Alkaline earth metal ions mediated coordination separation of valuable organic acids from depolymerization products of lignite

•Coordination separation was proposed to separate BPCAs from lignite depolymerized products.•Alkaline earth metal ions showed high selectivity to BPCAs.•Varieties of metal ions and pH of solution had significant influences on separation yields and selectivity.•Reaction temperature and time mainly affected the separation yields of BPCAs.