Sustainable recovery of critical elements from seawater saltworks bitterns by integration of high selective sorbents and reactive precipitation and crystallisation: Developing the probe of concept with on-site produced chemicals and energy

The availability of raw mineral resources containing elements included in the Critical Raw Materials (CRMs) list is a growing concern for European Union. Sea mining has been identified as promising secondary source. In particular, brines obtained solar saltworks (bitterns) contain relevant amounts valuable CRMs such Mg(II), B(III), other alkaline/alkaline earth metals (Rb(I), Cs(I), Sr(II)) and transition/post-transition (Co(II), Ga(III), Ge(IV)). However, low concentration some these (µg/L) requires an effort to develop recovery routes that are sustainable economically feasible where required chemicals energy produced on-site from bitterns (i.e. HCl NaOH). Even conventional processes ion exchange, sorption precipitation, which have proved be competitive recovery, challenged case Trace Elements (TEs). This work studies TEs after exchange processes. First, batch crystallisation reactive precipitation were tested target single-component solutions: Sr(II), Co(II), Ge(IV) B(III). Then, experiments carried out with multi-component synthetic solutions assuming different scenarios bittern streams coming selective extraction stage using targeted recovered except Ge(IV), alternative need evaluated, its involves use tannic acid or sulphide could not bitterns. further step would necessary achieve element concentrations closer phases saturation. Moreover, model simulations performed PHREEQC program, provided good prediction experimental trends most cases.