Mining Chemicals – Chemicals Used in Mining
In this post you will study some of the most widely traded and used mining chemicals.
Mine Explosives and Drilling Chemicals:
- Acetic Acid: Additive in industrial explosives
- Sodium Nitrate: Initiator in industrial explosives
- Sodium Nitrite: Initiator in industrial explosives
- Sodium Perchlorate: Initiator in industrial explosives
- AN Prills : base in industrial explosives
Flotation in Mining – Collectors and Modifiers:
There are many possible ways of categorizing sulfide collectors; e.g. copper collectors, lead collectors, soluble collectors, oily collectors, thiol collectors, etc. The terms “collector” and “promoter” are often used synonymously. Other reagents, which assist the adsorption of a collector on the mineral surface, are referred to as “activators”, and their use is also discussed below.
Xanthate:
Most widely used Xanthate in the flotation process in mining:
- Potassium Amyl Xanthate (PAX): Strong, unselective collector
- Sodium Ethyl Xanthate (SEX): Weak, highly selective collector
- Sodium Isobutyl Xanthate (SIBX): Good general purpose collector
- Sodium Isopropyl Xanthate (SIPX): Selective collector with higher recovery than SEX
Modifying Agents:
a huge number of reagents usually referred to as “Modifying agents” are used in the flotation of sulfide ores. This is especially true in the case of complex ores, where two or more valuable minerals have to be separated from each other, e.g. Pb/Zn ores, Cu/Zn ores Cu/Pb/Zn ores, Cu/Mo ores, Cu/Ni ores etc.
These modifying agents cover a variety of functions; for example, pH modifiers, depressants, activators and dispersants.
pH Modifiers:
Most minerals exhibit an optimum pH range for a given collector. While some minerals can often be floated at the natural pH of the ores, in most cases the pH has to be adjusted for maximum recovery and selectivity. The most widely used reagents for alkaline circuits are lime and soda ash.
For acid circuit flotation, the most commonly used reagent is sulfuric acid. These three modifiers are generally the most cost-effective ones. Other pH modifiers are also used rarely when difficult separations are required.
Common pH Modifiers:
- Sodium Cyanide /NaCN: Strong sulphide depressant for iron and zinc sulphides (e.g. pyrite, pyrrhotite, marcasite, arsenopyrite, sphalerite).
- Caustic soda/ Sodium Hydroxide /NaOH : Used to raise pH
- Soda ash /Sodium Carbonate / Na2CO3 : Used to raise pH
- Sulphuric Acid / H2SO4 : Used when flotation needs to be at a lower pH.
Depressants:
Inorganic Depressants:
The principal ones used and their typical applications are as follows:
- Sodium Cyanide: Depression of iron sulfide minerals such as pyrite, pyrrhotite and arsenopyrite. Depression of Zn minerals during Pb flotation from Pb/Zn ores.
- Sodium Ferro cyanide: Depression of Cu and Fe sulfide in Cu/Mo separation.
- Zinc Sulfate: Used alone, or in combination with cyanide, for depression of Zn minerals in the flotation of Pb/Zn, Cu/Zn, and Cu/Pb/Zn ores.
- Sodium Metabisulphite/SMBS: Depression of Zn sulphide (sphalerite) and Fe sulphide (e.g. pyrite, pyrrhotite) minerals.
- Hydrate Lime: Depressant for pyrite during copper and zinc flotation and in other sulphide ores where pyrite is a problem.
- Citric Acid: Organic Acid gangue depressant for ores containing oxide minerals
Sodium sulfide & Hydrosulfide (NaHS): Used for the depression of Cu and Fe sulfide minerals in Cu/Mo separation. - Nokes Reagent: Used for the depression of Cu and Fe sulfide minerals in Cu/Mo separation.
- DETA (Diethylene triamine): Used for the depression of pyrrhotite in Cu/Ni ores.
- Permanganates & other oxidizing agents: Can be useful in the separation of pyrite from arsenopyrite
- Yellow Dextrin, Starches: Used in the depression of weathered silicates and carbonaceous matter.
- Carboxymethyl cellulose /CMC: Used in the depression of magnesium silicates such as talc and pyroxene. Especially useful in the flotation of PGM and Ni ores.
- Guar gum: Depression of silicate gangue (e.g. talc, serpentine, lizardite, antigorite).
Activators:
Certain minerals do not float well with the use of only a collector, but require prior activation. The most commonly used activators are:
- Copper Sulphate /CuSO4: Activation of Zn sulfide and Fe sulfide minerals such as pyrite and pyrrhotite when the latter contain values such as Au, Ni and PGM elements.
- Lead (Pb) Nitrate or Pb Acetate: Used for the activation of antimony sulfide minerals such as stibnite and to reactivate copper sulphides depressed with cyanide.
- Sodium Sulphide (Na2S) /Sodium Hydrosulphide (NaHS): Commonly used prior to collector addition for the activation of Cu, Pb, and Zn minerals. The choice of whether to use Na2S or NaHS depends on the pH required in flotation, as Na2S is more alkaline and also, whichever works best (test to verify). Typically made up to 15-25 % solution strength.
- NaCN/ Sodium Cyanide: Acts as a surface cleaning agent or “activator” to improve the flotation of PbS.
Dispersants:
Many ores contain significant quantities of clay minerals and other “primary slimes”. These can have an adverse effect on flotation metallurgy. This can be due to a combination of factors such as, (a) increasing pulp viscosity, which adversely affects air bubble distribution, and froth drainage/mobility; (b) slimes can form a coating on the surface of valuable minerals thereby inhibiting their flotation.
The usual practice for minimizing the aforementioned effect of “slimes” is to conduct the flotation at lower percent solids to reduce the pulp viscosity. However, this also reduces the effective residence time in the flotation circuit. Consequently the use of both inorganic and organic dispersing and viscosity reducing agents is commonly practiced. Sodium silicate, soda ash, various poly- phosphate.
