Uptake of azaarenic 2-Methylpyridine by pre-cooled carboxyl functionalized graphene nanocomposite: Detection, sorption and optimization

Abstract

Sizable concentration (2.5–20 mg L−1) of refractory solvent 2-methylpyridine (2Mp) was detected in textile industry effluent that had been subjected to conventional biological treatment prior to discharge. A ratio of 55:45 (acetonitrile to water) was determined for HPLC detection of 2Mp. A novel adsorbent, exfoliated, carboxylic graphene oxide nanocomposite (GON) was synthesized with emphasis on pre-cooling to throttle synthesis exothermicity. Removal characteristics of GON were compared to commercially sold activated carbon (SAC). Similar BOD/COD ratio of the effluent (0.24) and synthetic 2Mp samples (0.22) were observed. SEM, FTIR, EDS, XRD and stability studies were carried out for GON pre-sorption and post-sorption of 2Mp leading to an understanding of interaction mechanism. Batch studies showed GON exhibiting ten times the adsorption capacity (1.5 g L−1), neutral operation pH (7), lower contact time (90 min), better thermodynamic stability and structural disintegration resistance than SAC. Kinetics (pseudo-second kinetics, distinct intraparticle diffusion phases) and equilibrium studies with χ2 error minimization (best fit isotherm - Redlich-Peterson) were conducted. Removal data was optimized by 4-Factor Doehlert design (DD) involving temperature, GON dosage, pH and initial 2Mp concentration. The model suggested a strong relation between neutral pH of solution and 2Mp removal efficiency. DD predicted pH = 7.04, GON dosage = 1.80 g L−1, initial 2Mp loading = 16.89 mg L−1 and temperature = 293.82 K as optimal conditions with a removal of 72.10 %. A high R2 = 0.992 and error < 2% suggests that the developed model was in coherence with experimental 2Mp-GON sorption results and successful in its prediction.