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 (qe, 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 qe of the two adsorbents, and the qe 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.