KR-102963981-B1 - METHOD FOR PREPARING POLYALUMINUM CHLORIDE WITH MEDIUM TO HIGH BASICITY

Abstract

The present invention relates to a method for producing high-pH polyaluminum chloride of excellent quality even at a low stirring speed by including a step of oxidizing a metal anode by performing electrolysis while stirring polyaluminum chloride and a basic compound.

Inventors

• 백민재
• 이병하
• 김영수

Assignees

• 케이지케미칼 주식회사

Dates

Publication Date

20260512

Application Date

20250729

Claims (8)

1. It includes a step of oxidizing a metal anode by performing electrolysis while stirring polyaluminum chloride and a basic compound, and The above stirring is performed at 5,000 rpm to 9,000 rpm, and A method for producing high pH polyaluminum chloride, wherein the above electrolysis is performed at a current density of 0.1 to 5.0 mA/cm² and a reaction time of 10 to 60 minutes.
2. A method for manufacturing high pH polyaluminum chloride according to claim 1, wherein the metal is aluminum, iron, or an alloy thereof.
3. A method for manufacturing high pH polyaluminum chloride according to claim 1, wherein metal ions dissolved from the metal anode through the electrolysis are combined with the polyaluminum chloride.
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5. A method for manufacturing high pH polyaluminum chloride according to claim 1, wherein the basic compound is one or more of sodium hydroxide, sodium carbonate, potassium carbonate, potassium hydroxide, rare earth hydroxide, and sodium aluminate.
6. A method for manufacturing high pH polyaluminum chloride according to claim 1, further comprising the step of reacting hydrochloric acid with aluminum hydroxide to produce the polyaluminum chloride.
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Description

Method for Preparing Polyaluminum Chloride with Medium to High Basicity The present invention relates to a method for manufacturing high pH polyaluminum chloride. Polyaluminum chloride (PAC) is an inorganic polymer coagulant widely used in water and sewage treatment and industrial wastewater treatment. Due to its superior coagulation performance and minimal pH fluctuation compared to conventional simple inorganic salt coagulants such as aluminum sulfate, its usage in the water treatment market is continuously increasing. Key factors determining the performance of polyaluminum chloride include basicity, Al₂O₃ content, and pH, and it is generally manufactured by dissolving aluminum hydroxide in hydrochloric acid via the acid dissolution method. However, currently commercialized polyaluminum chloride has several technical limitations. First, most products exhibit strong acidity with a pH of 3 to 5, requiring separate pH regulators at actual water treatment sites, which leads to increased operating costs and process complexity. Second, in existing manufacturing processes, high-speed stirring of 9,000 to 30,000 rpm is required to ensure sufficient reaction and uniform product quality. This requires significant energy consumption and increases equipment wear and maintenance costs. In addition, the shear force caused by high-speed stirring can destroy the polymer structure of polyaluminum chloride, which can adversely affect coagulation performance. Third, existing products exhibit relatively high turbidity and viscosity, making handling and storage difficult. High viscosity increases pump load and raises flow resistance within piping, leading to energy loss. Fourth, there are cases where a larger amount of coagulant must be added to achieve the same treatment effect because the aluminum ion concentration of the product is relatively low. Therefore, there is a need to develop new manufacturing technologies capable of ensuring excellent quality even at low stirring speeds, improving product turbidity and viscosity, and achieving high aluminum ion concentrations. Figures 1 to 3 show the results of evaluating the turbidity of the treated water according to the product treatment. The present invention will be described below. The present invention relates to a method for manufacturing high pH polyaluminum chloride. The method of the present invention includes the step of oxidizing a metal anode by performing electrolysis while stirring polyaluminum chloride and a basic compound. Polyaluminum chloride can be prepared through the reaction of hydrochloric acid and aluminum hydroxide. The reaction can be carried out, for example, at 120 to 135°C. The reaction time can be, for example, 2 to 7 hours. The reaction pressure can be, for example, 1 to 5 bar. After the reaction is complete, the solution can be cooled to 20 to 90°C and filtered to obtain a polyaluminum chloride solution. Basic compounds serve to regulate the pH of polyaluminum chloride. One or more of sodium hydroxide, sodium carbonate, potassium carbonate, potassium hydroxide, rare earth hydroxides, and sodium aluminate may be used as basic compounds. Sodium hydroxide can be used, for example, in the form of NaOH. Sodium carbonate can be used, for example, in the form of Na₂CO₃. Potassium carbonate can be used, for example, in the form of K₂CO₃. Potassium hydroxide can be used, for example, in the form of KOH. Rare earth hydroxides can be used, for example, lanthanum hydroxide (La(OH)₃), cerium hydroxide (Ce(OH)₃), neodymium hydroxide (Nd(OH)₃), etc. Sodium aluminate can be used, for example, in the form of NaAlO₂. These basic compounds can be used alone or in combination. Basic compounds are mixed with water and used in solution form. The metal may be aluminum, iron, or an alloy thereof. Aluminum with a purity of 99% or higher may be used. For iron, examples such as stainless steel or carbon steel may be used. For alloys, examples such as aluminum-magnesium alloy, aluminum-copper alloy, or iron-chromium alloy may be used. Through electrolysis, metal ions dissolved from the metal anode are combined with the polyaluminum chloride. During this process, the metal ions remain stable at a pH of 2 to 5, and then, as the metal anode is oxidized by electrolysis, multivalent metal ions are generated and combine with the polyaluminum chloride. Stirring is performed at 9,000 rpm or less. The stirring speed may be, for example, 1,000 to 9,000 rpm, 3,000 to 8,000 rpm, or 5,000 to 8,000 rpm. The stirring time may be, for example, 1 hour or more. Electrolysis is performed to generate multivalent metal ions by oxidizing a metal anode. As the aluminum anode is oxidized, Al³⁺ ions dissolve into the solution, which combine with polyaluminum chloride to form an improved product with high pH characteristics. Through electrolysis, excellent product quality can be secured even at low stirring speeds of 9,000 rpm or less. The electrolysis conditions can be set as follows. The current d