Valorisation of agro-industrial wastes by hydrometallurgical processes.

Main aim of the present experimental work was the development of hydrometallurgical innovative and environmentally friendly technologies, to re-use agro-industrial wastes. Manganese is an important commodity for application in the steel industry, in the battery manufacturing and as a fine chemical. The processes of manganiferous minerals are carried out by means of pyrometallurgical and hydrometallurgical treatments: the first ones present a more serious environmental impact especially considering the atmospheric emissions. The study started to develop a production process of manganiferous products of industrial interest, such as MnO2, by using an innovative chemical leaching, at low environmental impact, in presence of waste biomasses coming from agro-industrial activities (milk whey, molasses, vegetation waters and paper mill sludges). Important goal of this experimental work is to achieve products of industrial interest, such as electrolytic manganese dioxide (EMD), starting from manganiferous ores not treatable by conventional processes. The application of a chemical leaching in presence of carbohydrates as lactose was carried out. The study of the electrolytic process has been conducted utilising synthetic leaching solutions. The results show that it is possible to achieve high MnO2 recovery by hydrometallurgical processes (90%).