Adsorption of reactive yellow 145 onto chitosan in aqueous solution: kinetic modeling and thermodynamic analysis

Efficient adsorptive removal of levofloxacin using sulfonated graphene oxide: Adsorption behavior, kinetics, and thermodynamics

Water pollution by antibiotic residues poses a potential threat to environmental and human health. Graphene-based materials are highly stable, recyclable and effective adsorbents for efficiently removing antibiotics from polluted water. In this study, the adsorption behavior of levofloxacin onto sulfonated graphene oxide (SGO) was investigated by varying the contact period, solution pH, adsorbent quantity, levofloxacin concentration, inorganic ions, and solution temperature. Spectroscopic and microscopic techniques were employed to confirm the adsorptive interaction between levofloxacin and SGO. The adsorption process was most accurately characterized by the pseudo-second-order kinetic model and the Langmuir isotherm model, as indicated by their high correlation coefficients (R 2) and low root-mean-square error (RMSE) values. The maximal quantity of levofloxacin that can be adsorbed onto SGO was determined to be 1250 μmol/g at pH 4 and 25 °C using the Langmuir model. Thermodynamic studies reveal that the process of levofloxacin adsorption onto SGO is endothermic and spontaneous in nature. Taking into consideration the results of adsorption, desorption and regeneration studies, it is proposed that SGO can be applied as an economic viable agent for the adsorptive removal of levofloxacin from the aqueous environment.

Efficient removal of sparfloxacin antibiotic from water using sulfonated graphene oxide: Kinetics, thermodynamics, and environmental implications

Pharmaceutical contamination poses a significant threat to global health. Due to their high solubility in water, antibiotics are difficult to remove. This study produced and used sulfonated graphene oxide (SGO) to adsorb sparfloxacin from aquatic environments. UV-Visible, Fourier transform infrared (FTIR), X-ray diffraction (XRD), XPS, SEM, TEM, EDX, particle size, Thermogravimetric analysis (TGA), and acid-base titration were used to characterize synthesized SGO particles. The BET technique determined SGO's surface area (32.25 m2/g). The calculated pHPZC of SGO was 2.5. Sparfloxacin adsorption onto SGO was analyzed using adsorption duration, medium pH, adsorbent dosages, antibiotic concentration, cations, and solution temperature. The pseudo-second-order kinetic model better described experimental kinetic data than the pseudo-first-order and Elovich models. Equilibrium isotherm data supported the Langmuir model, revealing a peak absorption capacity of 1428.57 μmol/g at 25 °C. The kinetic and isotherm models' applicability was assessed using error analysis. A thermodynamic analysis revealed an endothermic, spontaneous adsorption process with a change in entropy (ΔS) of 114.15 J/mol K and enthalpy (ΔH) of 8.44 kJ/mol. A regeneration analysis showed that SGO adsorption efficiency topped 86.4 % after five cycles.

Adsorption Characteristics of Allura Red AC onto Sawdust and Hexadecylpyridinium Bromide-Treated Sawdust in Aqueous Solution

The Allura red AC (ARAC) dye adsorption onto natural sawdust (NSD) and hexadecylpyridinium bromide-treated sawdust (MSD) was investigated in aqueous solution as a function of contact time, solution pH, particle size, adsorbent dosage, dye concentration, temperature, and ionic strength. The adsorbents were characterized by Fourier transform infrared spectroscopy and X-ray diffraction crystallography. The dye adsorption onto both adsorbents was confirmed by field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The maximum dye adsorption was found within 120 min at pH 2.0 for NSD and pH 3.0 for MSD, respectively, with a particle size of 0-75 μm and an adsorbent dosage of 0.07 g/50 mL ARAC dye solution (50 μmol/L). The batch adsorption kinetic data were followed by the pseudo-second-order kinetic model rather than the pseudo-first-order and Elovich kinetic models. Equilibrium adsorption isotherms were explained by the Langmuir isotherm model, and the maximum extent of adsorption was found to be 52.14 μmol/g for NSD and 151.88 μmol/g for MSD at 55 °C. The values of activation energy (E _a) and thermodynamic parameters (ΔG ^⧧, ΔH ^⧧, ΔS ^⧧, ΔG°, ΔH° and ΔS°) proved that the ARAC dye adsorption onto both adsorbents NSD and MSD is a spontaneous-endothermic physisorption process. ARAC (98-99%) was released from dye-loaded adsorbents in aqueous solution (pH ≥ 12) within 120 min. The adsorbents NSD and MSD were reused for a second time without significant loss of their adsorption efficiency.

Preparation of aminated chitosan microspheres by one-pot method and their adsorption properties for dye wastewater

Polyamine chelating adsorbents have a good removal effect on dye wastewater. In this study, small molecule triethylenetetramine and macromolecular poly(ethylene imine) were selected as aminated reagent, and two kinds of aminated chitosan microspheres, TETA-CTSms and PEI-CTSms, were obtained by emulsion cross-linking method. The microspheres were fully characterized by FTIR, SEM, XRD, EDS and TGA. EDS results showed that the N content of the PEI-CTSms and TETA-CTSms microspheres increased significantly after the cross-linking reaction and can reach 5.7 wt% and 7.3 wt%, respectively. Adsorption experiments confirmed that TETA-CTSms and PEI-CTSms showed greater adsorption characteristics for anionic dye reactive yellow (RY) in aqueous solutions compared with CTSms, and the adsorption capacity per unit area was increased by 39.11% and 88.56%, respectively. The adsorption capacity of aminated microspheres for RY decreased with the increase of pH. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption process was in accordance with the Langmuir isotherm model. The negative value of ΔG confirmed that the adsorption process was spontaneous, and the dye adsorption was a multiple process dominated by chemical chelating and physical adsorption.

Albumin-mediated deposition of bone-like apatite onto nano-sized surfaces: Effect of surface reactivity and interfacial hydration

The bioactivity of an implant is displayed on its ability to induce heterogeneous nucleation of biogenic apatite onto its surface upon immersion in body fluids; forming, through this layer, a stable bond with the host tissue. The present article evaluates the bioactivity of different nanostructured substrates based on synthetic hydroxyapatite (HA) and titania (TiO₂) nanoparticles, where we extend the debate regarding the selective roles played by the presence of albumin on the biogenic apatite coating evolution. The substrates bone-bonding potential was evaluated by keeping the materials in contact with Simulated Body Fluid, while the influence of the presence of Bovine Serum Albumin in bioactivity was analyzed by a spectrophotometric technique. Our results show that materials' surface reactivity and their interfacial hydration are responsible for the bonding-site alteration and surface charge density distribution, which in turn, regulate the protein adsorption process. As a matter of fact, variations on the protein adsorbed density have a directly proportional impact on calcium binding sites, which should be responsible for the initiation of the mineralization process, disturbing the deposition of the interfacial calcium phosphate (Ca-P) mineralized coating.