Green synthesis of Fe/Cu oxides composite particles stabilized by pine needle extract and investigation of their adsorption activity for norfloxacin and ofloxacin

High reusability and adsorption capacity of acid washed calcium alginate/chitosan composite hydrogel spheres in the removal of norfloxacin

Calcium alginate (CA) hydrogel spheres were widely used as adsorbents to remove organics, but their adsorption capacities and reusability to some antibiotics are unsatisfactory. In this study, calcium alginate/chitosan (CA/CTS) hydrogel spheres were prepared as precursors. Acid-washed CA/CTS (CA/CTS-M) hydrogel spheres (310.6 mg/g) behaved much better adsorption capacity of norfloxacin (NOR) than CA (69.5 mg/g) and CA/CTS (87.7 mg/g) hydrogel spheres. Astonishingly, after being reused for 15 cycles, CA/CTS-M has no loss of NOR adsorption capacity. In the original idea, acid wash was expected to remove the chitosan in CA/CTS hydrogel spheres for obtaining a larger specific surface area. Both scanning electron microscopy and Brunauer-Emmett-Teller test showed that acid wash can remove CTS from CA/CTS hydrogel spheres to increase the specific surface area. However, part of the chitosan remained in CA/CTS-M, having a role to enhance the structural stability of the material, because the acid-washed CA (about 2 mm) has a significantly smaller diameter than CA/CTS-M (about 3 mm). According to the influence of pH and density functional theory calculations, electrostatic attraction is the key driving force of NOR adsorption. Importantly, acid wash led to more negative-charged surface characterized by Zeta potential, which is the main reason of the significantly enhanced adsorption capacity of CA/CTS-M in removal of NOR. In short, CA/CTS-M hydrogel spheres are environment friendly and highly stable adsorbents with high adsorption capacity in the removal of NOR.

A review of the adsorption method for norfloxacin reduction from aqueous media

Norfloxacin (NRFX) is one of a class of antibiotics known as broad-spectrum fluoroquinolone antibiotic that is frequently used to treat infectious disorders in both animals and humans. NRFX is considered an emergent pharmaceutical contaminate. This review's objective is to evaluate empirical data on NRFX's removal from aqueous medium. The environmental danger of NRFX in the aquatic environment was validated by an initial ecotoxicological study. Graphene oxide/Metal Organic Framework (MOF) based composite, followed by Magnesium oxide/Chitosan/Graphene oxide composite gave the highest NRFX adsorption capacities (Qmax) of 1114.8 and 1000 mg/g, respectively. The main adsorption mechanisms for NRFX uptake include electrostatic interactions, H-bonds, π-π interactions, electron donor-acceptor interactions, hydrophobic interactions, and pore diffusion. The adsorptive uptake of NRFX were most suitably described by Langmuir isotherm and pseudo-second order implying adsorbate-to-adsorbent electron transfer on a monolayer surface. The thermodynamics of NRFX uptake is heavily dependent on the makeup of the adsorbent, and the selection of the eluent for desorption from the solid phase is equally important. There were detected knowledge gaps in column studies and adsorbent disposal method. There's great interest in scale-up and industrial applications of research results that will aid in management of water resources for sustainability.

Fabrication of graphene oxide/inulin impregnated with ZnO nanoparticles for efficient removal of enrofloxacin from water: Taguchi-optimized experimental analysis

A novel nano-adsorbent zinc oxide impregnated graphene oxide/inulin (ZGI) was prepared for the investigation of the removal efficiency of enrofloxacin. Characterization of the nano-adsorbent was accomplished through Fourier transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDS, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The average crystallite size of nanomaterial (ZGI) calculated from XRD data was 14.82 nm. The adsorption of enrofloxacin onto ZGI was performed in batch mode. The variables of adsorption process such as adsorbent dose, pH, contact time and initial concentration of enrofloxacin were optimized by Taguchi method to achieve the maximum removal efficiency. The optimum values of variables were: adsorbent dose = 25 mg, pH = 7, contact time = 60 min and initial concentration = 50 mg/L. The maximum adsorption capacity and removal efficiency of the material for enrofloxacin were 317.83 mg/g and 98.60%, respectively at 303 K. Redlich-Peterson isotherm model was the best fitted among the various isotherm models based on highest R² values (0.9978-0.9981) and lowest χ² (3.43 ×10^-4-2.00×10^-3). Kinetic data followed pseudo-second order model (R² ≥ 0.9974) more accurately as compared to pseudo-first order model (R²≤0.9772). The adsorption mechanism was illustrated on the basis of XPS and Raman studies. Reusability investigation showed that the nano-adsorbent ZGI could be used up to 5 adsorption-desorption cycles with greater than 90% removal efficiency.

Preparation of Fe/Ni Bimetallic Oxide Porous Graphene Composite Materials for Efficient Adsorption and Removal of Sulfonamides

An iron-nickel bimetallic oxide porous graphene composite material (Fe/Ni-PG) was prepared by a simple partial combustion method, which can be used to effectively remove sulfonamides (SAs) from an aqueous solution. The adsorption performance of Fe/Ni-PG, Fe-PG, and Ni-PG on six kinds of SAs was compared, and the influence of time, temperature, pH, and initial concentration of SAs on the adsorption behavior of SAs of Fe/Ni-PG in an aqueous solution was studied. The adsorption kinetics and thermodynamics exhibited that the Langmuir model and pseudo-second-order kinetics model can describe the adsorption isotherm and kinetics. The maximum adsorption capacities of sulfadiazine (SD), sulfamerazine (SM), sulfamethazine (SDM), sulfathiazole (STZ), sulfapyridine (SPD), and sulfisoxazole (SIZ) calculated by the Langmuir model were 26.3, 50.3, 42.2, 27.3, 34.5, and 41.7 mg/g, respectively, which exceeded those of most reported adsorbents. In the adsorption process, hydrogen bonding, π-π electron donor-acceptor, electrostatic interaction, and bimetallic synergies play a major role, and the entire adsorption process is spontaneously endothermic. In addition, the material has excellent stability, and the Fe/Ni-PG after desorption is consistent with the raw material. This work provides a favorable way for the removal of SAs in the environment.