Effective removal of malachite green oxalate from aqueous solution using Newbouldia laevis husk/MWCNTs nanocomposite: equilibrium, kinetics, and thermodynamics.

Abstract

The discharge of colored effluent into water bodies is a big concern; hence, the current work was designed to fabricate a superior nanocomposite (NBM) using the Newbouldia laevis husk (NB) and functionalized multiwalled carbon nanotubes (f-MWCNTs) for the adsorption of malachite green oxalate (MGO). Brunauer-Emmett-Teller (BET) surface analysis was used to assess the specific surface area of NB (0.7699 m² g^-1) and NBM (94.006 m² g^-1). Fourier transform infrared spectroscopy (FTIR) was employed to determine the chemical moieties on the surface of the adsorbent. Field emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TGA) were used to analyze the surface morphology and the thermal behavior of the adsorbents. Essential factors of the adsorption process were investigated, and it was revealed that pH 6.0, adsorbent dose of 0.05 g, contact time 80 min, concentration of 100 mg dm^-3 and maximum adsorption capacity of 35.78 mg g^-1 (NB) and 69.97 mg g^-1 (NBM) were the optimal parameters. The NB and NBM adsorption processes followed a pseudo-first-order kinetic model. The exothermic and endothermic adsorptive processes were noticed to be the best descriptions of MGO elimination by NB and NBM, respectively. The uptake of MGO by NB and NBM was best described by models of Freundlich and Langmuir isotherms. Besides, NBM demonstrated uptake efficiency that is >80% after the fourth adsorption/desorption cycle. As a result, NBM has a wide range of possible uses in environmental remediation.