What role does flocculant play in sewage treatment

- Aug 27, 2019-

What are the essential differences between flocculants and coagulants?
According to their chemical composition, flocculants can be divided into inorganic flocculants and organic flocculants.
Inorganic flocculant includes inorganic coagulant and inorganic polymer flocculant.
Organic flocculant includes synthetic organic polymer flocculant, natural organic polymer flocculant and microbial flocculant.
Coagulation refers to the aggregation process of colloidal particles and tiny suspended substances in the water, which can play a role of flocculation and coagulation in the coagulation process called coagulant.
Coagulants are mainly used for the purification of drinking water and industrial wastewater, and the treatment of special water quality (such as oily sewage, dyeing and papermaking sewage, smelting sewage, radioactive characteristics, toxic heavy metals such as Pb,Cr and F sewage, etc.).
In addition, it is also widely used in precision casting, oil drilling, leather making, metallurgy and papermaking.
There are many kinds of flocculants on the market, from low molecular to high molecular, from simple to complex, the general trend is to cheap and practical,
Non-toxic and efficient development direction.
Inorganic flocculants are cheap, but have adverse effects on human health and ecological environment.
Although the amount of organic polymer flocculant is small, the output of scum is small, the flocculation ability is strong, the flocculant is easy to separate, and the effect of removing oil and suspension is good, the residual monomer of this kind of polymer has the effect of "three causes" (causing qi, causing cancer, causing mutation), so its application scope is limited.
Microbial flocculant has no secondary pollution, easy to use and attractive application prospect.
Microbial flocculants may replace or partially replace traditional inorganic polymers and synthetic organic polymers in the future.
The development and application of microbial flocculants are in the ascendant. Their characteristics and advantages show a broad prospect for the development of water treatment technology.
What are the varieties of inorganic flocculants?
Inorganic flocculants include aluminum sulfate, aluminum chloride, ferric sulfate, ferric chloride, etc. Aluminum sulfate was first developed in the United States and has been used up to now as an important inorganic flocculant.
Common aluminum salts are aluminum sulfate
AL2(SO4)3.18H2O and AL2(SO4)3. K2so4.24 H2O, another type of iron salt with ferric chloride hydrate FeCL3.6H2O, FeSO4.7H2O and ferric sulfate.
Simple inorganic polymer flocculant, this kind of inorganic polymer flocculant mainly
It's a polymer of aluminum and iron salts.
Such as polyaluminium chloride (PAC), polyaluminium sulfate (PAS), polyferric chloride (PFC)
And polyferric sulfate (PFS).
Inorganic polymer
The fundamental reason why flocculant has better effect than other inorganic flocculants is that it can provide a large number of complexing ions and strongly adsorb colloidal particles, so as to make colloidal coagulation through adsorption, bridging and cross-linking.
At the same time, physical and chemical changes took place to neutralize the charges on the surface of colloidal particles and suspended objects, reducing delta potential, so that the colloidal particles changed from repulsion to mutual attraction, damaging the stability of the micelles and causing the colloidal particles to collide with each other, thus forming a flocculent coagulation precipitation with a surface area of up to 200
M2 /g, very adsorption capacity.
Application of flocculant:
1. Used for the analysis of silver and the quantitative determination of sugar.
Used as a dye.
The ink.
Clean water.
The carving of aluminum.
Disinfection.
Polymerization catalyst, etc.
Polyacrylamide can be divided into super high relative molecular weight polyacrylamide, high relative molecular weight polyacrylamide, medium relative molecular weight polyacrylamide and low relative molecular weight polyacrylamide.
Ultra-high relative molecular weight polyacrylamide is mainly used for tertiary oil recovery in oil fields, high relative molecular weight polyacrylamide is mainly used as flocculant, medium relative molecular weight polyacrylamide is mainly used as dry strength agent for paper, and low relative molecular weight polyacrylamide is mainly used as dispersant.
Polyacrylamides are polymers.
Professional for all kinds of difficult to treat wastewater treatment and sludge dewatering treatment.
Cationic polyacrylamide (cationic polyacrylamide) is widely used in municipal sewage and sludge treatment of paper and dyeing industry.
The molecular formula of acrylamide is CH2 = ch-conh2
The molecular formula of sodium acrylate is CH2 = ch-coona
Non-ionic organic polymer flocculant,
Non - ionic organic polymer flocculant is mainly polyacrylamide.
It is obtained by polymerization of acrylamide.
Anionic organic polymer flocculant polyacrylic acid, polyacrylic acid sodium, polyacrylic acid calcium and polyacrylamide alkali hydrolyzed polymer.
Styrene sulfonate, lignosulfonate, acrylic acid, methacrylic acid and other copolymers.
Cationic organic polymer flocculant quaternized polyacrylamide ionon is obtained by hydroxymethylation and quaternization of -nh2, which can be divided into polyacrylamide cationization and acrylamide cationization polymerization.
Polyacrylamide (PAM)
First, it reacts with formaldehyde aqueous solution, amide-based partial hydroxymethylation, and then reacts with secondary amine to carry out amination, and then reacts with hydrochloric acid or amination reagent to quaternize tertiary amine.
Under alkaline conditions, acrylamide reacts with formaldehyde solution first, and then with dimethylamine. After cooling, quaternary ammonium hydrochloric acid is added.
The product was concentrated and filtered by evaporation to obtain quaternary ammonium acrylamide monomer.
The cationic derivatives of polyacrylamide are mainly obtained by copolymerization of acrylamide and cationic monomer.
Amphoteric polyacrylamide flocculant with carboxyl group and aminomethyl group was synthesized by manitz reaction by partially hydrolyzing polyacrylamide and adding appropriate amount of formaldehyde and dimethylamine.
Acrylamide graft copolymer because starch cheap source is rich, it is itself a polymer compound, it has a hydrophilic stiffness
Sex chains, which are rigid chains attached to flexible polyacrylamide branched chains, are networks of rigid and flexible macromolecules that, in addition to maintaining the function of proacrylamide, have some superior properties.