Mine waters purification by biosorption coupled with green energy production from wood and straw biomass

A new process for mine water purification has been proposed, based on biosorption followed by burning of the loaded biosorbents. Wheat straw and sawdust of trees are both convenient as biosorbents in the proposed process. Biosorption was performed in two stages, in a cross-flow regime between the mine water and the biosorbent. The achieved copper adsorption de-gree was > 95%. Based on the mine water volume and its chemical composition, the estimated amount of the biosorbent was 60.000 t/year. The cogenerative mode of the loaded biosorbent combustion was considered for green energy production. For recovery of metals, which are concentrated in the ash, it must be processed separately. Several possibilities of the ash pro-cessing were proposed and discussed. For an annual volume of mine water and the copper content in it, the balance of mass and energy of the process were both estimated, giving some economic data on the process efficiency. The analysis of the revenues and costs, based only on the energy value produced by the combustion of the biosorbent, has shown that the process can economically be viable regardless of the value of the recovered metal.