Evaluation of a novel activated carbon/graphene oxide as an efficient composite adsorbent for the removal of herbicide 2,4-Dichlorophenoxyacetic acid: Adsorption isotherm and kinetics study

Abstract

Thysanolaena maxima-derived activated carbon/graphene oxide (TMAC/GO) composite was synthesized through a one-step mixing process via ultrasonication and used as an adsorbent for the removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide from solution. Various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FESEM-EDX), X-ray diffractometer (XRD), Brunauer, Emmett, and Teller (BET) surface area analyzer, and Transmission electron microscopy (TEM) were employed to characterize the synthesized composite. Results showed that the TMAC/GO had a porous structure with a large surface area of 960 m2/g, an average pore diameter of 2.658 nm, and a total pore volume of 0.6372 cm3/g. A series of batch experiments were conducted for different adsorption parameters, which include TMAC/GO dosage (0.05–0.25 g/L), initial concentration (50–300 mg/L), pH (2–12), contact time (20–140 mins), and temperature (298–398 K). Adsorption thermodynamics, isotherm models, and kinetics were employed to understand the adsorption mechanism. The composite showed good adsorption ability with the Langmuir maximum adsorption capacity of 98.469 mg/g. When compared with TMAC, the composite exhibited higher removal efficiency under the same dosage, concentration, and temperature with variations in pH and time. The pseudo-second-order kinetics model justified the experimental results with an R2 value of 0.997. Furthermore, the composite displayed good reusability performance up to 5 cycles. These findings, along with the cost-effectiveness of the material and its selectivity towards the herbicide, suggest its practical importance for water decontamination.