Mineral Wastes are Revalued, Economy Gains. Mineral wastes are formed in large quantities in two main parts, from the extraction of the mine to the stage of becoming a market product. The first of these is the waste rocks that are largely formed during the extraction of the mine, especially if open pit mining is carried out. The second one occurs during the enrichment, that is, the ore preparation processes. In addition, many wastes such as metallurgical wastes, quarry wastes, thermal power plant wastes are also included in the mineral waste group in many classifications.
Waste materials of mineral origin have different properties according to their origin and the processes they have undergone, and they are sometimes also called by special names. E.g; The wastes generated as a result of metal production in the metallurgical smelting facility are known as slag, and the wastes generated as a result of obtaining energy from coal in the thermal power plant are known as fly ash. Again, the part taken as a cover layer in a mineral deposit is generally a less harmful waste due to its larger size and environmentally inert structure, while the ore preparation facility wastes are of finer size and waste due to both the chemicals used in the process and the finer minerals it contains. It can be a more harmful waste than rocks. The biggest difference of mineral wastes compared to other industrial wastes is that they are too much and natural material.
In the world where environmental awareness is increasing day by day, and in our country, the disposal of these wastes is an important issue. contain or be removed due to leaching or various flotation chemicals such as acid, cyanide used in enrichment processes. In general, mineral wastes are removed with three main options:
• Safe storage,
• Recovery of valuable minerals,
• Use of residues in other areas.
Landfilling is the most commonly used method for the removal of mining or mineral wastes. In these storage processes, which require very large areas, safety, that is, not causing soil, water and air pollution, is an important issue. Waste is generally used for new uses.
It can be kept in waste fields or pools for many years until it is found or as long as mining activities continue. While arranging the waste sites and dams, the climatic conditions of the area where the landfill will be stored and the risks of natural disasters such as earthquakes and floods should be taken into account in order to prevent major accidents, examples of which have happened in the past, from occurring. In modern applications, it is required to prepare projects for the stockpiling of wastes before a mineral deposit starts to operate.
Recovery of Precious Minerals:
The economically exploitable grades of ores are constantly being reduced due to both technological developments and the increasing need for raw materials. Thus, many heaps stored as waste can be accepted as ore deposits in terms of the values they contain today. Many studies in the world and in Turkey reveal that valuable minerals can be recovered from wastes.
For example: As a result of the chrome mining that has been going on for years in Turkey, wastes that can be considered as new mineral reserves today have been formed and are kept in waste sites. Chromite wastes mostly occur as a result of enrichment of chromite by gravity methods after size reduction in facilities. Studies show that these wastes, whose contents vary between 9-20% Cr2O3, can be re-enriched using both new and traditional methods and new products can be sold. Boron wastes remaining from the production of boron concentrates, which is one of the most important mineral resources of Turkey, are spread over very large areas and kept. Successful results have been obtained as a result of many researches on the recovery of boron from boron wastes.
Shen and Forssberg classify metallurgical wastes in three groups as ferrous, non-ferrous and wastes from combustion processes and give extensive information about metal recovery from these slags by chemical and physical means. There are many examples of recovering precious metals from waste, but a few examples can be given in this article.
Use of Waste in Other Areas:
The use of mineral wastes as raw material input in other industries and fields by passing through various processes is one of the important issues that have been studied in recent years. Instead of gaining certain values from the residue, using all or a large part of the residue provides a great advantage in terms of both economy and environment. It is stated in the studies that the wastes used can replace many raw materials and sometimes even provide superior properties in the area where they are used. It is useful to determine some data about the waste before bringing the waste into the economy as raw material. These can be listed as follows;
Determination of Waste Amount
Determination of physical and chemical properties of waste. Determining in which field it can be used as a raw material according to these properties. Investigation of market possibilities of products obtained from waste. Determining the technical and economic problems that may be encountered in converting the waste material into a salable product. The most common method used in the disposal of waste is to use it as a filling material. Filling the voids formed after production in underground mines, dam filling, creation of landfills, and their use as road filling material are quite common. Research on the use of wastes as construction materials is also very common. Many waste materials such as marble wastes, boron wastes, process wastes in aluminum production, red mud, feldspar wastes are used in the production of materials such as cement, brick, tile, ceramic, glass and concrete. The cement sector is one of the most important areas in the evaluation of waste. Mineral-based wastes, especially calcium-silicon-based mine wastes (Iron-Aluminium-Silicon-Copper), heat-treated wastes (energy, iron and steel, copper, aluminum, glass, ceramics) are widely used as alternative raw materials in cement. The use of wastes such as fly ash and blast furnace slag from heat-treated thermal power plants in the cement sector provides an advantage in terms of energy savings in the cement sector, which requires high heat.
It is possible to summarize the usage areas of some mineral wastes as follows; Waste Rocks: Minerals and metals can be reprocessed, used as filling material in mines, landfill, aggregate material in road construction, and raw material for concrete and cement.
Red Mud: Red mud, which is formed as a result of aluminum refining, finds use in many areas such as soil improvement, glass, brick making, cleaning of dirty water.
Fly Ashes:Fly ash from thermal power plants is one of the most recyclable sources of mineral waste. It is mostly used in the cement sector (about 50%). It is used in many areas such as soil improvement, brick, agriculture, road filling material.
Marble Waste: Re-evaluation of marble waste is an important issue for our country, which is one of the largest marble producers. Two different sizes of waste products are produced in marble enterprises. The first product is large-sized marble wastes, and the second product is cut dust waste in colloidal structure with a large amount under 150 microns and a maximum particle size of 2 mm. While large-size piece waste can be used as a building element in the construction sector, powder wastes have the opportunity to be used directly in different industries. Marble wastes are used in areas such as aggregate material, brick, tile, cement, lime production, active calcium carbonate production, calcined dolomite production, acid neutralization, sulfur removal from flue gases, CO2 production for carbonated beverages. In addition, it is possible to make artistic use of waste as a lesser usage area.
Sulfur Mineral Wastes: Sulfurous mineral wastes, especially those with high pyrite content, cause acid mine drainage (AMD) if they are left in atmospheric conditions for a long time, and therefore they are in the group of wastes that are considered harmful for the environment. In the evaluation of such wastes, besides the recovery of the remaining precious metals, it is possible to enrich the pyrite-rich ones by reflotation and use them for the production of sulfuric acid. In addition, the production of paste fillers from sulfide wastes is also becoming widespread. Wastes with high clay content: The best example of this type of waste is boron waste. Brick, groundwater, cement are waste materials that can be used in making. Slags: Slags are used in the concrete and cement sector in road construction as well as metal and mineral production.
Coal Waste: Coal wastes are widely used as mine advertisement and filling material. Again, recycling products such as humic acid production from coal slimes are produced.
In addition to solid mineral wastes, mine wastewater is used as a coagulant, in industry and agriculture, and even as city water after being purified. Again, from the smelting facilities SO2 gases There are also recycling processes for gaseous wastes, such as for use in the production of sulfuric acid. In the literature, it is possible to come across studies on almost every waste type regarding the reuse of solid mineral wastes, some examples of which are tried to be given in this article. With the increase of studies on this subject, both an input to the economy will be provided and large amounts of waste that cause environmental problems will be removed.
Source : turkchemonline