Synergetic adsorptive mechanisms, reusability and cost evaluations of green fabricated hybrid barium cobalt nanocomposites for methylene blue and lead removal from wastewater

• The BaCoNCs, with a crystalline structure and a surface area of 108 m²/g, were synthesized using an eco-friendly method. • Remarkably, the maximum adsorption capacities achieved were 487 mg/g for MB and 405 mg/g for Pb(II), which surpass most reported values in the literature. • Notably, the material maintained over 80% removal efficiency for both MB and Pb(II) even after six adsorption-desorption cycles, highlighting its exceptional reusability. • The hybrid adsorption mechanism demonstrated both physical and chemical control, further enhancing its performance. • The cost of MB and Pb(II) adsorption was evaluated at 0.47 and 0.44 US$/g, indicating its cost-effectiveness compared to other adsorbents in recent studies. Barium nanoparticles (BaNPs), cobalt nanoparticles (CoNPs), and hybrid barium-cobalt nanocomposites (BaCoNCs) were synthesized using an eco-friendly green technique with Anacardium occidentale leaf extract for sequestration of methylene blue (MB) dye and lead (Pb(II)) ions from industrial wastewater. The nanoparticles and nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), and Brunauer-Emmett-Teller (BET) analysis to assess their functional groups, crystalline structure, morphology, and surface properties, confirming successful synthesis. Batch adsorption studies showed that optimal pollutant removal occurred at pH values of 8 for MB and 5 for Pb(II), with a contact time of 60 minutes, adsorbent dosage of 25 mg/L, initial concentration of 100 mg/L, and temperature of 30°C. Overall, BaCoNCs outperformed BaNPs and CoNPs in adsorption, achieving maximum adsorption capacities of 487 mg/g for MB and 405 mg/g for Pb(II). Kinetic studies followed the pseudo-second-order model, while adsorption isotherm data fitted well to the Langmuir model. Thermodynamic analysis showed spontaneous and endothermic adsorption. BaCoNCs exhibited over 80% removal efficiency after 6 reuse cycles, demonstrating their potential for sustainable wastewater treatment. Additionally, the adsorption cost was 0.47 and 0.44 US$/g for MB and Pb(II), respectively, highlighting BaCoNCs as promising candidates for scalable industrial effluent remediation.