Cololorization technology of polymer iron sulfate (PFS) in printing and dyeing wastewater

1.Core advantages of polymeric iron sulfate decolorization technology

Efficient coagulation and decolorization capacity of polymer iron sulfate (PFS) hydrolysis in water to produce multi-core complex (such as [Fe ₂ (OH) ₃] ³), through charge neutralization, adsorption bridge and winding, rapid removal of colloidal particles and soluble dye molecules in printing and dyeing wastewater, and the decolorization rate of activated dyes and dispersed dyes can reach 90% -98%.

In addition to decolorization of dual pollutant removal, PFS can simultaneously reduce COD (removal rate of more than 80%) and total phosphorus content. The iron hydroxide catkins generated by it can physically absorb heavy metal ions and organic matter, and realize comprehensive purification of wastewater.

Compared with the economy and safety of aluminum coagulant, PFS does not contain the risk of aluminum residue, and the raw material cost is low (ferrous sulfate as raw material), and the treatment cost is 20% -50% lower than that of traditional agents.

2.Decolorization mechanism and the key control parameters

Mechanism of action-charge neutralization: PFS hydrolysis products with high positive charge, neutralize the negative charge on the surface of the dye colloid, and destroy the stability.-Adsorption bridge: multinuclear complexes connect multiple colloidal particles through molecular chains to form large flocculent settlement.-Chemical complexation: iron ions combine with groups such as amino (-NH ₂), hydroxyl (-OH) and other groups in the dye molecule to change the solubility].

Optimum operating conditions-pH range: 6-9 (acidic conditions inhibit hydrolysis, alkaline leads to failure of iron ion precipitation).-Add concentration: usually 5% -20% mother liquor is diluted to 0.2% -0.5% working concentration, which is easy to cause color return.-Temperature control: effective within 10-90℃, and the low temperature needs to extend the reaction time or increase the addition amount].

3.Engineering application key points and optimization strategies

Collaborative treatment technology-combined with PAM: 0.1-0.3 mg/L anionic polyacrylamide (PAM) can reduce the amount of PFS by 30% -50% and enhance the settlement of catkins.-Pre-oxidation process: ozone (0.2 mg/L) or potassium permanganate pretreatment can decompose refractory dyes and reduce the subsequent PFS requirements].

Establish a multi-parameter control formula: \ [C = 0.78T + 0.15pH-0.08 Temp \] (T is turbidity, Temp is water temperature), to achieve ± 10% injection error].

4.Typical case analysis

Waste water treatment of a printing and dyeing factory (COD 2000 mg/L, 800 times)

Process design: adopt the combination of PFS (50 mg/L) + anion PAM (0.2 mg/L), 200 r/min (1 min) + 80 r/min (15 min).

Effect: the effluent COD is <100 mg/L, the color degree is reduced to less than 10 times, and the sludge moisture content is <80%].

5.Precautions for operation

Dissolution control-use deionized water or low impurity water source, stirring for 5 minutes to prevent clumping].-Avoid direct contact with sulfide, otherwise the formation of black iron sulfide precipitation will affect the chromaticity, and lime should be added in advance to remove sulfide].

The combination of metering pump and static mixer is recommended to ensure uniform dispersion of agent; regular calibration equipment error is <5%].

Vi. Technological development trend

The intelligent dosing system is based on the real-time monitoring system of the Internet of Things, which dynamically adjusts the PFS dosage through the turbidity meter and pH sensor, and reduces the drug consumption by 15% -30%].

The composite modification technology PFS is combined with nanomaterials (such as modified attite) to improve the adsorption efficiency of hydrophobic dyes].3. Green preparation process Develop environmental friendly preparation technologies such as hydrogen peroxide oxidation method to reduce chlorate residues and improve product purity].

Application Suggestions: For high color dyeing wastewater, it is recommended to carry out beaker test to determine the optimal injection gradient (20-100 mg/L), and monitor the effluent iron ion residue (<0.3 mg/L) to meet the discharge standard].