Adsorption removal and photocatalytic degradation of azithromycin from aqueous solution using PAC/Fe/Ag/Zn nanocomposite

Light-driven photocatalysis as an effective tool for degradation of antibiotics

Antibiotic contamination has become a severe issue and a dangerous concern to the environment because of large release of antibiotic effluent into terrestrial and aquatic ecosystems. To try and solve these issues, a plethora of research on antibiotic withdrawal has been carried out. Recently photocatalysis has received tremendous attention due to its ability to remove antibiotics from aqueous solutions in a cost-effective and environmentally friendly manner with few drawbacks compared to traditional photocatalysts. Considerable attention has been focused on developing advanced visible light-driven photocatalysts in order to address these problems. This review provides an overview of recent developments in the field of photocatalytic degradation of antibiotics, including the doping of metals and non-metals into ultraviolet light-driven photocatalysts, the formation of new semiconductor photocatalysts, the advancement of heterojunction photocatalysts, and the building of surface plasmon resonance-enhanced photocatalytic systems.

Photodegradation of a Broad-Spectrum Antibiotic Azithromycin Using H2O2 under Ultraviolet Irradiation

The photodegradation of azithromycin present was carried out in water using H2O2 under UV irradiation. The reaction variables considered in this study were the amount of H2O2 solution and the initial concentration of azithromycin to evaluate the performance of the photodegradation process. The azithromycin degradation was not observed in the dark during stirring for 20 min. The study showed an efficient photodegradation of azithromycin using H2O2 as an oxidant in the presence of UV irradiation. The azithromycin degradation was altered significantly by the pH of the irradiated solution. The degradation was low at an acidic pH and showed an increasing trend as the pH changed to basic. The azithromycin degradation increased with a higher amount (higher concentration) of H2O2. The degradation of azithromycin decreased with a higher concentration of azithromycin in the reacting solution. The highest degradation of AZT was achieved in 1 h using a 1.0 ppm AZT solution containing 3 mL of H2O2. The experimental data obtained were well-fitted to zero-order reaction kinetics. The results of this study were found quite excellent. They showed 100% degradation in 1 h when compared with those reported in the literature, both with photocatalysis using nanomaterials and photolysis using light irradiation and/or H2O2. The UV/H2O2 system was found to be quite efficient for the photodegradation of azithromycin, and this system can be applied to degrade other organic pollutants present in industrial wastewater.

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.

Detoxification of fluoroglucocorticoid by Acinetobacter pittii C3 via a novel defluorination pathway with hydrolysis, oxidation and reduction: Performance, genomic characteristics, and mechanism

Biological dehalogenation degradation was an important detoxification method for the ecotoxicity and teratogenic toxicity of fluorocorticosteroids (FGCs). The functional strain Acinetobacter pittii C3 can effectively biodegrade and defluorinate to 1 mg/L Triamcinolone acetonide (TA), a representative FGCs, with 86 % and 79 % removal proportion in 168 h with the biodegradation and detoxification kinetic constant of 0.031/h and 0.016/h. The dehalogenation and degradation ability of strain C3 was related to its dehalogenation genomic characteristics, which manifested in the functional gene expression of dehalogenation, degradation, and toxicity tolerance. Three detoxification mechanisms were positively correlated with defluorination pathways through hydrolysis, oxidation, and reduction, which were regulated by the expression of the haloacid dehalogenase (HAD) gene (mupP, yrfG, and gph), oxygenase gene (dmpA and catA), and reductase gene (nrdAB and TgnAB). Hydrolysis defluorination was the most critical way for TA detoxification metabolism, which could rapidly generate low-toxicity metabolites and reduce toxic bioaccumulation due to hydrolytic dehalogenase-induced defluorination. The mechanism of hydrolytic defluorination was that the active pocket of hydrolytic dehalogenase was matched well with the spatial structure of TA under the adjustment of the hydrogen bond, and thus induced molecular recognition to promote the catalytic hydrolytic degradation of various amino acid residues. This work provided an effective bioremediation method and mechanism for improving defluorination and detoxification performance.

Impregnation of biochar with montmorillonite and its activation for the removal of azithromycin from aqueous media

An inexpensive and environmentally friendly composite synthesized from rice husk, impregnated with montmorillonite and activated by carbon dioxide, was investigated for the removal of azithromycin from an aqueous solution. Various techniques were used to characterize adsorbents in detail. The sorption process was primarily regulated by the solution pH, pollutant concentration, contact duration, adsorbent dose, and solution temperature. The equilibrium data were best analyzed using the nonlinear Langmuir and Sips (R² > 0.97) isotherms, which revealed that adsorption occurs in a homogenous manner. The adsorption capacity of pristine biochar and carbon dioxide activated biochar-montmorillonite composite was 33.4 mg g^-1 and 44.73 mg g^-1, respectively. Kinetic studies identified that the experimental data obeyed the pseudo-second-order and Elovich models (R² > 0.98) indicating the chemisorption nature of adsorbents. The thermodynamic parameters determined the endothermic and spontaneous nature of the reaction. The ion exchange, π-π electron-donor-acceptor (EDA) interactions, hydrogen-bonding, and electrostatic interactions were the plausible mechanisms responsible for the adsorption process. This study revealed that a carbon dioxide activated biochar-montmorillonite composite may be used as an effective, sustainable, and economical adsorbent for the removal of azithromycin from polluted water.

Plant-based green fabrication of CuO-CdO-bentonite S-scheme heterojunction with enhanced photocatalytic performance for the degradation of levofloxacin

In this research, for the first time, CuO and CdO nanoparticles (NPs) were synthesized using Ferula persica and anchored on layered bentonite as a novel S-scheme nano-heterojunction (denoted as CuO-CdO-BT). Ferula persica acted as a naturally-sourced reducing agent and stabilizer for the synthesis of NPs. The performance of CuO-CdO-BT was evaluated for the degradation of levofloxacin from an aqueous solution under sunlight. The characterization results clarified that the bentonite as a support not only reduced the agglomeration of CuO and CdO NPs but also decreased the size of biosynthesized NPs, which increased the active surface of NPs and the photodegardation efficiency. The effect of operational reaction system variables was examined to optimize the photocatalytic capability of CuO-CdO-BT. Under optimum conditions (catalyst dosage = 0.4 g/L, LVF concentration = 10 mg/L and pH = 8), 96.11% of levofloxacin was degraded using CuO-CdO-BT after 30 min with degradation kinetic of 0.108 min-1, which was about 2.4 and 4.2 times higher than those of bare CuO and CdO NPs, respectively. The improvement of the photocatalytic degradation efficiency of CuO-CdO-BT compared to CuO and CdO NPs was due to preventing the recombination of charge carriers in the S-scheme system. The radical quenching experiments ascertained the generation of [Formula: see text]·OH, and [Formula: see text] species in the CuO-CdO-BT system, indicating that ·OH radicals have a more prominent role than [Formula: see text] and [Formula: see text] in the photocatalytic reaction. The six possible levofloxacin pathways of LVF degradation were suggested based on HPLC-MS analysis. Over 88.5% LVF was removed using CuO-CdO-BT after three catalyst reuse cycles, indicating a cost-effectiveness potential of the biosynthesized photocatalyst reusability. Almost complete mineralization of LVF was obtained by the CuO-CdO-BT photocatalyst after 180 min of reaction. Based on findings, the S-scheme mechanism of photo-generated electron-hole pairs transfer in the CuO-CdO-BT system was found. The unique structural features of the new generation of S-scheme heterojunction and green synthesis of NPs using plants provide promising photocatalysts to improve wastewater treatment.

Highly effective water hyacinth (Eichhornia crassipes) waste-based functionalized sustainable green adsorbents for antibiotic remediation from wastewater

Azithromycin (AZIM) is considered as one of the most frequently prescribed antibiotics (ABs) in the world by medical professionals. This study explored, two novel, cheap and environmentally beneficial adsorbents i.e., alkali treated water hyacinth powder (AT-WHP) and graphene oxide-water hyacinth-polyvinyl alcohol (GO-WH-PVA) composite, fabricated from water hyacinth (Eichhornia crassipes) waste to remediate AZIM from wastewater. Biosorption experiments were performed by batch and packed-bed column studies and the adsorbents were characterized using various instrumental methods. The morpho-chemical profile of the adsorbents suggested noteworthy AZIM adsorption. AZIM adsorption data can be reasonably explained by pseudo second order (PSO) kinetic model with maximum regression coefficient (R² > 0.99) and lowest Marquardt's present standard deviation (MPSD) and root mean squared error (RMSE) values. The isotherm models recommended Langmuir and Temkin to be the best-fitted, providing highest regression coefficient and lowest error values. Conferring to Langmuir model, the theoretical highest adsorption potentials (q_max) were accounted to be 244.498 and 338.115 mg/g for AT-WHP and GO-WH-PVA, correspondingly, very close to experimental values (q_e, exp). AZIM adsorption processes were governed by the chemisorption mechanisms. The adsorbents had excellent regeneration potential and could be reused several times. In order to scale-up application of the adsorbents, performance of a 100 L packed-bed reactor was assessed and a breakthrough time of adsorption for GO-WH-PVA was 15 min in 5000 mg/L AZIM concentration. Thus, the absorbents synthesized in this study can be considered highly effective at removal of AZIM from wastewater.