Hydrochloric acid purification iron-removing resin, hydrochloric acid decolorization adsorption resin

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Industrial hydrochloric acid is generally produced by burning chlorine and hydrogen in a synthesis furnace to generate hydrogen chloride gas, which is then absorbed by water. The temperature in the furnace is very high; chlorine comes into contact with the furnace walls made of steel and reacts, resulting in hydrogen chloride gas that contains iron trichloride vapor ； This gas also introduces impurities such as iron during pipeline transportation, and the presence of iron causes hydrochloric acid to turn yellow. The iron content in hydrochloric acid reagent is subject to strict **standards**, which is why iron removal from hydrochloric acid is of great importance in its production. Reagent-grade hydrochloric acid is generally produced by evaporating hydrogen chloride gas in a glass reactor using industrial hydrochloric acid as raw material, or by directly purifying and removing impurities from hydrogen chloride gas generated in a synthesis furnace. The use of A-21S ion exchange resin for iron removal offers advantages such as high efficiency in removing iron, low operating costs, minimal equipment investment, and simple operation, resulting in successful performance in industrial installations. This process can be used in the industrial production of pure hydrochloric acid with low iron content as well as reagent-grade hydrochloric acid, with the iron content meeting the standards for analytically pure reagents. I. Principle of iron removal using A-21S resin ion exchange technology: In concentrated hydrochloric acid, metal ions exist mainly in the form of complexed anions. A-21S ion exchange resin can effectively remove iron ions from concentrated hydrochloric acid, and it can also remove other metal ions to varying degrees. 1. When concentrated hydrochloric acid containing impurities passes through special ion exchange resins, the exchange process can be illustrated using iron as an example as follows: 2. Once the A-21S ion exchange resin becomes saturated with iron ions, it can be regenerated using deionized water (distilled water); due to the decrease in hydrochloric acid concentration, the following regeneration process takes place: 3. After regeneration, the ion exchange resin returns to its original state, allowing it to undergo exchange and regeneration processes repeatedly. Technical support: 15271938854; same as WeChat. II. Pilot plant and process flow: The pilot plant can employ a fixed-bed ion exchange production process; the process flow is shown in the diagram. Process equipment: The materials used for the equipment can be high-quality polyvinyl chloride, polyethylene, and other materials resistant to hydrochloric acid corrosion, while pipes and valves can be made of polyvinyl chloride or glass. 1. Test sample: A-21S resin ； 2. Precautions for ion exchange column testing: · Determine the specific volume of the resin and select an appropriate exchange column ； ·Appropriate backwashing should be carried out before operation ； ·Consider the resin’s condition and environment in accordance with the test requirements ； ·The height of the resin bed should be between 1000mm and 1200mm ； ·The sump should be at least 2000 mm above the exchange column to achieve the desired flow rate ； ·The water from the resin column flows directly into a container with volume markers ； ·The workflow speed should be carefully considered, with attention paid to the research on the effluent ； ·Regularly analyze the sampled samples to plot graphs and fill in the appropriate record sheets ； ·The incoming water should not be turbid and should contain no visible particles. Regeneration mechanism: After the A-21S anion exchange resin becomes saturated with adsorbed substances, it can be eluted using deionized water to remove the iron ions; this causes the resin to revert to its original composition, thereby achieving regeneration. III. Use of ion exchange resins: The iron removal process using ion exchange requires low investment and a simple operational procedure; it enables the impurity level of hydrochloric acid (in terms of iron content) to be reduced from the ppm range to the ppb range. Resin treatment: This process uses the imported resin brand Tulsimer® A-21S, a special ion exchange resin. Resin is generally of the chlorinated type upon leaving the factory; before use, it must be soaked and rinsed with deionized water to remove mechanical impurities and suspended particles. Column filling: Fill the exchange column with the treated resin and water together (the valve at the bottom of the column should be closed), up to the specified height; care should be taken during filling to avoid the inclusion of bubbles. During column loading, adjust the waste liquid discharge valve so that the liquid level is 5 cm above the resin layer. Iron removal by exchange: Pump the hydrochloric acid to be treated into the resin column, open the acid inlet valve and the acid outlet valve, close all other valves, adjust the opening degree of the acid outlet valve to control the flow rate at 5–10 BV per hour (where BV refers to the volume multiple of the resin bed). When acid production begins, its concentration is low; it then gradually increases. The acid concentration is continuously measured using a hydrometer, and once it reaches the specified level, the acid is ready for packaging as the finished product. Weak acids that do not meet the concentration requirements should be stored separately for reuse as hydrogen chloride absorption solution. During the exchange process, samples should be taken periodically to analyze the iron content in hydrochloric acid; if the iron content exceeds the specified standard, the exchange process must be stopped and resin regeneration should be carried out. Regeneration: The resin is washed with deionized water in a counter-current manner, with a flow rate of 4 BV per hour. The effluent is a waste liquid containing large amounts of ferric trichloride, which requires separate treatment. During rinsing, it is necessary to continuously check the iron content in the flowing liquid, and rinsing is completed once no iron is detected. At this point, the resin regeneration process is complete, and the exchange process can be resumed. IV. Precautions (1) The acid concentration used for treatment should be ≥31%, with a minimum of 28% ； (2) This process is physical adsorption at low temperatures, with the hydrochloric acid temperature ranging between 20 and 30 ； (3) Operating time is related to the iron content of the raw material. The appropriate operating cycle is determined through calculation and practice to ensure that the treated iron-containing hydrochloric acid meets the required standards ； (4) After the resin is put into use, attention should be paid to the continuous operation of the equipment; if it stops operating for a long time, cleaning and regeneration are required.