Ultrasound-acid modified Merremia vitifolia biomass for the biosorption of herbicide 2,4-D from aqueous solution

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.

Ultrasonic Activated Biochar and Its Removal of Harmful Substances in Environment

Biochar has been widely used in the fields of environment and energy, and green preparation can make biochar-based materials more environmentally friendly. Particularly, in the low-temperature pyrolysis of biochar, labile C with low biological toxicity is the main influencing factor of bacteria in soil. Therefore, it is worth studying to develop the fabrication technology of low-temperature pyrolysis biochar with rich pore structure. The mechanical effect of ultrasonic cavitation is considered to be an effective strategy for the preparation of biochar. However, the sonochemical effects on biochar remain to be studied. In this review, ultrasonic modification and ultrasonic-chemical modification on biochar has been reviewed. Metal oxide/biochar composites can also be obtained by an ultrasonic-chemical method. It is worth mentioning that there have been some reports on the regeneration of biochar by ultrasound. In addition to ultrasonic preparation of biochar, ultrasound can also trigger the sonocatalytic performance and promote the adsorption ability of biochar for the removal of harmful substances. The catalytic mechanism of ultrasound/biochar needs to be further investigated. For application, biochar prepared by ultrasound has been used for the removal of heavy metals in water, the adsorption of carbon dioxide, and soil remediation.