Course:SPPH381B/TermProject/Alkaline battery- Samin/Hydrometallurgy

Introduction

Leaching processes used for hydrometallurgical treatment of mineral ores,concentrates and metals.

Hydrometallurgy, extraction of metal from ore by preparing an aqueous solution of a salt of the metal and recovering the metal from the solution. The operations usually involved are leaching, or dissolution of the metal or metal compound in water, commonly with additional agents; separation of the waste and purification of the leach solution; and the precipitation of the metal or one of its pure compounds from the leach solution by chemical or electrolytic means. The most common leaching agent is dilute sulfuric acid. In order to be processed by hydrometallurgical processes, portable batteries with Zn and Mn content require a pre-treatment before further chemical processing. This pre-treatment consists in a physical separation process of spent batteries that involves: cutting–crushing, magnetic separation, dimensional separation (screening), ECS separation (using eddy currents) and powder fraction milling.

The recycling processes that are implemented on industrial scale are generally based on pyro-metallurgical processes and on heat treatments. In terms of hydrometallurgical processes, in literature, there are various patents for the recovery of Mn and Zn from spent portable batteries,

Alkaline Zinc Air /Zinc Carbon Batteries are 99.9% recycled in an innovative mechanical dismantling process where the battery parts are sorted into three end products. These parts include steel, paper and plastic, and zinc and manganese concentrate. Hydrometallurgical processes are directed mainly to the recover zinc by cathodic reduction and manganese recovery by precipitation.

List of associated hazards

Physical hazards

1. Heat exposure (high temperatures)

2. Skin cuts, scrapes and abrasions (due to steel)

Chemical hazards

1. Burns to eye and skin (exposure to potassium hydroxide)

2. Skin burns, irritation the nose and throat and difficulties breathing if inhaled (exposure to sulfuric acid)

Biological hazards

1. Respiratory diseases-bronchitis, pneumonitis (exposure to manganese dioxide)

2. Exposure to zinc dust (short-term disease called metal fume fever)