Turning waste into treasure
The Bruce Logan team's approach is based on a previous set of air cathode microbial fuel cell (MFC) test equipment. The device is separated by a proton exchange membrane into a cathode chamber and an anode chamber. The anode chamber contains ferrous sulfate, and the ferrous iron is oxidized to ferric iron by hydrolysis, and electrons are released to form iron hydroxide precipitate to remove iron from the water. In the cathode chamber, protons and oxygen combine to form water, which consumes electrons. Since the action of the proton exchange membrane only allows the passage of protons and hinders the passage of electrons, most of the electrons generated in the anode chamber are transferred to the cathode through the anode through the external circuit to participate in the reaction, thereby forming a current.
The entire experiment was carried out at 30 °C. Logan's experiments show that the device produces a maximum electrical work density of 290 mW/m2, and the coulombic efficiency (current magnitude/theoretical current magnitude) is greater than 97%. The ferrous ions are oxidized to ferric iron precipitated in the anode cell and anode. Was completely removed. The pH of the solution and the concentration of ferrous ions are all factors affecting the electrical energy. The ideal operating conditions obtained by the research team are: pH 6.3. Professor for many years engaged in the study of acid mine water of China University of Mining (Beijing) Zhao Fenghua said: "The use of acid mine water in the fuel cell can not only remove and recycle the metal in acid mine water, but the technology can also produce electricity for the coal mine. Or acid mine water treatment in metal ore provides a potential new approach."
Wastewater is very harmful
Acid mine wastewater is a mine wastewater with a pH of less than 6.5 produced by the oxidation of mineral deposits containing sulfide minerals during the mining process. The pH is generally 3.0-6.5 and the total acidity is high.
Zhao Fenghua said that China's acid mine water is mainly distributed in metal mines and coal mines that produce sulfide minerals. About 10% of the total mine water is acidic water.
Acid mine water not only corrodes downhole drainage equipment and other mining equipment, but also causes economic losses and affects the health of underground workers. The concentration of certain heavy metal ions in acid mine water increases with acidity, and the toxicity increases, potentially harmful to organisms. According to reports, containing high concentrations of acid mine drainage Dexing copper mine of iron, aluminum, copper and other metals, after discharged into the nearby large dock River and Le'an River, leading to the river water quality deterioration of the aquatic ecological environment has been seriously polluted. Due to the increase of heavy metal ions in Dawuxi, the river water is brown, the fish and shrimp are extinct, and eventually become the wastewater ditch. At the same time, when using untreated acid mine water for irrigation, it can destroy the agglomerate structure of the soil and affect crop yield. Therefore, acid mine water must be treated before it can be discharged.
Processing methods have drawbacks
At present, the treatment technology of acid mine water mainly includes limestone , lime neutralization method, biochemical method and wetland ecological engineering treatment method. Among them, the lime neutralization method is a commonly used method for treating acidic water in coal mines. Its main advantages are simple process, convenient operation, pH value of effluent can reach discharge standard, high iron removal efficiency, but it is easy to produce a large amount of solid waste of calcium sulfate. , causing secondary pollution.
Wetland method has the advantages of low investment, low operating cost, easy management and strong ability to adsorb and remove organic matter, but it has a large area, and the treatment of hydrogen sulfide is not complete, resulting in air pollution. Microbial treatment of mine acid waste water has low cost. It has strong applicability and can recover the shortage of raw materials such as sulfur. However, they are still in the laboratory stage and have not been put into practical use in China. This is because the processing speed of the biochemical treatment method is much slower than the physicalization method, so the volume of the reactor is correspondingly increased, so that the investment is increased; in addition, there is also the problem of the adaptation of microorganisms to the water component of the complex coal mine acid mine.
The future has a long way to go
Zhao Fenghua said: "At present, acid mine water treatment is difficult and costly, and it is urgent to develop a high-tech treatment method. Fuel cell power generation technology using acid mine water is undoubtedly a promising new technology for acid mine water treatment."
Tao Huchun, a postdoctoral fellow at the School of Environment and City, Peking University Shenzhen Graduate School, said: "At present, there are scholars in China who are conducting research on fuel cell technology, hoping to combine pollution removal with energy regeneration."
Zhao Fenghua said: "The technology still needs a lot of research work, because the equipment developed by Bruce Logan uses synthetic 'acid mine water', which is very different from the actual acid mine water. In recent years, although some scholars in China have studied microbial fuel cells in recent years, research on the use of acid mine water for fuel cell power generation has not been carried out. I hope to strengthen this research in the future, focusing on the chemical characteristics of acid mines. Fuel cell structure and scale, electrode materials, etc."
Espresso Grinder,Rancilio Grinder,Automatic Grinding Machine,Electric Coffee Bean Milling
Heshan Zilong Home Appliance Technology CO.Ltd , https://www.techonele.com