Effective adsorption of heavy metal ions by sodium lignosulfonate reformed montmorillonite

Sodium lignosulfonate (Na-LS) was used to modified montmorillonite to form lignosulfonate-montmorillonite (LS-MMT). The as-prepared samples were characterized by various equipment to analyze the surface morphology and structure of the pure and reformed samples. The adsorption capability (q_e, mg/g) of LS-MMT or Ca/Na-MMT for Pb(II) and Cu(II) at different reaction intervals, the concentration of metal ions, temperature, and pH were studied by batch adsorption experiments. The results revealed that LS-MMT displayed a higher adsorption capacity than Ca/Na-MMT. The pH of solutions had a great influence on the q_e of the two adsorbents, and the q_e was slightly enhanced with temperature increasing. The isotherm and kinetic experiments studies indicated that the adsorption of heavy metal on LS-MMT or Ca/Na-MMT fit well with the Langmuir model and pseudo-second-order kinetic model. The competitive adsorption showed that LS-MMT had a stronger affinity for Pb(II) than Cu(II), which was different from Ca/Na-MMT. Additionally, the desorption experiment showed that LS-MMT had a stronger ability to lock heavy metal ions than Ca/Na-MMT in an acidic environment with pH ranging from 3 to 5.