The respective pH range applicable to polyaluminum chloride and polyferric chloride

1. The suitable pH range for polyaluminum chloride is 5-9. 2. Ferric chloride polymerization produces large flocs during flocculation, with a fast flocculation rate; it results in low residues of iron and water after treatment, and it is suitable over a wide pH range (pH 4–11, with the optimal pH being 6–9)

Properties and Applications of Polyaluminum Chloride (I) Polyaluminum chloride, abbreviated as PAC, is an inorganic polymer coagulant. It is a compound that lies between AlCl3 and Al(OH)3, and it polymerizes through hydroxyl group bridging. Its chemical formula is m. (In the formula, 1≤n≤5, m≤10.) ) (II) Coagulation characteristics and properties 1. Polyaluminum chloride is an inorganic polymer coagulant; it is an inorganic polymer water treatment agent with a high molecular weight and high charge, formed through the bridging action of hydroxide ions and the polymerization of polyvalent anions. 2. The water quality after purification is superior to that achieved with inorganic coagulants such as ferric chloride and aluminum sulfate, and the cost of water purification is relatively low. 3. It forms flocs rapidly and settles quickly, offering a higher treatment capacity compared to traditional coagulants such as ferric chloride and aluminum sulfate.  4. Adaptability to source water temperature, turbidity, alkalinity, etc., due to traditional coagulants such as ferric trichloride and aluminum sulfate. 5. The source water for adaptation has a wide pH range; flocculation can occur within the pH range of 5.0–9.0, with the best results achieved at pH 6.5–7.5. 6. Low corrosivity and favorable operating conditions. 7. Its solubility is better than that of ferric trichloride and aluminum sulfate.  8. The treated water contains low levels of residual aluminum and salts, which is beneficial for ion exchange treatment and preparation. (III) Product Features 1. No additional additives are required; the flocs form quickly and are large in size, with high activity and rapid precipitation. Therefore, its purification effect on water with high turbidity is particularly significant. 　 2. It has a wide range of pH tolerance; it can lower the pH value of raw water, thus causing no corrosion to pipeline equipment. 　　 3. Strong decolorizing and cleaning power. The water purification efficiency is 4–6 times that of Al2(SO4)3, and 3–5 times that of AlCl3. Low dosage, high efficacy ； Low cost, high efficiency. (IV) Uses 1. Purification of rivers, reservoirs, and groundwater for urban water supply.  2. Purification of industrial feed water and industrial circulating water.  3. Purification of polluted urban water.  4. Water purification for industrial dyeing and printing, papermaking, sugar production, leather processing, brewing, meat processing, coal washing, metallurgy, ore washing, pharmaceuticals, etc., as well as the purification of wastewater containing fluorine, oil, and heavy metals. 5. Recovery of coal powder from industrial coal washing wastewater, and recovery of kaolin from the ceramic manufacturing industry.  6. Refining of pharmaceuticals, refining of glycerin, refining of sugar solutions. 7. Rapid setting of cement, casting for shaping.  8. Tanning leather, preventing wrinkles in fabrics. 9. Cosmetic raw materials. 10. Catalyst carrier.  11. Paper sizing.     Properties of ferric chloride: 1. Polyferric chloride is an inorganic polymer; it is formed by combining polyaluminum chloride with polymeric iron, which increases the molecular structure and enhances its capabilities for electrical neutralization, adsorption and bridging, as well as sedimentation. It is an ideal chemical for treating source water with severe organic pollution, as well as source water with low temperature and low turbidity or low temperature and high turbidity. II. Physical and chemical properties: It appears as a yellow-brown, dark brown, or black transparent liquid or solid. III. Applications: Used as a flocculant, it can be employed to treat deinking water and pulping water from paper mills, as well as wastewater from the printing and dyeing industry. The dosage and other flocculation conditions are determined through experiments. IV. Product Performance 1. It combines the advantages of aluminum salts and iron salts in coagulation: it can rapidly form flocs, with tight floccules and a fast settling speed.  2. Suitable for source water at various temperatures, with good solubility. 3. The dosage required is lower compared to other aluminum-based water purification agents, which is more conducive to improving water quality.  4. Capable of adapting to automated alum addition systems. 5. The suitable range for the pH value is 6–9, with the optimal range being 8–9. V. Usage methods and precautions: 1. Liquid products can be added directly or after dilution; solid products should be dissolved in water before addition. The typical dilution ratio is: 2%–20% for solid products, and 5%–50% for liquid products (on a weight percentage basis). 2. The dosage of the chemical agent is generally as follows: 3–40 grams per ton for liquid products, and 1–15 grams per ton for solid products. The specific dosage should be determined by the user based on mixing tests and production trials.   This post was last edited by cdpulin on 2009-3-13 12:01]

It just seems that if chemicals are added through the pipes, the coagulation process is too slow.

Iron salts do not precipitate under acidic conditions; generally, the optimal precipitation conditions for iron salts are at pH 8-9. You can find this out by conducting some experiments.

The optimal range should be determined through experimentation, but polyaluminum ferric chloride does indeed have a wider applicable range than polyaluminum chloride in terms of pH.

The parallel experiments with beakers were completed in just one day, and the optimal ratios were also determined at the same time.