What is the Leaching Process?
The process of leaching is used to extract the substances from the solids. This process is carried out when the given substance is allowed to dissolve in a liquid. It is carried out either through a natural process or industrially.
The leaching process shows the release of both the organic as well as the inorganic radionuclides or contaminants from a solid-state to a liquid state when they get influenced by different processes like mineral dissolution, complexation, and desorption.
The process of leaching is known to be a universal process in which water tends to leach the material components that come in contact with it. This can be its surface or its interior depending on how porous the material is.
The ore of the given metal can be concentrated using this process when a chemical reaction is caused with the help of a reagent that would eventually lead to the ore getting dissolved and the impurities undissolved.
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Leaching Process Examples
The leaching process example includes the leaching of bauxite or Al₂O₃ . 2H₂O with the concentrated and heated sodium hydroxide. The concentrated NaOH here tends to dissolve the aluminium present in the given bauxite, while on the other hand, the impurities like SiO₂, TiO₂, and Fe₂O₃ do not get dissolved. The chemical reaction of this leaching process is given as follows.
Al₂O₃ . 2H₂O + 2NaOH → 2NaAlO₂ = 3H₂O
Another example of the process of leaching is leaching of the noble metals like silver and gold in the presence of the dilute aqueous solutions of either potassium cyanide or sodium cyanide in the presence of air. The chemical reaction for this process of leaching for silver is given below.
Ag₂S + 4 NaCN → 2Na[Ag(CN)₂] + Na₂S
The leaching process also causes the loss of nutrients that are present in the soil because of heavy rainfalls.
Advantages and Disadvantages of Leaching Process
Advantages of Leaching are as Follows.
The leaching process is easier when it comes for the execution.
It is not a harmful process in comparison to the other pyrometallurgical methods.
It does not lead to any sorts of gaseous pollutants.
Disadvantages of Leaching are as Follows.
The residual liquid waste that is generated from the leaching process is highly acidic in nature.
The effluent of the leaching process is toxic.
The efficiency of the leaching process is entirely dependent on temperature.
Types of Leaching Processes in Metallurgy
The different kinds of leaching processes which are used in industrial purposes for metallurgy are given below.
Heap leaching: It refers to a process which extracts uranium, copper and many other precious metals from their ores.
In-situ leaching: It is a process which recovers uranium and copper.
Tank leaching and vat leaching: They are the processes in which the ores are to be placed in vats or large tanks that consist of the leaching solutions. These processes are used for the extraction of the metals from their ores.