Valorization of Pea Husk Waste coated with γ-Al₂O₃ nanoparticles for cationic dye removal from water

The present study is aimed at valorization of Pea Husk Waste (PHW) by coating it with 40% wt γ-Al₂O₃ nanoparticles to obtain a waste derived bio-nano adsorbent (PHW/γ-Al₂O₃ NP) for adsorbed of Malachite Green (MG) cationic dye from aqua. FT-IR, SEM-EDX, XRD, zeta potential and BET surface area analyses were performed to prepare of adsorbent. The BET analysis of the sample gave surface area of ( 24.110 m². g -1 ) and the average pore diameter of 26.278 nm which is very well suited for adsorption. The pH of solution, initial concentration of toxic dye, dose, time of shaker, and temperature of solution were systematically studied. At the optimized adsorption condition, the maximum removal efficiency 96.42% was obtained for concentration of MG of 150 mg L⁻¹. The isotherm models that gave the best fitting to the equilibrium data was the Temkin isotherm and the pseudo second-order model to the kinetic data. The thermodynamic studies showed that the adsorption was exothermic and spontaneous in the range of temperatures studied. Additionally,the effect of ionic strength was tested to determine the effect of competing ions on the adsorption performance. The maximum of removal efficiency of approximately 81.03% for 5 cycles of regeneration shows good reusability, too. The proposed adsorption mechanism is an electrostatic attraction, hydrogen bonding, intraparticle diffusion, π–π bond between MG molecules and the functionalized adsorbent surface. In summary, γ-Al₂O₃ coated PHW is a potential waste-based bio-nano adsorbent which can effectively remove MG from water.