Ultrafast and high-capacity Pb(II) removal by interlayer-expanded MoS₂/ poly[pyrrole-2,5-diyl(4-carboxybenzyl)] nanocomposite via one-pot synthesis

Addressing the efficient extraction of lead (Pb(II)) from water solutions is vital for ecological integrity and societal welfare, especially considering the increasing prevalence of lead-containing perovskite photovoltaic materials. Although MoS₂ nanosheets exhibit excellent affinity for lead ions, their adsorption performance is constrained by a narrow interlayer spacing and limited adsorption sites. These limitations can be effectively mitigated through compositing with poly[pyrrole-2,5-diyl(4-carboxybenzyl)] (PPy-4CB). In this study, three novel PPy-4CB/MoS₂ nanocomposites were synthesized through hydrothermal synthesis, in-situ polymerization, and one-pot synthesis to study the impact of PPy-4CB on the Pb(II) adsorption of MoS₂. The one-pot-synthesized PPy-4CB₃/MoS₂ composite showed the highest Pb(II) adsorption capacity (332 mg·g⁻¹ at 298 K) with rapid adsorption kinetics (reaching equilibrium within 3 min). Notably, the composite showed significantly enhanced selectivity and anti-interference capability toward Pb(II) compared to PPy-4CB alone. The enhanced performance originated from synergistic effects between: (i) sulfur-rich MoS₂ with expanded interlayer spacing (1.03 nm) exposing additional sulfur binding sites and (ii) carboxyl-rich PPy-4CB providing supplementary coordination sites. FT-IR, XPS, and XRD analyses confirmed that Pb(II) removal was mainly governed by carboxyl groups and pyrrolic nitrogen in polypyrrole, exposed sulfur atoms on MoS₂, and Mo(VI) oxides formed by partial MoS₂ oxidation. This study demonstrates that PPy-4CB₃/MoS₂ exhibits outstanding adsorption performance and holds significant potential as an effective adsorbent for purifying Pb(II)-contaminated wastewater.