In this work, a new methodology has been developed for the elimination of cobalt, nickel and a mixture of both metals from synthetic wastewater in a continuous way. This methodology consists of the electrochemical formation of ferrites of these metals through the oxidation of iron sheets and the reduction of water. Two critical process parameters, current densities and initial pollutant concentration, were analysed. An initial batch prototype resulted in efficiencies on the order of 98% under conditions of applied densities of 50 mA/cm2 and concentrations of both metals of until 100 ppm of the ions. The obtained particles have been characterized by X-ray diffraction to determine the formation of ferrites without the appearance of secondary phases. The formed particle sizes are approximately 30 nm, with hemispherical or flower-like shapes. A flow system prototype was designed for the recirculation of the solution with 100 ppm of both contaminating metals, obtaining approximately 90% recovery with an easy magnetic harvesting.

This research was funded by the Spanish Ministry of Science, Innovation, and Universities under projects PGC2018-095642-B-I00 and PGC2018-096016-B-I00. L.G. acknowledges financial support from the Ramón y Cajal program (RYC-2014-15512). E. Mazario. acknowledges financial support from the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Universidad Autónoma de Madrid in the line of action encouraging youth research doctors, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation), (SI1-PJI-2019-00366). L. Duque acknowledges for the contract obtained from Ayudas para la contratación de ayudantes investigación y técnicos de laboratorio of Comunidad Autónoma de Madrid. The authors would like to acknowledge the use of the Advanced Microscopy Laboratory (INA-Universidad de Zaragoza) for access to their instrumentation and expertise.

Peer reviewed