Nitric Acid Leaching for Magnesium Extraction from Asbestos Ore Waste: From DoE to Predictive Modeling and Cost-Efficient Optimization

Our plain-English summary of Nitric Acid Leaching for Magnesium Extraction from Asbestos Ore Waste: From DoE to Predictive Modeling and Cost-Efficient Optimization, by N.S. Ivanov, O.S. Kholkin, A.Z. Abilmagzhanov, et al (Molecules, 2025).

The study

• Authors: N.S. Ivanov, O.S. Kholkin, A.Z. Abilmagzhanov, I.E. Adelbayev, S.K. Oparin, N. Ivanova, V. Kudryashov
• Journal: Molecules
• Published: 2025;30(22)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Kazakhstan's asbestos industry produces over 3 million tons of waste annually. The primary component of asbestos ore waste (AOW) is magnesium rich minerals. In this study, the extraction of magnesium from AOW with nitric acid (HNO3) was for the first time systematically studied. A series of experiments were conducted to optimize acid concentration (300-600 g/L), leaching temperature (55-95 °C), leaching time (60-180 min), solid-to-liquid ratio (1:3-1:7), and particle size, with the overall goal of maximizing magnesium extraction and cost efficiency. Our results provide dependence of magnesium extraction in the order of acid concentration > temperature > time > solid-to-liquid ratio, while particle size was found to be negligible. The cost-efficiency optimization demonstrated the positive impact of the relatively low acid concentrations (< 450 g/L) and temperatures between 65 and 85 °C, while the Protodyakonov model validated a linear dependence of the extraction rate on temperature and acid concentration. Our model demonstrates that extraction efficiencies of up to 90% can be achieved while reducing reagent use and lowering the overall cost of magnesium production. Leaching of magnesium by HNO3 also opens a pathway to a closed-cycle process, due to the formation of magnesium nitrate. The thermal decomposition of Mg(NO3)2 provides valuable products such as MgO and NO2 reused in HNO3 regeneration for subsequent cycles. The proposed model predicts magnesium extraction from asbestos ore depending on leaching parameters with reasonable accuracy.

In plain English

This was a laboratory chemistry study, not a health study. The authors tested whether nitric acid could dissolve magnesium out of asbestos ore waste, mainly chrysotile (85%), from Zhitikara, Kazakhstan. In 25 experiments on 15 g samples, they varied acid concentration (300 to 600 g/L), temperature (55 to 95 degrees Celsius), time (60 to 180 minutes), liquid-to-solid ratio and particle size. Acid concentration had the strongest effect, followed by temperature, time and the solid-to-liquid ratio. Particle size made little difference, with extraction ranging from 79.28 to 81.94%. The text gave 90.46% as the maximum extraction, reached after three hours, but its data table listed single runs of 98.70% and 100.42%. The model fitted the data it was built from with an R2 of 0.976. In five-fold cross-validation, the average R2 was 0.732 plus or minus 0.221. The leftover solid was mainly quartz with traces of magnetite. The authors concluded that nitric acid is a stable and effective leaching agent, with recovery of up to 90% at around 450 g/L and 65 to 85 degrees Celsius.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment (planned design of experiments using a Latin square, with mathematical modeling and cost estimation); no human or animal subjects
• Who was studied: A sample of asbestos ore waste (mainly chrysotile, 85%) from Kostanay Minerals JSC, Zhitikara, Kazakhstan; 15 g per experiment, 25 experiments
• Exposure: Leaching of the waste with nitric acid at 300 to 600 g/L, 55 to 95 degrees Celsius, 60 to 180 minutes, liquid-to-solid ratios of 3:1 to 7:1, and particle sizes from 71 to 1250 micrometres (per the experiment matrix)
• Main results:
  • Acid concentration had the strongest effect on magnesium extraction, followed by temperature, leaching time, and the solid-to-liquid ratio
  • Across the acid concentration range studied, extraction rose linearly from 75.92 to 85.96%
  • Raising the temperature increased extraction to about 63% higher than at 55 degrees Celsius
  • The text reported a maximum extraction of 90.46% after three hours. This is a figure for leaching time, not the highest single run.
  • In the data table, individual runs reached higher extractions: 98.70% in experiment 4 (180 minutes) and 100.42% in experiment 8 (150 minutes); the latter exceeds 100%
  • Particle size from 0.071 to 1.25 mm gave extraction between 79.28 and 81.94%, which the authors judged a negligible effect
  • At liquid-to-solid ratios of 5:1, 6:1 and 7:1, extraction reached a maximum of approximately 82%
  • On the training data, the regression model had an R2 of 0.976 and an RMSE of 2.57 percentage points
  • In five-fold cross-validation, the model's average R2 was 0.732 plus or minus 0.221, and its RMSE was 6.83 plus or minus 2.25 percentage points
  • In the cost-efficiency analysis, the best results fell at acid concentrations below 500 g/L and temperatures of 65 to 85 degrees Celsius
  • The solid left after leaching consisted mainly of quartz with trace amounts of magnetite
• The authors' conclusion: The authors concluded that nitric acid is a stable and effective leaching agent for extracting magnesium from waste asbestos ore. They suggested optimal conditions of around 450 g/L acid and 65 to 85 degrees Celsius, under which recovery can reach up to 90%.
• Limitations the authors state:
  • The cost model did not include the degradation of nitric acid at higher concentrations
  • The largest model error (9.44 points, in experiment 24) may reflect local mass-transfer limitations or small experimental imperfections near the edge of the studied range, which a polynomial model describes poorly
  • Concentrated nitric acid can produce NO2 in contact with minerals, which increases corrosion and generates hazardous gases

Related studies

• Leaching behaviour of hazardous demolition waste — N. Roussat, J. Méhu, et al. (2008)
• The Chick Embryo Xenograft Model for Malignant Pleural Mesothelioma: A Cost and Time Efficient 3Rs Model for Drug Target Evaluation — S.E. Barnett, A. Herrmann, et al. (2022)
• Efficient Management of Asbestos Waste Through Utilization as Mineral Additives in Portland Cement Production — K. Durczak, M. Pyzalski, et al. (2024)
• Acid leaching studies of chrysotile asbestos from mines in the Coalinga region of California and from Quebec and British Columbia — A. Morgan (1997)
• Acid leaching studies of neutron-irradiated chyrsotile asbestos — A. Morgan, R.J. Talbot (1997)
• Flocking asbestos waste, an iron and magnesium source for Pseudomonas — S.R. David, S. Fritsch, et al. (2020)

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