Can polyaluminum chloride be used as an oil sediment?

Polyaluminum Chloride (PAC) can be used as an oil sedimentation agent, especially in the treatment of oily sewage.

I. Basic Principles

Q1: Why can polyaluminum chloride treat oily wastewater?

A: PAC produces multinuclear complexes through hydrolysis and plays a triple role:

●Electro-neutralization: destroy the surface charge of oil droplets and promote the emulsified oil to break down and precipitate;

●Adsorption bridge: coagulate dispersed oil particles into large flocs to accelerate sedimentation;

●Net precipitation: collaborative removal of heavy metals, organic matter and other pollutants.

Q2: What kind of oil does PAC remove best?

A: It has significant efficiency on emulsified oil and colloidal oil particles (removal rate>80%), but it needs to be combined with oil separation pretreatment for high concentration of floating oil (such as crude oil).

II. Practical application

Q3: How to add PAC correctly?

A: It needs to be done step by step:

1.Dissolution: Solid PAC is mixed with water in a ratio of 1:3 to form the mother liquor;

2.Dilution: The mother liquor is diluted 10-30 times (the recommended concentration is 10-20%);

3.Investment:

●Turbidity 100-500mg/L wastewater: 5-20kg/ thousand tons of water;

●Highly concentrated oily wastewater: the dosage should be determined by pilot test.

Q4: Why do you need to mix with PAM? How to operate?

A：

●Reason: The strength of the floc is insufficient when PAC is used alone, and cationic PAM can enhance the compactness of the floc;

●Step: PAC is added first to break the emulsion, and then 0.1%-0.5% cationic PAM solution is added to help coagulation.

Q5: How to control environmental parameters?

A：

●PH Scope: The best range is 5.0-9.0, and too acid/alkali reduces the charge neutralization efficiency;

●Temperature: When the temperature is lower than 10℃, the reaction slows down, so it is necessary to increase the dosage or keep warm.

III. Industry scenarios and cases

Q6: Which industries are suitable for PAC to treat oily wastewater?

A: Typical scenarios include:

●Petrochemical: oil removal of refinery circulating water to reduce COD;

●Food processing: fat removal rate of slaughter wastewater **>80%**;

●Mechanical manufacturing: cutting fluid, emulsion demulsification;

●Textile printing and dyeing: synergistic removal of dyes and oils.

Q7: How to verify the actual effect?

A: The case shows that:

●A refinery: the oil content decreased from 200mg/L to 15mg/L after the combined use of PAC and PAM;

●Battery factory: synchronous deposition of heavy metals and fluoride.

IV. FAQ

Q8: What are the possible reasons for PAC processing failure?

A: Main risk points:

●Unpre-treated floating oil: high concentration of floating oil should be treated by air flotation/oil separation first;

●Low temperature without adjustment: below 5℃, no additional 20% dose is added, resulting in delayed flocculation 1;

●PAM selection error: high oil content wastewater should choose medium and low molecular weight cation PAM.

Flow chart suggestions:

Oil-containing wastewater → oil separator (to remove floating oil) → regulating tank (PAC to break emulsions) → flocculation tank (PAM to help coagulation) → sedimentation tank → discharge water up to standard

Adjust according to actual water quality.