Adsorption of Fe-modified peanut shell biochar for Pb(II) in mixed Pb(II), Cu(II), Ni(II) solutions

A Fe-modified black peanut shell biochar (Fe@BC) was fabricated using FeCl₃ as a magnetic modifier, its sorption for Pb(II) in mixed Pb(II), Cu(II), Ni(II) solutions was examined. It was showed that Fe@BC had better adsorption for Pb(II). While the optimal pH was 4.0, and equilibrium time was 8 h. The adsorption capacity of Fe@BC for Pb(II) was 22.535 mg/g in mixed systems. Interestingly, the adsorption of Fe@BC for Pb(II) and Ni(II) exhibited a decreasing trend. In contrast, its adsorption for Cu(II) increased with the rising temperature. The fitting of theoretical models showed that the adsorption of Fe@BC for them followed quasi-second kinetic model, and such an adsorption was a spontaneous process. Additionally, the adsorption of Fe@BC for Pb(II) fitted well with Freundlich isotherm model. Conversely, its adsorption for Cu(II) and Ni(II) obeyed Langmuir-Freundlich isotherm model. Mechanisms of Fe@BC for metal ions mainly enclosed ion exchange, surface physic-sorption, pore adsorption, groups' adsorption, and bonding effect. Regeneration of Fe@BC for Pb(II) showed that it can be cycled four times using HCl as a desorbent. Especially in the simulated wastewater, Fe@BC exhibited remarkable adsorption for metal ions and organic matters, demonstrating that it was a promising adsorbent for removing Pb(II) from wastewater.