2021-01-13
1、What is ferric sulphate used for?
ferric sulphate is used
in various fields such as dentistry and dermatology. It is thought to stop
bleeding by chemically interacting with certain proteins in the blood. Other
applications include odorants, solid separators, and water treatment chemicals.
Ferric sulfate acts as a coagulant and chemical
reaction. Like alum, ferrous sulfate requires alkalinity in water to form the
lambda particle iron hydroxide [Fe(OH)3]. When natural alkalinity is
insufficient, alkaline chemicals (e.g. soluble salts containing CO-2, OH- ions)
should be added.
Coagulation and flocculation are important
components of drinking water and wastewater treatment. Providing a reliable
process for treating water turbidity (cloudiness and ambiguity of normally
invisible liquids), turbidity is an important water quality test. In wastewater
treatment, suspended solids and organic loads can be reduced by up to 90%.
All water contains suspended particles. The
smallest particles (colloids) are stabilized by the particles' physical force
(electrostatic) and are loaded and repel each other when floating in the water.
This is not gathered in the water to precipitate but remains floating.
Precipitation may take days or even centuries.
Coagulation and coalescence are two separate
processes, used consecutively to overcome the forces that stabilize suspended
particles. Coagulation neutralizes the particles' charge, and condensation
binds them, making them larger and easier to separate from the liquid
Coagulation process.
This disrupts the process by which
micro-particles repel each other and promote larger particles that stick
together. The larger the particles, the easier they are to separate from the
liquid. The use of coagulants to treat water dates back to around 2000 B.C.
when the Egyptians used almonds, which were applied around boats to treat river
water.
These large "clumped" particles are
called microclusters and may not be visible to the naked eye today. The water
around these newly formed particles should be clear, indicating that the
particles' charges have been neutralized. If not, more coagulant may be needed.
Too much coagulant will cause the particles to revert to a mutually exclusive
state, but mainly reverse charges.
Rapid mixing ensures proper coagulant
dispersion and promotes particle collisions. Metal coagulant hydrolysis
products formed in 0.01 to 1.0 seconds or less are mostly the most effective
unstable products - adjusting the pH and adding more coagulant after the
initial addition of coagulant is the most effective reason.
Common rapid mixers are called back-mixing
reactors and usually consist of square tanks with vertical impellers. In many
cases, they produce poor results, and WCS tends to design in-line mixers with
velocity gradient control to provide optimal conditions for rapid mixing.
Type of coagulant.
There are two types of coagulants most commonly
used in water wastewater treatment today. Organic and inorganic.
Inorganic coagulants include:
· Aluminum coagulants, such as aluminum sulfate,
aluminum chloride, and sodium aluminate.
· Iron coagulants - such as ferric sulfate,
ferrous sulfate, ferric chloride, and ferric chloride sulfate.
· Organic coagulants include.
· Polyamines.
· Poly DADMAC's.
· Polytannic acid esters.
Inorganic coagulants.
Aluminum and iron coagulants have proven to be
very effective in removing most suspended solids. They have many advantages:
· Produces high charge density from highly charged ions, neutralizes suspended particles, forms hydrated inorganic hydroxides, produces short polymer chains and promotes micro-cotton bodies and heavy cotton bodies.
· Removes some organic precursors that may combine with chlorine to form disinfection by-products.
· Low unit cost and wide availability.
· Enables relatively low charge density to neutralize lower charge suspended particles more effectively. Do not use metals or hydroxides, producing long polymer chains that promote the formation of micro-cotton bodies.
· Removes some organic precursors that may combine with chlorine to form disinfection by-products.
· Produces small volume flocs.
· Liquid, non-corrosive, and ready for use.
· Unaffected by pH, little or no effect by pH.
There are also disadvantages.
· They produce large amounts of metal-rich flocs that must be treated with the proper environment, adding significant treatment costs.
· They will significantly change the water's pH,
which is critical for effective coagulation, so pH must be controlled.
Corrosion-resistant storage and supply equipment is also required.
· Aluminum and chloride sulfate, iron and
chloride sulfate, and ferrous sulfate are all strong acids that destroy
alkalinity and lower pH. Sodium aluminate increases alkalinity and raises pH.
· The cost of the unit is high.
· High dosage is required for high charge demand.
· Low-density flocculant-not always settles well.
Organic coagulants.
Polyamines and polyDADMAC coagulants have
proven to be very effective in removing most suspended solids. Tannates are
particularly effective at removing oils and fats.
They have many advantages.
· Enable relatively low charge densities to more
effectively neutralize lower charge suspended particles. Produce longer polymer
chains without the use of metals or hydroxides to promote the formation of
microbodies.
· Allows removal of some organic precursors that
may combine with chlorine to form disinfection by-products.
· Produces small volume flocs.
· Liquid, non-corrosive, and ready for use.
· Unaffected by pH, and little or no effect by
pH.
· They have some disadvantages.
· The cost of the unit is high.
· High dosage is required for high charge demand.
· Low-density flocculants-not always settles
well.
Flocculation process.
After coagulation ("charge
neutralization"), a second process is required, i.e., solidification. This
is the growth of small neutral particles into larger ones. Flocculants promote
the coagulation of fine particles into "flocs" that can be easily
separated from the water. Without exception, they are all polymers.
The flocculation process is a gentle mixing
phase that increases the particles' size from micro flocculation to large,
visible suspended particles called needle flocculation. The additional
collisions between the needle-like pieces create larger "blobs." Flocculants
participate in entanglement through long-chain polymers and low charges,
enhancing the van der Waals forces and hydrogen bonding between particles.
After these flocculants reach optimum size and strength, the water can be
separated from the solid-liquid. This can be by filtration, centrifugation,
sedimentation, or flotation.
The role of polymers.
Polymers are a series of water-soluble
polymeric compounds that stabilize or enhance the flocculation of components in
the water column. Adding them as part of the flocculation process helps to
enhance the flocs' settling weight and increase the settling weight of the
flocs.
Polymers can be natural or synthetic. Natural
polymers can also be traced back to ancient times, with Sanskrit texts from
around 2000 BC mentioning the use of crushed nuts to clarify water. Natural
polymers are virtually toxin-free and can break down organisms. Synthetic
polymers are more commonly used because they are more effective, reliable,
reproducible, and economical.
Summarization.
Coagulation and agglomeration are two separate
and important parts of water and wastewater treatment. Agglutination
destabilizes micro floating particles by static charge neutralization and
coagulation combines to form larger forms that are easily separated from the
liquid.
our range of coagulants and specially selected
coagulants can significantly reduce the occurrence of sludge, creating
alternative treatment pathways and new wastewater options for our customers. To
learn more, please contact us.