Chemical reagents for mineral processing form a crucial part of the mineral processing process, and are absolutely fundamental to maximising income. Metallic compounds generally are in the form of oxides, carbonates or sulfides. These metallic compounds are also called minerals. The extraction of metals from metallic compounds or from ores and minerals should be an economical, practical and environmentally viable process which must give maximum yield of metal. Mineral processing or beneficiation is a physical process however chemicals play a vital role while flotation process is being practiced in the beneficiation of sub-grade/lean-grade ores and minerals.
Mineral processing is the only way to separate valuable minerals of the ore from gangue minerals by exploiting the physical and surface properties of the minerals. Froth flotation process is practiced in a broad range of mineral separations by altering the surface properties of the minerals and by using appropriate chemical reagents.
Flotation is a selective process and can be used to achieve specific separations from complex ores such as lead-zinc, nickel-copper, rare earth, noble minerals, etc. Chemicals used in flotation process are collectors, frothers and a large group of modifiers viz., pH regulators, depressants, dispersing agents, activators, etc.
The industry has both commodity and specialised chemicals. However, modern classification of the reagents is based on the function of a particular reagent. Several thousands of chemicals were either tested or suggested as flotation reagents but only few were extensively implemented in practice. Metallic compounds can also be extracted by the process of leaching which involves the dissolution of a mineral from an ore; these include carbon adsorption, precipitation and solvent extraction. By far the most widely used reagent collector compound is the xanthate family. Xanthate remains the main chemical used in sulphide.
In the formulation of chemicals solutions, minimisation of environmental impact is also always taken into account. For instance Xanthates are supplied as powders and pellets in plywood covered bulk bags or drums, but for environmental and safety reasons, pellets are preferred. Dithiophosphates are supplied as liquids, while thionocarbamates as liquid and oxide collectors as liquids or pastes. Frothers are all supplied as liquids.
Over the last few years, requests for more environmentally sensitive reagents have become more common from the mining companies. This change can be attributed to government regulations that seek to protect the environment. Projects have even held-up specifically due to environmental concerns.
Also, while ores are becoming increasingly difficult to treat, environmental regulations are becoming more stringent. Water use is becoming a major concern. The industry is looking to the mining chemical manufacturers to develop specialty reagents that can meet their needs in treating difficult ores and to allow them to address the environmental and resource challenges.
Innovative chemistries are being introduced that allow regulations on waste water discharge and emission to be met and are cost effective from a total treatment cost perspective. Just as increasing metal prices now make the extraction of ‘dead deposits’ more economic, the industry foresees a similar impact from new chemistries enabling effective operation under new environmental regulations.