Question

Write chemical reactions taking place in the extraction of zinc from zinc blende.

Answer 1

Sphalerite is a zinc mineral and ore. When the iron concentration of sphalerite is high, it transforms into marmatite, an opaque black variant. It was discovered in 1847 by Ernst Friedrich Glocker, who called it after the Greek word "sphalerons," which means "deceiving," due to the difficulty in identifying sphalerite. Galena, chalcopyrite, pyrite (and other sulphides), calcite, dolomite, quartz, rhodochrosite, and fluorite are all found in conjunction with sphalerite. Sphalerite has been called zinc blende, black-jack, and ruby blende by miners. Sphalerite may be found in a number of deposit types, although it is most commonly found in exhalative sedimentary, Mississippi-Valley type, and volcanogenic massive sulphide deposits.

Complete answer:
The method of froth flotation is mostly used to remove gangue from sulphide ores. The ore is pulverised and mixed with water to form a suspension. Collectors and Froth Stabilizers are the most important components in froth flotation. Collectors (pine oils, fatty acids, etc.) make the metal component of the ore more wettable, allowing it to form a froth, while Froth Stabilizers (cresols, aniline, etc.) keep the froth in place. The oil lubricates the metal, while the water lubricates the gangue. The froth is created by continually stirring up the suspension with paddles and air. To recover the metal, the frothy metal is scraped off the top and dried. Roasting is the next stage in the zinc extraction process. The ore is finely crushed into little bits before being hung in a rising stream of air. With this method, the sulphur level may be drastically decreased. The Zinc Blende is also converted to ZnO, which is much more reactive. The reaction that is taking place here is
$2ZnS + 3{O^2} \to 2ZnO + 2S{O_2}$
In a method known as the Belgian Process, zinc oxide is combined with coke and crushed into fine bits before being burned at 1673 K in fire clay vessels. Zinc Oxide is converted to metallic Zinc in this step. In this process, the carbon from coke functions as a reducing agent. The reaction that occurs in the last phase of zinc extraction is
$2ZnO + C \to 2Zn + C{O_2}$
For the purification of impure zinc, electrorefining is used. The anode is made of impure zinc, whereas the cathode is made of pure zinc. Zinc sulphate and dilute sulphuric acid make up the electrolyte (small amount). Zinc is deposited on the cathode and collected when current is passed.
Anode: $Zn \to Z{n^{2 + }} + 2{e^ - }$
Cathode: $Z{n^{2 + }} + 2{e^ - } \to Zn$ .

Note:
Zinc's boiling point is 1180 K, thus the zinc produced rapidly evaporates and distils, leaving non-volatile contaminants like Cadmium, Lead, and Iron behind. The zinc vapours in this gas are collected and cooled to produce solid zinc. Spelter is the name given to this unprocessed metal. Fractional distillation can be used to further purify it. Zinc alloys with a variety of other metals include nickel silver, bronze, brass, and soft electrical solder. A large portion of the zinc produced is used to galvanise iron in order to avoid corrosion.