An inorganic coagulant
1. Low molecular inorganic coagulant
The most widely used simple inorganic flocculants are iron and
aluminum metal salts. Mainly ferric chloride, ferrous sulfate and
Ferric chloride (Fe: commonly used in the formation of ferric
chloride hexahydrate (FeCl3 6H20), the precipitation of a good,
low-temperature water or low turbidity water treatment is better
than aluminum salt, a wide range of suitable pH value, However, the
color of treated water is higher than that of aluminum and
Ferrous sulfate (FeS04H20) dissociates Fe2+ and produces only the
simplest mononuclear complexes, which is not as good as divalent
Aluminum sulfate (Al2(S04)3) is the most used flocculant in
wastewater treatment. It is easy to use and has good flocculation
effect. When the water temperature is low, it is difficult to be
hydrolyzed and the formed floc is loose. Its effective pH range is
Mingji (Al2(S04)3K2S04.24H20) has the same mechanism as aluminum
2. Inorganic polymer flocculant
Inorganic molecular flocculants have a high coagulation effect and
low price, and have gradually become the mainstream pharmaceutical
agents. The development of such flocculants in China is remarkable.
Inorganic polymer flocculants are of cationic type, such as
polyaluminum chloride (PACL polyaluminum sulfate (PAS),
polyaluminum phosphate (PAP), polyferric sulfate (PFS), polyferric
chloride (PFC), polyferric phosphate (PFP), polyferrous and
anionic, such as polymeric silicic acid [PS] .
Polyaluminum Chloride (PAC): It can achieve good flocculation
effect on various wastewaters, can quickly form large silk flowers,
has good precipitation performance, and has a wide range of
suitable pH values (pH is between 5 and 9), and After treatment,
the pH and alkalinity of the water decrease less.
When the water temperature is low, a stable flocculation effect can
still be maintained, and its degree of alkalization is higher than
other aluminum salts and iron salts, so that the chemical liquid
has little effect on the erosion of the equipment.
Polymeric Ferric Sulfate (PFS): The formation of the coagulant is
fast, dense and of high quality and the sedimentation speed is
fast. Especially for low temperature and low turbidity water, it
has excellent treatment effect. It is suitable for the pH range of
the water (pH is between 4 and 11), and has low corrosion.
Experiments show that using poly-iron to purify water can reduce
the content of nitrous nitrogen and iron. Therefore, it is an
excellent and safe drinking water coagulant, and it has a tendency
to replace polyaluminum coagulants that are harmful to the human
Polyferrous: Reduces high-valent metal ions to low-valent metal
ions without acidification. The coagulant has the dual functions of
charge neutralization and adsorption bridging in the water body. In
common with the active agent, the colloidal substance can be
converted into a coagulant, and at the same time, metal ions such
as Cu, Zn, and Ni in the waste water are removed, and it becomes an
efficient electroplating waste water purifier.
Polyaluminum sulphate (PAS): The turbidity removal effect is
significant, and there is a wide range of temperature use and
application of raw water. Not only industrial water but also
industrial wastewater can be treated. Polymeric aluminum sulfate
coagulants have been reported abroad.
Polymeric silicic acid (PS): The factors affecting the preparation
method, polymerization mechanism, and polymerization degree of
polysilicic acid have been studied thoroughly. Studies have found
that the difference in pH achieved by neutralization can be used to
control the polymerization rate.
Polysilicic acid has a strong adhesive aggregation and adsorption
bridging. Yang Xiu et al.  studied the gelling properties of
polysilicic acid and proved that polysilicon is anionic. The
biggest drawback of polysilicic acid is that the nature of the
product is not stable and it cannot be an independent commodity.
organic polymer coagulant
The organic polymer coagulant has the advantages of minimum use,
high coagulation speed, small influence of salt, pH and
temperature, less sludge generation and easy handling, and has
broad application prospects. Currently used coagulants are mainly
synthetic and natural modification.
Polyacrylamide: Among the synthetic organic polymer flocculants,
polyacrylamide is the most widely used. Polyacrylamides are
nonionic, cationic and anionic. Their molecular weight is between
Due to the presence of a certain amount of residual monomer
acrylamide in such flocculants, inevitably toxicity is introduced.
High molecular weight (above 106) polyacrylic nano-anionic
coagulant, strong coagulation and non-toxic.
The polyacrylic acid nanopa