Novel magnetic amine functionalized carbon nanotube/metal-organic framework nanocomposites: From green ultrasound-assisted synthesis to detailed selective pollutant removal modelling from binary systems

Site Energy Distribution Coupled with Statistical Physics Modeling for Cr(VI) Adsorption onto Coordination Polymer Gel

In this work, a novel pristine coordination polymer gel composed of zirconium and 2-amino-5-mercapto-1,3,4-thiadiazole is unveiled and explored to remove Cr(VI) from aqueous systems. A Box-Behnken design, coupled with a genetic algorithm and desirability function, was used for optimizing the controllable factors for maximum removal efficiency. Under optimized conditions (A = 50 mg L-1, B = 40 mg, C = 90 min, and D = 4), 99% of Cr(VI) was removed, and the saturation adsorption capacity recorded was 132.37 mg g-1. The adsorption data were investigated through statistical physics modeling. The most suited statistical physics model (monolayer with three energies; R2 = 0.994-0.997, χ2 = 0.008-0.024), combined with site energy distribution analysis, XPS, and FTIR, unraveled the uptake mechanism. At the first and third active sites, Cr(VI) uptake was multimolecular (n > 1), while at the second active site, it was a mixed multimolecular (298 K, n > 1) and multidocking (308 and 318 K, n < 1). The adsorption energy values indicated the involvement of coordination exchange (E1 = 53.40-58.47 kJ mol-1), electrostatic interaction (E2 = 29.56-32.29 kJ mol-1), and hydrogen bonding (E3 = 24.68-28.35 kJ mol-1) in Cr(VI) adsorption. The BSf(1.5, α) model fitted best (R2 = 0.976-0.994, χ2 = 0.023-0.377) to the kinetic data under all conditions. Common coexisting ions had no significant impact on removal efficiency (%R > 97% at 1:3), and the sorbent could be reutilized up to 5 uptake-elution cycles (>96% efficiency). The practical utility of ZrAMTD was investigated by remediating Cr(VI) contaminated real water samples (%R ≥ 92.91%).

Preparation of PdNi bimetallic loaded amino modified porous carbon material catalyst based on chitosan and its applications

The utilization efficiency of palladium-based catalysts has sharply increased in many catalytic reactions. However, numerous studies have shown that preparing alloys of palladium with other metals has superior catalytic activity than pure palladium. Additionally, hierarchical porous carbon has gradually developed into an excellent carrier for loading bimetallic nanoparticles. In this study, we firstly pyrolyzed chitosan, sodium bicarbonate and nickel nitrate to create highly dispersed porous carbon materials doped with Ni NPs. The carbon materials were then grafted with silane coupling agent (APTMS) to afford them with amino groups on the surface. Taking advantage of the fact that Pd2+ can react with Ni in spontaneous reduction reaction, Pd was deposited on the surface of Ni to produce PdNi bimetallic-loaded carbon catalysts containing amino groups. The resulting catalysts were examined by a series of characterizations and were found to have a hierarchically porous structure and large specific surface area, which increased the number of active sites of the catalysts. In comparison to other Pd catalysts, the PdNi/HPCS-NH2 catalysts displayed remarkable activity for Suzuki coupling reaction and hydro reduction of nitroaromatics, which exhibited a high turnover frequency value (TOF) of 37,857 h-1 and 680.9 h-1, respectively. These were mainly due to the high dispersion of the PdNi NPs and the superior structure of the carriers. Moreover, the catalysts did not experience a significant decline in activity after ten cycles. All in all, this investigation has created a new approach for the fabrication of novel carriers for Pd catalysts, which is in line with the concept of green chemistry and recyclable.

Electrochemical Sensing Systems for the Analysis of Catechol and Hydroquinone in the Aquatic Environments: A Critical Review

Because of their unique physical, chemical, and biological characteristics, conductive nanomaterials have a lot of potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and other fields. Recent breakthroughs in the manufacture of carbon materials, conductive polymers, metals, and metal oxide nanoparticles based electrochemical sensors and biosensors for applications in environmental monitoring by detection of catechol (CC) and hydroquinone (HQ) are presented in this review. To achieve this goal, we first introduced recent works that discuss the effects of phenolic compounds and the need for accurate, inexpensive, and quick monitoring, and then we focused on the use of the most important applications of nanomaterials, such as carbon-based materials, metals, and metal oxides nanoparticles, and conductive polymers, to develop sensors to monitor catechol and hydroquinone. Finally, we identified challenges and limits in the field of sensors and biosensors, as well as possibilities and recommendations for developing the field for better future applications. Meanwhile, electrochemical sensors and biosensors for catechol and hydroquinone measurement and monitoring were highlighted and discussed particularly. This review, we feel, will aid in the promotion of nanomaterials for the development of innovative electrical sensors and nanodevices for environmental monitoring.

Amine-functionalized Schiff base covalent organic frameworks supported PdAuIr nanoparticles as high-performance catalysts for formic acid dehydrogenation and hexavalent chromium reduction

Formic acid (FA) holds significant potential as a liquid hydrogen storage medium. However, it is important to improve the reaction rates and extend the practical applications of FA dehydrogenation and Cr(VI) reduction through the development of efficient heterogeneous catalysts. This study reports the synthesis of a uniformly dispersed PdAuIr nanoparticles (NPs) catalyst loaded with amine groups covalent organic frameworks (COFs). The alloyed NPs demonstrated exceptional effectiveness in FA dehydrogenation rate and Cr(VI) reduction. The initial turnover of frequency (TOF) value for FA dehydrogenation without additives was 9970 h-1 at 298 K, the apparent activation energy (Ea) was 30.3 kJ/mol and the rate constant (k) for Cr(VI) reduction was 0.742 min-1. Additionally, it showcased the ability to undergo recycling up to six times with minimal degradation in performance. The results indicate that its remarkable catalytic performance can be attributed primarily to the favorable mass transfer attributes of the aminated COFs supports, the strong metal-support interaction (SMSI), and the synergistic effects among the metals. This study offers a novel perspective on the advancement of efficient and durable heterogeneous catalysts with diverse capabilities, thereby making significant contributions to the fields of energy and environmental preservation.

One-pot synthesis of bimetallic Fe-Cu metal-organic frameworks composite for the elimination of organic pollutants via peroxymonosulphate activation

A series of bimetallic of FeCu metal-organic frameworks (MOFs) have been synthesised using a solvothermal process by varying the ratio between the two metals. Further, the bimetallic MOF catalysts were characterised by X-ray powder diffraction, scanning electron microscopy, and infrared spectroscopy techniques. Their catalytic properties for activation of peroxymonosulphate (PMS) have been tested by the removal of a model dye, rhodamine B. As a result, NH2-Fe2.4Cu1-MOF demonstrated the highest degradation, the effect of the ratio NH2-Fe2.4Cu1-MOF/PMS has been studied, and the main reactive species have been assessed. The application of these MOFs in powder form is difficult to handle in successive batch or flow systems. Thus, this study assessed the feasibility of growing NH2-Fe2,4Cu1-MOF on polyacrylonitrile (PAN) spheres using the one-pot solvothermal synthesis method. The optimisation of the catalytic activity of the synthesised composite (NH2-Fe2.4Cu1-MOF@PAN) has been evaluated by response surface methodology using a central composite face-centred experimental design matrix and selecting as independent variables: time, PMS concentration, and catalyst dosage. Based on the results, the optimisation of the operational conditions has been validated. At 2.5 mM PMS, 90 min, and 1.19 g·L-1 of catalyst dosage, maximum degradation (80.92%) has been achieved, which doubles the removal values obtained in previous studies with other MOFs. In addition, under these conditions, the catalyst has been proven to maintain its activity and stability for several cycles without activity loss.

Photo-assisted degradation of Rhodamine B by a heterogeneous Fenton-like process: performance and kinetics

This study presents the degradation of rhodamine B (RhB) by photo Fenton-like (PF-like) process under visible light irradiation (λ > 380 nm) using cobalt phosphate microparticles (CoP-MPs). The effects of the initial concentration of RhB, pH value, CoP-MPs dosage, hydrogen peroxide (H2O2) concentration, and salts found in textile wastewater (such as NaNO3, Na2SO4, and NaCl) were investigated in detail. It was found that CoP-MPs can maintain high catalytic activity with wide pH values varying from 4 to 8. This indicated that the use of CoP-MPs overcame the low efficiency of Fenton-like reaction at neutral and even weakly alkaline pH. The PF-like degradation of RhB followed pseudo-first order kinetics in various conditions. Moreover, a comparison of experimental results showed that the PF-like system has good degradation ability for RhB and methyl blue (MB) solution, but is poor for methyl orange (MO) solution. The repeat experiments indicated that the chemical structures of CoP-MPs were stable. Furthermore, the Co2+ ions leaching to the solutions were measured by an inductively coupled plasma mass spectrometer (ICP-MS). Analysis of UV-vis spectra suggested that RhB was degraded by the formation of a series of N-de-ethylated intermediates followed by cleavage of the whole conjugate chromophore structure.HighlightsRhB can be effectively degraded in the PF-like process under visible light irradiation by CoP-MPs.The PF-like process can maintain high catalytic activity at neutral and even weakly alkaline pH.Degradation kinetics exhibited pseudo-first-order kinetics and were influenced by the key parameters.The variation in the UV-vis spectra of RhB was analyzed in detail to infer a possible degradation pathway.

Photocatalytic degradation of a typical macrolide antibiotic roxithromycin using polypropylene fibre sheet supported N-TiO2/graphene oxide composite materials

The post-treatment of recycling the fine photocatalyst nanoparticles restricts their application. In this study, a new photocatalytic material was synthesized by immobilizing the N-doped TiO2 and graphene oxide (GO) composite on polypropylene (PP) (N-TiO2/GO/PP) fibre sheet, and characterized based on X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). The photocatalytic activity was evaluated using roxithromycin (ROX) as a typical antibiotic pollutant. XRD, Raman spectra and SEM images proved that N-TiO2/GO/PP fibre sheet was successfully synthesized. The photocatalytic degradation of 10 mg L-1 ROX can reach up to 90% and the degradation rate constant was 0.2299 h-1 in surface water with the application amount of TiO2/GO/PP fibre sheet of 24.6 cm × 2.7 cm and reaction time of 9 h under the irradiation of simulated sunlight. The application amount of TiO2/GO/PP fibre sheet, initial concentration of ROX and water matrix significantly affect the degradation of ROX. A low concentration of natural organic matter (NOM) slightly promoted the degradation of ROX, while a high concentration of NOM significantly inhibited the degradation of ROX. Alkaline condition (pH 8-9) is favourable for the photocatalytic degradation of ROX by TiO2/GO/PP fibre sheet. The photocatalytic reactivity of the TiO2/GO/PP fibre sheet showed no significant decrease after three runs. Two primary degradation products of ROX were identified and they showed lower ecotoxicity than ROX. The results demonstrate that the new synthesized TiO2/GO/PP fibre sheet shows promising application prospects in the treatment of antibiotics in wastewater and surface waters.

Green and Sustainable Membranes: A review

Membranes are ubiquitous tools for modern water treatment technology that critically eliminate hazardous materials such as organic, inorganic, heavy metals, and biomedical pollutants. Nowadays, nano-membranes are of particular interest for myriad applications such as water treatment, desalination, ion exchange, ion concentration control, and several kinds of biomedical applications. However, this state-of-the-art technology suffers from some drawbacks, e.g., toxicity and fouling of contaminants, which makes the synthesis of green and sustainable membranes indeed safety-threatening. Typically, sustainability, non-toxicity, performance optimization, and commercialization are concerns centered on manufacturing green synthesized membranes. Thus, critical issues related to toxicity, biosafety, and mechanistic aspects of green-synthesized nano-membranes have to be systematically and comprehensively reviewed and discussed. Herein we evaluate various aspects of green nano-membranes in terms of their synthesis, characterization, recycling, and commercialization aspects. Nanomaterials intended for nano-membrane development are classified in view of their chemistry/synthesis, advantages, and limitations. Indeed, attaining prominent adsorption capacity and selectivity in green-synthesized nano-membranes requires multi-objective optimization of a number of materials and manufacturing parameters. In addition, the efficacy and removal performance of green nano-membranes are analyzed theoretically and experimentally to provide researchers and manufacturers with a comprehensive image of green nano-membrane efficiency under real environmental conditions.

Insights into the statistical physics modeling and fractal like kinetic approach for the adsorption of As(III) on coordination polymer gel based on zirconium(IV) and 2-thiobarbituric acid

A novel coordination polymer gel based on zirconium(IV) and 2-thiobarbituric (ZrTBA) was synthesized and explored its potential to remediate As(III) from water. Box-Behnken design with desirability function and genetic algorithm yielded the optimized conditions (initial concentration=194 mg L^-1, dosage = 42.2 mg, time= 95 min and pH = 4.9) for maximum removal efficiency (99.19 %). The experimental saturation capacity for As(III) was 178.30 mg g^-1. The steric parameter n > 1 of the best fitted statistical physics model: monolayer with two energies (R² = 0.987-0.992) suggested multimolecular mechanism with vertical orientation of As(III) molecules onto the two active sites. XPS and FTIR confirmed the two active sites being zirconium and oxygen. The adsorption energies (E₁ = 35.81-37.63 kJ/mol; E₂ = 29.50-36.49 kJ/mol) and isosteric heat of adsorption indicated that physical forces governed the As(III) uptake. DFT calculations implied that the weak electrostatic interaction and hydrogen bonding were involved. The best fitted (R²>0.99) fractal like pseudo first order model established energetic heterogeneity. ZrTBA showed excellent removal efficiency in the presence of potential interfering ions and could be used up to 5 cycles of adsorption-desorption with < 8 % loss in the efficiency. ZrTBA removed ≥96.06 % As(III) from real water samples spiked at different levels of As(III).

Fabrication of HKUST-1/ZnO/SA nanocomposite for Doxycycline and Naproxen adsorption from contaminated water

Doxycycline and Naproxen are among the most widely used drugs in the therapy of CoVID 19 disease found in surface water. Water scarcity in recent years has led to research to treat polluted water. One of the easy and low-cost methods for treatment is adsorption. The utilize of Metal-Organic Frameworks (MOFs) to evacuate pharmaceutical contaminants from water sources has been considered by researchers in the last decade. In this research, HKUST-1/ZnO/SA composite with high adsorption capacity, chemical and water stability, recovery, and reuse properties has been synthesized and investigated. By adding 10 wt% of ZnO and 50 wt% of sodium alginate to HKUST-1, at 25 °C and pH = 7, the specific surface area is reduced by 60%. The parameters of drugs concentration C₀ =(5,80) mg/L, time=(15,240) min, and pH= (2,12) were investigated, and the results showed that the HKUST-1/ZnO/SA is stable in water for 14 days and it can be used in 10 cycles with 80% removal efficiency. The maximum Adsorption loading of doxycycline and Naproxen upon HKUST-1/ZnO/SA is 97.58 and 80.04 mg/g, respectively. Based on the correlation coefficient (R²), the pseudo-second-order and the Langmuir isotherm models were selected for drug adsorption. The proposed mechanism of drug uptake is by MOFs, hydrogen bonding, electrostatic bonding, and acid-base interaction.

Enhancing mechanism of arsenic(iii) adsorption by MnO2-loaded calcined MgFe layered double hydroxide

The use of MnO2/MgFe-layered double hydroxide (MnO2/MgFe-LDH) and MnO2/MgFe-layered double oxide (MnO2/MgFe-LDO400 °C) for arsenic immobilization from the aqueous medium is the subject of this research. Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to characterise MnO2/MgFe-LDH and MnO2/MgFe-LDO400 °C. Based on our developed method, MnO2 was spread on the clay composites' surfaces in the form of a chemical bond. The clay composite exhibited a good adsorption effect on arsenic. The experimental findings fit the pseudo-second-order model well, indicating that the chemisorption mechanism played a significant role in the adsorption process. Furthermore, the Freundlich model suited the adsorption isotherm data of all adsorbents well. The recycling experiment showed that MnO2/MgFe-LDH and MnO2/MgFe-LDO400 °C exhibited good stability and reusability. In summary, MnO2/MgFe-LDH and MnO2/MgFe-LDO400 °C are promising for developing processes for efficient control of the pollutant arsenic.

Facile method to synthesize fluorescent chitosan hydrogels for selective detection and adsorption of Hg2+/Hg. Carbohydr Polym 2022;288:119417. [PMID: 35450660 DOI: 10.1016/j.carbpol.2022.119417]

Fluorescent chitosan-based hydrogel for the selective detection and adsorption of Hg²⁺/Hg⁺ in aqueous environment was prepared through three-step synthesis strategy. NO₂-Boron-dipyrrolemethene (BODIPY) was prepared firstly, and then the -NO₂ group was reduced to -NH₂ group. Finally, the NH₂-BODIPY was introduced to chitosan by Schiff base formation reaction through bi-aldehyde. Eventually, fluorescent chitosan hydrogel was obtained. The as-prepared fluorescent hydrogel probe could detect Hg²⁺/Hg⁺ through PET mechanism with the detection limit of 0.3 μM. The recognition site which combines Hg²⁺/Hg⁺ is CN, it is just formed in the reaction with chitosan and the amino group on BODIPY. Adsorption capacity of the fluorescent hydrogel is 121 mg·g^-1, which is almost seven times of the original chitosan. The isotherm and kinetics of Hg²⁺/Hg⁺ removal follows Langmuir isotherm and pseudo-second order kinetics, respectively. Besides, a series of fluorescent hydrogels were prepared to compare the elasticity, hydropHilicity, fluorescence intensity and adsorption capacity.

Adsorption Behaviors of Cationic Methylene Blue and Anionic Reactive Blue 19 Dyes onto Nano-Carbon Adsorbent Carbonized from Small Precursors

In this work, an innovative nano-carbon material (N-CM) adsorbent was reported for exploring its adsorption behaviors toward cationic methylene blue (MB) and anionic reactive blue 19 (RB19) pollutants. The proposed N-CM was synthesized by a one-step solvothermal treatment of citric acid and zinc gluconate small precursors. N-CM consists of nanosheets that have an advantageous specific surface area, large sp2/sp3 hybridized domains, and abundant nitrogen/oxygen-containing surface functional groups. The synergistic effects of these features are conducive to the MB and RB19 adsorption. Different from anionic RB19 adsorption (79.54 mg/g) by the cooperative π-π stacking and hydrogen bonding, cationic MB adsorbed onto N-CM mainly by the electrostatic attraction at the natural pH solution (> pHpzc), with an adsorption capacity up to 118.98 mg/g. Interestingly, both MB and RB19 adsorption conformed to the pseudo-second order kinetic (R2 ≥ 0.995) and Langmuir isothermal (R2 ≥ 0.990) models, accompanied by similar maximum monolayer adsorption capacities of 120.77 and 116.01 mg/g, respectively. Their adsorption processes exhibited spontaneously endothermic characteristics. Moreover, N-CM showed superior selective capability toward MB in different mixed dye systems, with high removal efficiencies of 73−89%. These results demonstrate that the high-performance carbon adsorbent prepared from small precursors via low-temperature carbonization shows great potentials in wastewater treatment.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

On the Behavior of Newly Synthesized Functionalized Imidazolium-Based Ionic Liquids for Highly Efficient Extraction and Separation of Pirimicarb from Orchard Real Wastewater

The presence of pirimicarb compounds as pollutants in orchard wastewater has sparked rising worries about their detrimental impacts on the ecosystem and human health, and their removal is critical for Pakistan’s aquatic environment. It not only contaminates fruit, but it also leaches into the soil and contaminates groundwater. However, there is little data on the effective removal of pirimicarb from orchard wastewater. The main purpose of this study is to create a novel family of functionalized imidazolium-based ionic liquids (ILs) using a simple chemical process, which will be utilized for the first time to extract pirimicarb from orchard wastewater in an efficient, cost-effective, and environmentally acceptable manner. FTIR, SEM, XRD, TGA, BET, and 1H NMR spectroscopy were used to characterize the functionalized samples. The impact of the IL substituent on the separation capacity was studied. In addition, the extraction and separation of pirimicarb from orchard wastewater were investigated under a variety of conditions (time, concentration, and temperature) in order to better understand the adsorption behaviors of distinct ILs in an aqueous solution. The adsorption equilibrium was reached in 30 minutes, and the maximum removal of pirimicarb was achieved utilizing the synthesized [C2im][C3H6NH2]Br-, according to the data. The pseudo-first-order model and the Langmuir model both suit well with the adsorption mechanism of pirimicarb with very good adsorptive capacities. Thermodynamic analyses indicated spontaneous, endothermic, and entropy-driven adsorption processes. The synthesized imidazolium-based ILs have good regeneration capability and recycling at least for six adsorption-desorption runs and have also been used to successfully detect pirimicarb orchard wastewater samples. The superior safety of the proposed method nominates it as a promising future strategy for pollution prevention. Consequently, this work has proven that the pirimicarb adsorption to various imidazolium-based ILs was dependent on the structures of the produced imidazolium-based ILs, which specifies its potential for practical applications in water pollutant removal and environmental remediation.

Removal of aqueous pharmaceuticals by magnetically functionalized Zr-MOFs: Adsorption Kinetics, Isotherms, and regeneration

The functionalization of metal-organic frameworks (MOFs) is imperative and challenging for the development of practical MOF-based materials. Herein, a magnetically functionalized Zr-MOF (Fe₃O₄@MOF-525) was synthesized via secondary-growth approach to obtain an easily-separated and recyclable adsorbent for the removal of pharmaceuticals (tetracycline (TC) and diclofenac sodium (DF)). After loading Fe₃O₄ nanoparticles (NPs), due to the increase of micropore volume and specific surface area caused by defects, the adsorption performance of Fe₃O₄@MOF-525 was improved. The kinetics could be described by the pseudo-second-order kinetic model. The different adsorption capacity and initial rate were attributed to the properties of the pharmaceuticals, including the molecular size and hydrophobicity/hydrophilicity. In isotherm experiments, the maximum adsorption capacities of DF and TC on Fe₃O₄@MOF-525 calculated by Sips model reached 745 and 277 mg·g^-1, respectively. The thermodynamic studies indicated the adsorption was endothermic and spontaneous. The effect of pH suggested that electrostatic interaction, π-π interaction, anion-π interaction, and H-bonding were possibly involved in the adsorption process. The adsorbent was separated by magnetic and regenerated. Washed with ethanol, Fe₃O₄@MOF-525 remained about 80% adsorption capacity after four cycles. In-situ photo-regeneration under visible-light irradiation was another attractive method, where > 95% TC was degraded in 4 h. The reaction with scavengers revealed that ¹O₂ was the dominant reactive species in our system, indicating the occurrence of Type II photosensitization. The separability, excellent adsorption performance, and recyclability of Fe₃O₄@MOF-525 may lead to its beneficial applications in water treatment.

Amino-Functionalized Magnetic Porous Organic Polymer for Selective Removal of Toxic Cationic Dyes from Textile Wastewater

Porous organic polymers (POPs) with fascinating porous properties are promising candidates for the removal of organic dyes from textile wastewater. In this research work, an amino-functionalized magnetic POP (FC-POP-EDA@Fe3O4) containing...

A silanized magnetic amino-functionalized carbon nanotube-based multi-ion imprinted polymer for the selective aqueous decontamination of heavy metal ions

A novel adsorbent comprising a silanized magnetic amino-functionalized carbon nanotube-based multi-ion imprinted polymer is introduced as an ideal candidate for the simultaneous and selective adsorptive remediation of heavy metal ions from contaminated water.

Carbon Nanotube Based Metal-Organic Framework Hybrids From Fundamentals Toward Applications

Metal-organic frameworks (MOFs) materials constructed by the coordination chemistry of metal ions and organic ligands are important members of the crystalline materials family. Owing to their exceptional properties, for example, high porosity, tunable pore size, and large surface area, MOFs have been applied in several fields such as gas or liquid adsorbents, sensors, batteries, and supercapacitors. However, poor conductivity and low stability hamper their potential applications in several attractive fields such as energy and gas storage. The integration of MOFs with carbon nanotubes (CNTs), a well-established carbon allotrope that exhibits high conductivity and stability, has been proposed as an efficient strategy to overcome such limitations. By combining the advantages of MOFs and CNTs, a wide variety of composites can be prepared with properties superior to their parent materials. This review provides a comprehensive summary of the preparation of CNT@MOF composites and focuses on their recent applications in several important fields, such as water purification, gas storage and separation, sensing, electrocatalysis, and energy storage (supercapacitors and batteries). Future challenges and prospects for CNT@MOF composites are also discussed.

Application of biodegradable cellulose-based biomass materials in wastewater treatment

Water bodies contain a large number of harmful environmental pollutants, including oil, heavy metal ions and dyes, which has become a major global problem. The current work focusses on the development and future prospect of sustainable application of biodegradable cellulose-biomass materials in water treatment, considering that they show an important prospect in wastewater treatment. This paper summarizes the advantages and disadvantages of cellulose-biomass materials in removing harmful substances and pollutants from water and the key problems the technology faces. Cellulose-biomass material has unique structure, is environment friendly, degradable, renewable and provides low energy cost benefits, among other advantages. In this paper, the research progress of wastewater treatment in recent years is reviewed from the following three aspects: oil-water separation, heavy metal ions in water, and dye adsorption. The future research direction is also discussed.

A reusable mesoporous adsorbent for efficient treatment of hazardous triphenylmethane dye wastewater: RSM-CCD optimization and rapid microwave-assisted regeneration

In this research, mesoporous calcium aluminate nanostructures (meso-CaAl2O4) were synthesized using a citric acid-assisted sol-gel auto-combustion process as the potential adsorbent to eliminate toxic triphenylmethane dye malachite green (MG) from synthetic/real effluent. The surface morphology of meso-CaAl2O4 was highly porous with nanometric size and non-homogeneous surface. The specific surface area, total pore volume, and BJH pore diameter of meso-CaAl2O4 were 148.5 m2 g-1, 1.39 cm3 g-1, and 19 nm, respectively. The meso-CaAl2O4 also showed a very high heat resistance, due to losing only 7.95% of its weight up to 800 °C, which is mainly related to the moisture loss. The optimal adsorption conditions were obtained based on response surface methods (RSM)-central composite design (CCD) techniques. The Langmuir isotherm model was used for fitting the adsorption measurements, which presented 587.5 mg g-1 as the maximum adsorption capacity of the dye. The data obtained from the adsorption kinetics model were found to correspond to the pseudo-second-order model. Also, the thermodynamic parameters including enthalpy change (ΔH°), entropy change (ΔS°), and Gibbs free energy change (ΔG°) indicated that MG dye adsorption by the meso-CaAl2O4 was feasible, endothermic, and occurred spontaneously. Furthermore, the meso-CaAl2O4 was regenerated by microwave irradiation under 900 W at 6 min, and the MG dye removal efficiency was remained over 90% after the five cycles of microwave regeneration.

Synthesis of Nanocomposites of V₂O5©Selenium Nanoparticles and Multiwalled Carbon Nanotubes for Antimicrobial Activity

The authors report the preparation of the nanocomposite comprising of vanadium pentoxide (V₂O₅) and selenium (Se) nanoparticles and functionalized multiwalled carbon nanotubes (MWCNTs) (V₂O₅@Se NPs/MWCNTs). Since Se NPs possesses extraordinary physicochemical properties including larger surface area with higher adsorption capacity, V₂O₅ NPs were adsorbed onto Se NPs surface through physisorption process (designated as V₂O₅@Se NPs). The nanocomposite synthesized hydrothermally was evaluated for its antimicrobial activity. The morphology and microstructure of the nanocomposite were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, respectively. Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy (UV-Vis) were employed to analyze the spectral properties of nanocomposite. The microbicidal efficacy of nanocomposite was tested against Gram-negative (G-)ZGram-positive (G+) bacteria and fungus. This is the first report on the synthesis of V₂O₅@Se NPs/MWCNTs nanocomposites by chemical method that showed microbicidal effect on micro-organisms. The thiol (-SH) units facilitates the enrichment of V₂O₅@Se NPs onto MWCNTs surface. Ultimately, it reflects on the significant antimicrobial activity of V₂O₅@Se NPs/MWCNTs.

Synthesis of magnetic tungsten disulfide/carbon nanotubes nanocomposite (WS2/Fe3O4/CNTs-NC) for highly efficient ultrasound-assisted rapid removal of amaranth and brilliant blue FCF hazardous dyes

In this research, the potentiality of magnetic tungsten disulfide/carbon nanotubes nanocomposite (WS₂/Fe₃O₄/CNTs-NC) as an adsorbent for the ultrasound-assisted removal of amaranth (AM) and brilliant blue FCF (BB FCF) dyes was investigated. The experiments were conducted using a central composite design (CCD) with the inputs of solution pH (X₁: 2.0-10), adsorbent mass (X₄: 4-20 mg), AM concentration (X₂: 10-50 mg L^-1), BB FCF concentration (X₃: 10-50 mg L^-1), and sonication time (X₅: 2-12 min). At the optimum conditions, the removal percentages of 99.30% and 98.50% were obtained for AM and BB FCF, respectively. The adsorption of the dyes was described by Langmuir isotherm and pseudo-second-order (PSO) kinetic models. The maximum adsorption capacities of AM and BB FCF were 174.8 mg g^-1 and 166.7 mg g^-1, respectively. The adsorption thermodynamic study showed that the adsorption of the dyes occurred endothermically and spontaneously. The removal percentages of AM and BB FCF from the real samples were in the range of 94.52-99.65% for the binary solutions. The removal percentage for each dye after five cycles of adsorption/desorption was > 90%. This work provides a useful insight to the potential application of CNTs-based magnetic nanocomposite for the treatment of wastewaters contaminated with dyes.

Biodegradation pathway of penicillins by β-lactamase encapsulated in metal-organic frameworks

The pollution caused by the abuse of antibiotics has posed a serious threat to the ecological environment and human health, so development of effective strategies for degradation and disposal of antibiotic residues is urgently needed. In this work, penicillinase, a kind of β-lactamase, was immobilized into zeolitic imidazolate framework-8 (ZIF-8) by self-assembly method and the catalytic performance of the β-lactamase@ZIF-8 porous materials for degradation of penicillins has been investigated by high performance liquid chromatography coupled with mass spectrometry. The results illustrated that the catalytic activity of the encapsulated enzyme was significantly enhanced comparing with that of free enzyme. Meanwhile, the β-lactamase@ZIF-8 exhibited excellent stability under denaturing conditions including high temperature, organic solvent and the enzyme inhibitor. The catalytic degradation mechanism of the β-lactamase@ZIF-8 for penicillins has been probed and verified, and it has been found that the Zn (II) ion on ZIF-8 frameworks could form the complex with the target molecule, which weakened the bond of the four-membered β-lactam ring in the penicillin molecule, and thus enhanced the degradation efficiency of the enzyme. This work provided a promising strategy for eliminating the penicillin residues in water environment.

High performance of ultrasonic-assisted synthesis of two spherical polymers for enantioselective catalysis

Chiral polymers have aroused great attention in among chiral supramolecular materials based on their features. Herein, for the first time, the synthesis of chiral polymeric composites (CMNPs/1,4-Zbtb & 1,3-Zbtb) have been reported with entrapment through three strategies: ultrasonic irradiation, solvothermal, and mechanical stirring. According to the obtained results, it is found that ultrasound-assisted synthesis can be considered as an inexpensive and efficient method than the others, from the point ofviewof energy and time consuming. In this strategy, encapsulation of chiral magnetic nanoparticles (CMNPs) by using tetrazole-based polymers (Zbtbs) happens, in-situly. These chiral sphere-like inorganic-organic polymers can be considered as core and shell composites with catalytic activity due to their acidic (semi unsaturated Zn: open metal sites) and basic (abundant basic nitrogens) centers. In these structures, the unprecedented chirality induction can happen from the core to shell by non-covalent interaction, easily. They could catalyze symmetric oxidation and asymmetric henry condensation to give chiral β-nitroalkanol. Circular dichroism and chiral gas chromatography were used to characterize the produced enantiomers. These chiral polymeric materials can be considered as unique acid-base bifunctional catalysts with efficient properties such as high stability, enantiomeric excess, enantioselectivity to the main product, and protecting from CMNPs leaching.

Magnetic nanocomposites for sustainable water purification-a comprehensive review

Numerous contaminants in huge amounts are discharged to the environment from various anthropogenic activities. Waterbodies are one of the major receivers of these contaminants. The contaminated water can pose serious threats to humans and animals, by distrubing the ecosystem. In treating the contaminated water, adsorption processes have attained significant maturity due to lower cost, easy operation and environmental friendliness. The adsorption process uses various adsorbent materials and some of emerging adsorbent materials include carbon- and polymer-based magnetic nanocomposites. These hybrid magnetic nanocomposites have attained extensive applications in water treatment technologies due to their magnetic properties as well as combination of unique characteristics of organic and inorganic elements. Carbon- and polymer-related magnetic nanocomposites are more adapted materials for the removal of various kinds of contaminants from waterbodies. These nanocomposites can be produced via different approaches such as filling, pulse-laser irradiation, ball milling, and electro-spinning. This comprehensive review is compiled by reviewing published work of last the latest recent 3 years. The review article extensively focuses on different approaches for producing various carbon- and polymer-based magnetic nanocomposites, their merits and demerits and applications for sustainable water purification. More specifically, use of carbon- and polymer-based magnetic nanocomposites for removal of heavy metal ions and dyes is discussed in detail, critically analyzed and compared with other technologies. In addition, commercial viability in terms of regeneration of adsorbents is also reviewed. Furthermore, the future challenges and prospects in employing magnetic nanocomposites for contaminant removal from various water sources are presented.

Metal-organic framework MIL-100(Fe) for dye removal in aqueous solutions: Prediction by artificial neural network and response surface methodology modeling

In this study, a metal organic framework MIL-100(Fe) was synthesized for rhodamine B (RB) removal from aqueous solutions. An experimental design was conducted using a central composite design (CCD) method to obtain the RB adsorption data (n = 30) from batch experiments. In the CCD approach, solution pH, adsorbent dose, and initial RB concentration were included as input variables, whereas RB removal rate was employed as an output variable. Response surface methodology (RSM) and artificial neural network (ANN) modeling were performed using the adsorption data. In RSM modeling, the cubic regression model was developed, which was adequate to describe the RB adsorption according to analysis of variance. Meanwhile, the ANN model with the topology of 3:8:1 (three input variables, eight neurons in one hidden layer, and one output variable) was developed. In order to further compare the performance between the RSM and ANN models, additional adsorption data (n = 8) were produced under experimental conditions, which were randomly selected in the range of the input variables employed in the CCD matrix. The analysis showed that the ANN model (R² = 0.821) had better predictability than the RSM model (R² = 0.733) for the RB removal rate. Based on the ANN model, the optimum RB removal rate (>99.9%) was predicted at pH 5.3, adsorbent dose 2.0 g L^-1, and initial RB concentration 73 mg L^-1. In addition, pH was determined to be the most important input variable affecting the RB removal rate. This study demonstrated that the ANN model could be successfully employed to model and optimize RB adsorption to the MIL-100(Fe).

Interfacial growth of metal-organic framework on carboxyl-functionalized carbon nanotubes for efficient dye adsorption and separation

Hybrid nanocomposites based on UiO-66-NH₂ and carboxyl-functionalized carbon nanotubes were developed in this study via different synthetic pathways. Combining them through interfacial in situ growth was beneficial for the better dispersity of UiO-66-NH₂ in the CNTs@UiO-66-NH₂ composite than physically mixing CNTs/UiO-66-NH₂ and chemically bonded CNTs-CONH-UiO-66. Coordination between carboxyl groups of CNTs and zirconium ions resulted in the interfacial growth of UiO-66-NH₂ on CNTs. Adsorption experiments showed that CNTs@UiO-66-NH₂ exhibited the highest adsorption efficiency towards methyl orange (MO). The adsorption capacity of CNTs@UiO-66-NH₂ was up to 392 mg g^-1, which was 77.45% and 201.5% higher than those of CNTs-CONH-UiO-66 and CNTs/UiO-66-NH₂ respectively. Moreover, CNTs@UiO-66-NH₂ could selectively adsorb MO from the MO/MB mixture.

Improved photocatalytic degradation of ketoprofen by Pt/MIL-125(Ti)/Ag with synergetic effect of Pt-MOF and MOF-Ag double interfaces: Mechanism and degradation pathway

It is a central issue to improve the separation efficiency of photogenerated charge carriers and the utilization of visible light in the field of photocatalysis. Herein, taking MIL-125(Ti) as a host material, the Pt/MIL-125(Ti) was first prepared by solvothermal method to build the interface of Schottky junction. Ag was then introduced onto the surface of Pt/MIL-125(Ti) to form the interface with the surface plasmon resonance effect. These double interfaces in the composite play a synergistic role on the photodagradation. The morphology, crystallinity and photochemical properties of the material were tested. By comparison, Pt/MIL-125(Ti)/Ag (4 wt% Ag) exhibited the best performance in the photodegradation of ketoprofen (KP, 10 mg/L) and the degradation process conformed to the pseudo-first-order kinetics. The photodegradation rate is 0.0253 min^-1, which was higher than MIL-125(Ti) (0.0009 min^-1). The TOC removal efficiency of KP reached approximately 51.5%. The electron paramagnetic resonance (EPR) and free radical capture tests verified that h⁺ and ·OH played the prominent roles during the reaction system. The degradation process, possible pathways and reaction mechanism were proposed. The design of the double interfaces between semiconductor and noble metals is a novel strategy to enhance the photocatalytic performance.