ZIF-mediated N-doped hollow porous carbon as a high performance adsorbent for tetracycline removal from water with wide pH range

Carboxymethyl chitosan modification of cobalt-zinc bimetallic MOF for tetracycline hydrochloride removal: Exploration of the enhancement mechanism of the process

This study synthesized a carboxymethyl chitosan-modified bimetallic Co/Zn-ZIF (CZ@CMC) with strong hydrophilicity and adsorption performance via the one-pot method. Tetracycline hydrochloride (TCH) was used as the model contaminant to evaluate the adsorption and peroxymonosulfate (PMS) activation properties of CZ@CMC. Mechanism showed that the adsorption behavior occurred through pore filling, electrostatic attraction, surface complexation, hydrogen bonding, and π-π stacking. In addition, a CZ@CMC/PMS system was constructed, which had excellent catalytic performance. The hydrophilicity and selective adsorption properties of CMC conferred a greatly accelerated CZ@CMC in catalyzing the PMS process with kobs of 0.095 min-1, in which OH, 1O2, SO4-, O2-, and Co(III) were the main ROS which quenching tests, EPR, and chemical probe experiments verified. In addition, the degradation pathways of TCH were obtained utilizing DFT and HPLC-MS and analyzed to show that the system possessed a good detoxification capacity. This work is expected to provide a green, efficient, and stable strategy to enhance the adsorption properties of catalytic materials and subsequently their co-catalytic properties.

Multiporous ZIF-8 carbon/cellulose composite beads: Highly efficient and scalable adsorbents for water treatment

Metal-organic framework (MOF) particles are one of the most promising adsorbents for removing organic contaminants from wastewater. However, powder-type MOF particles face challenges in terms of utilization and recovery. In this study, a novel bead-type adsorbent was prepared using activated carbon based on the zeolitic imidazolate framework-8 (AC-ZIF-8) and a regenerated cellulose hydrogel for dye removal. AC-ZIF-8 particles with a large surface area were obtained by carbonization and chemical activation with KOH. The AC-ZIF-8 powders were efficiently immobilized in hydrophilic cellulose hydrogel beads via cellulose dissolution/regeneration. The prepared AC-ZIF-8/cellulose hydrogel (AC-ZIF-8/CH) composite beads exhibit a large specific surface area of 1412.8 m2/g and an excellent maximum adsorption capacity of 565.13 mg/g for Rhodamine B (RhB). Moreover, the AC-ZIF-8/CH beads were effective over a wide range of pH, temperatures and for different types of dyes. These composite beads also offer economic benefits through desorption of dyes for recycling. The AC-ZIF-8/CH beads can be produced in substantial amounts and used as fillers in a fixed-bed column system, which can purify the continuous inflow of dye solutions. These findings suggest that our simple approach for preparing high-performance adsorbent beads will broaden the application of dye adsorbents, oil-water separation, and catalysts.

Highly enhanced chloramphenicol adsorption performance of MIL-53-NH2(Al)-derived porous carbons modified with tannic acid

The worldwide demand for antibiotics has experienced a notable surge, propelled by the repercussions of the COVID-19 pandemic and advancements in the global healthcare sector. A prominent challenge confronting humanity is the unregulated release of antibiotic-laden wastewater into the environment, posing significant threats to public health. The adoption of affordable carbon-based adsorbents emerges as a promising strategy for mitigating the contamination of antibiotic wastewater. Here, we report the synthesis of novel porous carbons (MPC) through a direct pyrolysis of MIL-53-NH2(Al) and tannic acid (TANA) under N2 atmosphere at 800 °C for 4 h. The effect of TANA amount ratios (0%-20%, wt wt-1) on porous carbon structure and adsorption performance was investigated. Results showed that TANA modification resulted in decreased surface area (1,600 m2 g-1-949 m2 g-1) and pore volume (2.3 cm3 g-1-1.7 cm3 g-1), but supplied hydroxyl functional groups. Adsorption kinetic, intraparticle diffusion, and isotherm were examined, indicating the best fit of Elovich and Langmuir models. 10%-TANA-MPC obtained an ultrahigh adsorption capacity of 564.4 mg g-1, which was approximately 2.1 times higher than that of unmodified porous carbon. 10%-TANA-MPC could be easily recycled up to 5 times, and after reuse, this adsorbent still remained highly stable in morphology and surface area. The contribution of H bonding, pore-filling, electrostatic and π-π interactions to chloramphenicol adsorption was clarified. It is recommended that TANA-modified MIL-53-NH2(Al)-derived porous carbons act as a potential adsorbent for removal of pollutants effectively.

Bimetal doped Cu-Fe-ZIF-8/g-C3N4 nanocomposites for the adsorption of tetracycline hydrochloride from water

Bimetal doped Cu-Fe-zeolitic imidazole framework-8 (ZIF-8)/graphitic carbon nitride (GCN) (Cu-Fe-ZIF-8/GCN) nanocomposites were prepared via one-pot and ion-exchange methods. The main influencing factors, such as adsorbent concentration, TC concentration, initial pH, and coexisting ions, were evaluated in detail. Due to the suitable pore structures and the presence of multiple interactions on the surface, the nanocomposite showed a high adsorption capacity up to 932 mg g-1 for tetracycline hydrochloride (TC), outperforming ZIF-8 by 4.8 times. The adsorption kinetics and adsorption isotherm were depicted in good detail using pseudo-second-order kinetic and Langmuir models, respectively. Thermodynamic calculation revealed that the adsorption of the nanocomposite under experimental conditions was a spontaneous heat absorption process, and was primarily driven by chemisorption. After four cycles of use, the nanocomposite retained 87.2% of its initial adsorption capacity, confirming its high reusability and broad application prospects in removing tetracycline-type pollutants from wastewater.

Removal of pharmaceutical and personal care products (PPCPs) by MOF-derived carbons: A review

Nowadays, the increasing demand for pharmaceuticals and personal care products (PPCPs) has resulted in the uncontrolled release of large amounts of PPCPs into the environment, which poses a great challenge to the existing wastewater treatment technologies. Therefore, novel materials for efficient treatment of PPCPs need to be developed urgently. MOF-derived carbons (MDCs), have many advantages such as high mechanical strength, excellent water stability, large specific surface area, excellent electron transfer capability, and environmental friendliness. These advantages give MDCs an excellent ability to remove PPCPs. In this review, the effects of different substances on the properties and functions of MDCs are discussed. In addition, representative applications of MDCs and composites for the removal of PPCPs in the field of adsorption and catalysis are summarized. Finally, the future challenges of MDCs and composites are foreseen.

Rapid adsorption of triclosan and p-chloro-m-xylenol by nitrogen-doped magnetic porous carbon

Contamination of water resources with organic substances like phenolic fungicides is undesirable due to the improvement of living standards, the huge production of chemicals, the heavy consumption of daily chemical products, and the growth of the population. In this study, Co-based zeolitic imidazole framework-67 (ZIF-67(Co)) was synthesized using the "one-pot method," and the best Co-based N-doped magnetic porous carbon (Co-NPC) was prepared by ZIF-67(Co) carbonization in an atmosphere of N₂. The materials were tested using an X-ray diffractometer (XRD), scanning electron microscope (SEM), infrared spectroscopy (IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption, and magnetization analysis. These characterizations indicated that the Co-NPC was successfully prepared. With the original morphology of ZIF-67(Co) crystals, the Co-NPC also has good porosity, magnetic properties, and a large specific surface area. In water, Co-NPC-800 has a good adsorption capacity for triclosan (TCS) and p-chloro-m-xylenol (PCMX), which are kinds of aromatic fungicides. The adsorption of Co-NPC-800 on both reached equilibrium within 3 min, which is in accordance with the quasi-second-order kinetic model. At 298 K, the maximum adsorption capacity of Co-NPC-800 for TCS and PCMX was 163 and 39 mg·g^-1, respectively. The adsorption of TCS and PCMX by Co-NPC-800 is a spontaneous endothermic process with reduced entropy. The combination of Co-NPC-800 and phenols come from multiple actions of electrostatic, π-π, and hydrogen bond effects. Moreover, Co-NPC-800 can be regenerated through simple washing and can be reused at least three times by a magnet. The Co-NPC-800 has good porosity, large specific surface area, comparable adsorption capacity, rapid adsorption time, so it could be broadly used in sewage treatments and other environmental fields.

Nano-architecture of MOF (ZIF-67)-based Co3O4 NPs@N-doped porous carbon polyhedral nanocomposites for oxidative degradation of antibiotic sulfamethoxazole from wastewater

Co₃O₄ NPs in N-doped porous carbon (Co₃O₄ NPs@N-PC) materials were prepared by one-pot pyrolysis of a ZIF-67 powder under N₂ atmosphere and followed by oxidation under air atmosphere (200 °C) toward promotion catalytic activity and activation of peroxymonosulfate (PMS) to degradation sulfamethoxazole (SMZ). 2-methylimidazole was used as a nitrogen source and a competitive ligand for the synthesis of Co₃O₄ NPs@N-PC, which in addition to affecting nucleation and growth of the crystal, promotes the production of active Co-N sites. Co₃O₄ NPs@N-PC nano-architecture has high specific surface areas (250 m² g^-1) and is a non-toxic, effective and stable PMS activator. The effect of operating parameters including SMZ concentration, catalyst dosage, temperature and pH in the presence of Co₃O₄ NPs@N-PC was investigated. The Co₃O₄ NPs@N-PC composite showed superior performance in activating PMS over a wide range of pH (2-10) and different temperatures so that complete degradation of SMZ (50 μM, 100 mL) was achieved within 15 min. The role of Co^2+/Co³⁺ redox system in the mechanism before and after PMS activation was determined using XPS analysis. Surface-generated radicals led to the degradation of SMZ, in which the SMZ degradation rate attained 0.21 min^-1 with the mineralization of 36.8%. The feasible degradation mechanism of SMZ was studied in the presence of different scavengers and it was revealed that the degradation reaction proceeds from the radical/non-radical pathway and in this process most of the SO₄^- and OH radicals are dominant. The recoverability and reuse of Co₃O₄ NPs@N-PC were evaluated to confirm its stability and potential for SMZ degradation and it was observed that the catalyst maintains its catalytic power for at least 5 cycles.

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.

Facile fabrication of N-doped hierarchical porous carbons derived from soft-templated ZIF-8 for enhanced adsorptive removal of tetracycline hydrochloride from water

N-doped hierarchical porous carbons (NHPCs) were successfully prepared from soft-templated zeolitic imidazolate framework-8 (ZIF-8) precursors using sodium dodecylbenzene sulfonate (SDBS) as a template through facile one-step carbonization and applied in tetracycline hydrochloride (TCH) adsorption. The NHPC synthesized at 1000 °C with an SDBS/Zn²⁺ molar ratio of 0.075 exhibited the highest TCH adsorption (q_m = 80.92 mg g^-1) owing to its relatively large BET surface area (1067.41 m² g^-1) and pore volume (1.22 cm³ g^-1) and the stronger surface interaction between TCH and NHPCs (HC1000-0.075). Compared with surfactant-free ZIF-8-derived carbon (HC), introduction of SDBS in the ZIF-8 precursor not only improved the pore structure of the carbon materials but also increased the nitrogen content and the number of surface functional groups. Adsorption kinetics and isotherms showed that the pseudo-second-order model and Sips model fit the TCH adsorption behavior on HC and HC1000-0.075 well. Adsorption experiments and characterizations revealed that the adsorption mechanism involved in TCH adsorption on HC1000-0.075 mainly depended on the synergistic effect of pore filling, H-bonding, π-π interactions, and weak electrostatic interactions. This study provides an effective and simple strategy for fabricating MOF-derived NHPCs as a promising adsorbent for the removal of antibiotics from water.

Utilization of porous carbon synthesized with textile wastes via calcium acetate template for tetracycline removal: The role of template agent and the formation mechanism

A porous carbon obtained from cotton/polyester textile wastes was synthesized by the calcium acetate template method. This research studied the effect of preparation conditions and evaluated the characterization of porous carbon, and further explored its formation mechanism. The porous carbon possessed a high specific surface area of 1106.63 m²/g under an optimum condition (pyrolysis temperature = 800 °C, mass ratio of CA: CPW = 1.5:1, pyrolysis time = 1.5 h). It was found that calcium acetate played the role of catalyst to promote the degradation of cotton/polyester textile. CaCO₃ and CaO fabricated by calcium acetate acted as the template to generate a mesoporous structure. The generated CO₂ etched carbon skeleton to create a large number of micropores. Besides, it was supported as the carbon source to fuse with carbon structures, further consolidating the aromatic structures of porous carbon. The optimized porous carbon has a high adsorption capacity of 506.40 mg/g for tetracycline. And the adsorption data fitted better by the first-pseudo-order model and Langmuir isotherms with an endothermic and spontaneous adsorption process. The cotton/polyester-based porous carbon was a promising economical material for tetracycline.

CoZn-ZIF-derived carbon-supported Cu catalyst for methanol oxidative carbonylation to dimethyl carbonate

Carbon materials derived from CoZn-ZIFs were used to load Cu catalysts and were applied for DMC synthesis, and the effects of the graphitization degree and the (N1 + N3)/N2 ratio were studied.

Effectively removing tetracycline from water by nanoarchitectured carbons derived from CO2: Structure and surface chemistry influence

Understanding of the correlation between physico-chemical property of adsorbent and the adsorption performance of contaminant is very significant for developing high-efficient materials to remove antibiotic contamination from water. In this work, a novel kind of carbon adsorbent (EC) derived from CO₂ and activated ECs with modified structure via a facile chemical method using H₂ and KOH were prepared. The synthetic carbon materials (EC, EC-H₂, and EC-KOH) were then applied to remove tetracycline (TC). The kinetics of adsorption for these three carbon materials all well fitted the pseudo-second-order kinetic model. The experimental data of adsorption isotherm had good compatibility with Langmuir and Freundlich models (R² > 0.90), but the Temkin model was the most applicable for all adsorbents (R² > 0.98). A super-high adsorption capacity of EC-KOH obtained from Langmuir fitting was 933.56 mg g^-1, which was much higher than that of EC-H₂ (538.91 mg g^-1) and EC (423.30 mg g^-1), possibly due to its larger specific surface area (S_BET), pore volume, and specific surface chemical structure. Moreover, it was found that surface functional groups and large aperture of adsorbents had a positive effect on adsorption rate. More adsorption sites and surface functional groups of adsorbents were beneficial to enhance the adsorption affinity. These results are of great benefit to the directional control of carbon structure to increase the adsorption performance in rate, capacity, and affinity of antibiotics.

Potential threats of zeolitic imidazolate framework-8 nanoparticles to aquatic fungi associated with leaf decomposition

Synthesis of zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) and evaluation of their potential threats on ecosystem functioning has been reported in this work. A 45-day indoor experiment was conducted to explore the effects of ZIF-8 NPs at three different concentrations (10, 100, and 1000 μg L^-1) on the aquatic fungal community associated with Populus nigra L. leaf litter decomposition. After chronic exposure, ZIF-8 NPs at 1000 μg L^-1 significantly inhibited fungal biomass and extracellular enzyme activities as a result of inhibition on carbon and nitrogen loss of leaves. Besides, ZIF-8 NPs at 10 μg L^-1 increased the percentage of Anguillospora in the fungal community and led Monographella cucumerina and Mycosphaerella tassiana to become the hub species, which eventually significantly promoted the decomposition of leaf litter. In conclusion, our study provides a reference for the possible ecotoxicity of ZIF-8 NPs on aquatic fungi, confirms the influence of ZIF-8 NPs on nutrient cycling in streams, and also emphasizes the importance of fungal community structure and hub species in the process of leaf litter decomposition.

Adsorptive removal of pharmaceuticals from water using metal-organic frameworks: A review

Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.

Simultaneous removal of rhodamine B and Cr(VI) from water using cellulose carbon nanofiber incorporated with bismuth oxybromide: The effect of cellulose pyrolysis temperature on photocatalytic performance

A series of biomass cellulose-derived carbon nanofibers (CCNF) were prepared at different pyrolysis temperatures in this study. Subsequently, this CCNF was combined with bismuth oxybromide (BiOBr) to form BiOBr/CCNF composite. The feasibility of BiOBr/CCNF as photocatalyst was investigated for the treatment against organic dye, rhodamine B (RhB) and inorganic metal ion, hexavalent chromium (Cr(VI)). The effect of the pyrolysis temperature on the properties (e.g., crystalline structure, functional group distribution, and graphitization degree) of the prepared CCNF was investigated in relation to its photocatalytic performance. A pyrolysis temperature over 800 °C resulted in CCNF with higher degrees of graphitization which was accompanied by a better photocatalytic performance of its composite against RhB and Cr(VI). Their reaction kinetic rates were estimated as 8.15 × 10^-2 and 0.21 mmol/g/h, respectively (at the initial concentration of 10 mg/L), while their quantum yield values were 1.56 × 10^-6 and 3.83 × 10^-6 molecules per photon, respectively. BiOBr/CCNF catalysts were efficient enough to simultaneously remove RhB and Cr(VI) through the generation of active oxidative and reductive oxygen species, respectively. The strategies used in this study offer a new pathway for preparing cost-effective photocatalysts with biomass derived carbonaceous materials for the efficient removal of multicomponent contaminants in water.