Synthesis of novel mesoporous polyvinylamine functionalized with 2-Mercapto-N-methylbenzamide for mercury ions removal from industrial wastewater effluent

Abstract

This research introduces a groundbreaking, high-efficiency adsorbent for the remediation of mercury ion contamination in industrial wastewater effluents. A novel chelating polymer, 2-Mercapto-N-methylbenzamide-functionalized polyvinyl amine (PVAm-MMB), was synthesized via a facile acid-catalyzed condensation reaction, strategically incorporating amine, imine, and thiol functionalities to facilitate robust mercury sequestration. Rigorous structural characterization was undertaken utilizing a comprehensive suite of analytical techniques, including elemental CHNS analysis, FTIR spectroscopy, NMR spectroscopy, SEM-EDX microscopy, BET surface area analysis, GC–MS spectrometry, TGA analysis, and XPS spectroscopy, definitively confirming the desired structural attributes of the synthesized material. Subsequent adsorption studies demonstrated the exceptional performance of the mesoporous PVAm-MMB, exhibiting a significant specific surface area (S_BET) of approximately 73.7 m²/g, a total pore volume (V_m) of approximately 0.31 cm³/g, and an average pore width of approximately 21.4 nm. Remarkably, the PVAm-MMB achieved a maximum adsorption capacity of approximately 62.9 mg/g under optimized conditions (pH 4.5, 25 °C, 20 min contact time, 1 g/L adsorbent concentration, and 200 mg/L Hg²⁺ initial concentration). Langmuir isotherm modeling provided a superior fit to the experimental adsorption data compared to the Freundlich model, indicating a monolayer adsorption mechanism. Furthermore, pseudo-first-order kinetics accurately described the adsorption process; the calculated value for q_e,1 was 49.88 mg/g, which is quite aligned with the actual value of 48.6 mg/g. Thermodynamic analyses revealed the adsorption process to be spontaneous, exothermic (ΔH = −88.07 kJ/mol), and thermodynamically favored at lower temperatures. A plausible adsorption mechanism is proposed, and importantly, the adsorbent demonstrated excellent reusability. The efficacy of the PVAm-MMB was validated through the successful treatment of real-industrial mining wastewater effluent, achieving significant removal of mercury, thereby showcasing its substantial potential for practical environmental remediation applications.