This study investigates and compares the use of raw kaolinite and kaolinite modified with sodium benzene dodecyl sulfonate in removing water hardness. To prepare modified kaolinite, first wash raw kaolinite three times with distilled water to remove surface contaminants and then dry it in a ceramic pot for 5 hours at 100 °C and 2 grams of kaolinite are extracted. Weigh on a precision balance and add 200 ml of sodium dodecyl benzene sulfonate solution with a concentration of 4 mmol/L and stir by magnetic stirrer for 90 minutes to absorb sodium dodecyl benzene sulfonate by calcium phosphate. The kaolinite precipitate is obtained and the supernatant is discarded. The precipitate is dried in an oven and the bonding between kaolinite and sodium dodecyl benzene sulfonate is examined by titration with sodium hydroxide, and finally the resulting particles are examined by XRD. Then, synthetic solutions of calcium carbonate and magnesium carbonate will be prepared as hard water samples at concentrations of 100, 200 and 500 mg/L and with a volume of 500 mL in three 1-L reactors, followed by raw and modified kaolinite adsorbents. was used to determine the removal rate of these carbonates. . The results obtained indicate the removal of water hardness (calcium carbonate and magnesium carbonate) at concentrations of 100, 200 and 500 by both raw kaolin and kaolin dodecyl benzene sulfonate at concentrations of 0.3, 1 and 2 mg per liter. The dodecyl benzene sulfanate type has the highest hardness absorption.
Introduction

Water hardness and water-soluble solids lead to corrosion or sedimentation in water distribution pipes, which in addition to creating heavy economic costs leads to numerous health problems and user dissatisfaction and water wastage. Studies also show that water hardness affects cardiovascular mortality, growth retardation, reproductive failure and other health problems. Among the types of clay soils, kaolin has a high potential in removing pollutants from the aquatic environment. Kaolinite is the most important mineral component of kaolin, which has received great attention as an adsorbent due to its high adsorption capacity, large specific surface area and good physical and chemical stability. will bring. Several studies have been conducted on the removal of water hardness by natural kaolinite or kaolinite modified with hydrochloric acid and sodium, but no study has been conducted on the removal of water hardness by kaolinite modified with sodium benzene dodecyl sulfonate. This is therefore addressed in this study.

Materials and methods
First, the modified kaolinite was prepared with the help of sodium dodecylbenzene sulfonate and raw kaolinite, and then a solution consisting of calcium carbonate and magnesium carbonate in a volume of 500 mL with three concentrations of 100, 200 and 500 mg/liter was prepared in three volumes of 1 liter. Then, raw and modified kaolinite with 3 different doses will be added to the solution and stirred at 150 rpm. Every 15 minutes, 20 ml of sample will be taken from the solution and the hardness of calcium and magnesium will be examined by titration. became. Finally, the results were analyzed.

Results and discussion
Initially, kaolinite modified with sodium dodecylbenzene sulfonate was prepared. Then, synthetic solutions of calcium carbonate and magnesium carbonate were prepared as hard water samples. In the third step, the titration of the solutions was carried out, and then. Calcium and magnesium hardness measurements were performed. To determine the calcium removal rate, a synthetic calcium carbonate solution was first prepared as a hard water sample containing calcium carbonate and magnesium carbonate with concentrations of 100, 200 and 500 mg/L and a volume of 500 mL in three 1-L reactors. The dose of sodium dodecyl benzene sulfonate-modified absorbent is 30 mg, 1 g and 2 g. All the above steps were performed on magnesium and calcium 100, 200, 500 samples in order to compare the absorption rate of calcium ions by the two types of kaolinite.

Conclusion
Based on the results of the analyzes obtained from the laboratory samples of the removal of water hardness (calcium carbonate and magnesium) by raw kaolin and kaolin dodecyl benzene sulfonate, it can be acknowledged that both kaolin show very good performance in hardness removal and between the two kaolin Kaolin of the dodecylbenzene type shows a much higher efficiency in removing both magnesium and calcium hardness. This removal is much higher at high kaolin concentrations. Thus, at a concentration of 1 mg per liter of kaolin, the hardness removal rate is higher than at a concentration of 0.3 mg per liter and hardness removal at a concentration of 2 mg per liter is higher than the other two concentrations.

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