Sustainable and selective molybdenum recovery from acidic matrices simulating metal rich wastewater using non-modified spent coffee grounds

Molybdenum (Mo) is an essential element used in a variety of applications, including the production of steels and other alloys, catalysts, and microelectronics. Global production and consumption of Mo are expected to increase steadily over the next few years, underscoring the need to develop new, sustainable, and cost-effective recovery methods for Mo from industrial waste. Here, we present our study on using common and inexpensive biowaste from non-modified spent coffee grounds (SCGs) to selectively and fully recover Mo from a wide range of model solutions with a complex ion mix. Both static and dynamic adsorption studies have confirmed that it is possible to fully adsorb and desorb Mo from an acidic solution matrix, enabling full recovery and concentration of Mo from wastewater even at low concentrations (1.5 – 10 ppm). The matrix conditions used in the study mimic the composition of typical industrial wastewater (HCl- and HNO 3 -matrix). We were able to recover up to 100% of Mo from the HNO 3 matrix and up to 80% of Mo from the HCl matrix in the presence of 21 other metals. Only Sb and Ti are partially co-present in the recovered and concentrated Mo elute. Additional experiments showed excellent SCGs reusability across several adsorption-desorption cycles with minimal loss of quality. Therefore, this adsorption method is highly sustainable, cost-effective, and scalable for industrial wastewater treatment. This process could be used to concentrate Mo from large volumes of wastewater and, under the right conditions (absence of Sb or Ti), could even enable highly selective, low-cost Mo recycling compared to other relevant processes in use.