Cationic polyacrylamide (cationic polyacrylamides, referred to as CPAM) is a linear polymer, its synthesis is in the molecular chain of polyacrylamide with a positive charge on the introduction of groups (mostly quaternary ammonium salt group, but Due to the different monomers obtained CPAM cost and performance are also quite different), thus giving the polymer a new performance, because the structure has a variety of lively groups, with many substances affinity, adsorption hydrogen bonds, The use of PAM.
CPAM in accordance with the different forms can be divided into:
Solid particles and emulsion two, the most widely used on the market is solid granular, and emulsion products as a new form of product market applications less.
CPAM synthesis method
There are two main methods for the preparation of CPAM:
1, macromolecule pendant modification method
The high molecular weight CPAM can be obtained by the modified method, but the viscosity of the aqueous solution of high molecular weight nonionic polyacrylamide is large and it is difficult to mix evenly and must be diluted to cause the effective content of the modified product to be very low (generally <5% ), And the stability of the modified product is poor, the validity period is short, some modified products are higher prices.
2, monomer copolymerization method
Conventional copolymerization methods include aqueous solution polymerization, emulsion polymerization (conventional emulsion polymerization, inverse emulsion polymerization, reverse microemulsion polymerization) and precipitation polymerization, photoinitiation polymerization.
The copolymerization method uses less equipment, the production process is simple, easy to obtain different molecular weight, but not easy to obtain a higher molecular weight. The molecular weight of the CPAM prepared by the copolymerization method is generally not as good as that produced by the modified method, but the stability is good and the performance is good. The processing is easy and the price is acceptable.
The influencing factors of cationic aqueous solution polymerization have many important factors, such as temperature, time and pH value, and the polymerization additive has a very important effect on its performance.
Commonly used cationic monomers:
1, dimethyldiallylammonium chloride (DMDAAC) and its modified compounds such as hexane diallyl ammonium chloride;
2, acryloyloxyalkyl quaternary ammonium salt monomer (DAC, DMC) and its modified body such as benzyl-dimethyl- (2-propenyl-2-acyloxyethyl) ammonium chloride;
3, (meth) acrylamide alkyl ammonium chloride quaternary ammonium salt (DMPMA, DMPAA)
4, other types of cationic monomer
Cationic degree of calculation
CPAM cation degree:
DC% = [M × N × (V - V0)] / (1000 × W × solid content) * 100%
V - volume of silver nitrate standard solution consumed by sample (ml);
V0 --- blank consumption of silver nitrate standard solution volume (ml);
M - cationic monomer average molecular weight (207.5);
N - concentration of silver nitrate standard solution (mol / L);
W - sample quality (g);
CPAM is mainly to see the degree of ionization, the higher the degree of ionization in the sewage, the greater the effect of impurities in the more stringent, cations mainly for urban sewage and sewage with a negative charge of sewage, when the cation into the water after one thousand can be wrapped in sewage Of the impurities play a bridge sedimentation effect, which is often said that the sewage mud. After the CPAM into the sewage can see the impurities will be very fast precipitation, so that water and impurities separated, so that the late desalination equipment operation. Cationic 10% -20% Mainly used in the cabinet pressure dehumidifier; Cation 30% -40% Mainly used in crawler degreaser; Cation 50% -60% Mainly used in high-speed centrifuge.
Features of CPAM:
1, cationic - polyacrylamide water-soluble, in cold water can also be completely dissolved.
2, add a small amount of cationic - polyacrylamide products, can be a great flocculation effect. General only need to add 0.01 ~ 10ppm (0.01 ~ 10g / m3), you can fully play a role.
3, while the use of cationic - polyacrylamide products and inorganic flocculants (polyferric sulfate, poly aluminum chloride, iron salts, etc.), can show a greater effect.
CPAM application areas:
CPAM is mainly flocculated with a negative charge colloid, with the turbidity, decolorization, adsorption, bonding and other functions, for dyeing, paper, food, construction, metallurgy, mineral processing, coal, oil, aquatic products processing and fermentation industry organic colloid High content of wastewater treatment, especially for urban sewage, urban sludge, paper sludge and other industrial sludge dewatering treatment.
1, as a flocculant, CPAM is mainly used in industrial solid-liquid separation process, including sedimentation, clarification, enrichment and sludge dewatering and other processes, the main industries are: urban sewage treatment, paper industry, food processing industry, petrochemical industry, metallurgy Industrial, mineral processing, dyeing and sugar industries and various industrial waste water treatment, but also used in urban sewage and meat, poultry, food processing wastewater treatment process of sludge sedimentation and sludge dewatering, through its contained Of the positive charge groups in the sludge in the negative charge of organic colloid neutralization and high polymer excellent bridging function, to promote the colloidal particles gathered into large pieces of floc, separated from its suspension. , Less dosage
2, in the paper industry can be used as paper dry strength agent, retention aid, filter aid, can greatly improve the quality of paper, cost savings, improve the production capacity of paper mills. Can be directly with the inorganic salt ions, fibers and other organic polymer electrostatic bridge in order to enhance the physical strength of the paper to reduce the loss of fiber or filler, to speed up the filter, from the enhanced, retention, help filter, can also be used White water treatment, at the same time, cationic polyacrylamide in the deinking process can play a significant flocculation effect.
3, the fiber slurry (asbestos - cement products) can be formed asbestos - cement products, drainage improved, so that the strength of asbestos blanks increased; in the insulation board, can improve the ability of additives and fiber binding.
4, in the mining, coal preparation industry can be used for mine wastewater, coal washing wastewater clarifier.
5, can be used for dyeing wastewater, leather waste water, oily wastewater treatment, so that in addition to turbidity, decolorization, in order to meet the emission standards.
6, phosphoric acid purification, contribute to the wet phosphoric acid process gypsum separation.
7, for the river water source of the water plant flocculant water treatment.