Surface sodium lignosulphonate-immobilized sawdust particle as an efficient adsorbent for capturing Hg2+ from aqueous solution.

In this work, the soluble sodium lignosulphonate (LSNa) molecules were successfully grafted onto the surface of pine sawdust (PSD) particles to obtain an efficient adsorbent (PSD-LS) for removing Hg2+ from wastewater. In advance, the surface of sawdust particles were carboxymethylated by chloroacetic acid, the LSNa would be anchored on the surface by a heterogeneous esterification reaction occurred between the hydroxyl of LSNa and carboxyl on PSD surface. The resultant product (PSD-LS) exhibited a good adsorption performance for Hg2+ with adsorption capacity up to 164.77 mg/g and it was characterized by scanning electron microscope (SEM), energy dispersive X-ray diffraction (EDX), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The effects of pH, contact time, adsorption temperature and initial concentration on the adsorption of Hg2+ were investigated. Results showed that the pseudo-second-order kinetics and Langmuir isotherm model could describe the adsorption process better. In addition, the composite adsorbent has outstanding reusability with high and stable desorption rates under several continuous cycle. These findings suggested that PSD-LS was a potential adsorbent to remove hazardous metal ions from wastewater.