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.

Novelty statement

The husk of Newbouldia laevis is a frequent waste that must be managed properly. This paper describes the application of Newbouldia laevis husk as a value-added material for the design of a water treatment agent. The use of carbon nanotube in the modification of Newbouldia laevis husk would have a synergistic effect on the overall property of the nanocomposite. Nanocomposite synthesized from multiwalled carbon nanotubes (MWCNTs) and Newbouldia laevis husk were characterized and used for the sequestration of malachite green oxalate from contaminated water. Our primary goal is to optimize the nanocomposite by varying factors of adsorption such as solution pH, equilibrium, kinetic, thermodynamic, and regeneration studies. We believe that this study will contribute to the existing knowledge of Newbouldia laevis husk. Owing to the exceptional potential of the nanocomposite, this adsorbent can be extended to possible field applications.

Graphical Abstract

Keywords:

• Adsorption capacity
• isotherms
• kinetics
• Newbouldia laevis
• optimization
• regeneration

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research received no funds.