Copper Recovery from Metallurgical Slags Using Biomass in the Form of Fruit Seeds/Stones as a Reducing Agent

Civilizational development, which depends on the availability of raw materials, has accelerated tremendously in recent decades. This is due to globalization and the growth of emerging markets. It represents a huge opportunity for an innovative approach to both production and consumption. Along with civilizational growth, we also face negative consequences that lead to climate change. To meet the demands regarding climate neutrality, people have started analyzing the possibility of running production processes using substrates that either eliminate or significantly reduce the use of non-renewable resources. Considering the specifics of metal extraction and production, it is important to note that chemistry and thermodynamics play a key role here. This involves, on the one hand, understanding how carbon or its oxides are absorbed, which is essential for plant growth, and on the other, using components of so-called biomass for controlled chemical reactions. These regulations regarding climate neutrality and the type of raw materials are reflected in detail in the relevant European Union directives. Copper production in Poland is a strategic sector of the economy. Considering the scale of production and the consumption of natural resources, developing the possibility of partially replacing them will constitute a process innovation. Research into copper recovery from slag to date has focused primarily on improving the efficiency of the slag reduction process by intensifying bath mixing and improving the mass transfer process in the liquid phase. Given that biomass contains a significant proportion of volatile matter, this may additionally have a beneficial impact on the efficiency of using this type of material in the process. Many parameters still need to be investigated before the obtained results can be tested on a larger scale, enabling transfer to industrial conditions. The study presented the results of research on the potential use of biomass to reduce secondary raw materials coming from the copper industry. A Gibbs free enthalpy analysis was carried out for possible chemical reactions and their likelihood of occurring. As a source of metals, a material similar in composition to slag generated in the copper industry was used. Considering that copper ores contain about 1 wt. %, it makes even more sense to use secondary slag, which contains up to 10 wt. % copper. As part of the work, tests of the pyrometallurgic slag reduction process were carried out with the use of selected types of biomass. The tests were carried out in a metallurgical aggregate, at a temperature of 1300 °C in the time range from 1 to 5 h. The main parameters determining the efficiency of the process were to determine the degree of removal of the main metals, i.e., Cu and Pb, as well as to determine the content of these elements in the secondary slag. Verification of the possibility of replacing coal with biomass in real industrial conditions requires verifying primarily the effectiveness of metal removal as well as the possibility of determining the effect of climate neutrality. The results show the huge potential biomass has in terms of use in metal production processes. Also, in the near future the aspect of climate neutrality in the European Union may become an important factor for the economics of the process and competitiveness in the market.