New Ion Exchange Resin

New ion-exchange resin from LANXESS for lithium extraction Specialty chemicals company LANXESS is adding Lewatit TP 308 to its range of selective ion-exchange resins, ideal for purifying lithium salt solutions. Dirk Steinhilber, Technical Marketing Manager at LANXESS's Liquid Purification Technologies business unit, said: "Such purification processes play an important role in the production of ultra-pure lithium salts required in the manufacture of lithium batteries and rechargeable lithium-ion batteries." [caption id="attachment_136289" align="aligncenter"] Ion analysis in an analytical laboratory at LANXESS in Leverkusen. Photo source: LANXESS AG[/caption]

Cost-effective softening of dilute lithium salt water

The use of ion-exchange resins offers a number of advantages over conventional final polishing methods for lithium salt water, which are based primarily on precipitation processes. As Steinhilber explained, "Using ion-exchange processes for calcium removal significantly reduces both time and costs." Macro-porous Lewatit TP 308 has been specially developed to process low-concentration lithium salt solutions (cLi < 2 g/l) containing alkali, alkaline earth and heavy metals at relatively high concentrations ranging from 100 mg to several grams per litre. Such solutions occur, for example, during the processing of geothermal brine after desorption from the primary adsorbent material. The removal of polyvalent ions—particularly calcium—from these solutions is highly efficient with low leakage and at high flow rates, thanks to exceptional exchange kinetics. At the same time, pressure drop across the resin bed is also low. Laboratory tests have demonstrated the superior performance of Lewatit TP 308 compared to various competitor products. A particularly striking feature of the resin is its high total capacity of more than 4.3 eq/l (equivalents per litre). This means better service lives than in standard resins and therefore longer intervals between regeneration cycles. As a result, the specific demand for regeneration chemicals and water is reduced. This results in a general improvement in system availability coupled with lower operating costs. Steinhilber said: "A polymer structure specially modified for the resin ensures long service life even under frequent regeneration conditions, making the process a much more financially attractive proposition." [caption id="attachment_136290" align="aligncenter"] Laboratory tests have demonstrated the superior performance of Lewatit TP 308 compared to competitor products. The removal of polyvalent ions—particularly calcium—from lithium salt solutions is highly efficient with minimal leakage and at high flow rates, thanks to exceptional exchange kinetics. Pressure drop across the resin bed is also low. The graph shows calcium concentration in the waste water from the ion-exchange process (ppm) on the Y axis; this is a measure of the purity of the lithium salt water produced. Flow rate in bed volumes per hour (BV/h) is shown on the X axis. Photo source: LANXESS AG[/caption]

Custom-built resins for different lithium concentrations

In addition to the application range of Lewatit TP 308, LANXESS also offers custom-built ion-exchange resins for purifying concentrated lithium salt solutions. The monodisperse resins Lewatit MonoPlus TP 208 and Lewatit MonoPlus TP 260 can thus be used to remove divalent ions—namely calcium, magnesium, strontium and barium—from brines with a typical lithium content of 10 g/l at concentration ranges of 1–100 mg/l. Lewatit MonoPlus TP 208, a resin with chelating iminodiacetic acid (IDA) groups, is best suited for lithium chloride, lithium hydroxide and lithium sulphate solutions. In addition to the monodisperse resin types in the MonoPlus series, LANXESS offers MDS types of both resins with polymer beads of approximately 0.4 mm diameter, smaller than the standard types (0.6–0.7 mm). As a result of significantly larger specific surface area, MDS resins exhibit faster exchange kinetics and considerably higher usable capacity. They are also more stable both osmotically and mechanically. They enable near-complete removal of impurities. For example, in a concentrated lithium chloride and sodium chloride solution containing 10 ppm calcium, only trace amounts of calcium in the ppb range remain after treatment with Lewatit MDS TP 208. Ultra-pure lithium salt solutions obtained in this manner are required primarily for direct LiOH production via chlor-alkali electrolysis, where expensive membranes must be protected from scale and clogging formation. Source