Efficient removal of 2,4-D from solution using a novel antibacterial adsorbent based on tiger nut residues: adsorption and antibacterial study

We engineered a tiger nut residue (TNR, a low-cost agricultural waste material) through a facile and simple process to take advantage of the introduced functional groups (cetylpyridinium chloride, CPC) in the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in batch mode and further investigated its impingement on bacterial growth in a yeast-dextrose broth. The surface characterizations of the adsorbent were achieved through Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller method (BET), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The batch adsorption studies revealed that solution pH, adsorbent dose, temperature, and salt affected the adsorptive capacity of TNR-CPC. The equilibrium data were best fitted by Langmuir isotherm model with a maximum monolayer adsorption capacity of 90.2 mg g–¹ at 318 K and pH 3. Pseudo-second-order model best fitted the kinetics data for the adsorption process. Physisorption largely mediated the adsorption system with spontaneity and a shift in entropy of the aqueous solid-solute interface reflecting decreased randomness with an exothermic character. TNR-CPC demonstrated a good reusability potential making it highly economical and compares well with other adsorbents for decontamination of 2,4-D. The adsorption of 2,4-D proceeded through a probable trio-mechanism; electrostatic attraction between the carboxylate anion of 2,4-D and the pyridinium cation of TNR-CPC, hydrogen bonding between the hydroxyl (–OH) group inherent in the TNR and the carboxyl groups in 2,4-D and a triggered π-π stacking between the benzene structures in the adsorbate and the adsorbent. TNR-CPC reported about 99% inhibition rate against both gram-positive S. aureus and gram-negative E. coli. It would be appropriate to investigate the potential of TNR-CPC as a potential replacement to the metal oxides used in wastewater treatment for antibacterial capabilities, and its effects against airborne bacteria could also be of interest.