Tetracycline Adsorption Capacity Research Articles

Uniformly formed copper-modulation ZIF-8 pellets for efficient removal of tetracycline from wastewater

Removal tetracycline (TC) from wastewater is necessary due to its excessive use and environmental hazards. Herein, Cu-modulation zeolite imidazolate frameworks-8 powders (Cu-ZIF-8) and the shaped pellets composite with chitosan (CS-1Cu-ZIF-8) were successfully fabricated to adsorb TC. All Cu-ZIF-8 samples well preserved the structure of the original ZIF-8 and 1Cu-ZIF-8 sample had the excellent performance with TC adsorption capacity up to 213.8 mg/g. Besides, 0.5CS-1Cu-ZIF-8 pellets retained excellent TC adsorption capacity (203.6 mg/g), with almost no decrease compared to the powders. The powders and pellets adsorbents both fitted well with pseudo-second-order and Langmuir models, suggesting that chemisorption was dominant during adsorption process. Adsorption thermodynamic studies implied that the adsorption process was spontaneous and exothermic. Besides, the mechanism for TC adsorption was revealed to be hydrogen bonding, π-π interactions and electrostatic interactions between TC and adsorbents. Furthermore, the 1Cu-ZIF-8 powder and 0.5CS-1Cu-ZIF-8 pellets both displayed outstanding catalytic performance in complex water environments and had great reusability yet water stability. This work provided a facile and efficient strategy to fabricate MOFs-based adsorbent for water purification.

Tuning the wettability of alginate-based nanocomposite beads for efficient removal of pharmaceuticals from water

Long-term exposure to pharmaceuticals, such as diclofenac (DCF) and tetracycline (TC), poses various risks to human health, including antibiotic resistance and endocrine disruption. In this work, we investigated the removal of DCF and TC from water and probed the removal performance of contaminants in a complex matrix consisting of DCF and TC mixtures using alginate (AL)-based nanocomposite beads with tunable wettability. We improved the selectivity of the beads towards hydrophobic contaminants by reducing graphene oxide (GO) to rGO in the presence of AL using a mild and green reducing agent (Vitamin C). Thein-situchemical reduction of GO in AL matrix resulted in amphiphilic rGO-containing beads,as confirmed by several characterization techniques.Thein-situreduction, apart from restoring the sp2hybridized carbon, greatly improved the mechanical properties and stability of the nanocomposite, ensuring reusability beyond 10 adsorption/desorption cycles.Compared to neat AL beads, the addition of only 3.5% rGO (AL:3.5rGO) improved the beads adsorption capacity for TC and DCF by 660% and 747%, respectively. The beads exhibited remarkable performance in the simultaneous removal of TC and DCF from contaminant mixtures. The superior performance of AL:3.5rGO beads is attributed to the enhanced π-π interactions between the aromatic rings of the contaminants and the sp2domains of rGO-containing adsorbents.

Effects of tire-road wear particles on the adsorption of tetracycline by aquatic sediments.

Tire-road wear particles (TRWPs) are formed by friction between the tire and the road. TRWPs are ubiquitous across the globe, especially in sediments. However, the possible effects of TRWPs on tetracycline (TC) in aquatic sediments are unknown. To investigate the potential role of TRWPs as carriers of co-pollutants, this study investigated the pore surface properties and TC adsorption behavior of TRWP-contaminated sediments and explored the TC behavior in water sediments, as well as the role of aging processes and TRWPs abundance. The results showed that the surface morphology of TRWP-contaminated sediments changed and the adsorption capacity of sediments to TC increased. The TC adsorption capacity of sediments contaminated by 2% TRWPs increased from 3.15 to 3.48mg/g. Moreover, the surface physical and chemical properties of TRWPs after UV aging changed, which further increased the TC adsorption capacity. The TC adsorption capacity of the sediments contaminated by aged TRWPs increased from 3.48 to 3.65mg/g. Changing the proportion of aged TRWPs, we found that the adsorption capacity of sediments contaminated by different proportions of TRWPs for TC was 2% > 1% > 0.5% > 4% > blank sediment. These results may contribute to predicting the potential environmental risks of TRWPs in aquatic sediments.

Synthesis of a hybrid nanocomposite: Incorporating MoS2 within a ZIF-8 for fluorescence-based detection and adsorption of tetracyclines antibiotics

Molybdenum disulfide quantum dots (MoS2 QDs), a transition-metal disulfide nanomaterial, have aroused an increasing attentions in the last 20 years. Zeolitic imidazolate framework 8 (ZIF-8), a kind of metal-organic frameworks (MOF), have been widely used for pollutant disposal, drug delivery, etc. Due to its well porousness and biocompatibility. We developed a novel course for the synthesis of MoS2 QDs under atmospheric pressure. Ammonium persulfate were introduced into the sodium molybdate and glutathione (GSH) solutions, and blue fluorescent MoS2 QDs can be obtained after heating at 60 °Cfor 2 h. The MoS2 QDs exhibited a redshift of fluorescence emission peak from 440 to 570 nm as excitation wavelength changed from 360 to 460 nm. Furthermore, MoS2 QDs were further encapsulated in ZIF-8, and the prepared nanohybrids (named as MoS2@MOF) were successfully applied into the fluorescence detection antibiotics including tetracycline (TC), oxytetracycline (OTC) and chlorotetracycline (CTC) based on different fluorescent response mode. Moreover, MoS2@MOF exhibited excellent adsorption performance for TC, OTC and CTC. The maximum adsorption capacity for TC, OTC or CTC after 300 min incubation of MoS2@MOF can reach 163, 154 or 197 mg g−1.

Modified biochar activated by traditional Chinese medicine extract and its removal of tetracycline

Traditional Chinese medicine (TCM) has been widely used during the outbreak of Covid-19 in the past few years, causing waste of resources and environmental pollution. This paper will convert TCM into porous carbon-based materials through pyrolysis technology, and then combine it with TCM extract activator to synthesize a new type of adsorbent. The two main ingredients of Chinese patent medicine “Lianhua Qingwen Capsules”, Honeysuckle and Forsythia suspensa, will be used as raw materials. After the two herbs are crushed, the leachate is extracted, and the remaining residue is collected. The dried residue is activated and carbonized at high temperature to generate biochar. Further, the biochar will be soaked in TCM extraction liquid to load active ingredients. The adsorption mechanism of tetracycline (TC) by TCM biochar was explored based on the adsorption kinetics and adsorption isotherm fitting results. The microstructure, surface functional groups and crystal structure of TCM biochar will reveal the material properties of the adsorbent. The results show that compared with biochar without extract activation, the adsorption effect of combined biochar (BC-C) with the proportion of “Lianhua Qingwen Capsules” is greatly improved. BC-C has richer surface functional groups through TCM extract loading, which provides superior TC adsorption capacity (36.92 mg/g). The adsorption process of TC by TCM biochar follows the pseudo-second-order adsorption kinetic model and Freundlich adsorption isotherm model. The adsorption mechanism mainly involves pore filling, hydrogen bonding, electrostatic interaction and π-π interaction.

Sustainable efficient utilization of magnetic porous biochar for adsorption of orange G and tetracycline: Inherent roles of adsorption and mechanisms

Iron-doped biochar has been widely used as an adsorbent to remove contaminants due to the high adsorption performance, but it still suffers from complicated preparation methods, unstable iron loading, unsatisfactory specific surface area, and uneven distribution of active sites. Here, a novel magnetic porous biochar (FeCS800) with nanostructure on surface was synthesized by one-pot pyrolysis method of corn straw with K2FeO4, and used in orange G (OG) and tetracycline (TC) adsorption. FeCS800 exhibited outstanding adsorption capacities for OG and TC after K2FeO4 activation and the adsorption data were fitted satisfactorily to Langmuir isotherm and Pseudo-second-order kinetic model. The maximum adsorption capacities of FeCS800 for OG and TC were around 303.03 mg/g and 322.58 mg/g, respectively, at 25 °C and pH 7.0, which were 16.27 and 24.61 times higher than that before modification. Thermodynamic studies showed that the adsorption of OG/TC by FeCS800 were thermodynamically favorable and highly spontaneous. And the adsorption capacity of OG and TC by FeCS800 remained 77% and 81% after 5 cycles, respectively, indicating that FeCS800 had good stability. The outstanding adsorption properties and remarkable reusability of FeCS800 show its great potential to be an economic and environmental adsorbent in contaminants removal.

Synthesis of N,S-containing hyper-cross-linked polymers and their efficient tetracycline and diclofenac sodium adsorption in water

Novel N,S-containing hyper-cross-linked polymers were designed for the adsorption of tetracycline (TC) and diclofenac (DCF) in water. The surface area, pore volume, and average pore diameter of N,S-containing hyper-cross-linked polymers were 32.5 m2/g, 0.11 cm3/g, and 16.8 nm, respectively. The pseudo-second-order and Langmuir isotherm models indicated that TC and DCF adsorption was chemisorption-dominated and exhibited a monolayer homogeneous adsorption. This adsorbent exhibited the highest TC and DCF adsorption capacity around 138.1 and 140.5 mg/g. Moreover, the adsorption capacity still maintained 85 % of the initial adsorption capacity after 10 adsorption–desorption cycles. Continuous fixed-bed runs demonstrated that this adsorbent reduced the TC and DCF concentrations to 1 mg/L at 738 and 612 BVs, respectively. The TC and DCF adsorption mechanism was primarily derived from pore-filling, π-π interaction, H-bonding, and electrostatic interaction. Therefore, N,S-containing hyper-cross-linked polymers proves to be an efficient adsorbent of TC and DCF during wastewater treatment.

Adsorption of tetracycline by nitrogen-enriched biochar prepared at different pyrolysis temperatures: Considering the crucial role of nitrogen configuration

Nitrogen atom doping is widely employed to prepare efficient adsorbents to handle target pollutants thanks to its similarity in radius to carbon atoms and excellent functionality. In this study, three types of nitrogen-enriched biochars (NBCs) were prepared to use the corn straw as the raw material and melamine as the nitrogen source by pyrolyzing at 700, 800, and 900 °C (named 700NBC, 800NBC and 900NBC), which were used to remove tetracycline (TC) from water. Results showed that the 900NBC exhibited the highest specific surface area (324.29 m2/g) as well as the maximum adsorption capacity (194.42 mg/g) for TC, compared to 800NBC (176.44 mg/g) and 700NBC (163.32 mg/g). What’s more, the adsorption kinetics and adsorption isotherms were well-fitted by the pseudo-second-order and Langmuir models, indicating that for the adsorption of TC by NBCs, monolayer adsorption and chemisorption were dominant. Specifically, the excellent adsorption performance of NBCs for TC was mostly attributed to the pore filling, hydrogen bonding, π-π interactions, Lewis acid-base interactions, and electrostatic interactions. Importantly, the graphitic N serves as the primary TC adsorption site, followed by pyridinic N. This study would provide new insight into the impact of nitrogen configuration on the adsorption mechanism of NBCs for TC.

Three-dimensional porous La(OH)3/g-C3N4 adsorption-photocatalytic synergistic removal of tetracycline.

La(OH)3/g-C3N4 composites were successfully synthesized via one-step calcination using urea, melamine, and La(NO3)3·nH2O as raw materials, and applied to UV-induced photocatalytic tetracycline (TC) removal. Comprehensive characterization by an X-ray diffraction (XRD), Fourier transform infrared reflection (FT-IR), high-resolution transmission electron microscope (HRTEM), and other techniques analyzed effects of La3+ doping, especially N vacancies and cyano groups as active sites. Compared to pure g-C3N4 and La(OH)3, synthesized La(OH)3/g-C3N4 composites exhibited a three-dimensional porous nanosheet structure with specific surface area of 83.62 m2/g and equilibrium TC adsorption capacity up to 285.59 mg/g; La(OH)3 doping significantly improved composite structure. After dispersing 10 mg La-CN-0.5 photocatalyst in 60 mL 40 mg/L TC solution, TC removal reached 91.08% in 30 min under UV irradiation, exhibiting excellent performance. Additionally, La-CN-0.5 showed significant adsorption-photocatalytic synergism, with the quasi-primary kinetic constant increased by 1.83-fold. The efficiency of high tetracycline (TC) concentration treatment through adsorption photocatalytic degradation by La-CN-0.5 was confirmed by the utilization of free radical trapping and electron spin resonance (ESR) tests. The significant involvement of ∙O2-, ∙OH, and h+ in this process was observed. These findings propose that the prepared La-CN-0.5 material exhibits a unique capability for adsorption photocatalysis, providing a promising approach for the efficient removal of high TC concentrations.

Liquid-waste derived magnetic porous carbon sphere for effective removal of tetracycline from aqueous solution

Effective removal of tetracycline (TC) from wastewater is highly important while still faces challenges especially in adsorption capacity. Herein, a novel N-doped magnetic porous graphitic carbon sphere (N-MPGCS) adsorbent was fabricated by a green strategy using tannic acid (TA) as organic ligand and stainless steel pickling wastewater as metal source. Melamine was also introduced to increase nitrogen-containing functional groups. Among the obtained carbon spheres, N-MPGCS1–800 sample shows a large specific surface area (up to 922.78 m2 g−1), appropriate O/N functional groups, suitable sp2 carbon, and good magnetic responsivity. Benefiting from these merits, this optimal material exhibits a high Langmuir adsorption capacity (1005.5 mg g−1 at 45 °C) for TC, fast adsorption kinetics (5 min for adsorption equilibration time at 50 mg L−1), and good applicability towards pH (3−10) and co-existing ions. Besides, the excellent magnetism permits the convenient and rapid recovery of adsorbent from the adsorption system. Moreover, the high TC removal ratio (92.3% after three cycles) presents its outstanding regeneration. Adsorption studies and characterizations show that H-bond, π-π stacking, metal-organic complexation interactions, and pore-filling effect contribute to the adsorption together. In addition, N-MPGCS1–800 also shows good removal on enrofloxacin, moxifloxacin, and norfloxacin. This work proves that N-MPGCS material can serve as a potential adsorbent, and more importantly, it gives a new path for mining industrial waste to produce high-effective magnetic carbon materials.

Sulu Çözeltide Tetrasiklin Giderimi için Fındık ve Antep Fıstığı Kabuklarının Eş-karbonizasyonundan Elde Edilen Yeni Hidrokömürün Kullanımı

In present work, the use of a new hydrochar (HSPSHC) produced by the combined hydrothermal carbonization (co-HTC) of hazelnut and pistachio shells (HS and PS) as a sorbent material in tetracycline (TC) antibiotic removal from water was investigated. It was obtained from hydrothermal carbonization of HSPSHC, hazelnut and pistachio shells by mixing 1:1 by mass at 220 oC for 6 h. Mass yield, energy density and higher heating value parameters were calculated for HSPSHC, and the surface chemistry was characterised using Fourier transform infrared spectroscopy (FTIR). TC adsorption on HSPSHC was carried out by kinetic and isotherm studies using batch method. The experimental kinetic results were qualified in pseudo first-order (PFO) and second-order (PSO) kinetic equations and it was observed that the adsorption complied with the PSO kinetics. The experimentally obtained results were applied to Langmuir and Freundlich model equations and isotherm modeling was performed. The adsorption isotherm of TC on the prepared hydrochar was well fitted by the Langmuir equation, which yielded a maximum monolayer adsorption capacity of TC of qm: 137.06 mg/g at 323 K and pH 4.0 on the HSPSHC hydrochar. In addition, thermodynamic studies revealed that the adsorption of TC by HSPSHC is spontaneous and is an endothermic process.

Adsorption Performance and Mechanisms of Tetracycline on Clay Minerals in Estuaries and Nearby Coastal Areas.

Clay minerals in sediments have strong adsorption capacities for pollutants, but their role in the distribution of antibiotics in estuaries and nearby coastal areas is unclear. We evaluated the clay mineral montmorillonite (SWy-2) adsorption capacity for tetracycline (TC). We assessed the adsorption capacity of SWy-2 for TC by measuring the removal percentage of 30 mg/L TC over time. The effects of pH and ionic strength on the TC adsorption onto SWy-2 were investigated. We analyzed the kinetics of TC adsorption using a pseudo-second-order model and determined the adsorption isotherm using the Langmuir equation. SWy-2 particles were characterized using zeta potential, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses before and after TC adsorption. The removal percentage of 30 mg/L TC by SWy-2 reached 70.76% within 0.25 h and gradually increased to 78.64% at 6 h. TC adsorption was influenced by pH and ionic strength, where low pH enhanced and high ionic strength reduced the adsorption. The kinetics of TC adsorption followed a pseudo-second-order model, and the adsorption isotherm adhered to the Langmuir equation. The saturated adsorption capacity (qmax) of SWy-2 for TC was 227.27 mg/g. Zeta potential, FTIR, and XRD analyses confirmed that electrostatic interactions and chemical bonds played a significant role in the TC adsorption by SWy-2. SWy-2 clay mineral exhibits a substantial adsorption capacity for TC, indicating its potential as an effective sorbent to mitigate antibiotic contamination in estuaries and nearby coastal areas. The observed effects of pH and ionic strength on TC adsorption have implications for the environmental fate and transport of antibiotics. The pseudo-second-order kinetic model and Langmuir isotherm equation provide valuable insights into the adsorption behavior and capacity of TC on SWy-2. Characterization analyses support the involvement of electrostatic interactions and chemical bonds in the SWy-2-TC adsorption mechanism.

Novel durable and recyclable Cu@MoS2/polyacrylamide/copper alginate hydrogel photo-Fenton-like catalyst with enhanced and self-regenerable adsorption and degradation of high concentration tetracycline

A durable and recyclable Cu@MoS2/polyacrylamide/copper alginate nanocomposite double network (Cu@MoS2/PAAm/CA NCDN) hydrogel photo-Fenton-like catalyst was prepared for efficient removal of high concentration tetracycline (TC) in pharmaceutical wastewater. This hydrogel catalyst exhibits a remarkable synergistic effect between adsorption and catalytic degradation of TC. Consequently, this hydrogel catalyst shows a larger TC adsorption capacity of 122.2 mg g−1 and a higher TC degradation efficiency of 90% (degradation amount = 70.2 mg g−1) at the TC concentration of 200 mg L−1, while the TC degradation efficiency by Cu@MoS2 catalyst is only 19% (degradation amount = 38.2 mg g−1). This hydrogel catalyst can effectively remove high concentration TC under both light and dark conditions. Moreover, the tensile strength of Cu@MoS2/PAAm/CA NCDN hydrogel catalyst reaches an extraordinary 1.46 MPa and maintains 0.68 MPa after 15-day immersion in water, indicating high durability. In addition, the flexible hydrogel catalyst can keep good integrity after being deformed by stretching, bending, and knotting, etc., enabling its easy recovery. This investigation provides an innovative and versatile strategy to develop high-performance hydrogel catalysts for treating antibiotics-polluted water.

Dyeing sludge-derived biochar for efficient removal of antibiotic from water

Adsorption is one of the most effective methods for ecotoxic antibiotics removal, while developing high-performance adsorbents with excellent adsorption capacity is indispensable. As the unavoidable by-product of wastewater, sewage sludge has dual properties of pollution and resources. In this study, dyeing sludge waste was converted to biochar by KOH activation and pyrolysis, and used as an efficient adsorbent for aqueous antibiotics removal. The optimized dyeing sludge-derived biochar (KSC-8) has excellent specific surface area (1178.4 m2/g) and the adsorption capacity for tetracycline (TC) could reach up to 1081.3 mg/g, which is four and five times higher than those without activation, respectively. The PSO (pseudo-second-order) kinetic model and the Langmuir isotherm model fitted better to the experimental data. The obtained KSC-8 has stabilized adsorption capacity for long-term fixed-bed experiments, and maintained 86.35% TC removal efficiency after five adsorption-regeneration cycles. The adsorption mechanism involves electrostatic attraction, hydrogen bonding, π-π interactions and pore filling. This work is a green and eco-friendly way as converting the waste to treat waste in aiming of simultaneous removal of antibiotics and resource recovery of dyeing sludge.

Effects of chicken manure‐modified biochar on the adsorption capacity of tetracycline and abundance of antibiotic resistance genes in soil

AbstractLarge quantities of livestock manure not only occupy farmland but also serve as the primary source of antibiotics and antibiotic resistance genes (ARGs) in agricultural soil. To enhance the resource utilization of animal manure and mitigate ecological risks associated with antibiotics in agroecosystems, chicken manure was used as a raw material for biochar production. The manure derived biochar (MB) was modified with an alkali–acid two‐step modification process. The results showed that the total pore volume and surface area of alkali–acid modified MB (AMMB) was significantly increased about three and five times, respectively after modification. The SEM images showed that the surface of AMMB had a more regular and clearer structure with fewer impurities. The improvement of surface properties of AMMB significantly increased its adsorbing capacity of tetracycline in the soil. The adsorption kinetics of tetracycline by AMMB were better fitted by the pseudo‐second‐order kinetic model, suggesting that the adsorption of tetracycline on biochar followed the process of chemisorption. The adsorption mechanisms mainly involved the pore filling, hydrophobic effect, and π–π EDA interaction. Moreover, after a 60 days amendment of AMMB, the total relative abundances (RAs) of tested tetracycline resistance genes (TRGs) in soil decreased significantly, which suggested that AMMB can be a potential material to reduce risks of antibiotics and its resistance genes.

Small microplastic particles promote tetracycline and aureomycin adsorption by biochar in an aqueous solution

Biochar (BC) has been used to remove antibiotics from wastewater. Microplastics are emerging contaminants of wastewater. The capacities of microplastics for adsorbing antibiotics and the effects of microplastics of different types and particle sizes on antibiotic adsorption by BC have not been studied. Here, adsorption isotherm and kinetics experiments were performed to investigate tetracycline and aureomycin adsorption to polyvinyl chloride particles with diameters of 10, 100, 500, and 2000 μm, polylactic acid particles with diameters of 30, 100, 500, and 2000 μm (PLA30, PLA100, PLA500, and PLA2000, respectively), and wheat straw BC. The highest tetracycline adsorption capacity (25.00 mg g−1) was found for a PLA30 + BC. The tetracycline adsorption capacities of the other microplastic particles were 20.44–24.57 mg g−1. The highest aureomycin adsorption capacity (39.50 mg g−1) was found for 10 μm polyvinyl chloride particles and BC. The aureomycin adsorption capacities of the other microplastic particles were 32.21–38.42 mg g−1. The tetracycline adsorption capacities were 13.69%, 6.28%, 5.49%, and 4.54% higher for PLA30 + BC, PLA100 + BC, PLA500 + BC, and PLA2000 + BC, respectively, than for only BC. This may have been because there were more sites available per unit mass of microplastic for adsorbing tetracycline and dissolved organic carbon on small microplastic particles than large microplastic particles. The results indicated that microplastics can adsorb antibiotics and increase the amounts of antibiotics adsorbed by BC. Therefore, it is essential to consider potential interactions between BC and microplastics when BC is used to remove antibiotics from wastewater.

Understanding the structure-dependent adsorption behavior of four zirconium-based porphyrinic MOFs for the removal of pharmaceuticals

The adsorptive removal of typical pharmaceuticals, carbamazepine (CBZ) and tetracycline (TC), was investigated with four zirconium-based porphyrinic metal-organic frameworks (MOFs) (PCN-221, PCN-222, PCN-223, and PCN-224). For both CBZ and TC, the adsorption capacities of the PCNs were ranked in the following order: PCN-221 < PCN-223 < PCN-224 < PCN-222. Notably, this order aligns with the BET surface areas of the PCNs. Cage-type PCN-221 showed a lower adsorption capacity than the other three channel-type MOFs due to its small apertures, which were not conducive to the activation of PCN-221 and space utilization. The amount of adsorption was proportional to the cumulative pore volume in PCNs with a width larger than that of the CBZ/TC molecule. Therefore, with high pore volume and large one-dimensional channels formed by ordered linker vacancies, PCN-222 was the best adsorbent in this work. According to the Langmuir model, PCN-222 exhibited exceptional adsorption capacities for CBZ and TC, reaching 305 mg/g and 280 mg/g, respectively. Additionally, the mechanisms for CBZ removal involved hydrogen bonding and π-π interactions/stacking, while electrostatic interactions, hydrogen bonding, and π-π interactions/stacking played crucial roles in TC adsorption onto MOFs. These findings establish a profound comprehension of the interplay between pore structure and performance, providing helpful guidance for designing MOFs to remove emerging contaminants effectively.

Selective adsorption of tetracycline and copper(II) on ion-imprinted porous alginate microspheres: performance and potential mechanisms.

A novel epichlorohydrin and thiourea grafted porous alginate adsorbent (UA-Ca/IIP) was synthesized using ion-imprinting and direct templating to remove copper ions (Cu(II)) and tetracycline (TC) in aqueous solution. UA-Ca/IIP demonstrated great selectivity for Cu(II) and TC among different coexisting anions (CO32-, PO43- and SO42-), cations (Ca2+, Mg2+ and NH4+), and antibiotics (oxytetracycline and sulfamethoxazole). The adsorption of TC and Cu(II) by UA-Ca/IIP was significantly affected by the pH of the solution, and the quantity of TC and Cu(II) adsorbed reached a maximum at pH 5. A pseudo-second-order model better fitted the kinetic data; the Langmuir model predicted the maximum adsorption quantities 3.527 mmol TC g-1 and 4.478 mmol Cu(II) g-1 at 298 K. Thermodynamic studies indicated that the TC and Cu(II) adsorption was more rapid at a higher temperature. Antagonistic and synergistic adsorption experiments showed that the adsorption capacity of TC would increase significantly with the increase of Cu(II) concentration. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that along with the influence of pH, electrostatic interaction and complexation were the main mechanisms of TC and Cu(II) adsorption. Regeneration experiments revealed that TC and Cu(II) were removed efficiently and that UA-Ca/IIP was recyclable over the long term. These results show that the modified porous alginate microsphere is a green and recyclable adsorbent, which has good selectivity and high adsorption performance for the removal of TC and Cu(II).

Ferrous ion-induced cellulose nanocrystals/alginate bio-based hydrogel for high efficiency tetracycline removal

The complex synthesis process, high cost, toxicity and difficult separation of traditional adsorbents have limited their application for the removal of emerging organic contaminants (EOCs) from the aquatic environment. A completely bio-based alginate reinforced with cellulose nanocrystals hydrogel via Fe2+ cross-linking (CNC/Alg-Fe2+), was successfully fabricated as an effective adsorbent under unique low temperature heat treatment (100 °C) for tetracycline (TC) removal. The metal ions (Fe3+, Fe2+ and Ca2+) enabled bindings with hydroxyl, sulfate half ester and carboxyl groups coexisted on CNC/Alg surface via chelation, strong hydrogen bonds and electrostatic interactions. Among composite materials with varied cation cross-linkers, hydrogel cross-linked with Fe2+ showed the maximum adsorption capacity of TC (741.66 mg·g−1), circa 1.9 and 6.9 times higher than that of hydrogel cross-linked with Fe3+ (394.16 mg·g−1) and Ca2+ (108.14 mg·g−1) respectively at 298 K, due to enhanced chelation between Fe2+ and TC. The efficient adsorption of TC was attributed to surface complexation, cation bridging, n-π electronic donator-acceptor interactions, hydrogen bonds and electrostatic interactions synergistically. Besides, adsorption capacity of CNC/Alg-Fe2+ retained 84.6% after 5 regeneration cycles indicating high reusability. This study provides a simple but effective bio-based hydrogel absorbent with stable structure, ultrahigh adsorption capacity, excellent reusability and easy-separation for the purification of TC-containing biomedical wastewater.

Cobalt nanoparticles encapsulated in Nitrogen-Doped carbons derived from Co-Metal-Organic frameworks with superb adsorption capacity for tetracycline

The enrichment of tetracycline (TC) in the environment will harm human and animal tissues and lead to bacterial resistance. The MIL or ZIF derived magnetic carbon adsorbents have great potential for the removal of TC, whereas its low concentration of metals limits the adsorption efficiency. By one-step annealing Co-hexamine coordination frameworks at 700 °C, the ultrahigh Co concentration (86.10 wt%) and abundant doped nitrogen (2.85 at%) are achieved in the nitrogen-doped carbons encapsulated cobalt nanoparticles (Co@NC-700). The optimized Co@NC-700 composite exhibits a supercolossal TC adsorption capacity of 3496.54 mg g−1, which is ∼ 6 times that of the traditional adsorbents, and the removal capacity maintains at 94.22% after four cycles. The adsorption of TC follows Pseudo-second-order and Elovich kinetic models, suggesting a chemisorption process. The adsorption isotherm had good compatibility with Freundlich model, confirming the crucial role of multi-layer adsorption on the high adsorption capacity. Experiments and characterizations revealed the dominant effect of π-π electron donor–acceptor (EDA) interaction and surface complexation on the adsorption of TC. Density functional theory calculations demonstrate that the encapsulated cobalt formed complex bond with TC through the pore and pyridinic-N enhance the π-π EDA interaction. This work demonstrates a strategy of preparing magnetic carbon material with ultrahigh metal concentration, which opens up a new avenue for highly efficient adsorbent development in the removal of antibiotics and pollutants.