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<p>In response to the limitations of the traditional acid leaching process in terms of environmental impact and safety, this study developed a ternary mixed acid system (hydrochloric acid - oxalic acid - citric acid) without the use of hydrofluoric acid and nitric acid. The influence of three process parameters, namely, the concentration of the mixed acids, the liquid-solid ratio, the acid leaching temperature, and the acid leaching time, on the removal efficiency of impurities such as Fe, Mn, Al, K, and Na in quartz sand was systematically investigated. The experimental results revealed that the optimal acid leaching conditions were a hydrochloric acid concentration of 4.5&#xa0;mol·L<sup>− 1</sup>, an oxalic acid concentration of 0.03&#xa0;mol·L<sup>− 1</sup>, a citric acid concentration of 0.04&#xa0;mol·L<sup>− 1</sup>, a liquid-solid ratio (mass ratio) of 5:1, a constant temperature of 60 ℃, and a holding time of 3&#xa0;h. Under these conditions, the removal rates of Fe, Mn, and Al reached 89.2%, 71.0%, and 60.1%, respectively. Moreover, K and Na were also removed to a certain extent, with removal rates of 39.6% and 25.5%, respectively. Mechanistic analysis revealed that in the ternary mixed acid system, hydrochloric acid provides an acidic environment, and the combination of oxalic acid and citric acid synergistically promotes the dissolution of impurities through complexation, reducing impurities on the surface of quartz sand, improving the cleanliness, and forming micro-porous structures. Compared with the traditional hydrogen fluoride-nitric acid leaching process, the fluorine-free ternary mixed acid system proposed in this study has a similar or even better removal efficiency for impurities such as Fe and avoids the environmental and safety risks associated with hydrogen fluoride. This system can achieve the simultaneous removal of various impurities in quartz sand under normal pressure and medium-low-temperature conditions, providing a new technical path for the development of quartz sand purification technology for safety and environmental protection.</p>

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Removal Mechanism of Fe-Al-Na-K-Mn Impurities in Quartz Sand by Hydrochloric Acid-Oxalic Acid-Citric Acid Ternary Mixed Acids

  • 期刊论文

  • 发表日期：

    2026年5月4日

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  • Guangdong Wang,
  • Ziyang Bai,
  • Maohui Li,
  • Xishan Mao,
  • Jie Yu,
  • Chang Su,
  • Wenwen Hu,
  • Bo Ma,
  • Wenzhou Sun,
  • Youjun Lu

摘要

In response to the limitations of the traditional acid leaching process in terms of environmental impact and safety, this study developed a ternary mixed acid system (hydrochloric acid - oxalic acid - citric acid) without the use of hydrofluoric acid and nitric acid. The influence of three process parameters, namely, the concentration of the mixed acids, the liquid-solid ratio, the acid leaching temperature, and the acid leaching time, on the removal efficiency of impurities such as Fe, Mn, Al, K, and Na in quartz sand was systematically investigated. The experimental results revealed that the optimal acid leaching conditions were a hydrochloric acid concentration of 4.5 mol·L− 1, an oxalic acid concentration of 0.03 mol·L− 1, a citric acid concentration of 0.04 mol·L− 1, a liquid-solid ratio (mass ratio) of 5:1, a constant temperature of 60 ℃, and a holding time of 3 h. Under these conditions, the removal rates of Fe, Mn, and Al reached 89.2%, 71.0%, and 60.1%, respectively. Moreover, K and Na were also removed to a certain extent, with removal rates of 39.6% and 25.5%, respectively. Mechanistic analysis revealed that in the ternary mixed acid system, hydrochloric acid provides an acidic environment, and the combination of oxalic acid and citric acid synergistically promotes the dissolution of impurities through complexation, reducing impurities on the surface of quartz sand, improving the cleanliness, and forming micro-porous structures. Compared with the traditional hydrogen fluoride-nitric acid leaching process, the fluorine-free ternary mixed acid system proposed in this study has a similar or even better removal efficiency for impurities such as Fe and avoids the environmental and safety risks associated with hydrogen fluoride. This system can achieve the simultaneous removal of various impurities in quartz sand under normal pressure and medium-low-temperature conditions, providing a new technical path for the development of quartz sand purification technology for safety and environmental protection.