Polyaluminum Chloride in Water Treatment


Raw materials and methods for synthesis of polyaluminum chloride


Polyaluminum chloride is an inorganic polymer flocculant with good application effect in water treatment field in recent years. It has low cost, good water purification effect and is welcomed by users. So what is the raw material for its synthesis? What is the synthesis method?

1. Raw materials for the synthesis of polyaluminum chloride

There are many raw materials for the synthesis of polyaluminum chloride, which can be roughly divided into three categories according to the source of raw materials.

1) Bauxite, kaolin, clay, coal gangue, chert clay and alunite are bauxite bearing ores.

2) Industrial waste includes waste aluminum, aluminum ash, aluminum slag, waste aluminum foil, aluminum trichloride wastewater, etc.

3) Chemical products and intermediates include crystalline aluminum hydroxide, aluminum trichloride and sodium aluminate.

Polyaluminum Chloride in Water Treatment

2. Synthesis of polyaluminum chloride

According to the different raw materials, the synthesis methods of polyaluminum chloride can be divided into metal aluminum method, active aluminum hydroxide method, alumina method, aluminum chloride method, etc. It can also be divided into acid method, alkali method, neutralization method, pyrolysis method, pressurized reaction method, mixed gel method, electrodialysis method, electrolysis method, etc.

Which synthetic method or raw material is used in the production of polyaluminum chloride mainly depends on the production process and production conditions of the manufacturer.

Can PFS and PAC be used together


Polyferric sulfate and polyaluminum chloride are inorganic flocculants. Polyferric sulfate is a kind of high molecular iron flocculant widely used in recent years. Polyaluminum chloride is an aluminum coagulant. The flocculation effect of wastewater is good, which has the effect of removing phosphorus, deodorization, chemical oxygen demand and heavy metals. Then, if PFS and PAC are mixed in the process of chemical flocculation of wastewater, what kind of effect will be produced and whether the coagulation effect will be enhanced?

First of all, the basicity of PFS and PAC is not consistent. The basicity of PFS is relatively low. If the two are mixed, a neutralization reaction will occur. This will lead to the transfer of hydrolysis equilibrium. Most of the hydrolysis causes aluminum and iron to form jelly like hydroxides. Some metal salts that have not been hydrolyzed will also depolymerize. Metal salts will form ionic forms and lose their original polymerization. The flocculation effect can not be produced by continuous hydrolysis in wastewater.

Secondly, the mixing of PFS and PAC will lead to the change of basicity. This makes storage and transportation more difficult. In addition, the change of alkalinity will also affect the coagulation effect. The formation of hydroxide colloid between aluminum and iron will also affect the coagulation effect.

This is true of most of the above sewage. But in some specific sewage, PFS and PAC can be used together. They have the same effect and similar pH. The application of PFS and PAC in some sewage treatment plants in South China has achieved good results.

Whether poly ferric sulfate and polyaluminum chloride can be used together depends on the quality of sewage. Before use, it is necessary to do a small test, then a pilot test, and then test on the machine. Do not use directly on the machine, causing waste!