmful
bacteria and chemicals.
For Industrial consumption, the quality requirements vary greatly, due to the varying requirements
Water to meet municipal and industrial requirements must be produced from a variety of sources
ranging from wells to different sources of surface waters requiring a corresponding variety of
The most important chemical used in water treating is aluminum sulfate as a coagulant.
Coagulation is employed to remove the turbidity caused by suspended and colloidal matter. It also helps
to remove bacteria and control taste and color. With lime and soda ash, aluminum sulfate is used for
Alum, when added to the inflowing water supply reacts with the alkalinity naturally present, or the
alkaline materials added to adjust pH, to form gelatinous flocs of aluminum hydroxide which absorb
and entangle the colloidal impurities present and cause them to settle out. Equation 1 below
illustrates the reaction of alum with the natural alkalinity of calcium bicarbonate; the second equation
shows the reaction with lime and the third equation shows the reaction with soda ash. In each case
Experience has shown that the reduction in alkalinity which takes place where alum is added is far less
than that called for by any of the above reactions. Thus there are other distinct reactions which product
1. The trivalent positive aluminum ion, when added to negative particles of color or turbidity,
exerts its great coagulating power, neutralizes and charges particles of color or turbidity,
and coagulation begins.
2. The tiny particles first agglomerated, micro-flocs, may still possess positive charge and can
therefore continue to neutralize negatively charged particles which settle rapidly to produce
clean, sparkling water.
3. As it grow, the gelatinous floc tends to occlude or envelop; some adsorption may take place.
This results in suspended turbidity forming larger particles which settle rapidly to produce
clean, sparkling water.
In any water supply many factors influence the conditions which are needed to produce a good floc
which will ensure cleat, sparkling water: Among these are:
- The nature and concentration of color turbidity and other impurities (such as organic
compounds, bacteria, algae) in the raw water.
- Alum dosage-which is usually predetermined by the jar test influences both the amount of
floc and ate of flocculation.
- The pH. Every raw water has its own optimum pH at which the floc Performs most efficiently.
The effective range for alum is 5.0 to 9.0 It is often necessary to adjust the pH of raw
water with alkali to the effective range.
- The temperature. The rate of floc formation varies directly withthe temperature. Lower
temperature means slower floc formation which is sometimes hastended by increased
dosage of alum.
In practies, alum is usually fed to the raw water from a dry feed machines at an optimum rate
(dosage) predetermined by a jar test. If alum liquor is used instead of the dry material, the feed is
governed by a calibrated flow meter. Stauffer’s alum liquor is supplied at constant strength to
in sure the operate of correct dosage. After flash mixers distribute the alum uniformly through
the water, the water is slowly agitated in the flocculators. The small particles now coalesce
as settleable “floc”. After the floc has settles, the clarified water is usually passed through sand
filters to remove any remaining suspended matter.
Sewage treatment: Alum is also used by some municipalities for the sewage. Its purpose is twofold:
1. As in water purification, to coagulate the suspended any colloidal particles of the sewage.
2. For conditioning of sewage sludge on sludge-drying beds.
When alum is added to raw sewage, it forms a floc which envelops and adsorbs both the
suspended particles and colloidal matter. Coagulation is faster than in the purification of water
because the concentration of solids is higher is sewage.
As in water purification, the sewage treating equipment consists of a preliminary settling basin,
a flash mixer, coagulation tank and sedimentation basin. The process is much the same.
After preliminary settling, the flash mixer mixes the dosage of alum uniformly. This coalesces
the floc and suspended matter, which is removed in the sedimentation basin. When
used properly, alum reduces efficiently both the suspended solids and Biological Oxygen
Demand (B.O.D) within a pH range of 5.5 to 9.0. Actual dosage of alum is determined by
experience or preliminary jar test.
The presence of alum in the settling sludge will not affect further digestion and makes the
dewatering problem easier. The settled digested sludge is usually driend in sludge beds.
Alum at this point is used as a conditioner which will produce a good semi-dry cake for easy
removal and further drying in a kiln. The dry sludge from the kiln is used as the organic
nitrogen component in mixed fertilizers.
Water flooding: In petroleum production water may be injected into subsurface strata for either
of tow major purposes:
1. To simulate production: (In some cases the additional production stimulated by water
flooding exceeds the primary recovery from the reservoir)
2. To dispose of the residual water produced with the oil to prevent Contamination of fresh
In both situations the water must be treated before injection into the well. To remove organic and
other suspended matter, sedimentation with alum is customary. Alum is used here in conventional
water treatment for flocculation or coagulation.
Fire Fighting: Most large petroleum refineries and/or outlying tank farms employ a two-solution
wet-foam system for smothering tank fires. Foam solutions of aluminum sulfate and bicarbonate of
soda are stored in separate tanks in these areas in case of fire in an oil tank.
The tanks are equipped with foam-mixing chambers, located at the top ring or roof of the tank,
which combine the two solutions to make a chemical foam. The foam, spreading on the surface
of the burning oil, starves the fire by removing the oxygen.
Synthetic Rubber: In the rubber industry, alum is used for the conditioning of process water and
as a coagulant in the manufacture of synthetic rubber of the butadiene-styrene copolymer type,
known as SBR. In making SBR, the butadiene and styrene are fed separately into a reactor with
water and a catalyst, all subjected to agitation at controlled temperature. When most of the material
is reacted, the process is stopped to forestall diminishing efficiency, the unreacted material stripped
off and returned to raw stock.
The remainder, which is almost identical with latex from a rubbertree, must be coagulated and
aluminum sulfate is one of the agents used for this purpose. The coagulated rubber polymer,
know as “crumb”, is drained, filtered, washed, dried in hot-air dryers and pressed into bales
ready for processing to finished products.
Waste Disposal: Increasing regulation by state and local agencies is forcing many manufacturing
plants to treat waste effluents previous to discharge into streams or sewers. Alum is used to
coagulate and solids in these wastes.
Grease and Oil Recovery: By the use of aluminum sulfate in pneumatic type waste
disposal plants, valuable oils and greases are reclaimed. KA type of reverse settling and
coagulation is used whereby the flocs of alum and entrained or trapped oil are floated to the
surface by air- bubbling and are removed by skimmers.
Other Uses of Aluminum Sulfate is a raw material for the manufacture of the double salts-
the true alums- and other aluminum salts and as astringent in deodorants. It is used in the
purification of by- product glycerin and as a fire-retarding agent for insulating materials.
Iron-free aluminum sulfate is used as a dye reagent in making greenish blue lakes; as a tanning
reagent in the manufacture of white leather such as that used for baseballs; as a mordant or
color-fixing agent in textile dyeing. Leached with lime, it makes "satin white" a paper coating material.
- 이 게시물의 QR코드