Exploring the mechanism of lead(II) adsorption from aqueous solution on ammonium citrate modified spent Lentinus edodes

Ammonium citrate modified spent Lentinus edodes was investigated as a novel adsorbent for Pb(II) removal from aqueous solution. The results of Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis showed that modification by ammonium citrate obviously changed the property of spent L. edodes that enhanced the adsorption capacity. In batch studies, pH, initial Pb(II) concentration and adsorbent dose were found to significantly affect Pb(II) removal by a two-level Plackett–Burman design. The effects of foreign substances (ion strength, inorganic ions (anions, cations) and surfactants) on Pb(II) removal were studied. The adsorption process was well described by the pseudo-second-order model. The adsorption equilibrium data followed the Langmuir model and gave the maximum adsorption capacity of 59.17 mg/g at 35 °C. The adsorption mechanism was found to be dominated by ion exchange and electrostatic attraction on exterior, accompanying with the intraparticle diffusion transporting adsorbed Pb(II) from exterior to interior. The adsorbent could be regenerated by 0.1 M HNO3, which led only a tiny decrease in adsorption capacity after three adsorption–desorption cycles.

► Modified spent Lentinus edodes is an effective adsorbent for Pb(II) removal.
► pH, initial Pb(II) concentration and adsorbent dose are key factors on Pb(II) removal.
► Adsorption mechanism is dominated by ion exchange and electrostatic attraction.
► The mechanism can also be described by the intraparticle diffusion model.