Effective Utilization of Grinding and Mechanochemistry to Recycling and Separation

Abstract

The authors introduce novel research results on material synthesis and recycling by grinding. The research is focused at first mechanical activation of fine particles of solid material caused by grinding, and this leads to synthesize functional material from two starting materials without heating. One of the examples is to show the formation of complex oxides such as CaTiO₃ from CaO and TiO₂. Another one is dechlorination of PVC by its grinding with CaO to form CaOHCl and hydrocarbon. This means that it is possible to separate chlorine from PVC by its washing with water. Grinding operation enables us to reduce indium (In) by from indium oxide (In₂O₃) and ITO in the presence of Li₃N under NH₃/N₂ gaseous environment. The reaction can be given by: In₂O₃ + Li₃N + NH₃→2In + 3LiOH + N₂. The purity of In and its recover are quite high over 90%. Further example of the mechanical activation followed by heating up to about 400°C is to generate hydrogen (H₂) from biomass such as wood and straw. The biomass is milled with inorganic substance such as CaO, followed by heating at non-oxidative environment. The generation of H₂ in high concentration can be attained during heating, due to adsorption of CO₂ and CO by CaO to form CaCO₃. This implies that the grinding plays a big role to bring out many possible applications for material synthesis, material and waste processing.