Response surface methodology optimizing the adsorptive removal of azithromycin using mesoporous silica SBA-15: Mechanism, thermodynamic, equilibrium, and kinetics modeling studies

Bioinspired chitosan/PVA beads cross-linked with LTH-doped bacterial cellulose hydrochar for high-efficiency removal of antibiotics

This study presents the development of eco-friendly, bioinspired Chitosan (CS)/Polyvinyl alcohol (PVA) composite beads cross-linked with layered triple hydroxide (LTH) doped bacterial cellulose microfilament (BCM) Hydrochar as a highly efficient adsorbent for removing Vancomycin (VAN) and Azithromycin (AZM) from aqueous solutions. The composite beads were synthesized using a bioinspired approach that integrates 1D BCM Hydrochar and 2D LTH plates into a 3D hybrid structure, offering high porosity, diverse functional groups, and pH sensitivity. The adsorbents were characterized using FTIR, EDX, SEM, XRD, and zeta potential analysis. Optimal adsorption conditions, including 60 min of contact time, 0.133 g·L-1 dosage, and pH levels of 8 for VAN and 8.5 for AZM, achieved maximum adsorption capacities of 1845 mg·g-1 for AZM and 2182 mg·g-1 for VAN at a 500 mg·L-1 concentration. The adsorption mechanisms involved physisorption and chemisorption, influenced by surface heterogeneity and interactions. VAN exhibited stronger adsorption, while AZM displayed more uniform adsorption due to weaker interactions. The adsorbent retained high adsorption capacity across multiple regeneration cycles and demonstrated resilience in the presence of coexisting compounds, making it suitable for long-term wastewater treatment. This work highlights the promise of carbohydrate-derived, sustainable LTH@BCM char-CS/PVA composite beads as high-capacity adsorbents, offering an effective, eco-friendly solution for mitigating pharmaceutical pollutants in water.

Azithromycin removal from water via adsorption on drinking water sludge-derived materials: Kinetics and isotherms studies

In this study, we utilized drinking water treatment sludge (WTS) to produce adsorbents through the drying and calcination process. These adsorbents were then evaluated for their ability to remove azithromycin (AZT) from aqueous solutions. The L-500 adsorbent, derived from the calcination (at 500°C) of WTS generated under conditions of low turbidity in the drinking water treatment plant, presented an increase in the specific surface area from 70.745 to 95.471 m2 g-1 and in the total pore volume from 0.154 to 0.211 cm3 g-1, which resulted in a significant AZT removal efficiency of 65% in distilled water after 60 min of treatment. In synthetic wastewater, the rate of AZT removal increased to 80%, in comparison, in a real effluent of a municipal wastewater treatment plant, an AZT removal of 56% was obtained. Kinetic studies revealed that the experimental data followed the pseudo-second-order model (R2: 0.993-0.999, APE: 0.07-1.30%, and Δq: 0.10-2.14%) suggesting that chemisorption is the limiting step in the adsorption using L-500. This finding aligns with FTIR analysis, which indicates that adsorption mechanisms involve π-π stacking, hydrogen bonding, and electrostatic interactions. The equilibrium data were analyzed using the nonlinear Langmuir, Freundlich, and Langmuir-Freundlich isotherms. The Langmuir-Freundlich model presented the best fitting (R2: 0.93, APE: 2.22%, and Δq: 0.06%) revealing numerous interactions and adsorption energies between AZT and L-500. This adsorbent showed a reduction of 19% in its AZT removal after four consecutive reuse cycles. In line with the circular economy principles, our study presents an interesting prospect for the reuse and valorization of WTS. This approach not only offers an effective adsorbent for AZT removal from water but also represents a significant step forward in advancing sustainable water treatment solutions within the framework of the circular economy.

Modeling of adsorptive removal of azithromycin from aquatic media by CoFe2O4/NiO anchored microalgae-derived nitrogen-doped porous activated carbon adsorbent and colorimetric quantifying of azithromycin in pharmaceutical products

Herein, it was aimed to optimize the removal process of Azithromycin (Azi) from the aquatic environment via CoFe2O4/NiO nanoparticles anchored onto the microalgae-derived nitrogen-doped porous activated carbon (N-PAC), besides developing a colorimetric method for the swift monitoring of Azi in pharmaceutical products. In this study, the Spirulina platensis (Sp) was used as a biomass resource for fabricating CoFe2O4/NiO@N-PAC adsorbent. The pores of N-PAC mainly entail mesoporous structures with a mean pore diameter of 21.546 nm and total cavity volume (Vtotal) of 0.033578 cm3. g-1. The adsorption studies offered that 98.5% of Azi in aqueous media could remove by CoFe2O4/NiO@N-PAC. For the cyclic stability analysis, the adsorbent was separated magnetically and assessed at the end of five adsorption-desorption cycles with a negligible decrease in adsorption. The kinetic modeling revealed that the adsorption of Azi onto the CoFe2O4/NiO@N-PAC was well-fitted to the second-order reaction kinetics, and the highest adsorption capacity was found as 2000 mg. g-1 at 25 °C based on the Langmuir adsorption isotherm model at 0.8 g. L-1 adsorbent concentration. The Freundlich isotherm model had the best agreement with the experimental data. Thermodynamic modeling indicated the spontaneous and exothermic nature of the adsorption process. Moreover, the effects of pH, temperature, and operating time were also optimized in the colorimetric Azi detection. The blue ion-pair complexes between Azi and Coomassie Brilliant Blue G-250 (CBBG-250) reagent followed Beer's law at wavelengths of 640 nm in the concentration range of 1.0 μM to 1.0 mM with a 0.94 μM limit of detection (LOD). In addition, the selectivity of Azi determination was verified in presence of various species. Furthermore, the applicability of CBBG-250 dye for quantifying Azi was evaluated in Azi capsules as real samples, which revealed the acceptable recovery percentage (98.72-101.27%). This work paves the way for engineering advanced nanomaterials for the removal and monitoring of Azi and assures the sustainability of environmental protection and public health.