The environmental problem of acid mine waters
Acidic mine waters remain one of the most acute environmental problems of mining regions worldwide. After the closure of coal mines, dangerous runoff continues to surface for 50-100 years, polluting the soil, groundwater and rivers. These aggressive solutions contain high concentrations of sulfuric acid and dangerous metals such as iron, aluminum, nickel and cadmium.
Lithium, which belongs to the 2nd hazard class (highly hazardous substances), is particularly difficult. Traditional methods of mine water treatment are not able to completely remove it from the drain, while requiring significant financial and material costs. As a result, the content of pollutants can exceed the maximum permissible concentration many times over. For example, the level of iron in acid mine waters sometimes reaches 16 thousand MPC.
History and causes of the problem
The global closure of coal mines began at the end of the 20th century due to depletion of deposits, economic crises and the transition to oil and gas. In Russia, this problem has particularly affected old coal basins, including the Kizel basin, where improper liquidation of enterprises has led to extensive environmental pollution.
The main cause of pollution is flooding of abandoned mines. Water passing through coal seams and pyrite layers is saturated with sulfuric acid and various metals, turning into a highly toxic solution. Restoration of affected ecosystems may take at least 30 years.
Innovative technology of Perm Polytechnic University
Scientists at Perm National Research Polytechnic University (PNRPU) have developed a fundamentally new approach to acid mine water treatment. The technology has received a patent and allows not only to safely neutralize dangerous drains, but also to extract valuable materials from them for industrial and agricultural use.
The principle of operation of the method consists of two stages:
At the first stage, the base metals are removed by adding a small amount (1-2% by volume) of a 10% aqueous ammonia solution. In 2-3 minutes, a reaction occurs: metal ions interact with ammonia and form insoluble hydroxides, which precipitate out safely. After settling, this sediment can be used in industry to extract valuable iron and aluminum compounds.
At the second stage, only ammonium sulfate and lithium hydroxide remain in the drain. Ammonium carbonate is used to neutralize lithium, which converts a dangerous element into lithium carbonate, a harmless precipitate.
“At the first stage, we get rid of the base metals by adding a small amount (1-2% of the total volume) of 10% aqueous ammonia solution to the toxic runoff. At this concentration, a reaction occurs in just 2-3 minutes: metal ions interact with ammonia and precipitate out as insoluble hydroxides, a safe precipitate. Then we separate it from the water in a special sump, and in the future it can be used in industry to extract valuable compounds, for example, iron or aluminum,” explains Olga Ruchkinova, Head of the Department of Heat and Gas Supply, Ventilation and Water Supply, Sanitation, PNRPU, Doctor of Technical Sciences.
Practical results and scope of application
The research was conducted using the example of acid mine waters from the Kizel coal basin. Experimentally, scientists have established optimal concentrations of reagents: 15-20 ml of 10% ammonia solution per 1 liter of water provides complete purification in 2 minutes.
The resulting products turned out to be multifunctional. The metal-containing concentrate is used in industry for the production of various materials. Lithium carbonate in dry form is used to coat the combustion chambers of rocket engines, manufacture porcelain, enamel, glazes and primers.
An alternative option is to leave lithium in purified water together with ammonium sulfate to form a ready-made ammonium-lithium fertilizer. This fertilizer effectively improves the mineral nutrition of plants in agriculture.
Advantages over existing methods
The new mine water treatment technology differs significantly from its existing counterparts in several key characteristics:
— Versatility: removes heavy and light metals at the same time
— Effectiveness: transfers substances from hazard class 2 to class 4-5 (harmless)
— Simplicity: does not require expensive reagents or complex equipment
— Cost-effective: allows you to extract valuable materials that compensate for costs
— Flexibility: adapts to both stationary sewage treatment plants and water treatment in mine channels
Implementation prospects and importance for the region
Perm Polytech’s development offers a comprehensive solution to the acute environmental problems of the mining regions of Russia and the world. The method makes it possible to transform abandoned mines from sources of danger into resource centers, while simultaneously restoring damaged ecosystems.
The introduction of this technology opens up new opportunities for:
— Removal of accumulated environmental damage in regions with closed coal mines
— Obtaining valuable materials for industry and agriculture
— Reducing the environmental impact on soil and water resources
— Creation of a cost-effective hazardous waste recycling system
A patent for the innovative technology has already been obtained, which indicates that the method is ready for practical use. Perm Polytechnic University’s scientific breakthrough demonstrates how modern research can solve large-scale environmental problems, turning a threat into an opportunity for sustainable development.