Reducing Energy Use and Costs of Zero Liquid Discharge for Lithium Brine Mining, Battery Manufacturing, and Battery Recycling

INTRODUCTION Water is key at every step of the lithium ion battery life cycle. This paper discusses four case studies involving the use of novel reverse osmosis (RO) membrane processes and energy recovery devices (ERDs) for lithium related water reuse, zero liquid discharge (ZLD), and resource recovery applications in China. The cases include several key stages of the li-ion battery life cycle including lithium brine mining, battery manufacturing, and battery recycling and how RO and ERDs are used to add value within these applications. 1. RO Related Trends for Industrial Wastewater Zero Liquid Discharge in China China has made water conservation and environmental protection key priorities and is ramping up regulations around wastewater discharge, limiting both the concentration of contaminants and discharge volumes. Industrial wastewater treatment is a crucial, but oftentimes expensive process. ZLD is becoming a requirement in many highly polluting industries. An example in the lithium industry is battery manufacturing, which includes many facilities that have been required to implement ZLD to prevent the discharge of certain contaminants and nutrients into the environment. The first case study will discuss and present data for a lithium battery manufacturing facility in central China that implemented ultra-high pressure reverse osmosis (UHPRO) operating at 1,500 psi with new UHPRO energy recovery devices (ERDs) to reduce energy use when implementing ZLD and resource recovery. The waste streams contain primarily ammonium sulfate, a valuable fertilizer sold as a byproduct. Recovering ammonium generates sufficient revenue to cover the ZLD system operating costs and eliminates a harmful discharge into the environment. 2. RO Related Trends for Lithium Mining in China Western China has significant amounts of lithium in salt lakes and in brines located in subsurface geological deposits. Some of the salt lakes in Tibet have low concentrations of magnesium and other divalent salts that can make it more challenging and expensive to extract lithium from the brine. In these locations, evaporation ponds are used to concentrate the brines and eventually precipitate out different salts into different ponds to allow the separation of monovalent salts so that when lithium bicarbonate (Li2CO3) precipitates, it is of sufficient quality for some lithium ion battery manufacturing. However, demand is growing for high purity lithium to help make higher quality cathodes. In the Qinghai province, there is more lithium in salt lakes and subsurface geological brines than in Tibet; however, the chemistry of these brines makes lithium extraction more challenging and expensive to implement with evaporation ponds, thus direct lithium extraction (DLE) is required. Novel nanofiltration (NF) and RO membranes are becoming common as tools to improve lithium quality and/or to increase lithium production in both of these mining applications. The second case study will discuss and present data from a lithium brine mining project in Tibet China that uses osmotically assisted RO (OARO) and ERDs to generate high-purity, battery grade lithium. The purity is improved by a OARO process designed to separate key monovalent salts, while also reducing by half the time it takes to concentrate lithium bicarbonate (Li2CO3) using evaporation ponds in an environment not ideal for solar evaporation. The third case will discuss and present data for a combination of low pressure RO, seawater RO, and UHPRO membrane systems with ERDs at a direct lithium extraction (DLE) facility at a salt lake in the Qinghai region of China. The RO systems concentrate lithium chloride (LiCl) downstream of an ion exchange based DLE system and upstream of a thermal evaporator used prior to conversion from LiCl to Li2CO3. UHPRO was added during a plant expansion to reduce the cost per ton of Li2CO3 from one of the first commercial DLE projects in the world. 3. RO Related Trends for Lithium Recycling in China In Europe and North America, various startups are conducting research and development (R&D) to demonstrate and commercialize recycling of lithium ion batteries to recover lithium and other key components for reuse. In China, however, the government has put the responsibility of recycling batteries onto the makers of EV materials such as automakers and/or battery manufacturers. While RO membranes are used to concentrate lithium chloride at battery recycling facilities in the US, it is not yet common and R&D is ongoing. In China, however, the use of RO systems for battery recycling is already common and a unique process has been developed to separate and concentrate lithium, nickel and cobalt with RO membranes prior to further processing to recover battery grade material. The fourth case study will be on a lithium battery recycling facility in China that is using a unique combination of pretreatment and a single RO system with ERDs designed for a unique operating strategy to recover lithium chloride, lithium sulfate, nickel sulfate, and cobalt sulfate from recycled batteries that include manganese and other challenging constituents prior to additional refining to recover lithium, nickel and cobalt for reuse in batteries.