Many metals are now considered “critical” because of demand, their geographical concentration and the political stability of supply. But with limited options for supply there has been an examination of other potential sources, in particular recycling of these metals.
Mine waste has the potential to provide some of this supply while mitigating the environmental impact of the waste. BIOMIMIC has investigated the recovery of vanadium, considered a critical metal, from bauxite waste using environmentally sustainable adsorption techniques to remove it from aqueous solution.
The potential of using sustainable biochar (a waste biomass in this case made from sawdust heated in the absence of air to make a type of charcoal) to adsorb vanadium was analysed. The maximum uptake was shown to occur when the biochar was treated with mud and dried. Uptake of up to 16.45 milligrams of vanadium per gram of biochar was initially discovered but this level was improved by simple modifications of the process and the biochar type. All the adsorption took place within 60 minutes.
It was discovered that the vanadium bound weakly to the biochar, allowing it to be easily released with mild heating, which released the vanadium and allowed the biochar to be reused. Such biosorption processes could be utilised widely to recover some critical metals in an environmental friendly and sustainable way.