Synthesis of poly (acrylic acid) modified graphene/MoS2 heterostructure-based composite: an effective removal of Pb(II), Cd(II) and Zn(II) from wastewater

Heavy metal contaminants have attracted widespread attention due to their severe toxicity and bioaccumulation. In this study, a novel graphene (EG)/molybdenum disulfide (MoS₂) modified with poly (acrylic acid) (PAA) composites (EG/MoS₂/PAA) were successfully synthesized via a one-step hydrothermal method and effectively removed Pb(II)_, Zn(II)_, and Cd(II) ions from wastewater. The incorporation of PAA within the EG/MoS₂ significantly improved sorption ability. The EG/MoS₂/PAA composite was characterized using XRD, FTIR, TEM, Raman, SEM-EDS, EIS, and cyclic voltammetry, which confirmed the successful synthesis of the EG/MoS₂/PAA composite. The adsorption isotherm and kinetic of Pb(II), Zn(II), and Cd(II) were fitted with the Temkin isotherm and pseudo-second-order model, respectively. The maximum adsorption capacities (q_max) obtained using the Langmuir model were 47.13 mg/g for Pb(II) at pH 5, while 12.59 and 12.89 mg/g for Zn(II) and Cd(II) at pH 7. In the presence of interfering cations (i.e., Na⁺, Cu²⁺, Co²⁺, Fe³⁺, and Mg²⁺), the EG/MoS₂/PAA adsorbent exhibited high selectivity and excellent reusability after three cycles. The adsorption mechanism of Pb(II), Zn(II), and Cd(II) onto the EG/MoS₂/PAA composite surface was found to be primarily controlled by complexation and electrostatic interaction. This novel EG/MoS₂/PAA adsorbent has excellent suitability for practical application in the treatment of highly contaminated wastewater.