What is the specific mechanism of action of liquid polyaluminium ferric chloride in treating industrial wastewater?
Publish Time: 2025-01-20
Liquid polyaluminium ferric chloride is a highly efficient inorganic polymer flocculant, which is widely used in industrial wastewater treatment. Its mechanism of action is mainly based on its chemical structure and charge characteristics, and can effectively remove suspended matter, colloids, heavy metal ions, organic pollutants, etc. in water.1. Electrical neutralizationCharge neutralization: Liquid polyaluminium ferric chloride can undergo hydrolysis in water to generate positively charged hydroxide ions. These positively charged ions can neutralize the negatively charged suspended particles and colloids in the wastewater, reduce their surface charge, make them lose stability, and then condense into larger particles.Particle aggregation: Through charge neutralization, tiny particles and colloids in the wastewater begin to aggregate to form larger flocs, which are convenient for subsequent precipitation and separation.2. Adsorption and bridging effectAdsorption: The active groups (such as hydroxyl groups, chloride ions, etc.) on the molecular chain of polyaluminium ferric chloride can be adsorbed on the surface of suspended particles and colloidal substances in water. The adsorption of these active groups enhances the mutual attraction between particles.Bridging effect: The molecular chain of polyaluminium ferric chloride can adsorb multiple suspended particles in water at the same time, so that these particles are connected by molecular chains, forming a "bridge" effect, further promoting the aggregation and flocculation of particles.3. Netting and sweeping effectNetting effect: As the flocculation reaction proceeds, the flocculent particles formed gradually increase in size, forming a "net-like" structure. These large-particle floccules can net tiny particles and colloidal substances in the water and sweep them into the floccules.Sedimentation effect: As the floccules continue to grow, their density increases, and they eventually settle to the bottom of the water, thereby achieving solid-liquid separation and completing the wastewater purification process.4. Removal of heavy metal ionsComplexation: The iron ions (Fe³⁺) in polyaluminium ferric chloride can react with heavy metal ions (such as lead, mercury, copper, etc.) in water to form stable metal-iron complexes. These complexes are generally easier to precipitate than heavy metal ions alone.Coprecipitation: The formed metal-iron complex precipitates together with the flocculants, thereby effectively removing heavy metal ions in water.5. Removal of organic pollutantsAdsorption removal: The active groups on the molecular chain of polyaluminium ferric chloride can adsorb organic pollutants in water, such as organic dyes, phenolic compounds, etc. After being adsorbed, these organic pollutants are precipitated together with the flocculants and thus removed.Oxidative degradation: In some cases, the iron ions in polyaluminium ferric chloride can catalyze the oxidation of organic pollutants, degrading them into smaller molecules or harmless substances, further improving the purification effect of wastewater.6. Improve the efficiency of subsequent treatmentEnhance the filtration effect: Through flocculation, polyaluminium ferric chloride can condense the suspended matter and colloidal substances in the wastewater into larger particles, which are easier to separate through filtering equipment (such as sand filter, membrane filter), improving the efficiency of subsequent treatment.Reduce the volume of sludge: Due to the strong flocculation ability of polyaluminium ferric chloride, the flocs formed are relatively dense, which reduces the volume of sludge and reduces the cost of sludge treatment and disposal.7. Adaptability and stabilitypH adaptability: polyaluminium ferric chloride can effectively play a flocculation role in a wide pH range (usually 5-9) and adapt to the pH conditions of different wastewaters.Temperature stability: polyaluminium ferric chloride can maintain good flocculation performance at different temperatures (usually 5-40℃), which is suitable for treatment needs in different seasons and water temperature changes.8. Environmental friendlinessLow toxicity: Compared with other flocculants, polyaluminium ferric chloride has lower toxicity, less impact on the environment, and is suitable for long-term use.Easy to degrade: polyaluminium ferric chloride can be gradually degraded in the natural environment and will not cause long-term pollution to the ecosystem.The mechanism of action of liquid polyaluminium ferric chloride in treating industrial wastewater mainly includes electrical neutralization, adsorption bridging, net capture and sweeping, removal of heavy metal ions and organic pollutants, etc. Through these mechanisms, it can efficiently remove suspended matter, colloids, heavy metals and organic pollutants in wastewater, improve the efficiency of subsequent treatment, reduce sludge volume, adapt to different water quality conditions, and have a lower environmental impact. These advantages make polyaluminium ferric chloride an ideal flocculant for industrial wastewater treatment.
