Removal of the unwanted materials (e.g., sand, clays, etc.) from the ore is known as concentration, dressing or benefaction. Before proceeding for concentration, ores are graded and crushed to reasonable size. Concentration of ores involves several steps and selection of these steps depends upon the differences in physical properties of the compound of the metal present and that of the gangue. The type of the metal, the available facilities and the environmental factors are also taken into consideration. Some of the important procedures for concentration of ore are:

(i) Hydraulic washing

(ii) Magnetic separat

(iii)Froth-floatation process

(iv) Leaching

Which of the following equipment is used for concentration by hydraulic washing?

Wilfley tables

The correct answer is option 3. Wilfley tables.

Hydraulic washing, also known as gravity separation or levigation, is a method of concentration used to separate minerals or ores based on differences in their densities. This technique relies on the principle that heavier particles will settle more quickly in a moving fluid (such as water) than lighter particles. Here's how hydraulic washing works and how Wilfley tables are used in this process:

Preparation of the Ore: The ore is first crushed and ground into a fine powder to increase the surface area for efficient separation. This powdered ore is then mixed with water to form a slurry or suspension.

Separation in the Wilfley Table: The slurry is fed onto the Wilfley table, which is a specialized shaking table used for gravity concentration. The Wilfley table consists of a flat, inclined deck with riffles (raised ridges) running across its surface. The deck is mounted on a shaking mechanism that causes it to oscillate horizontally.

Turbulent Flow of Water: Water is continuously introduced onto the Wilfley table and flows along its length. The shaking motion of the table creates a turbulent flow of water, which helps to stratify the particles based on their densities.

Settling of Heavier Particles: As the slurry flows over the riffles, the heavier ore particles settle into the spaces between the riffles due to their higher density. The riffles act as barriers, preventing the heavier particles from being washed away by the flowing water.

Removal of Lighter Gangue: In contrast, the lighter gangue particles are carried away by the flowing water and are eventually discharged from the end of the Wilfley table. This selective separation allows for the concentration of the valuable mineral particles in the concentrate.

Adjustment for Optimal Separation: The tilt and water flow rate of the Wilfley table can be adjusted to optimize the separation process for different types of ores and operating conditions. By controlling these parameters, the efficiency of hydraulic washing can be maximized, leading to higher yields of concentrated ore.

Overall, hydraulic washing using Wilfley tables is an effective and widely used method for concentrating minerals based on differences in density. It is particularly suitable for ores where the valuable minerals have significantly different densities from the gangue minerals, allowing for efficient separation and concentration of the desired minerals.