Synthesis of biochar/MoS ₂ composite modified with poly(acrylic acid) (BC/MoS ₂ /PAA) for the removal of Cd( <scp>ii</scp> ) and Pb( <scp>ii</scp> ) from wastewater

The present study focuses on the synthesis of coconut shell-derived biochar (BC), molybdenum disulfide (MoS₂), and poly(acrylic acid) (PAA) (BC/MoS₂/PAA) composite. The composite was synthesized <i>via</i> a simple hydrothermal method. The structural and morphological features of the resulting composite were thoroughly characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET) surface analysis, and Raman spectroscopy. These analyses confirmed the successful formation and integration of the composite components. Adsorption isotherm studies revealed that Cd(ii) and Pb(ii) ions uptake by the BC/MoS₂/PAA composite adhered to the Langmuir model, indicating monolayer adsorption onto a homogeneous surface. The maximum adsorption capacities for Cd(ii) and Pb(ii) were determined to be 8.23 mg g^-1 and 26.47 mg g^-1, respectively. Kinetic investigations indicated that the adsorption process followed a pseudo-second-order model, suggesting that chemisorption was the dominant mechanism. Moreover, the composite exhibited excellent reusability and selectivity towards Cd(ii) and Pb(ii) ions. Oxygen-containing functional groups, sulfide ions (S^2-), and π-π interactions within the composite imply that electrostatic attraction, surface complexation, and cation-π interactions were the primary forces governing the adsorption process. These findings highlight the BC/MoS₂/PAA composite's significant potential for effectively removing Cd(ii) and Pb(ii) from contaminated wastewater.