Empowering clean water whilst safeguarding water distribution pipeline integrity: towards manganese- and iron-free lime hydrate for water treatment

Abstract

Hydrated limes are amongst the most economically valuable alkalis used by the water industry for the treatment of potable water. They are typically manufactured from the thermal decomposition of high...

Oxidative dissolution of lithium and manganese from lithium manganospinel (LiMn2O4): towards climate-smart processes for critical metal recycling

“…18–97 kJ mol −1 . Furthermore, for Mn 3 O 4 , the activation energy for manganese dissolution as MnO 4 − determined by our previous work using alkaline hypochlorite 27 is ca. 40% smaller than that reported for sulfuric acid above.…”

“…at an appropriate pH, during industrial symbiotic chemical processes. In line with previous work, 27 in taking this forward, a cascading leaching process will need to be developed, to overcome the thermal decomposition of hypochlorite, 63 in order enable optimisation of the process conditions.…”

“…In this communication, following our earlier work on the redox removal of iron and manganese impurities in slaked lime using alkaline hypochlorite, 27 we report a redox method for breaking down the framework of lithium managnospinel, LiMn 2 O 4 – a material used as a lithium-ion battery cathode. 19,23 This enables the solubilisation of both lithium and manganese as a pathway for total recovery, rather than merely recovery of one species, with the remainder being used for direct recycling.…”

“…Accordingly, oxidative leaching experiments were undertaken through refluxing 80 mL of alkaline hypochlorite (r2% alkalinity, Z8% available chlorine), with a fixed mass of LiMn 2 O 4 (m 0 = 0.1 g or 1.0 g) at a known temperature, T, in the range 50 o T/1C o 100, for a constant time period (1 h), see ESI1 (ESI †). Our previous work, 27 suggests that this time period is sufficient for the initial rate to be monitored. where the factor of 1 2 results from the 1 : 2 stoichiometry of LiMn 2 O 4 : MnO 4…”

“…We focus on the initial dissolution kinetics, since our previous work has illustrated how such initial kinetics can be maintained in a “cascading” mineral processing flowsheet. 27 Moreover, this enables the unravelling of the activation energy required for the dissolution – for reactions under activation control, the lower this is, compared with conventional, reductive acidic leaching 28 of LiMn 2 O 4 , the more climate-smart the recovery process becomes, assuming all other variables (such as leaching time) remain constant.…”