Polyacrylamide for yellow phosphorus wastewater treatment. Yellow phosphorus is an important basic chemical raw material, widely used in medicine, food, chemical, pesticide and other fields. However, because lime milk is used in the production of yellow phosphorus, a large amount of waste water will be produced during the production. The waste water contains a lot of harmful substances. If it is discharged directly without treatment, it will cause environmental pollution. Polyacrylamide is used as a flocculant and sedimentation aid, and plays an important role in the treatment of yellow phosphorus wastewater. Polyacrylamide for yellow phosphorus wastewater treatment.

Since the pH value of yellow phosphorus wastewater is weakly acidic, the acid calcium phosphate salt is generated after the wastewater is neutralized with lime milk, which hardly precipitates under weak acid and neutral conditions. Therefore, cationic polyacrylamide is used in the treatment of yellow phosphorus wastewater. Better. Use lime milk, which is recycled after simple neutralization. Waste water is produced during the production process from yellow phosphorus. These waste water contains a lot of harmful substances and cannot be discharged directly. However, because the sewage is weakly acidic, the acid calcium phosphate salt generated after the neutralization of lime milk and sewage is weakly acidic and Almost no precipitation under neutral conditions, resulting in high suspended solids content in sewage, poor water quality, high turbidity, scale (crystals) on the pipe wall, pump inlet and outlet, and impeller, making the pipe diameter smaller and reducing the water flow Small, seriously affecting the normal production of yellow phosphorus, and the off-white scale (crystal) formed on the pipe wall is difficult to handle.

Polyacrylamide (PAM) is a water-soluble high-molecular polymer. Its molecular chain contains a certain number of very functional groups, which can absorb solid particles suspended in water to promote the filtering effect. Polyacrylamide (PAM) is a good coagulation adsorbent and sedimentation aid. It can remove suspended particles, colloidal particles and certain harmful impurities in yellow phosphorus wastewater, so that particles can bridge between particles or be neutralized by electric charges. Make the particles agglomerate into larger flocs, accelerate the sedimentation of the particles in the suspension, and accelerate the clarification of the solution. The principle of its role in the treatment of yellow phosphorus sewage is as follows:

　　 Bridging effect: It acts as a bridge on the suspended solids and colloids of the polydisperse phase in the yellow phosphorus sewage, which connects the colloidal particles and becomes larger aggregates to accelerate the settlement;

　　 dehydration effect: polymer cationic polyacrylamide has a stronger affinity for water, and its dissolution and hydration effect dehydrate the colloidal particles, losing the hydration shell and coagulation;

　　Electric neutralization effect: Cationic polymer compound-cationic polyacrylamide is adsorbed on the particles on the charged colloid, which can neutralize the surface charge of the dispersed phase particles, reduce the repulsive potential between the particles, and make the sol agglomerate.

Cationic polyacrylamide is a linear macromolecule compound with a variety of active groups, which can affinity with many substances and adsorb to form hydrogen bonds. It has adsorption bridging and dehydration effects in wastewater treatment, and can connect suspended particles. Together, and because of its strong affinity for water, it can dehydrate the suspended colloidal particles, lose their digestion shell, and coagulate and settle. Cationic polyacrylamide (CPAM) was chosen because the colloids in yellow phosphorus wastewater are generally negatively charged. The addition of cations produces electric neutralization, eliminates the repulsive potential energy of the colloidal surface charges in the wastewater, and makes the colloids easy to agglomerate and precipitate.

The yellow phosphorus wastewater treatment process is:

Yellow phosphorus wastewater enters the phosphorus sludge tank, and most of the phosphorus sludge is separated and settled, and then flows into the first tank of the zigzag settling tank through the sewage ditch. The suspended solids in the wastewater undergo advection sedimentation and then remove a part, and then enter the second tank Neutralize with the lime milk from the lime milk preparation tank, adjust the pH value to 5.0~5.5, the lime reacts with fluoride to remove fluoride, and at the same time it is mixed with the prepared polyacrylamide flocculant, and the suspended solids and colloids in the wastewater are generated Flocculation accelerates the sedimentation and separation, and then flows into other sedimentation tanks to further sediment and separate the suspended solids, and finally pump them back to the workshop for recycling.

Too little PAM cannot completely react with the suspended solids in the yellow phosphorus wastewater to form a precipitate and be removed from the wastewater. Although excessive PAM can react with the suspended solids in the yellow phosphorus wastewater to form a precipitate and remove, the added PAM itself also causes yellow phosphorus Wastewater ss and turbidity increase.

The effect of pH on the treatment of yellow phosphorus wastewater by PAM. With the increase of pH, the effect of PAM treatment on yellow phosphorus wastewater is getting better and better. When the pH is 7, that is, when the yellow phosphorus wastewater is neutral, the PAM treatment effect is better. As the pH continues to increase, the effect of PAM in treating yellow phosphorus wastewater has decreased. This is because the calcium ions in the added lime milk have the effect of neutralization and de-emulsification. With the addition of the lime milk, the suspended matter in the yellow phosphorus wastewater is neutralized and emulsified, resulting in ss and turbidity in the yellow phosphorus wastewater When the yellow phosphorus wastewater is neutral, PAM has a better effect on treating yellow phosphorus wastewater, but as the lime milk continues to be added, the excessive lime milk will cause the increase of ss and turbidity. Therefore, choosing a neutral range with a pH of about 7 to investigate the effect of different addition amounts of PAM in treating yellow phosphorus wastewater is ideal.