The use of ion exchange resins offers several advantages over the traditional method of final polishing for lithium brine, which is based primarily on precipitation operations. Using ion exchange processes for calcium removal cuts both the time and expenditure required.
The macroporous Lewatit TP 308 from Lanxess has been developed specifically to treat low-concentration lithium salt solutions (cLi < 2 g/l) containing alkali, alkaline earth and heavy metals at relatively high concentrations ranging from 100 mg up to several g/l. This is needed for example, during the treatment of geothermal brine following the desorption from primary adsorber material.
The removal of the polyvalent ions – mainly calcium – from these solutions takes place very efficiently, with low leakage, and at high flow rates owing to the exceptional exchange kinetics. At the same time, the pressure drop across the resin bed is low. Laboratory testing has demonstrated the superior performance of Lewatit TP 308 compared with competitor products.
One feature of the resin is its high total capacity of more than 4.3 equivalents per litre. This offers improved service lives and thus longer intervals between the regeneration phases than is the case with standard resins. Consequently, the specific need for regeneration chemicals and scarce water is reduced. This results in an overall improvement in system availability coupled with lower operating costs.
