**Sefiu O. Adewuyi \*, Hussin A. M. Ahmed and Haitham M. A. Ahmed**

Mining Engineering Department, King Abdulaziz University Jeddah, Jeddah 21589, Saudi Arabia; hussien135@gmail.com (H.A.M.A.); hmahmed@kau.edu.sa (H.M.A.A.)

**\*** Correspondence: sefiuadewuyi@gmail.com; Tel.: +234-8070583557

Received: 3 April 2020; Accepted: 5 May 2020; Published: 9 May 2020

**Abstract:** The comminution of ores consumes a high portion of energy. Therefore, different pretreatment methods of ores prior to their comminution are considered to reduce this energy. However, the results of pretreatment methods and their technological development are scattered in literature. Hence, this paper aims at collating the different ore pretreatment methods with their applications and results from published articles, conference proceedings, and verified reports. It was found that pretreatment methods include thermal (via oven, microwave, or radiofrequency), chemical additive, electric, magnetic, ultrasonic, and bio-milling. Results showed that the chemical pretreatment method has been used at an industrial scale since 1930, mainly in cement production. The microwave pretreatment results showed positive improvements at pilot scale mining applications in 2017. The results of ore pretreatment using electric and ultrasonic methods showed up to 24% and 66% improvement in energy consumption, respectively. The former and the latter have been piloted for gold and carbonate ore, respectively. Findings also showed that magnetic, radiofrequency, and bio-milling methods have not led to significant reductions in comminution energy. Based on energy reduction, safety, costs, stage of application, and downstream benefits, microwave and electrical pretreatment methods may be focused for applications in the mining industry.

**Keywords:** mining operation; ore milling; ore grinding; rock; liberation
