Fabrication of MnFe2O4 nanoparticles embedded chitosan-diphenylureaformaldehyde resin for the removal of tetracycline from aqueous solution

Adsorption of emerging pollutants utilizing chitosan derivatives: Recent advances and future perspective

Globalization resulted in technological advancement, and urban population growth. Consequently, pollution emerged as an imminent risk to the survival of all species on Earth. Consequently, on a worldwide basis, sustainability become a major issue for legislators. Inconsistent impacts on both human and animal growth and wellness triggered health issues associated with water contamination through the chronic toxicants. Micropollutants' pollution prompted severe concerns due to their malignant, indestructible, and accumulative properties. The elimination of these toxins from industrial processes has become one of the most significant ecological challenges. A variety of both organic and simulated sorbents are available, and each of these have unique benefits. In the recent years, chitosan and its composite materials have been attempted and have been proven to be applicable for the resolution of many challenging issues related to water pollution. Among various notable benefits of adsorption processes, economic viability, ease of access, and adherence to environmental regulations are notable. Considering the above-mentioned issues, the article targets the assessment of chitosan and its composite materials for relevant environmental applications. Accordingly, the article aims to examine the performance, advantages, and disadvantages of chitosan as an adsorbent.

Synthesis of a novel CuO@GO@IR nanocomposite for the removal of tetracycline from wastewater

In this study, water extract from Indian rosewood tree leaves was used to synthesize copper oxide nanoparticles (CuO NPs), further loaded on graphene oxide sheets to synthesize a novel nanocomposite (CuO@GO@IR). The maximum tetracycline removal was achieved at optimum conditions of pH 3, adsorbent dose 0.03g/50 mL, and 240 min contact time. The maximum adsorption capacity of the adsorbent was 769.23 mg/g. Experimental data was better fitted with the Freundlich isotherm and followed pseudo-second-order. The adsorption process was thermodynamically spontaneous and feasible. Nanocomposite has shown excellent regeneration efficiency with 0.1 M HCl as a desorbing agent. The overall performance of the nanocomposite suggests that it can be used as a promising adsorbent for treating antibiotics containing wastewater.

Chitosan-based hydrogel beads with molecularly imprinted receptors on halloysite nanotubes for tetracycline separation in water and soil

Tetracycline (TC), a commonly utilized broad-spectrum antibiotic, is frequently detected in water and soil, posing a significant risk to the natural environment and human health. In the present study, the composite hydrogel beads based on chitosan (CS) and halloysite-supported molecularly imprinted polymers, synthesized by two procedures with significantly different solvent volumes (Hal@MIPa(b)), were obtained and used to adsorb the antibiotic. The presence of Hal improved the thermal stability of the hydrogel beads. The system with a thinner polymer layer (CS_Hal@MIPb), containing polymers produced under conditions of significantly higher reagent dilution, was more resistant to higher temperatures than CS_Hal@MIPa. The adsorptive properties were compared with pure CS beads, those containing incorporated Hal, and free polymers obtained by different protocols (MIPa(b)). In the optimized pH 5.0, the maximum adsorption capacities were 175.24 and 178.05 mg g-1 for CS_Hal@MIPa and CS_Hal@MIPb, respectively. The values were slightly lower compared to the systems with free polymers, but the materials achieved equilibrium more rapidly (12 h). The adsorption process was spontaneous and exothermic. Freundlich isotherm and pseudo-second-order kinetic models most accurately described the experimental data. The hydrogel beads retained high selectivity in the presence of other antibiotics, and their high efficiency in the TC removal from real water samples was maintained. Their addition to soil enhanced adsorption capacities, surpassing that of chitosan-based beads containing free polymers. Significantly, the quantity of TC desorption diminished due to the halloysite's presence, which limited its penetration into groundwater. The primary mechanism of tetracycline adsorption on the hydrogel beads studied is pore filling, but other interactions (hydrogen bonding, π-π stacking, electrostatic attraction) are also involved.

Development of Variable Charge Cationic Hydrogel Particles with Potential Application in the Removal of Amoxicillin and Sulfamethoxazole from Water

Cationic hydrogel particles (CHPs) crosslinked with glutaraldehyde were synthesized and characterized to evaluate their removal capacity for two globally consumed antibiotics: amoxicillin and sulfamethoxazole. The obtained material was characterized by FTIR, SEM, and TGA, confirming effective crosslinking. The optimal working pH was determined to be 6.0 for amoxicillin and 4.0 for sulfamethoxazole. Under these conditions, the CHPs achieved over 90.0% removal of amoxicillin after 360 min at room temperature, while sulfamethoxazole removal reached approximately 60.0% after 300 min. Thermodynamic analysis indicated that adsorption occurs through a physisorption process and is endothermic. The ΔH° values of 28.38 kJ mol-1, 12.39 kJ mol-1, and ΔS° 97.19 J mol-1 K-1, and 33.94 J mol-1 K-1 for AMX and SMX, respectively. These results highlight the potential of CHPs as promising materials for the removal of such contaminants from aqueous media.

Higher efficiency of vanadate iron in heterogeneous Fenton-like systems to pretreat sugarcane bagasse and its enzymatic saccharification

Pretreatment is crucial for effective enzymatic saccharification of lignocellulose such as sugarcane bagasse (SCB). In the present study, SCB was pretreated with five kinds of heterogeneous Fenton-like systems (HFSs), respectively, in which α-FeOOH, α-Fe2O3, Fe3O4, and FeS2 worked as four traditional heterogeneous Fenton-like catalysts (HFCs), while FeVO4 worked as a novel HFC. The enzymatic reducing sugar conversion rate was then compared among SCB after different heterogeneous Fenton-like pretreatments (HFPs), and the optimal HFS and pretreatment conditions were determined. The mechanism underlying the difference in saccharification efficiency was elucidated by analyzing the composition and morphology of SCB. Moreover, the ion dissolution characteristics, variation of pH and Eh values, H2O2 and hydroxyl radical (·OH) concentration of FeVO4 and α-Fe2O3 HFSs were compared. The results revealed that the sugar conversion rate of SCB pretreated with FeVO4 HFS reached up to 58.25%, which was obviously higher than that under other HFPs. In addition, the surface morphology and composition of the pretreated SCB with FeVO4 HFS were more conducive to enzymatic saccharification. Compared with α-Fe2O3, FeVO4 could utilize H2O2 more efficiently, since the dissolved Fe3+ and V5+ can both react with H2O2 to produce more ·OH, resulting in a higher hemicellulose and lignin removal rate and a higher enzymatic sugar conversion rate. It can be concluded that FeVO4 HFP is a promising approach for lignocellulose pretreatment.

Construction of magnetic MoS2/NiFe2O4/MIL-101(Fe) hybrid nanostructures for separation of dyes and antibiotics from aqueous media

In this study, MoS2/NiFe2O4/MIL-101(Fe) nanocomposite was synthesized by hydrothermal method and used as an adsorbent for the elimination of organic dyes and some antibiotic drugs in aqueous solutions. The synthesized nanocomposite underwent characterization through different techniques, including scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), zeta potential analysis, vibrating sample magnetometry (VSM), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). These results demonstrated the successful insertion of MoS2within the cavities of MIL-101(Fe). The as-prepared magnetic nanocomposite was used as a new magnetic adsorbent for removing methylene blue (MB) and rhodamine B (RhB) organic dyes and tetracycline (TC) and ciprofloxacin (CIP) antibiotic drugs. For achieving the optimized conditions, the effects of initial pH, initial dye and drug concentration, temperature, and adsorbent dose on MB, TC, and CIP elimination were investigated. The results revealed that at a temperature of 25 °C, the highest adsorption capacities of MoS2/NiFe2O4/MIL-101(Fe) for MB, TC, and CIP were determined to be 999.1, 2991.3, and 1994.2 mg g-1, respectively. The pseudo-second-order model and Freundlich model are considered suitable for explaining the adsorption behavior of the MoS2/NiFe2O4/MIL-101(Fe) nanocomposite. The magnetic nanocomposite was very stable and had good recycling capability without any change in its structure.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Magnetic hydrochar grafted-chitosan for enhanced efficient adsorption of malachite green dye from aqueous solutions: Modeling, adsorption behavior, and mechanism analysis

Water pollution by organic dyes is one of the most serious environmental problems worldwide. Malachite green (MG) is considered as one the serious organic dyes which is discharged in wastewater by leather and textile manufacturing plants. MG dye can cause severe hazards to the environment and human health. Therefore, the removal of MG dye from wastewater is very important and essential. This study aims to synthesize a new magnetic hydrochar grafted to chitosan (MWSHC@CS) for the removal of MG dye from the aqueous solutions. Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, and Zeta potential analysis were used to characterize the synthesized MWSHC@CS. Batch experiments were conducted to optimize MG dye adsorption conditions, including adsorbent mass, pH, temperature, initial concentration, and contact time. The results revealed that MWSHC@CS had an excellent removal efficiency (96.47 %) for MG dye at the optimum condition (at m: 20 mg, pH: 7.5, t: 420 min, and T: 298 K). Adsorption isotherms outcomes revealed the MG adsorption data were best fit by the Langmuir model with a maximum adsorption capacity (420.02 mg/g). Adsorption kinetics outcomes exhibited that the adsorption process of MG dye fitted well to the Elovich model. The thermodynamic results revealed that the adsorption process was physical, exothermic, and spontaneous. The adsorption mechanisms of MG onto MWSHC@CS were hydrogen bonding, electrostatic interaction, and π-π interactions. Furthermore, MWSHC@CS showed excellent reusability for the removal of MG over five cycles of adsorption-desorption (83.76 %). In conclusion, the study provides a new, low-cost, and effective magnetic nanocomposite based on chitosan as a promising adsorbent for the high-performance removal of MG dye from aqueous solutions.

Facile fabrication of carboxymethylcellulose/ZnO/g-C3N4 containing nutmeg extract with photocatalytic performance for infected wound healing

New topical antibacterial agents are required to inhibit and development of bacteria and also promoting the wound healing process. This study was evaluating the healing effect of Myristica fragrans extract coated with carboxymethyl cellulose, zinc oxide and graphite carbon nitride (CMC/ZnO/g-C3N4/MyR) by photocatalytic process on the healing process of full-thickness infectious excision wounds in mice. Nanosheets were prepared and physicochemical properties were evaluated. Safety, in vitro release, antibacterial activities under in vitro and in vivo condition, wound contraction, histopathological properties and the protein expressions of tumor necrosis factor-α (TNF-α), collagen 1A (COL1A) and CD31 were also evaluated. Physicochemical properties confirmed their successful synthesis. Nanosheets exhibited antibacterial activity under in vitro and in vivo conditions. The formulations containing CMC/ZnO/g-C3N4/MyR, significantly (P < 0.05) competed with standard ointment of mupirocin for accelerating the wound healing process due to their effects on bacterial count and the expression of TNF-α and also accelerating the proliferative phase. This structure can be used as a safe structure in combination with other agents for accelerating the wound healing process following future clinical studies.

Sodium Alginate-Aldehyde Cellulose Nanocrystal Composite Hydrogel for Doxycycline and Other Tetracycline Removal

A novel composite hydrogel bead composed of sodium alginate (SA) and aldehyde cellulose nanocrystal (DCNC) was developed for antibiotic remediation through a one-step cross-linking process in a calcium chloride bath. Structural and physical properties of the hydrogel bead, with varying composition ratios, were analyzed using techniques such as BET analysis, SEM imaging, tensile testing, and rheology measurement. The optimal composition ratio was found to be 40% (SA) and 60% (DCNC) by weight. The performance of the SA-DCNC hydrogel bead for antibiotic remediation was evaluated using doxycycline (DOXY) and three other tetracyclines in both single- and multidrug systems, yielding a maximum adsorption capacity of 421.5 mg g^-1 at pH 7 and 649.9 mg g^-1 at pH 11 for DOXY. The adsorption mechanisms were investigated through adsorption studies focusing on the effects of contact time, pH, concentration, and competitive contaminants, along with X-ray photoelectron spectroscopy analysis of samples. The adsorption of DOXY was confirmed to be the synergetic effects of chemical reaction, electrostatic interaction, hydrogen bonding, and pore diffusion/surface deposition. The SA-DCNC composite hydrogel demonstrated high reusability, with more than 80% of its adsorption efficiency remaining after five cycles of the adsorption-desorption test. The SA-DCNC composite hydrogel bead could be a promising biomaterial for future antibiotic remediation applications in both pilot and industrial scales because of its high adsorption efficiency and ease of recycling.

Adsorption and Desorption Study of Reusable Magnetic Iron Oxide Nanoparticles Modified with Justicia adhatoda Leaf Extract for the Removal of Textile Dye and Antibiotic

The release of tetracycline hydrochloride (TCH) and methylene blue (MB) dye into the aquatic system uncontrollably caused major environmental and health problems; hence, their prevention required serious attention. Adsorption process is now being researched in order to increase adsorption efficiency and reprocess to alleviate environmental issues. The use of magnetic nanoparticle as an adsorbent for wastewater treatment has a lot of prospective. A magnetic iron oxide nanoparticle surface modified by Vasaka (Justicia adhatoda) leaf extract (JA-MIONs) is used to give a fast removal approach for MB dye and TCH antibiotics. Dynamic light scattering, UV-Vis and band gap measurement, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy were operated to analyse the formation and size of these magnetic nanoparticles. The impacts of different factors such as contact time (30-150 min), adsorbate concentration (10-50 mg/L), pH (4-10), and adsorbent dose (2-10 mg) were explored. Adsorption kinetics and isotherms show that it follows the pseudo-first-order kinetic and the Freundlich isotherm, with maximum adsorption capacities of 76.92 mg/g for MB and 200 mg/g for TCH at 298 K. The reusability of the JA-MIONs eventually exhibited a decline in the adsorption percentage of MB and TCH after five and four times respectively. After the desorption-adsorption cycles, this adsorbent continued to exhibit significant adsorption capacity. This investigation furnished the significant reference data for the synthesis of JA-MIONs as a novel and auspicious adsorbent for the industrial clean-up of toxic dyes and heavily used antibiotics from water.

Graphical abstract

Natural phenol-inspired porous polymers for efficient removal of tetracycline: Experimental and engineering analysis

Efficient and feasible removal of trace antibiotics from wastewater is extremely important due to its environmental persistence, bioaccumulation, and toxicity, but still remains a huge challenge. Herein, three natural phenol-inspired porous organic polymers were fabricated from natural phenolic-derived monomers (p-hydroxy benzaldehyde, 2,4-dihydroxy benzaldehyde and 2,4,6-trihydroxy benzaldehyde) and melamine via polycondensation reaction. Characterization highlighted that the increasing contents of hydroxyl groups in monomers induced an increase of the polymer total porosity and promoted the formation of a highly microporous structure. With mesopore-dominated pore (average pore diameter 9.6 nm) and large pore volume (1.78 cm³/g), p-hydroxy benzaldehyde-based porous polymer (1-HBPP) exhibited ultra-high maximum adsorption capacity (q_max) of 697.6 mg/g for tetracycline (TC) antibiotic. Meanwhile, the porous networks and plentiful active sites of 1-HBPP enabled fast adsorption kinetics (within 10 min) for TC removal, which could be well described by the pseudo-second-order model. Dynamic adsorption studies showed that 1-HBPP could be used in fixed-bed adsorption column (FBAC) with high removal efficiency (breakthrough volume per unit mass, 13.2 L/g) and dynamic adsorption capacity (201.6 mg/g), which were much higher than other reported adsorbents. The breakthrough curves both well matched with Thomas and Yoon-Nelson models in FBAC treatment. Moreover, removal mechanism analysis affirmed that pore-filling, hydrogen bonding, electrostatic interactions and π-π stacking interactions were main driving forces for TC adsorption. The prepared natural phenol-inspired porous adsorbents show great potential in antibiotics removal from wastewater, and this strategy would promote the sustainable and high-value utilization of natural phenolic compounds.

Polyoxometalate supported on a magnetic Fe3O4/MIL-88A rod-like nanocomposite as an adsorbent for the removal of ciprofloxacin, tetracycline and cationic organic dyes from aqueous solutions

In this work, a magnetic H3PW12O40/Fe3O4/MIL-88A (Fe) rod-like nanocomposite as a stable and effective ternary adsorbent was fabricated by the hydrothermal method and utilized for the removal of ciprofloxacin (CIP), tetracycline (TC) and organic dyes from aqueous solution. Characterization of the magnetic nanocomposite was accomplished by FT-IR, XRD, Raman spectroscopy, SEM, EDX, TEM, VSM, BET specific surface area and zeta potential analyses. The influencing factors on the adsorption potency of the H3PW12O40/Fe3O4/MIL-88A (Fe) rod-like nanocomposite including initial dye concentration, temperature and adsorbent dose were studied. The maximum adsorption capacities of H3PW12O40/Fe3O4/MIL-88A (Fe) for TC and CIP were 370.37 mg g-1 and 333.33 mg g-1 at 25 °C, respectively. In addition, the H3PW12O40/Fe3O4/MIL-88A (Fe) adsorbent had high regeneration and reusability capacity after four cycles. In addition, the adsorbent was recovered through magnetic decantation and reused for three consecutive cycles without a considerable reduction in its performance. The adsorption mechanism was mainly ascribed to electrostatic and π-π interactions. According to these results, H3PW12O40/Fe3O4/MIL-88A (Fe) can act as a reusable effective adsorbent for the fast elimination of tetracycline (TC), ciprofloxacin (CIP) and cationic dyes from aqueous solutions.

Adsorptive removal of tetracycline and ciprofloxacin drugs from water by using a magnetic rod-like hydroxyapatite and MIL-101(Fe) metal-organic framework nanocomposite

A novel porous nanocomposite composed of hydroxyapatite nanorods (HAP), a MIL-101(Fe) metal-organic framework, and Fe₃O₄ nanoparticles was successfully fabricated in this work. The magnetic HAP/MIL-101(Fe)/Fe₃O₄ ternary nanocomposite was identified by various techniques, namely FT-IR spectroscopy, XRD, Raman spectroscopy, SEM, EDX, TEM, BET specific surface area, zeta potential, and VSM measurements. Tetracycline (TC) and ciprofloxacin (CIP) aqueous solutions were used to evaluate the adsorption performance of the resulting HAP/MIL-101(Fe)/Fe₃O₄ composite. The adsorption rate and capacity of HAP/MIL-101(Fe)/Fe₃O₄ were increased as compared with HAP, MIL-101(Fe), and HAP/MIL-101(Fe) samples due to the increased attraction. The influence of initial drug concentration, adsorbent dosage, temperature, and pH on the adsorption process was investigated. The results showed that the removal efficiencies of HAP/MIL-101(Fe)/Fe₃O₄ for TC and CIP were 95% and 93%, under the determined optimum conditions: pH of 7, drug concentration of 50 mg L^-1, adsorbent dosage of 30 mg, and temperature of 25 °C. The maximum adsorption capacities of HAP/MIL-101(Fe)/Fe₃O₄ for TC and CIP were 120.48 mg g^-1 and 112.35 mg g^-1, respectively. Reusability of the prepared nanocomposite was easily achieved up to three times without significant change in its structure. As a result, the synthesized magnetic nanocomposite can be reused as a suitable absorbent for TC and CIP removal from aqueous solutions.

Arsenic removal from solution using nano-magnetic compound: optimization modeling by response surface method

This study was aimed to investigate the effectiveness of compounds containing iron and manganese to reduce the mobility of arsenic and its effective adsorption and optimize the arsenic adsorption process by CCD. In this study, MnFe₂O₄ nanoparticles (MFO-n) were synthesized using the co-precipitation method to remove arsenic and reduce its toxicity in solution. Several tests including Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray fluorescence (XRF), and Brunauer-Emmett-Teller (BET) tests were used to characterize the synthesized MFO-n. To model and optimize the As adsorption process using the response surface methodology, four independent variables affecting the efficiency of arsenic adsorption were investigated. These variables including pH (3 to 11), concentration of arsenic in solution (1000 to 4000 µg/L), concentration of nanoparticles (1 to 5 g/L), and time (15 to 195 min) were investigated. The central composite design (CCD) approach was used to design the experiments and optimize the model parameters. The variance analysis indicated that the prediction of As adsorption from solution by the synthesized nanoadsorbent using the CCD model was well performed (p < 0.0001) with high accuracy (R² = 0.97). The results further indicated that the optimum quantity of pH, concentration of nanoparticles, time, and initial concentration of As are 5, 2 g/L, 60 min, and 3250 µg/L, respectively. The highest As elimination from the solution was estimated to be 94.77%. Our results further indicated that MFO-n had high efficiency in eliminating both toxic arsenic species from the solution.

Recyclable aminophenylboronic acid modified bacterial cellulose microspheres for tetracycline removal: Kinetic, equilibrium and adsorption performance studies for hoggery sewer

Significant concerns have been raised regarding to the pollution of antibiotics in recent years due to the abuse of antibiotics and their high detection rate in water. Herein, a novel super adsorbent, boronic acid-modified bacterial cellulose microspheres with a size of 415 μm in diameter was prepared through a facile water-in-oil emulsion method. The adsorbent was characterized by atomic force microscopy, scanning electron microscopy, and fourier transform infrared spectroscopy analyses to confirm its properties. The microspheres were applied as packing materials for the adsorption of tetracycline (TC) from an aqueous solution and hoggery sewer via the reversible covalent interaction between cis-diol groups in TC molecules and the boronic acid ligand. TC adsorption performance had been systemically investigated under various conditions, including the pH, temperature, TC concentration, contact time, and ionic strength. Results showed that the adsorption met pseudo-second-order, Elovich kinetic model and Sips, Redlich-Peterson isothermal models. And the adsorption process was spontaneous and endothermic, with the maximum TC adsorption capacity of 614.2 mg/g. After 18 adsorption-desorption cycles, the adsorption capacity remained as high as 84.5% compared with their original adsorption capacity. Compared with other reported adsorption materials, the microspheres had high adsorption capacity, a simple preparation process, and excellent recovery performance, demonstrating great potential in application on TC removal for water purification and providing new insights into the antibiotic's adsorption behavior of bacterial cellulose-based microspheres.

Ring defects-rich and pyridinic N-doped graphene aerogel as floating adsorbent for efficient removal of tetracycline: Evidence from NEXAFS measurements and theoretical calculations

The rational design of carbon-based adsorbents with a high uptake efficiency for polar organic molecules is a key challenge in water purification research. Herein, we report a graphene aerogel that is doped with pyridinic-N and has abundant ring defects (denoted by DNGA). The aerogel sample exhibits a high adsorption capacity of 607.1 mg/g toward tetracycline (TC), a fast adsorption process (20 min), and good reusability (with a declining efficiency < 10.0% after five cycles), while being easy to recycle. C/N K-edge X-ray absorption near-edge structure (XANES) measurements demonstrate that the efficient adsorption capacity of the DNGA sample is related to the presence of ring defects and the pyridinic-N species. Density functional theory (DFT) calculations demonstrate that ring defects of type 5-8-5 and the pyridinic-N species at the edge location are primarily responsible for TC removal. In this study, we resolve a controversial issue regarding the origin of the adsorption performance origin of N-doped carbon-based adsorbents. The findings of this study can guide the development of novel and improved N-doped carbon-based adsorbents for the removal of target contaminants.

Electrospun chitosan/polyethylene oxide nanofibers mat loaded with copper (II) as a new sensor for colorimetric detection of tetracycline

Using electrospun chitosan/polyethylene oxide nanofibers mat (CS/PEO NFM) as carrier, Cu@CS/PEO NFM, a new tetracycline (TC) solid-state colorimetric sensor, were simply prepared by directly immobilizing Cu²⁺ on surface of CS/PEO NFM. After immersing in TC solutions, Cu@CS/PEO NFM can display visible color changes to the naked eye within 5.0 min, and the TC concentration-dependent color changes can also be quantitatively analyzed with a smartphone. Because Cu²⁺ can enhance the adsorption of CS/PEO NFM for TC, Cu@CS/PEO NFM possess a more sensitive response ability to TC, ensuring that the colorimetric sensing detection will not be interfered by other coexisting drugs. Due to the reversible combination of chitosan and Cu²⁺, the colorimetric sensing ability of Cu@CS/PEO NFM can be regenerated even after being reused at least 4 times. In addition, the naked eye detection limit of Cu@CS/PEO NFM-based colorimetric sensing is 65 μg kg^-1, which does not exceed the maximum residue limit in milk samples set by China (100 μg kg^-1). The obtained results fully indicated the practical application value of this method in preventing the hazard of TC residues.

Sustainable adsorptive removal of antibiotic residues by chitosan composites: An insight into current developments and future recommendations

During COVID-19 crisis, water pollution caused by pharmaceutical residuals have enormously aggravated since millions of patients worldwide are consuming tons of drugs daily. Antibiotics are the preponderance pharmaceutical pollutants in water bodies that surely cause a real threat to human life and ecosystems. The excellent characteristics of chitosan such as nontoxicity, easy functionality, biodegradability, availability in nature and the abundant hydroxyl and amine groups onto its backbone make it a promising adsorbent. Herein, we aimed to provide a comprehensive overview of recent published research papers regarding the removal of antibiotics by chitosan composite-based adsorbents. The structure, ionic form, optimum removal pH and λmax of the most common antibiotics including Tetracycline, Ciprofloxacin, Amoxicillin, Levofloxacin, Ceftriaxone, Erythromycin, Norfloxacin, Ofloxacin, Doxycycline, Cefotaxime and Sulfamethoxazole were summarized. The development of chitosan composite-based adsorbents in order to enhance their adsorption capacity, reusability and validity were presented. Moreover, the adsorption mechanisms of these antibiotics were explored to provide more information about adsorbate-adsorbent interactions. Besides the dominant factors on the adsorption process including pH, dosage, coexisting ions, etc. were discussed. Moreover, conclusions and future recommendations are provided to inspire for further researches.

New Polymeric Adsorbents Functionalized with Aminobenzoic Groups for the Removal of Residual Antibiotics

In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chloromethylated styrene-divinylbenzene (DVB) copolymers with different cross-linking degrees functionalized with the following aminobenzoic groups: styrene-6.7% DVB (PAB1), styrene-10% DVB (PAB2), and styrene-15% DVB (PAB3). The new polymeric products, PAB1, PAB2, and PAB3, were characterized by FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis, respectively. The evolution of the functionalization reaction was followed by FTIR spectroscopy, which revealed a decrease in the intensity of the γCH2Cl band at 1260 cm-1, and, simultaneously, the appearance of C=O carboxylic bands from 1685-1695 cm-1 and at 1748 cm-1. The thermal stability increased with the increase in the cross-linking degree. The data obtained from the EDX analysis of the novel cross-linked copolymers confirmed the functionalization with aminobenzoic groups through the presence and content of nitrogen, as follows: PAB1: N% = 0.47; PAB2: N% = 0.85; and PAB3: N% = 1.30. The adsorption performances of the novel polymeric adsorbents, PAB1, PAB2, and PAB3, were tested in the adsorption of three antibiotics, tetracycline, sulfamethoxazole, and amoxicillin, from aqueous solutions, by using extensive kinetic, equilibrium, and thermodynamic studies. The best adsorption capacity was demonstrated by the tetracycline. Amoxicillin adsorption was also attempted, but it did not show positive results.

Chitosan as a Tool for Sustainable Development: A Mini Review

New developments require innovative ecofriendly materials defined by their biocompatibility, biodegradability, and versatility. For that reason, the scientific society is focused on biopolymers such as chitosan, which is the second most abundant in the world after cellulose. These new materials should show good properties in terms of sustainability, circularity, and energy consumption during industrial applications. The idea is to replace traditional raw materials with new ecofriendly materials which contribute to keeping a high production rate but also reducing its environmental impact and the costs. The chitosan shows interesting and unique properties, thus it can be used for different purposes which contributes to the design and development of sustainable novel materials. This helps in promoting sustainability through the use of chitosan and diverse materials based on it. For example, it is a good sustainable alternative for food packaging or it can be used for sustainable agriculture. The chitosan can also reduce the pollution of other industrial processes such as paper production. This mini review collects some of the most important advances for the sustainable use of chitosan for promoting circular economy. Hence, the present review focuses on different aspects of chitosan from its synthesis to multiple applications.

Magnetic alginate/glycodendrimer beads for efficient removal of tetracycline and amoxicillin from aqueous solutions

The release of antibiotic drugs into aquatic environments is a serious environmental and health problem in recent years. Therefore, the development of potential adsorbents for the effective removal of tetracycline (TC) and amoxicillin (AMX) of aqueous media is of great importance. In this study, new alginate beads were successfully prepared by encapsulation of Fe₃O₄@maltose-functionalized triazine dendrimer in alginate (Alg/Fe₃O₄@C@TD) for the first time. The obtained beads were utilized as a well adsorbent for the removal of TC and AMX antibiotics from aqueous solutions by batch adsorption procedure. The characteristics of the synthesized beads were investigated using FT-IR, Zeta potential, SEM, XRD, EDX, VSM, and BET. The effects of various operation factors such as adsorbent dose, pH of the solution, contact time, antibiotic initial concentration, temperature, and ionic strength on the removal of antibiotics were studied. Moreover, Langmuir and Freundlich adsorption isotherm results showed that the Langmuir model fitted well for the adsorption of both antibiotics onto Alg/Fe₃O₄@C@TD beads. Based on the Langmuir model, the maximum adsorption capacity of TC and AMX onto Alg/Fe₃O₄@C@TD beads at 25 °C was 454.54 and 400 mg/g, respectively. Kinetic and thermodynamic studies also indicated that the TC and AMX adsorption were found to be well fitted with a pseudo-second-order kinetic model, feasible, endothermic, and spontaneous in nature. In addition, the Alg/Fe₃O₄@C@TD beads showed excellent reusability for removal from both antibiotics after six adsorption cycles. Overall, the obtained results suggest that Alg/Fe₃O₄@C@TD beads could be considered as a low-cost and eco-friendly adsorbent for antibiotic contaminants removal from aquatic media.

Synthesis of glutaraldehyde-modified silica/chitosan composites for the removal of water-soluble diclofenac sodium

Composite materials are effective adsorbents for the removal of various types of contaminants, such as pharmaceutical products. However, they require improvement to achieve a good adsorption capacity. This study presents the development of a promising adsorbent: silica/chitosan modified with different proportions of glutaraldehyde, which involves the D-glucosamine units from chitosan. The developed materials were evaluated for their ability to remove diclofenac sodium. The adsorption data showed that the diclofenac adsorption efficiency increased with increasing degree of glutaraldehyde crosslinking. The equilibrium and kinetic data were well fit by the Liu and Elovich models, respectively, and the maximum adsorption capacity was 237.8 mg/g. Therefore, it can be assumed that the process is predominantly chemical and exothermic, with a high affinity between the adsorbents and diclofenac sodium. The adsorption mechanisms were investigated to better understand the interactions, and the predominance of covalent bonds with the self-polymerized glutaraldehyde was verified.

Designing Phenyl Porous Organic Polymers with High-Efficiency Tetracycline Adsorption Capacity and Wide pH Adaptability

Adsorption is an effective method to remove tetracycline (TC) from water, and developing efficient and environment-friendly adsorbents is an interesting topic. Herein, a series of novel phenyl porous organic polymers (P-POPs), synthesized by one-pot polymerization of different ratios of biphenyl and triphenylbenzene under AlCl₃ catalysis in CH₂Cl₂, was studied as a highly efficient adsorbent to removal of TC in water. Notably, the obtained POPs possessed abundant phenyl-containing functional groups, large specific surface area (1098 m²/g) with abundant microporous structure, high pore volume (0.579 cm³/g), favoring the removal of TC molecules. The maximum adsorption capacity (fitted by the Sips model) could achieve 581 mg/g, and the adsorption equilibrium is completed quickly within 1 h while obtaining excellent removal efficiency (98%). The TC adsorption process obeyed pseudo-second-order kinetics and fitted the Sips adsorption model well. Moreover, the adsorption of POPs to TC exhibited a wide range of pH (2–10) adaptability and outstanding reusability, which could be reused at least 5 times without significant changes in structure and efficiency. These results lay a theoretical foundation for the application of porous organic polymer adsorbents in antibiotic wastewater treatment.

Biosynthesis of SiO2 nanoparticles using extract of Nerium oleander leaves for the removal of tetracycline antibiotic

Tetracycline (TC) is one of the antibiotics that is found in wastewaters. TC is toxic, carcinogenic, and teratogenic. In this study, the tetracycline was removed from water by adsorption using dioxide silicon nanoparticles (SiO₂ NPs) biosynthesized from the extract of Nerium oleander leaves. These nanoparticles were characterized using SEM-EDX, BET-BJH, FTIR-ATR, TEM, and XRD. The influences of various factors such as pH solution, SiO₂ NPs dose, adsorption process time, initial TC concentration, and ionic strength on adsorption behaviour of TC onto SiO₂ NPs were investigated. TC adsorption on SiO₂ NPs could be well described in the pseudo-second-order kinetic model and followed the Langmuir isotherm model with a maximum adsorption capacity was 552.48 mg/g. At optimal conditions, the experimental adsorption results indicated that the SiO₂ NPs adsorbed 98.62% of TC. The removal of TC using SiO₂ NPs was 99.56% at conditions (SiO₂ NPs dose = 0.25 g/L, C₀ = 25 mg/L, and t = 40 min) based on Box-Behnken design (BBD) combined with response surface methodology (RSM) modelling. Electrostatic interaction governs the adsorption mechanism is attributed. The reusability of SiO₂ NPs was tested, and the performance adsorption was 85.36% after the five cycles. The synthesized SiO₂ NPs as promising adsorbent has a potential application for antibiotics removal from wastewaters.

Reducing tetracycline antibiotics residues in aqueous environments using Tet(X) degrading enzymes expressed in Pichia pastoris

Tetracycline antibiotics (TCs) are massively produced and consumed in various industries resulting in large quantities of residuals in the environment. In this study, to achieve safe and efficient removal of residual TCs, a Pichia pastoris (P. pastoris) was gained to stably express glycosylated TCs degrading enzyme Tet(X) followed codon and expression parameter optimization of tet(X4). As expected, glycosylated Tet(X) still maintains efficient capacity of degrading TCs. The expressed Tet(X) maintained efficient TCs degrading ability over a pH range of 6.5 - 9.5 and temperature range of 17 - 47 °C. We tested this recombinant protein for its ability to degrade tetracycline in pond water and sewage models of tetracycline removal at starting levels of 10 mg/L substrate. 80.5 ± 3.8% and 26.2 ± 2.6% of tetracycline was degraded within 15 min in the presence of 0.2 μM Tet(X) and 50 μM NADPH, respectively. More importantly, the direct use of a Tet(X) degrading enzymes reduces the risk of gene transmission during degradation. Thus, the Tet(X) degrading enzyme expressed by P. pastoris is an effective and safe method for treating intractable TCs residues.

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.

Fabrication of Highly Porous Polymeric Nanocomposite for the Removal of Radioactive U(VI) and Eu(III) Ions from Aqueous Solution

In the present study, a polymeric nanocomposite, CoFe2O4@DHBF, was fabricated using 2,4 dihydroxybenzaldehyde and formaldehyde in basic medium with CoFe2O4 nanoparticles. The fabricated nanocomposite was characterized using FTIR, TGA, XRD, SEM, TEM, and XPS analyses. The analytical results revealed that the magnetic nanocomposite was fabricated successfully with high surface area 370.24 m2/g. The fabricated CoFe2O4@DHBF was used as an efficient adsorbent for the adsorption of U(VI) and Eu(III) ions from contaminated water. pH, initial concentration, adsorption time, and the temperature of the contaminated water solution affecting the adsorption ability of the nanocomposites were studied. The batch adsorption results exposed that the adsorption capacity for the removal of U(VI) and Eu(III) was found to be 237.5 and 225.5 mg/g. The adsorption kinetics support that both the metal ions follow second order adsorption kinetics. The adsorption isotherm well fits with the Langmuir adsorption isotherm and the correlation coefficient (R2) values were found to be 0.9920 and 0.9913 for the adsorption of U(VI) and Eu(III), respectively. It was noticed that the fabricated nanocomposites show excellent regeneration ability and about 220.1 and 211.3 mg/g adsorption capacity remains with U(VI) and Eu(III) under optimum conditions.

Comparison between removal of Ethidium bromide and eosin by synthesized manganese (II) doped zinc (II) sulphide nanoparticles: kinetic, isotherms and thermodynamic studies

The present work seeks to investigate the kinetics and thermodynamic studies of ethidium bromide (EtBr) and eosin adsorption onto the synthesized Manganese (II) doped Zinc (II) Sulphide nanoparticles. A convenient scheme of co-precipitation was used for the synthesis of Manganese (II) doped Zinc (II) Sulphide nanoparticles. The Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and X-ray diffractogram (XRD) techniques were used for the characterization of synthesized nanoparticles. The adsorption study was undertaken in a systematic manner. Effects of different experimental parameters were studied using batch adsorption method. It was evident from the results that EtBr and eosin removal was inversely proportional to the concentration of initial dye and directly proportional to contact time and adsorbent used. To study the adsorption equilibrium three different isotherm models like Langmuir, Freundlich and Flory-Huggins were used. It was observed that adsorption data synced most successfully with Langmuir isotherm model as compared to Freundlich and Flory-Huggins isotherm model. To fit the investigational statistics, the kinetic models pseudo 1st order, pseudo 2nd order and intra particle diffusion were taken onto consideration. The maximum dye removal of 98.19% and 97.16% for EtBr and eosin, was observed during the synthesis of nanoparticles.

Sonication alkaline-assisted preparation of Rhizopus oryzae biomass for facile bio-elimination of tetracycline antibiotic from an aqueous matrix

The present study aimed to remove tetracycline (TET) antibiotic molecule from an aqueous medium using adsorbents prepared from Rhizopus oryzae biomass. The TET adsorption process was discontinuous and the adsorbent biomass was crude and NaOH-sonication-modified Rhizopus oryzae fungi. Specific active surface area for crude and modified Rhizopus oryzae was 10.38 m²/g and 20.32 m²/g, respectively. The results showed that the maximum TET adsorption efficiency was determined at pH 4, temperature 25 °C, initial TET concentration 10 mg/L, contact time 80 min, and biomass quantity 2 g/L. The equilibrium behavior showed that the Langmuir model suitably described the process. The maximum TET adsorption capacity was determined to be 38.02 mg/g and 67.93 mg/g, respectively, indicating that the method of biomass modification promoted the bio-adsorption capacity. A higher correlation coefficient (R²) and lower RMSE for the pseudo-first-order kinetic than other models showed its ability to describe the behavior of TET bio-adsorption. The enthalpy thermodynamic parameter (ΔH°) for the TET adsorption process was determined - 63.847 kJ/mol and - 85.226 kJ/mol for the raw and modified Rhizopus oryzae, respectively. Therefore, it can be suggested that the biomass of Rhizopus oryzae especially the modified version can be effectively used for the TET removal from aqueous environments.

A review on tetracycline removal from aqueous systems by advanced treatment techniques

Tetracycline (TC), a frequently used drug for human and veterinary therapeutics, is among the most common antibiotic residues found in nature. Lack of advanced treatment techniques in the wastewater treatment plants (WWTPs) to remove residual TC from domestic and hospital wastewater poses a serious environmental risk. It is important to have an insight into the different advanced treatment techniques for efficient removal of TC from the surface water and in the WWTPs. The aim of this review is to discuss the nature and occurrence of TC in surface water and to present an overview of the various advanced treatment techniques for TC removal. The advanced treatment techniques include advanced oxidation processes (photolysis, ozonation, and catalytic/UV light-based degradation), membrane filtration, reverse osmosis, and adsorption techniques. Adsorption and integrated oxidation treatment techniques are the most widely studied methods, and they are widely accepted because of less cost, reusability, and toxic-free nature. Further, the uses of various types of catalysts for photodegradation and various sorbents for adsorption of TC are also presented. Finally, the importance of green nanocomposite for environmental sustainability in TC removal is emphasized.

A water resistance magnetic graphene-anchored zeolitic imidazolate framework for efficient adsorption and removal of residual tetracyclines in wastewater

Water-resistant magnetic graphene-anchored zeolite imidazolate (Fe₃O₄/ZIF-8-G) composite materials with the largest surface area are formed by directly growing a hydrophobic ZIF-8 skeleton onto a graphene support through self-assembly in methanol. Fe₃O₄/ZIF-8-G hybrid composite has water resistance and super strong adsorption capacity, and is used as an effective adsorbent for adsorption and removal of residual tetracycline in wastewater. The morphologies and structure, as well as water resistance of Fe₃O₄/ZIF-8-G, were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA), N₂ adsorption and pH_PZC. The adsorption for tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) followed pseudo-second-order kinetics and fitted the Freundlich adsorption model with the simultaneous adsorption capacity for TC (382.58 mg g^-1), OTC (565.94 mg g^-1) and CTC (608.06 mg g^-1) at pH 5-6 for 10 h. These were much higher than previously reported results for the removal of tetracycline from aqueous solutions. The used Fe₃O₄/ZIF-8-G could be effectively reused and recycled at least five times without significant loss of adsorption capacity. The hydrophobic and π-π interaction between the aromatic rings of TCs and the aromatic imidazole rings of the ZIF-8-G framework were the main adsorption mechanism on the surface of Fe₃O₄/ZIF-8-G. Constructing a hydrophobic surface of ZIF-8/G framework resulted in a reduction of the hydrophilic sites of the surface. This can improve stability and selective adsorption of ZIF-8-G framework. In addition, the results show no significant difference in the adsorption kinetics and adsorption capacity of Fe₃O₄/ZIF-8-G for TC, OTC and CTC in pure water and wastewater.

Application of Biochar Derived From Pyrolysis of Waste Fiberboard on Tetracycline Adsorption in Aqueous Solution

In this study, biochars derived from waste fiberboard biomass were applied in tetracycline (TC) removal in aqueous solution. Biochar samples were prepared by slow pyrolysis at 300, 500, and 800°C, and were characterized by ultimate analysis, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), etc. The effects of ionic strength (0–1.0 mol/L of NaCl), initial TC concentration (2.5–60 ppm), biochar dosage (1.5–2.5 g/L), and initial pH (2–10) were systemically determined. The results present that biochar prepared at 800°C (BC800) generally possesses the highest aromatization degree and surface area with abundant pyridinic N (N-6) and accordingly shows a better removal efficiency (68.6%) than the other two biochar samples. Adsorption isotherm data were better fitted by the Freundlich model (R² is 0.94) than the Langmuir model (R² is 0.85). Thermodynamic study showed that the adsorption process is endothermic and mainly physical in nature with the values of ΔH⁰ being 48.0 kJ/mol, ΔS⁰ being 157.1 J/mol/K, and ΔG⁰ varying from 1.02 to −2.14 kJ/mol. The graphite-like structure in biochar enables the π-π interactions with a ring structure in the TC molecule, which, together with the N-6 acting as electron donor, is the main driving force of the adsorption process.

Preparation of chitosan based magnetic nanocomposite for tetracycline adsorption: Kinetic and thermodynamic studies

In the present study, the magnetic nanocomposite is fabricated using chitosan, thiobarbituric acid, malondialdehyde and Fe₃O₄ nanoparticles (CTM@Fe₃O₄). The fabricated nanocomposite (CTM@Fe₃O₄) is characterized using FTIR, TGA, BET, XRD, Raman, XPS, FESEM, and HRTEM techniques. The results of BET analysis confirmed that the nanocomposite has a mesoporous structure with high surface area of 376 m² g^-1 and high pore volume 0.3828 cm³ g^-1. The adsorption of tetracycline (TC) onto CTM@Fe₃O₄ adsorbent is carried out using batch technique by changing several factors such as pH, concentration, contact time, and temperature. Langmuir and pseudo-second-order nonlinear models were found to be the best-fit models to predict isotherms and kinetics of adsorption, respectively. The highest adsorption capacity of 215.31mg/g was achieved at the optimum conditions of 0.05g adsorbent dosage, 60mg/L TC concentration. Overall, results demonstrated that CTM@Fe₃O₄ nanocomposite was an excellent adsorbent material with superparamagnetic properties, which allowed the separation as well as recovery of the adsorbent from aqueous solution using external magnet for effective industrial applications.