Quantification and characterization of metals in alkaline leachates and the potential for Vanadium adsorption using biochar and hydrochar

With escalating demand for metals, an increasing global population and rapid technology development, there is a worldwide challenge to secure a sustainable metal supply for industry. Current recycling rates for such metals are extremely low, mainly due to a lack of feasible recovery technologies. As a consequence, valuable metal resources are being landfilled each year from sources such as municipal and industrial solid wastes. The practice of landfilling these resources not only impacts the environment due to potential leaching of metal rich toxic liquids, but also represents a significant long term loss to the economy. Recovery of metals from industrial process wastes, such as bauxite residue and incinerator ashes potentially offers significant quantities of metals to the benefit of the environment and economy alike. The difficulty with their recovery, however is that metals of concern tend to be present in low concentrations within complex matrices and can be technically difficult to extract. Here the extent of unrecovered metals in leachates from bauxite residue and incinerated bottom and fly ashes from municipal solid wastes are quantified and their potential economic value assessed. The potential of saw dust modified biochar and KOH modified hydrochar to remove Vanadium (V) from aqueous solutions in batch study experiments are also assessed, yielding optimum uptakes of 16.5 and 12.3 mg g-1 respectively at a solution pH 4. Finally consideration is given to future research needs to improve the sustainability and overall performance of biosorption of leachate metals.