Enhanced soil washing with copper recovery using chemical precipitation. (15th April 2019) - Fedje, Karin Karlfeldt
Abstract: Worldwide, the number of contaminated sites is large, and remediation methods including recovery of metals have potential to be key aspects of a sustainable and circular economy. Soil washing, followed by chemical precipitation is a possible method for recovery of metals. The purpose of this study is to propose a complete recovery method, where Cu is efficiently leached from samples with contaminated bark ash and soil. Thereafter the Cu is precipitated as metal hydroxide. The results show that pH is the most important parameter that controls the leaching of Cu. The leaching process was independent of the liquid to solid ratio (L/S) for the soil, while the leaching increased with the L/S ratio for the bark ash. The shaking method used for leaching affected the results, as a low leaching efficiency was achieved with the turn-over-end technique used. The final Cu precipitation product from the bark ash contained ≥40 wt % Cu, whereas the corresponding soil precipitation product contained ≤15 wt % Cu. The conclusion is that the bark ash precipitation product is of interest for further refining within the metal industry. Due to inefficient leaching and washing, the soil and bark ash residues left after leaching are classified as hazardous waste. Graphical abstract: Image 1 Highlights: The bark ash leachate precipitation products contained ≥40 wt % Cu. The bark ash precipitate is of interest for further refining in the metal industry. The shaking procedure used for Cu leaching strongly affected the results. Leaching of Cu from soil and bark ash with acid was highly controlled by pH. Leaching of Cu from bark ash using acid increased with the L/S ratio.