Removal of tetracycline antibiotics from aqueous solution by amino-Fe (III) functionalized SBA15

Iron‑calcium dual crosslinked graphene oxide/alginate aerogel microspheres for extraordinary elimination of tetracycline in complex wastewater: Performance, mechanism, and applications

Antibiotics have been considered as a group of emerging contaminants for their stable chemical structure, significant pseudo-persistence, and biological toxicity. Tetracycline (TC), as one of the typical antibiotics frequently detected in environmental media, can cause the dissemination and accumulation of antibiotic resistance gene (ARG), ultimately threatening human health and environmental safety. Herein, a novel iron‑calcium di-crosslinked graphene oxide/alginate (GO/SA-Fe3+-Ca2+) aerogel was facilely synthesized for TC uptake. It was found that the introduction of GO nanosheets and Fe3+ sites into composite enormously enhanced TC removal. Specifically, TC can be stably and efficiently eliminated over the wide pH range of 5-8. The fitted maximum qe with Liu isotherm model at 308 K reached 1664.05 mg/g, surpassing almost all reported sorbents. The pseudo-second-order kinetic model with chemical sorption characteristics better fitted TC adsorption process, which was endothermic and spontaneous in nature. Multifarious adsorptive sites of GO/SA-Fe3+-Ca2+ synergically participated in TC uptake through multi-mechanisms (e.g., π-π EDA, cation-π bonding, H-bonding, Fe3+-coordination, and electrostatic attraction, etc.). The as-prepared composite showed satisfactory TC removal in several runs of adsorption-desorption operations, high salinity, and model aquaculture wastewater. Moreover, the packed-column could continuously run for >200 h until adsorption saturation was achieved with a dynamic adsorption capacity of 216.69 mg/g, manifesting its scale-up engineering applications. All above merits make as-constructed composite an alternative sorbent for eliminating TC from complex wastewater.

Ultrafast and simultaneous removal of four tetracyclines from aqueous solutions using waste material-derived graphene oxide-supported cobalt-iron magnetic nanocomposites

In this work, a graphene oxide-supported cobalt-iron oxide (GO/Co-Fe) magnetic nanocomposite was successfully synthesized using waste dry cells for the efficient and simultaneous removal of tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DTC) from aqueous solutions. The GO/Co-Fe nanocomposite was thoroughly characterized using Fourier transform infrared spectroscopy, vibrating sample magnetometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and zeta potential analysis. This multi-faceted characterization provided clean insights into the composition and properties of the synthesized nanocomposite. The adsorption of tetracyclines (TCs) was systematically investigated by assessing the influence of critical factors, such as adsorbent dosage, contact duration, initial pH of the solution, initial concentration, and temperature. The GO/Co-Fe adsorbent showed high removal efficiencies of 94.1% TC, 94.32% CTC, 94.22% OTC, and 96.94% DTC within 30 s contact period. The maximum removal efficiency of TCs was found at a low adsorbent dose of 0.15 g L-1. Notably, this superior removal efficiency was achieved at neutral pH and room temperature, demonstrating the adsorbent's efficacy under environmentally viable conditions. The kinetic studies demonstrated that the adsorption process was fitted satisfactorily with the pseudo-second-order model. Additionally, the adsorption behaviour of TCs on the GO/Co-Fe adsorbent was assessed by isotherm models, Langmuir and Freundlich. The experimental data followed the Langmuir isotherm, signifying a monolayer adsorption mechanism on the surface of the adsorbent. The adsorption capacities (qm) of GO/Co-Fe for TC, CTC, OTC and DTC were determined to be 64.10, 71.43, 72.46 and 99.01 mg g-1, respectively. Importantly, the GO/Co-Fe adsorbent showed reusability capabilities. The super magnetic properties of GO/Co-Fe made it easy to use for several cycles. These results clearly establish GO/Co-Fe as an exceptionally effective adsorbent for the removal of TCs from aqueous systems, highlighting its great potentiality in water treatment applications.

Boosting Tetracycline Degradation with an S-Scheme Heterojunction of N-Doped Carbon Quantum Dots-Decorated TiO2

N-doped carbon quantum dots (N-CQDs) derived from the Rumex crispus L. plant were incorporated into TiO₂ via a facile hydrothermal method. As-prepared materials were characterized and used in the photocatalytic tetracycline (TC) degradation under UVA light irradiation by examining several operational parameters involving the N-CQDs amount, initial TC concentration, pH, and photocatalytic reaction time. XRD analysis revealed the conversion of the rutile phase to the anatase phase after the incorporation of N-CQDs into the TiO₂ structure. The results revealed that the N-CQDs/TiO₂ photocatalysts demonstrated the highest efficiency in TC degradation compared to other processes of adsorption, photolysis (UVA), and photocatalysis with TiO₂ (TiO₂/UVA). Under optimized conditions, 10 mg/L TC at pH 5.15 with 0.2 g/L N-CQDs/TiO₂ catalyst showed 97.7% photocatalytic degradation for 120 min under UVA irradiation. The formation of an S-scheme heterojunction between N-CQDs and TiO₂ provided enhanced charge separation and strong redox capability, causing significant improvement in the photocatalytic performance of N-CQDs/TiO₂. Trapping experiments showed that O₂^•- and h⁺ are the predominant reactive species for the TC elimination in an aqueous solution.

In-situ modified biosynthetic crystals with lanthanum for fluoride removal based on microbially induced calcium precipitation: Characterization, kinetics, and mechanism

In this research, in-situ modified biosynthetic crystals with lanthanum (BC-La) were synthesized based on anaerobic microbially induced calcium precipitation (MICP) and investigated its capacity for groundwater defluoridation under various operational conditions. The kinetic and thermodynamic models were simulated to explore the effect of the material on the removal of fluoride ion (F^-) under various parameters (pH, initial concentration of F^-, and temperature). BC-La had the maximum F^- adsorption capacity of 10.92 mg g^-1 and 96.66% removal efficiency. The pseudo-second-order kinetic model and Langmuir isotherm model were the best kinetic and isotherm models for F^- removal from BC-La, which indicated that F^- were mainly spontaneously removed through chemisorption and adsorption processes. The specific surface area was 54.26 m² g^-1 and the average pore size was 9.0670 nm. BC-La mainly contained LaCO₃OH, LaPO₄, CaCO₃, Ca₅ (PO₄)₃OH, and F^- was mainly removed through ion exchange with the material surface. Moreover, OH^-, PO₄^3-, and CO₃^2- significantly influenced the F^- removal. This work suggested a novel method for in-situ modification of anaerobic biosynthetic crystals, which improved the defluoridation effect of traditional biosynthetic crystals, increased the stability of the BC-La and allowed to remove F^- from groundwater consistently.

Structuring alginate/dopamine powder into macroscopic aerogel microsphere for exceptional removal of tetracycline from water: Performance and mechanisms

Aerogel was selected as one of IUPAC Top Ten Emerging Technologies in Chemistry in 2022, and has attracted tremendous concerns of scientists in removal of emerging contaminants. In this work a novel Fe³⁺ cross-linked alginate aerogel (SA/DA-Fe³⁺) with multiple sorption sites were facilely fabricated and applied for highly efficient removal of tetracycline (TC) from water. Results showed that Fe³⁺ and DA cooperatively improve adsorption of TC and TC was efficiently removed over a broad pH range of 4-8. The kinetics process can be better described by a chemisorption controlled pseudo-second-order kinetics model and Langmuir isotherm equation with characteristics of monolayer coverage. The fitted q_max value of TC at ambient temperature was 804.6 mg g^-1 higher than those of other reported adsorbents. Multiple interactions including π-π EDA, complexation, hydrogen bonding, electrostatic attraction, etc. were involved in adsorption process. Moreover, SA/DA-Fe³⁺ aerogel exhibited satisfactory stability, reusability, and recyclability for consecutive applications. Most importantly, after consecutively running for >1000 h with dynamic sorption capacity over 500 mg g^-1, the packed-column was still not saturated, manifesting its great potentials for treating actual wastewaters. Thus, above superiorities make SA/DA-Fe³⁺ a promising candidate adsorbent for treating TC-containing wastewater.

Selective adsorption and separation of methylene blue by facily preparable xanthan gum/amantadine composites

In this work, xanthan gum-based composites were successfully graft-modified by amantadine (XG-Fe³⁺/AM) with higher adsorption capacity and selectivity on recycling cationic dye (methylene blue, MB) from aqueous solution. The adsorption equilibrium of MB could be achieved approximately within 5 min when the initial concentration was 100 mg/L, and the maximum adsorption capacity was up to 565 mg/g. After 5 desorption-regeneration cycles, the removal rate of XG-Fe³⁺/AM for MB could still be as high as 95 % with slight decrement. Additionally, the effects of pH, contact time, temperature and initial dye concentration on the adsorption performance of MB were systematically examined. Furthermore, the adsorbent was characterized by FT-IR, BET and XPS analysis. In mixed anionic and cationic dyes, the adsorption selectivity of XG-Fe³⁺/AM on MB in the mixture of MB and methyl orange (MO) reached up to 99.69 %. Molecular dynamics simulation revealed that the trend of adsorption energy for dyes was in good agreement of the experimental order of adsorption capacities and molecular sizes among seven anionic and cationic dyes based on molecular matching effect and electrostatic interaction. Therefore, XG-Fe³⁺/AM is an eco-friendly, facile-synthesis and high-selectivity adsorbent, which remove cationic dyes in multi-component systems through electrostatic interaction and molecular matching effect.

One-Step Synthesis of Al-Doped UiO-66 Nanoparticle for Enhanced Removal of Organic Dyes from Wastewater

In this study, a series of Al-doped metal-organic frameworks (Al_xZr_(1-x)-UiO-66) were synthesized through a one-step solvothermal method. Various characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and N₂ sorption measurement, suggested that the Al doping was uniform and barely influenced the crystallinity, chemical stability, and thermal stability of the materials. Two cationic dyes, safranine T (ST) and methylene blue (MB), were selected for investigating the adsorption performances of Al-doped UiO-66 materials. Al_0.3Zr_0.7-UiO-66 exhibited 9.63 and 5.54 times higher adsorption capacities than UiO-66, 498 mg/g and 251 mg/g for ST and MB, respectively. The improved adsorption performance can be attributed to π-π interaction, hydrogen bond, and the coordination between the dye and Al-doped MOF. The pseudo-second-order and Langmuir models explained the adsorption process well, which indicated that the dye adsorption on Al_0.3Zr_0.7-UiO-66 mostly occurred through chemisorption on homogeneous surfaces. A thermodynamic study indicated the adsorption process was spontaneous and endothermic. The adsorption capacity did not decrease significantly after four cycles.

A critical review on retaining antibiotics in liquid digestate: Potential risk and removal technologies

Substantial levels of antibiotics remain in liquid digestate, posing a significant threat to human safety and the environment. A comprehensive assessment of residual antibiotics in liquid digestate and related removal technologies is required. To this end, this review first evaluates the potential risks of the residual antibiotics in liquid digestate by describing various anaerobic digestion processes and their half-lives in the environment. Next, emerging technologies for removing antibiotics in liquid digestate are summarized and discussed, including membrane separation, adsorption, and advanced oxidation processes. Finally, this study comprehensively and critically discusses these emerging technologies' prospects and challenges, including techno-economic feasibility and environmental impacts.

Chelation in Antibacterial Drugs: From Nitroxoline to Cefiderocol and Beyond

In the era of escalating antimicrobial resistance, the need for antibacterial drugs with novel or improved modes of action (MOAs) is a health concern of utmost importance. Adding or improving the chelating abilities of existing drugs or finding new, nature-inspired chelating agents seems to be one of the major ways to ensure progress. This review article provides insight into the modes of action of antibacterial agents, class by class, through the perspective of chelation. We covered a wide scope of antibacterials, from a century-old quintessential chelating agent nitroxoline, currently unearthed due to its newly discovered anticancer and antibiofilm activities, over the commonly used antibacterial classes, to new cephalosporin cefiderocol and a potential future class of tetramates. We show the impressive spectrum of roles that chelation plays in antibacterial MOAs. This, by itself, demonstrates the importance of understanding the fundamental chemistry behind such complex processes.

Efficient removal of pefloxacin from aqueous solution by acid-alkali modified sludge-based biochar: adsorption kinetics, isotherm, thermodynamics, and mechanism

In this paper, one kind of acid-alkali modified sludge-based biochar (ASBC) was synthesized, characterized, and employed as adsorbent for the removal of pefloxacin. The characterization results showed that the specific surface area (SSA) of ASBC (53.381 m²/g) was significantly higher than that of SBC (24.411 m²/g). ASBC had a rougher surface, larger particle distribution, lower zero point charge, and richer functional groups (e.g., C-O and O-H) than SBC. The adsorption capacity of ASBC was 1.82 times than that of SBC. After 8 adsorption cycles in reuse experiment, the adsorption capacity of ASBC for pefloxacin still reached 144.08 mg/L, indicating that ASBC has good reusability. Static experiments showed that the optimal pH value was 6.0 in the adsorption of pefloxacin on SBC and ASBC. The result of adsorption kinetics indicated that the pseudo-second-order model could describe well the adsorption process. The Freundlich model was better than the Langmuir model to describe the adsorption of pefloxacin by ASBC, indicating that the adsorption process was mainly multilayer adsorption. Thermodynamic result showed that the adsorption of pefloxacin by ASBC was spontaneous and endothermic. The removal mechanism of pefloxacin by ASBC is mainly the substitution reaction and π-π EDA interaction. In summary, acid-alkali modified biochar is an effective adsorbent for pefloxacin in aqueous solution, and has great application prospects.

Phenol and 17β-estradiol removal by Zoogloea sp. MFQ7 and in-situ generated biogenic manganese oxides: Performance, kinetics and mechanism

The pollution of multifarious pollutants such as heavy metal, organic compounds, and nitrate are a hot research topic at present. In this study, the functions of Zoogloea sp. MFQ7 and its biological precipitation formed during bacterial manganese oxidation on the removal of phenol and 17β-estradiol (E2) were investigated. Strain MFQ7, a manganese-oxidizing bacteria, can remove 98.34% of phenol under pH of 7.1, a temperature of 30 ℃ and Mn²⁺ concentration of 24.34 mg L^-1, additionally, the optimum E2 removal by strain MFQ7 was 100.00% at pH of 7.1, temperature of 28 ℃ and Mn²⁺ concentration of 28.45 mg L^-1 by using response surface methodology (RSM) based on Box-Behnken design (BBD) model. The maximum adsorption capacity of bio-precipitation for phenol and E2 was 201.15 mg g^-1 and 65.90 mg g^-1, respectively. Furthermore, adsorption kinetics and isotherms analysis, XPS, FTIR spectra, Mn(III) trapping experiments elucidated chemical adsorption and Mn(III) oxidation contribute to the removal of phenol and E2 by biogenic manganese oxides. These findings indicated that the adsorption and oxidation of manganese are expected to be one of the effective means to remove these typical organic pollutants containing phenol and E2.

Adsorption of chlortetracycline in aquaculture wastewater by lanthanum modified multi-walled carbon nanotubes

The lanthanum modified multi-walled carbon nanotubes (La-CNTs) prepared by an impregnation method were investigated for the adsorption of chlortetracycline (CTC) in aquaculture wastewater. The adsorbents were characterized by SEM, EDS, XRD and BET. The effects of some factors including La-containing impregnant concentration, adsorbent dosage, CTC adsorbate concentration, adsorption time, pH of the adsorbate solution and additional ions on the CTC adsorption by La-CNTs were investigated in detail, and the optimal adsorption conditions were determined. The adsorption kinetics obeyed the quasi-second-order kinetic model. The adsorption isotherms obeyed the Langmuir model and the fitted maximum capacity of La-CNTs for CTC adsorption was 55.3 mg/g.

Simultaneous adsorption of tetracycline, ammonium and phosphate from wastewater by iron and nitrogen modified biochar: Kinetics, isotherm, thermodynamic and mechanism

The simultaneous removal of various pollutants in wastewater is increasingly deserved attention. In this study, an efficient adsorbent Fe/N@BC was synthesized by Fe-N co-modification. The adsorbability of Fe/N@BC was evaluated using a mixture with tetracycline (TC), NH₄⁺-N and PO₄^3-P. In comparison to BC, N@BC and Fe@BC, Fe/N@BC exhibited an excellent performance for simultaneously absorbing TC, NH₄⁺-N and PO₄^3-P. The pseudo-first-order was used to describe the adsorption process of NH₄⁺-N and PO₄^3-P, while the pseudo-second-order could be well fitted to TC adsorption data. The adsorption isotherms of TC, NH₄⁺-N and PO₄^3-P were more in line with Sips model (Adj.R² > 0.97). The maximum adsorption capacities of Fe/N@BC towards TC, NH₄⁺-N and PO₄^3-P were 238.94, 111.87 and 165.02 mg g^-1, respectively, which were 1.31-1.91 times than that of BC, N@BC and Fe@BC. The simultaneous adsorption mechanism mainly involved pore filling, electrostatic interaction, ion exchange, surface complexation, surface precipitation, H bond and π-π interaction. Furthermore, after six cycles, the removal efficiencies of TC, NH₄⁺-N and PO₄^3-P were 75.3, 66.1 and 64.5% by Fe/N@BC, highlighting its promising potential to adsorb multi-pollutants from aqueous solution.

Rapid and efficient adsorption of tetracycline from aqueous solution in a wide pH range by using iron and aminoacetic acid sequentially modified hierarchical porous biochar

The object of this work was to synthesize an iron and aminoacetic acid sequentially modified hierarchical porous biochar (AC-Fe@HPBC) for tetracycline (TC) removal from aqueous solution. Results showed that AC-Fe@HPBC had a larger surface area (362.5370 m²/g), developed microporous structure (0.1802 cm³/g), and numerous functional groups, which provided more adsorption sites. The maximum adsorption capacity towards TC by AC-Fe@HPBC was 457.85 mg/g, 1.43, 1.29 and 1.20-fold than that of HPBC, AC@PHBC and Fe@HPBC, respectively, and the super-fast adsorptive equilibrium was achieved within 10 min. Additionally, introducing amino and carboxyl functional groups on the AC-Fe@HPBC surface significantly broadened the operation pH range (3-11). Site energy analysis indicated TC and AC-Fe@HPBC had stronger adsorption affinity at a higher temperature. The adsorption mechanism involved pore filling, surface complexation, H-bond and π-π interaction. Moreover, the reusability experiments proved AC-Fe@HPBC as an effective adsorbent for TC removal from aqueous solution.

Microwave-assisted hydrothermal synthesis of MoS2-Ag3PO4 nanocomposites as visible light photocatalyst for the degradation of tetracycline hydrochloride

In the modern era, industrialization has facilitated the human life but produced several severe pollutants as well that are hazardous in nature. Thus the degradation of these hazardous material has drawn considerable attention. This study deals with the synthesis of MoS₂/Ag₃PO₄ heterojunction nanocomposite with 1-50% wt. using a microwave-assisted hydrothermal process as well as photocatalytic activity of tetracycline hydrochloride (TCH) degradation has been analysed. The compositional properties of nanocomposite catalysts have been studied through X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy as well as structural and morphological studies were conducted through scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller, photoluminescence, N₂ physical adsorption, UV-vis diffuse reflectance spectroscopy. This provides an excellent and efficient mechanism for the remediation of residual organic contaminants under visible light that could be used to decontaminate the atmosphere.

Efficient Removal of Chromium(VI) Using a Novel Waste Biomass Chestnut Shell-Based Carbon Electrode by Electrosorption

Biomass-derived porous carbon materials have a good application prospect in electrosorption because of their low cost, abundant natural resources, and excellent performance. In this work, three-dimensional interconnected structure porous carbon (CPC) was successfully synthesized from waste biomass chestnut shells by carbonization and chemical activation processes. The unique structure of CPC could offer superior double-layer capacitance and excellent conductivity. The as-obtained CPC was applied as an electrosorption electrode. In the deionization experiments, the removal efficiency of the CPC electrode in a 30 mg L^-1 chromium(VI) aqueous solution at 1.0 V was 90.5%. The electrosorption follows pseudo-second-order kinetics. The CPC electrode also presented good regeneration performance in the regeneration test. These results demonstrate that the as-prepared carbonaceous material is an ideal material for capacitive deionization electrodes.

Effective removal of tetracycline antibiotics from wastewater using practically applicable iron(III)-loaded cellulose nanofibres

The non-toxic and completely biodegradable cellulose within bamboo is one of the most abundant agricultural polysaccharide wastes worldwide, and can be processed into cellulose nanofibres (CNFs). Iron(III)-loaded CNFs (Fe(III)@CNFs) derived from bamboo were prepared to improve the adsorption of tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC) from an aqueous solution. The preparation conditions of Fe(III)@CNFs suitable for the simultaneous adsorption of three tetracycline antibiotics (TCs) were investigated. Various analyses proved the abundance of oxygen-containing functional groups and the existence of Fe(III) active metal sites in Fe(III)@CNFs. In batch experiments, Fe(III)@CNFs were applied under a wide pH range and the maximum adsorption capacities were 294.12, 232.56 and 500.00 mg g-1 (for TC, CTC and OTC, respectively). In addition, different concentrations and types of coexisting anions have a weak effect on TCs adsorption. The original TCs adsorption capacities of Fe(III)@CNFs remained stable (greater than 92%) after five cycles when UV + H2O2 was used as the regeneration method. Four adsorption mechanisms (surface complexation, hydrogen bonding, electrostatic interaction and van der Waals force) were obtained for the endothermic adsorption of TCs, among which surface complexation between Fe(III) and TCs always dominates. The practically applicable Fe(III)@CNFs adsorbents are promising for TCs enrichment and remediation in engineering applications.

Luminescent cellulose-based porous binary metal-organic gels in an adsorption bed for effective adsorption and sensitive detection of chlortetracycline hydrochloride

Three novel (Fe-Eu) JLUE-MOGs were successfully fabricated through a solvothermal method and employed to construct the double-effect system for antibiotics adsorption and detection. The characterizations highlighted the properties of ample active sites, large surface areas and hierarchical porous structures, which did contribute to superb and rapid chlortetracycline hydrochloride (CTC) adsorption by JLUE-MOGs. Besides, the effects of initial pH values, JLUE-MOG dosages and co-existing inorganic ions on the CTC adsorption could be explained by pore filling, π-π EDA interaction, electrostatic interaction, water affinity as well as hydrogen bonding. Moreover, the optimized condition was cross-explored by response surface methodology (RSM) with tiny differences compared to actual experiments. In addition, fluorescent JLUE-MOG-7 was implemented for sensitive recognition of CTC and reflecting adsorption processes. Furthermore, shaping JLUE-MOG-7@cellulose aerogels were fabricated as filter materials for applying into an adsorption bed. The breakthrough process was fitted well by Bohart-Adams model and Thomas model, along with recognizable fluorescence changes of immobilized adsorbents. This work develops efficient and luminescent powder-like JLUE-MOGs for antibiotics adsorptive enrichment and sensitive detection. More importantly, immobilized JLUE-MOG@cellulose aerogels, as promising and alternative adsorbents with real-time fluorescence changes, can be utilized for continuously pollutants removal in real wastewater treatment.

Interaction of Carboxyalkylated Cellulose Nanocrystals and Antibiotics

Although antibiotics are beneficial for treating infections, their release into the environment has raised global concerns. In this work, the interactions of cellulose nanocrystal (CNC) derivatives with sulfamethoxazole (SMX), ciprofloxacin (CIP), and doxycycline (DOX) antibiotics were studied fundamentally. CNC was carboxyalkylated to bear different carbon chain lengths but similar negative charges on its surface. The highest level of adsorption of DOX on the carboxypantadecanated CNC (i.e., carboxyalkylated CNC with more carbon spacer, PCNC) occurred at pH 6.0, which was due to the electrostatic and π interactions along with hydrogen bonding. The contact angle and quartz crystal microbalance (QCM) adsorption analyses revealed a faster interaction and adsorption of DOX than other antibiotics on PCNC. The results also depicted the diffusion of DOX into the porous structure of CNC derivatives, especially that of PCNC. Also, a more compact adsorbed layer of DOX was formed on PCNC than on other CNC derivatives. Carboxyalkylation was observed to slightly reduce the surface area of CNC, while the antibiotic adsorption drastically increased the surface area of CNC due to their adsorption on the surface. XPS analysis revealed that carboxyalkylation significantly enhanced the C-C/C-H bond, while antibiotic adsorption on PCNC enhanced C-N/C-O and C-C/C-H bonds in antibiotic-loaded CNC samples. Overall, carboxyalkylated CNC was observed to have an outstanding affinity for capturing antibiotics, especially DOX, which could pave the way for the use of CNC in such applications that surface/antibiotic interactions were essential.

Effective tetracycline removal from liquid streams of dairy manure via hierarchical poly (vinyl alcohol-co-ethylene)/polyaniline metal complex nanofibrous membranes

Antibiotic residues from animal wastes enter underground and surface water streams, posing high risks to public health. Novel technologies capable of removing the residues from the matrix of concern such as animal waste should be developed. This research investigates the development of nanofiber absorbent for removing tetracycline (TC) antibiotic residues from liquid streams of dairy manure produced in a typical dairy farm. Hierarchically structured nanofibrous adsorbent was developed through growing a uniform polyaniline (PAni) nanodots on poly (vinyl alcohol-co-ethylene) (EVOH) nanofiber membrane (NFM). Moreover, Cu²⁺ ions were chelated on the developed EVOH/PAni-Cl NFM to improve TC adsorption efficiency and selectivity. The TC adsorption capacities of EVOH/PAni-Cl-Cu²⁺ and EVOH/PAni-Cl) NFM were 1100 mg g^-1 and 600 mg g^-1 within 120 min., respectively. The NFMs adsorption efficiency was investigated using dairy wastewater. Initial TC concentrations in dairy wastewater sample varied between 20 and 50 ppm. The EVOH/PAni-Cl-Cu²⁺ NFM showed TC removal of 86% from dairy manure samples at 25 ppm initial TC concentration within 60 min. during batch mode treatment. Results showed that the dynamic binding efficiency of 450 mg g^-1 can be achieved at an initial TC concentration of 50 ppm. Furthermore, the NFM displayed efficient chemical and physical stability even after 8 cycles of reusing without significant changes in its performance or hazardous Cu²⁺ leaching.

Removal of antibiotics from aqueous solution by using porous adsorbent templated from eco-friendly Pickering aqueous foams

The aqueous foam template without any solvent and only using the particles stabilizer has attracted much attention for preparation of the porous adsorbents. Herein, a novel porous adsorbent was fabricated via thermal-initiated polymerization of Pickering aqueous foams, which was stabilized by the natural sepiolite (Sep) and pine pollen, and utilized for the removal of antibiotic from aqueous solution. The stabilizing mechanism of Pickering aqueous foam of that the Sep was modified with the leaching substance from pine pollen and arranged orderly around the bubble to form a dense "shell" structure was revealed. The adsorbents possessed the hierarchical porous structure and excellent adsorption performance for antibiotic of chlorotetracycline hydrochloride (CTC) and tetracycline hydrochloride (TC). The equilibrium adsorption capacities of CTC and TC were achieved with 465.59 and 330.59 mg/g within 60 min at 25°C, respectively. The adsorption process obeyed Langmuir model and pseudo-second-order adsorption kinetic model. This work provided eco-friendly approach for fabricate porous adsorbents for wastewater treatment.

Isolation of biosynthetic crystals by microbially induced calcium carbonate precipitation and their utilization for fluoride removal from groundwater

Biosynthetic crystals (BC) were prepared through microbially induced calcium carbonate precipitation (MICP) for fluoride (F^-) removal from the groundwater. Batch experiments were conducted to evaluate the fluoride adsorption capacity and the impacts of critical factors (organic matter, pH, initial fluoride concentration and BC dosage) on defluorination efficiency of BC. The maximum adsorption amount and defluorination efficiency were recorded as 5.10 mg g^-1 and 98.24%, respectively. The adsorption kinetics and isotherms studies showed that pseudo-second-order kinetic model and Freundlich isotherm model were best fitting to the reaction. Adsorption thermodynamic parameters indicated a spontaneous, endothermic and thermodynamically favorable adsorption process. Moreover, the mechanism of F^- removal by BC was further analyzed by SEM, XPS, XRD and FTIR. The method can cope with the problem of applying the external organic substances in MICP, and avoid the microbial safety risk in the effluent. As an economically and environmentally friendly adsorbent, BC can be used for F^- removal from groundwater.

Efficient Adsorption of Tetracycline from Aqueous Solutions by Modified Alginate Beads after the Removal of Cu(II) Ions

This work dealt with a potential and effective method to reuse modified alginate beads after the removal of Cu(II) ions for efficient adsorption of tetracycline (TC) from aqueous solutions. The modified alginate beads were fabricated by a polyacrylamide (PAM) network interpenetrated in alginate-Ca2+ network (PAM/CA) decorated with polyethylene glycol as a pore-forming agent. The porous PAM/CA was characterized using scanning electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The adsorption kinetics, isotherms, adsorption stability, and reusability studies of the adsorbent toward Cu(II) ions were scrutinized. The column performance of porous PAM/CA was tested with Cu(II)-containing electroplating wastewater. After Cu(II) adsorption, the Cu(II)-adsorbed PAM/CA (PAM/CA@Cu) was applied to remove TC from aqueous solutions without any regeneration process. The effects of pH, initial TC concentration, ionic strength, and coexisting ions on the adsorption were also discussed in detail. Compared with many reported adsorbents, the PAM/CA@Cu exhibited an excellent adsorption performance toward TC with a maximum adsorption capacity of 356.57 mg/g predicted by the Langmuir model at pH 5.0 and 30 °C with the absence of coexisting ions. The possible adsorption mechanism of TC onto the PAM/CA@Cu was revealed.

Chlortetracycline hydrochloride removal by different biochar/Fe composites: A comparative study

In the last years, the synthesis and applications of biochar/Fe composites have been extensively studied, but only few papers have systematically evaluated their removal performances. Herein, we successfully synthesized and structurally characterized Fe⁰, Fe₃C, and Fe₃O₄-coated biochars (BCs) for the removal of chlortetracycline hydrochloride (CH). Evaluation of their removal rate and affinity revealed that Fe⁰@BC could achieve better and faster CH removal and degradation than Fe₃C@BC and Fe₃O₄@BC. The removal rate was controlled by the O-Fe content and solution pH after the reaction. The CH adsorption occurred on the O C groups of Fe⁰@BC and the OC and OFe groups of Fe₃C@BC and Fe₃O₄@BC. Electron paramagnetic resonance analysis and radical quenching experiments indicated that HO and ¹O₂/ O₂^- were mainly responsible for CH degradation by biochar/Fe composites. Additional parameters, such as effects of initial concentrations and coexisting anions, regeneration capacity, cost and actual wastewater treatment were also explored. Principal component analysis was applied for a comprehensive and quantitative assessment of the three materials, indicating Fe⁰@BC is the most beneficial functional material for CH removal.

Sorption of pharmaceuticals and personal care products on soil and soil components: Influencing factors and mechanisms

The sorption of pharmaceuticals and personal care products (PPCPs) on soil and soil components makes an important contribution to the fate, migration and bioavailability of PPCPs. Previous reviews have mostly focused on the sorption of PPCPs on single soil components (e.g., minerals and soil organic matter). However, the sorption of PPCPs within the whole soil system has not been systematically analyzed. This paper reviews the recent progress on PPCP sorption on soil and soil components. We have evaluated the sorption of a wide range of PPCPs in research fields that are usually considered in isolation (e.g., humic acids (HAs), montmorillonite, kaolinite, and goethite), and established a bridge between PPCPs and sorbent. The sorption mechanisms of PPCPs, e.g., cation exchange, surface complexation, electrostatic interaction and hydrogen bonding, are discussed and critically evaluated. We also assessed the influence of environmental factors (pH, ionic strength, organic matter and temperature) on sorption. This review summarizes the knowledge of PPCPs sorption on soil gained in recent years, which can provide new strategies for solving the problem of antibiotic pollution.

Removal of tetracycline by denitrifying Mn(II)-oxidizing bacterium Pseudomonas sp. H117 and biomaterials (BMO and MBMO): Efficiency and mechanisms

Coexistence of multiple pollutants such as antibiotic, nitrate and heavy metal has received increasing attention resently. In this study, the functions of Pseudomonas sp.H117 on the removal of tetracycline(TC), nitrate and Mn(II), and biological materials (BMO(biogenic manganese oxides), MBMO(magnetic BMO)) on the removal of TC were investigated. Strain H117 showed higher TC removal efficiency of 68.86% (0.071 mg·L^-1·h^-1) within 96 h. Meanwhile, NO₃-N and Mn(II) achieved high removal efficiency of 100% (0.211 mg·L^-1·h^-1) and 64.64% (0.265 mg·L^-1·h^-1), respectively. Furthermore, trapping experiments testified that Mn(III) intermediate formed during the biological manganese oxidation process, which contribute to the TC degradation. 91.29% and 96.63% of TC removal efficiency within 12 h were achieved by BMO and MBMO. Moreover, XPS, FTIR spectra, kinetics analysis and adsorption isotherms elucidated Mn(III) oxidation, chemical adsorption and ligand exchange reactions contribute to the removal of TC by biomaterials.

Magnetic spent bleaching earth carbon (Mag-SBE@C) for efficient adsorption of tetracycline hydrochloride: Response surface methodology for optimization and mechanism of action

The utilization of spent bleaching earth (SBE)-based materials for adsorption of pollutants from water and wastewater has received growing attention. In this work, a comparative study of magnetic spent bleaching earth carbon (Mag-SBE@C) and spent bleaching earth carbon (SBE@C) was performed to remove tetracycline hydrochloride (TCH) from aqueous solutions. Mag-SBE@C exhibits the larger adsorption capacity (0.238 mmol/g) obtained by the Langmuir model than the original SBE@C (0.150 mmol/g). The adsorption process fits well with the pseudo second-order model and is found to be exothermic (ΔH₀ < 0) and spontaneous (ΔG₀ < 0). The optimal adsorption conditions (Mag-SBE@C dose 2.217 g/L, initial TCH concentration 0.113 mmol/L, initial solution pH 6.533) predicted by the response surface methodology (RSM) are consistent with the actual verification results. The inhibition extents of coexisting cations are ranked in a decline: Al³⁺ > Cu²⁺ > Fe³⁺ > Mg²⁺ > K⁺ > Na⁺. Various characterization results indicate that the adsorption mechanism of TCH by Mag-SBE@C likely includes the π-π interactions, hydrogen bonding, electrostatic interactions, π-cations interactions, FeN covalent bonding, and changes in physical and chemical properties. Mag-SBE@C is easily solid-liquid separated using magnetic field, and can be potentially reused for 13 times before completely losing its activity, exhibiting great potential to antibiotics elimination.

Manure anaerobic digestion effects and the role of pre- and post-treatments on veterinary antibiotics and antibiotic resistance genes removal efficiency

This review was aimed to summarize and critically evaluate studies on removal of veterinary antibiotics (VAs), antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) with anaerobic digestion (AD) of manure and demonstrate areas of focus for improved removal efficiency. The environmental risks associated to the release of the same were also critically evaluated. The potential of AD and advanced AD of manure on removal rate of VAs, ARGs and MGEs was thoroughly assessed. In addition, the role of post and pre-AD treatments and their potential to support VAs and ARGs removal efficiency were evaluated. The overall review results show disparity among the different groups of VAs in terms of removal rate with relatively higher efficiency for β-lactams and tetracyclines compared to the other groups. Some of sulfonamides, fluoroquinolones and macrolides were reported to be highly persistent with removal rates as low as zero. Within group differences were also reported in many literatures. Moreover, removal of ARGs and MGEs by AD was widely reported although complete removal was hardly possible. Even in rare scenarios, some AD conditions were reported to increase copies of specific groups of the genes. Temperature pretreatments and temperature phased advanced AD were also reported to improve removal efficiency of VAs while contributing to increased biogas production. Moreover, a few studies also showed the possibility of further removal by post-AD treatments such as liquid-solid separation, drying and composting. In conclusion, the various studies revealed that AD in its current technological level is not a guarantee for complete removal of VAs, ARGs and MGEs from manure. Consequently, their possible release to the soils with digestate could threaten the healthcare and disturb soil microbial ecology. Thus, intensive management strategies need to be designed to increase removal efficiency at the different manure management points along the anaerobic digestion process.

Evaluation of the performance of zirconia-multiwalled carbon nanotube nanoheterostructures in adsorbing As(III) from potable water from the perspective of physical chemistry and chemical physics with a special emphasis on approximate site energy distribution

In this study, the performance of zirconia-multiwalled carbon-nanotube nanoheterostructure in adsorbing the highly toxic water-contaminant As(III) from water has been probed from the perspective of physical chemistry and chemical physics. The adsorbent found extremely efficient in adsorbing As(III) from potable water. Moreover, its ability to oxidize As(III) to As(V) in the aqueous solution has been evinced by the XPS studies. The values of the maximum adsorption capacities (q_m) depend on the isotherm studied and in this study, no wonder different values of q_m are obtained for different adsorption isotherms. The thermodynamic studies advocate the exothermic and spontaneous nature of the adsorption process. Calculation on density functional theory (DFT) also suggested the exothermic nature of the adsorption process. DFT calculation further revealed the role of the Zr-O and Zr-OH bridges in binding As(III) species on the zirconia surface. However, this study finds an adverse effect of visible light-irradiation on the adsorption process. Furthermore, this study propounds an approach to estimate the maximum solubility of As(III) in water combining the Cerofolini's condensation-approximation and Polanyi adsorption potential. Detailed analysis on the approximate adsorption site energy distribution (f(E*)) further finds an inconsistency in the formula used to estimate q_m using f(E*), which underestimates q_m. The inconsistency, for the very first time, has successfully been resolved by modifying the heterogeneity related parameter in f(E*).

Adsorption of chlortetracycline from aquaculture wastewater using modified zeolites

In this study, lanthanum modified zeolite (La-Z) was used to adsorb chlortetracycline (CTC) from aquaculture wastewater. La-Z was characterized by SEM, TEM, EDS, XRD, FTIR and BET. The effects various factors on the adsorption of CTC by La-Z were investigated, including the lanthanum modification concentration on zeolites, the dosage of La-Z, solution pH and reaction time. Orthogonal experiments were performed to determine the optimal adsorption conditions. Adsorption kinetics were studied by quasi-first-order model, quasi-second-order model, Weber-Morris, Boyd and Bangham models, while isotherms were analyzed by the Langmuir and Freundlich models. The removal rate reached 98.4%, when the modified concentration was 0.02 mol/L, the adsorbent dosage was 0.04 g, the initial concentration of CTC was 5 mg/L, the adsorption time was 20 min, and the pH was 7. The initial CTC concentration had the greatest influence on the adsorption process. The kinetic results showed a significant linear correlation between the experimental results and the quasi-second-order kinetic model. From the results of the internal diffusion model, it was found that the La-Z adsorption rate was controlled by both internal diffusion and external diffusion, in a multi-step process. The adsorption isotherm conforms to the Langmuir model, with the maximum adsorption quantity reaching 127.55 mg/g. Thermodynamic analysis showed that the adsorption process was an endothermic process of entropy increase, which occurs spontaneously.

Removal of Pharmaceutical Contaminants in Wastewater Using Nanomaterials: A Comprehensive Review

BACKGROUND

The limitless presence of pharmaceutical contaminants in discharged wastewater has emerged as a threat to aquatic species and humans. Their presence in drinking water has although raised substantial concerns, very little is known about the fate and ecological impacts of these pollutants. As a result, these pollutants are inevitably introduced to our food chain at trace concentrations. Unfortunately, the conventional wastewater treatment techniques are unable to treat pharmaceuticals completely with practical limitations. The focus has now been shifted towards nanotechnology for the successful remediation of these persistent pollutants. Thus, the current review specifically focuses on providing readers brief yet sharp insights into applications of various nanomaterials for the removal of pharmaceutical contaminants.

METHODS

An exhaustive collection of bibliographic database was done with articles having high impact and citations in relevant research domains. An in-depth analysis of screened papers was done through standard tools. Studies were categorized according to the use of nanoscale materials as nano-adsorbents (graphene, carbon nanotubes), nanophotocatalysts (metal, metal oxide), nano-filtration, and ozonation for promising alternative technologies for the efficient removal of recalcitrant contaminants.

RESULTS

A total of 365 research articles were selected. The contemporary advancements in the field of nanomaterials for drinking and wastewater treatment have been thoroughly analyzed along with their future perspectives.

CONCLUSION

The recommendations provided in this article will be useful to adopt novel strategies for on-site removal of the emerging contaminants in pharmaceutical effluents and related industries.

A novel Biochar modified by Chitosan-Fe/S for tetracycline adsorption and studies on site energy distribution

A novel wasted sludge-based Biochar modified by Chitosan and Fe/S (BCFe/S) was prepared for tetracycline (TC) removal from water. To investigate the similarities and differences in adsorption behaviors between Biochar and BCFe/S, characterization, kinetics, isotherms and thermodynamics were discussed. The studies on site energy distribution (SED) were also presented. The results showed that the maximum TC adsorption amount was 51.78 mg/g for Biochar, while it was 183.01 mg/g for BCFe/S-4. Meanwhile, electrostatic attraction, π-π stacking, pore filling, silicate bonding and hydrogen bonding were the main adsorption mechanisms for TC removal by Biochar. Besides above mechanisms, chelating and ion exchange were also accounted for adsorption mechanisms for TC uptake by BCFe/S-4. Moreover, SED results revealed that the surface of Biochar was more homogeneous while the surface of BCFe/S-4 was more heterogeneous at higher temperature. Findings of this work could offer valuable information in designing adsorbents and investigating adsorption mechanisms.

Magnetic aluminum-based metal organic framework as a novel magnetic adsorbent for the effective removal of minocycline from aqueous solutions

In this paper, Fe₃O₄@MIL-68 (Al), a magnetic aluminum-based metal organic framework, was synthesized by a simple method and used as a novel and effective adsorbent for the removal of minocycline (MC) from aqueous solutions. The material was thoroughly characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and N₂ adsorption isotherms. The characterization results showed that the original structure of MIL-68(Al) was unchanged by the addition of Fe₃O₄ nanoparticles, and that the obtained material had a strong magnetic response which also promoted its adsorption. Batch adsorption experiments were conducted by the varying the adsorption time, temperature, initial MC concentration and pH. The maximum adsorption amount of MC onto Fe₃O₄@MIL-68 (Al) was 248.05 mg g^-1 (t = 160 min, pH = 6, C_o = 60 mg L^-1), and the adsorption kinetics followed a pseudo-second-order model, and the adsorption isotherms conformed to the Freundlich equation. The adsorption mechanism of the magnetic metal organic framework materials were determined to involve complex interactions, including Al-N and Fe-N covalent bonds, hydrogen bonding, electrostatic adsorption, and π-π stacking. Combined the results indicate that Fe₃O₄@MIL-68 (Al) is an outstanding adsorbent for the removal of MC from water.