Adsorption Of 4-nitrophenol Research Articles

In situ construction of covalent-organic framework on hydrogen-bond organic framework: Fluorescence detection and removal of 4-nitrophenol and metamitron in aqueous media

A multifunctional COF@HOF (ETTA-DFP@TCBP-HOF) composite is prepared by adding red-fluorescent ETTA-DFP COF to the blue-fluorescent TCBP-HOF preparation system through molecular hydrogen bonding or π − π stacking interactions in situ one-pot synthesis. ETTA-DFP@TCBP-HOF is a multifunctional material for the quantitative detection and simultaneous adsorption of 4-nitrophenol (4-NP) and metamitron (MET) in aqueous solution. As a dual-emission fluorescent sensor, the ETTA-DFP@TCBP-HOF has both fluorescence of TCBP-HOF at 474 nm and ETTA-DFP COF at 592 nm, which shows a ratiometric response to 4-NP and MET with high selectivity, good sensitivity, good anti-interference performance and fast response. As a adsorbent, ETTA-DFP@TCBP-HOF displays rapid adsorption kinetics, and acceptable adsorption capacity for 4-NP and MET. In conclusion, this work constructs a novel multifunctional hybrid material with dual-emission center of HOF and COF, which can not only be used as a ratiometric fluorescent probe for detection, but also for removal of hazardous pollutants, suggesting a new strategy for environmental remediation and human health.

Dynamic adsorption of 4-nitrophenol over shaped activated carbon produced from agriculture stones through microwave-assisted technique.

The aim of current work is to develop the uptake of 4-nitrophenol from the liquid phase in a dynamic system by the shaped activated carbon produced through the microwave-assisted technique. The emphasis of research is to understand the effects of production factors on the performance of adsorbents in the dynamic adsorption. Hence, the phosphoric acid ratio, microwave irradiation power, carbonization temperature, and time were changed to identify the suitable conditions for the fabrication of granular and rod-like beds from the cherry, and date stones. It was found that the stone structure and H3PO4/waste ratio significantly affect the adsorption efficiency. The proper acid/waste ratio was determined to be 1.43, and 1.80 for the activation of cherry and date stones to achieve the maximal efficiency in which the power should be fixed at the levels of 600 and 400 W respectively. The equilibrium efficiency increases with the rise in carbonization temperature and time which should be controlled exactly to reach the maximal adsorption capacity, ~ 45 mg g-1 according to the Langmuir isotherm. Owing to the high specific surface area of shaped adsorbents, 350-450 mg g-1, the fabricated beds indicated the appropriate performance for the uptake of nitrophenol due to development of micropores, < 2 nm, in the framework of activated carbon.

Synthesis of size-controllable urchin-like covalent organic frameworks for adsorption of nitrophenols

The adsorption of nitrophenols by covalent organic frameworks (COFs) has gained increasing attention, due to their feasible designability, which could provide abundant open active sites for their binding to nitrophenols. Herein, we developed a novel method to synthesize uniform urchin-like COFs (TTA-DVA-COF) with tunable sizes using a temperature-controlling method at atmospheric pressure. The size of the TTA-DVA-COF can be tuned and controlled gradually from 0.95 μm to 2.85 μm as the synthesis temperature decreases from 80 °C to 20 °C. By using the principle that the interlaced benzene rings, imine bonds (C=N) and triazine structures of TTA-DVA-COF can capture free nitrophenols through hydrogen bonding and conjugation interaction, the COFs can be used as an efficient adsorbent for adsorption and removal of nitrophenols, especially,o-nitrophenol. The research provides a new strategy for the controllable synthesis of uniform COFs and extends the application of COFs as efficient adsorbents for the removal of nitrophenols.

Preparation of hierarchical self-assembled SiO2/ZnO composite by low-temperature hydrothermal approach for enhanced adsorption of 4-nitrophenol and dyes

Here, we initially fabricated the hierarchical SiO2/ZnO nanospheres via a facile low temperature (LT) 90 °C hydrothermal approach and the prepared SiO2/ZnO nanospheres show an excellent surface area of about 1280.8 m2/g. The prepared composite has been investigated for the removal of mixture of cationic (rhodamine B, crystal violet, methylene blue) and anionic dyes (congo red, methyl orange) to understand the industrial point of view. On the basis of the selectivity test, a detailed study has been carried out for the removal of organic pollutant Rhodamine B, and the effect of pH, contact time, initial dye concentration, and adsorbent dosage were among the optimal parameters that led to the maximum RhB adsorption (pH-11, 10 min, and 5 mg of adsorbent). It has been noticed that SiO2/ZnO shows an impressive adsorbent property for basic cationic dyes. The ability of the SiO2/ZnO adsorbent to be reproduced and reused was evaluated. Furthermore, the produced adsorbent was known to adhere to pseudo-second-order kinetics and the Langmuir isotherm with R2 = 0.96 and R2 = 0.98, respectively. The catalytic property of the prepared material was also tested for 4-nitrophenol reduction using NaBH4. The adsorption capacity (max.) for the removal of RhB was reported to be 83.33 mg/g, and on the other hand, 4-NP was 89% removed by the prepared adsorbent. The experiments confirmed that the processed nanocomposite can successfully eliminate organic pollutants, implying the practical applicability of the material for waste-water remediation.

Application potential of zero-valent aluminum in nitrophenols wastewater decontamination: Enhanced reactivity, electron selectivity and anti-passivation capability

Nitrophenols (NPs) are highly toxic and easy to accumulate to high concentrations (> 500 mg/L) in real wastewater. The nitro group contained in NPs is an electron-absorbing group that is easy to reduce and difficult to oxidize, so there is an urgent need to develop reduction removal technology. Zero-valent aluminum (ZVAl) is an excellent electron donor that can reductively transform various refractory pollutants. However, ZVAl is prone to rapid deactivation due to non-selective reactions with water, ions, etc. To overcome this critical limitation, we prepared a new type of carbon nanotubes (CNTs) modified microscale ZVAl, CNTs@mZVAl, through a facile mechanochemical ball milling method. CNTs@mZVAl had outstanding high reactivity in degrading p-nitrophenol even 1000 mg/L and showed up to 95.50% electron utilization efficiency. Moreover, CNTs@mZVAl was highly resistant to the passivation by dissolved oxygen, ions and natural organic matters coexisting in water matrix, and remained highly reactive after aging in the air for 10 days. Furthermore, CNTs@mZVAl could effectively remove dinitrodiazophenol from real explosive wastewater. The excellent performance of CNTs@mZVAl is due to the combination of selective adsorption of NPs and CNTs-mediated e-transfer. CNTs@mZVAl looks promising for the efficient and selective degradation of NPs, with broader prospects for real wastewater treatment.

Adsorption of nitrophenol onto a novel Fe3O4-κ-carrageenan/MIL-125(Ti) composite: process optimization, isotherms, kinetics, and mechanism

Water pollution is a dreadful affair that has incessantly aggravated, exposing our planet to danger. In particular, the persistent nitro aromatic compound like nitrophenols causes anxiety to the researchers due to their hazardous impacts, excessive usage, and removal difficulty. For this purpose, a novel multi-featured composite was constructed based on κ-Carrageenan (κ-Carr), MOF (MIL-125(Ti)), and magnetic Fe3O4 for efficient adsorptive removal of o-nitrophenol (o-NP). Interestingly, BET measurements revealed the high surface area of Fe3O4-κ-Carr/MIL-125(Ti) of about 163.27 m2/g, while VSM showed its excellent magnetic property (20.34 emu/g). The comparison study pointed out the synergistic effect between Fe3O4, κ-Carr, and MIL-125(Ti), forming a composite with an excellent adsorption performance toward o-NP. The adsorption data obeyed pseudo-second-order kinetic model, and Freundlich isotherm model was better fitted than Langmuir and Temkin. Furthermore, Langmuir verified the supreme adsorption capacity of o-NP onto Fe3O4-κ-Carr/MIL-125(Ti) since the computed qmax reached 320.26 mg/g at pH 6 and 25 °C. Furthermore, the XPS results postulated that the adsorption mechanism pf o-NP proceeded via H-bonding, π-π interaction, and electron donor–acceptor interactions. Interestingly, Fe3O4-κ-Carr/MIL-125(Ti) composite retained good adsorption characteristics after reusing for five cycles, suggesting its viable applicability as an efficient, renewable, and easy-separable adsorbent for removing nitro aromatic pollutants.

Dextrin‐graft‐poly(2‐dimethylamino ethyl acrylate‐co‐2‐acrylamido‐2‐methyl propane sulfonic acid) polymer: A potential adsorbent for the fast removal of nitrophenols from aqueous medium

AbstractA graft copolymer is synthesized by grafting a mixture of 2‐(dimethylamino) ethyl acrylate (DMAEA) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) monomers onto the dextrin, polysaccharide backbone via free radical polymerization process using potassium peroxydisulfate (KPS) as radical initiator in aqueous phase. Various characterization techniques like 1H and 13C NMR, FT‐IR, SEM, EDAX, and XRD analysis are used to characterize the copolymer. The polymer is used as an adsorbent for the removal of nitrophenols namely ortho‐nitrophenol (ONP), para‐nitrophenol (PNP), and 2,4‐ dinitrophenol (DNP) from their water solutions. Adsorption dynamics, kinetics, isotherms, and thermodynamics are studied. The maximum nitrophenol adsorption occurs at time 80 min, temperature 45°C, pH 3.5 (DNP), and 4.5 (ONP and PNP), polymer dose 30 mg/L. The nitrophenol adsorption data are well‐fitted with the Langmuir isotherm model with maximum adsorption capacity () 215.26 mg g−1 for ONP, 223.60 mg g−1 for PNP, and 288.24 mg g−1 for DNP. The equilibrium kinetics follow pseudo‐second‐order kinetic model. Thermodynamic values unfold that the following nitrophenol adsorption onto the polymer surface is spontaneous and endothermic in nature. The value of Gibb's free energy for the nitrophenol adsorption is in the range of −6.5 to −9.5 kJ mol−1. The preferential nitrophenol adsorption by the copolymer is followed in the order ONP&lt;PNP&lt;DNP.

Application of response surface methodology to optimize 4-nitrophenol adsorption by prepared molecular imprinting polymers

Application of response surface methodology to optimize 4-nitrophenol adsorption by prepared molecular imprinting polymers

A Thermally Promoted Homogenous-Floating-Concentrating Strategy Synthesizing Highly Crystalline Triazine/hydroxyl-Rich COFs for 4-Nitrophenol Adsorption.

In this work, a "thermally promoted homogenous-floating-concentrating" strategy is reported for the rapid synthesis of highly crystalline triazine/hydroxyl-rich COFs under mild conditions, using for the effectively adsorbing 4-nitrophenol (4-NP) in aqueous solutions. This strategy originates from an optimized "homogenous-floating-concentrating" method as reported in the previous work. Both gradually improving concentration and heat treatment promote the condensation reaction between amino and aldehyde groups, resulting in high crystallinity and shorter reaction time. The obtained COFs demonstrate better crystallinity and higher surface area in comparison with the counterparts prepared by solvothermal strategy. A maximum surface area of 2391 m2 g-1 is achieved. The COFs exhibit excellent 4-NP adsorption capacity (Qmax = 1402.0mg g-1 ), which is attributed to abundant triazine/hydroxyl-groups on the COF skeleton and their strong H-bonding interaction with 4-NP.

Kinetic studies on the uptake of phenols by linear and cyclic organic sulfonic acid-modified Cu-Al layered double hydroxides

• The adsorption follows a pseudo-second-order kinetic equation. • The Δ G values for adsorption systems ranged from −20 to 0 kJ/mol. • It indicates that adsorption could be classified as physical adsorption. • NP was adsorbed on OS•Cu-Al LDH by hydrophobic interaction. • AP was adsorbed on SCD•Cu-Al LDH by CH/π interactions. Our previous study revealed that Cu-Al layered double hydroxides (LDHs) intercalated with 1-octanesulfonate and sulfonated β-cyclodextrin showed good adsorption selectivity toward m -nitrophenol (NP) and m -aminophenol (AP), respectively. We also found that the adsorption behaviors of these LDHs fit the Freundlich equation. Herein, we performed a kinetic analysis to elucidate the adsorption mechanism of the LDHs for phenols in greater detail. The adsorption results were fitted to a pseudo-first-order kinetic equation, a pseudo-second-order kinetic equation, and an intraparticle diffusion model. The correlation coefficients of the pseudo-second-order kinetic equation for each adsorption process were fairly high, and the measured and calculated equilibrium adsorption amounts were relatively close. Thus, the adsorption of NP and AP by OS•Cu-Al LDH and SCD•Cu-Al LDH, respectively, fits the pseudo-second-order kinetic equation. Because the ΔG values for each system ranged from −20 to 0 kJ/mol, the adsorption processes in these systems may be classified as physical adsorption. Specifically, NP was adsorbed on OS•Cu-Al LDH by hydrophobic interactions, whereas AP was adsorbed on SCD•Cu-Al LDH by CH/π interactions. Our findings provide new insights into the adsorption of phenols onto modified Cu-Al LDHs and could serve as a foundation for future studies on the adsorption properties of LDHs intercalated with anions as guest layers.

Effective adsorption and catalytic reduction of nitrophenols by amino-rich Cu(I)–I coordination polymer

Nitrophenols are identified as the priority organic pollutants due to the chemical stability, water solubility, persistence, and toxicity to human health and the environment. Hence, removal of nitrophenols from waste water is vitally essential. In this study, amino-rich coordination polymer Cu2I2(MA)2 (MA = melamine) has been applied for efficient adsorption and catalytic reduction of nitrophenols, like 4-nitrophenol (4-NP), 2, 4-dinitrophenol (DNP) and 2, 4, 6-trinitrophenol (TNP). The effect of various parameters like contact time, initial concentrations, pH, and temperature on adsorption were investigated. The adsorption of nitrophenols fitted the pseudo-second-order kinetic model and Langmuir isotherms model well. The maximum adsorption capacities were 285.71, 232.02, and 131.57 mg g−1 for 4-NP, DNP, and TNP when initial concentrations were 50 mg L−1 at 293.15 K, respectively. The adsorption of nitrophenols is a spontaneous, endothermic, and entropy-driven process. The reduction reaction followed the pseudo-first-order kinetics, and the kinetic rate constants were 0.4413, 0.3167, and 0.17538 min−1 for 4-NP, DNP, and TNP, respectively. The effect of initial nitrophenols concentration, anions, and temperature on reduction process was investigated. The mechanism of adsorption and catalytic reduction of Cu2I2(MA)2 was studied. The results demonstrated that Cu2I2(MA)2 exhibits excellent adsorption and catalytic activity to remove nitrophenols.

Adsorption of 4-Nitrophenol onto Iron Oxide Bentonite Nanocomposite: Process Optimization, Kinetics, Isotherms and Mechanism

Despite its importance in chemical industry, 4-Nitrophenol (4-NP) is a persistent organic pollutant that has serious effects on the ecosystem. In the present study, Box–Behnken design in response surface methodology was used to optimize the adsorption process parameters for the maximum 4-NP removal at 30 ℃ using Fe3O4/Bt NC. The regression model results suggested that the optimum adsorbent dosage, initial concentration, pH and contact time were 0.3182 g, 85 mg/L, 11 and 137.2 min, respectively. The regression model showed an optimum removal of 100%, while 99.5% removal was obtained from batch experiments at the optimum conditions suggested by the regression model, which confirm the model validity. The adsorption data best fitted to Freundlich isotherm model and Pseudo second-order kinetic model suggesting the existence of physical and chemical interaction between the fabricated composite and 4-NP. FTIR analysis suggested that the adsorption mechanism included an electrostatic attraction and the formation of new chemical bonds. Obtained results suggest that Fe3O4/Bt NC can be an effective adsorbent for complete 4-NP removal at the indicated optimum conditions.Graphical

Construction of Two-Dimensional Fluorescent Covalent Organic Framework Nanosheets for the Detection and Removal of Nitrophenols.

In this work, we synthesized a two-dimensional fluorescent covalent-organic framework (TFPB-TTA COF) nanosheet by selecting and designing reactive monomers to realize the dual-functional processing of nitrophenols. The staggered benzene ring, triazine structure, and imine bond (C═N) of the TFPB-TTA COF can capture free nitrophenols through hydrogen bonding and conjugation interaction, and then, the photoinduced electron transfer and fluorescence resonance energy transfer (FRET) between the TFPB-TTA COF and nitrophenols affects the fluorescence emission of the TFPB-TTA COF, realizing the fluorescence sensing of nitrophenols. The large Ksv values and the low detection limit suggest that the TFPB-TTA COF can serve as sensitive and selective fluorescence sensors for nitrophenol detection in an aqueous system. At the same time, the strong interaction combined with the porous network structure of the TFPB-TTA COF facilitates the efficient adsorption and removal of nitrophenols. Especially for 2,4,6-trinitrophenol, the maximum adsorption capacity can reach 1045.53 mg/g with good recyclability and high structural stability of the TFPB-TTA COF. This work proposed a simple synthetic method for the construction of a fluorescent COF platform for the sensitive determination and efficient adsorption of nitrophenols.

Adsorption of 4-Nitrophenol on calcium alginate-multiwall carbon nanotube beads: Modeling, kinetics, equilibriums and reusability studies

In this study calcium alginate-multiwall carbon nanotube (CA/MWCNTs) was synthesized using (CA) calcium alginate and multiwall carbon nanotube (MWCNTs), and its efficiency in adsorption of 4-Nitrophenol (4-NP) in aqueous solution was studied. The structure and properties of the synthesized adsorbent were investigated using scanning electron microscope (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The experimental design was performed using Box–Behnken design (BBD) in which variables pH, CA/MWCNTs, and temperature were examined. The results of the effect of temperature on the removal efficiency of 4-NP showed that the adsorption efficiency decreases with increasing temperature. The results of nonlinear isotherm and kinetics models showed that Langmuir and pseudo-second-order models were more consistent than other models. The maximum adsorption capacity of 4-NP in this study by CA, MWCNTs, and CA/MWCNTs was 136, 168.4, and 58.8 mg/g, respectively, which indicates that the use of MWCNTs on CA could increase the adsorption capacity. The results of reuse of the synthesized adsorbent at 4-NP removal also showed that after 5 reuse of the adsorbent, the removal of 4-NP using CA/MWCNTs is reduced by about 10%, which shows that the synthesized adsorbent can be used several times to adsorb contaminants without significant reduction in the efficiency.

DMAEMA-grafted cellulose as an imprinted adsorbent for the selective adsorption of 4-nitrophenol

4-Nitrophenol is a highly toxic environmental pollutant. It is a challenge to selectively remove it from a mixture of various pollutants. Herein, we report a study on the selective adsorption of 4-nitrophenol by using molecularly imprinted polymers (MIPs). The imprinted polymer was synthesized using cellulose as a framework, onto which, the complex of the imprinting molecule (i.e., 4-nitrophenol) and a candidate material [namely, 2-(dimethylamino)ethyl methacrylate. DMAEMA] was grafted. The obtained MIP showed an excellent adsorption capacity with good selectivity. Also, the adsorption of 4-nitrophenol by the obtained MIP was fast and the adsorbent exhibited good recyclability. The thermodynamics and kinetics of the adsorption process of 4-nitrophenol by MIP was thoroughly studied, where an otherwise-equivalent non-imprinted polymer was used as a control in the experiments. The selectivity of the MIP adsorbent for 4-niteophenol was evaluated by two types of experiments: (1) adsorption experiments in single-component adsorbate systems (containing 4-nitrophenol, 3-nitrophenol, catechol, or hydroquinone), and (2) competitive adsorption experiments in binary adsorbate systems (containing 4-nitrophenol plus either 3-nitrophenol, catechol or hydroquinone). The selectivity coefficient for 4-nitrophenols was twice of those of other phenols (that were all around 2), indicative of the extent of the affinity of MIPs to these phenolic compounds. The recyclability of the adsorbent was evaluated for 5 adsorption–desorption cycles, where the adsorption capacity of the last cycle remained over 90.2% of that of the first cycle.Graphic

Nitrophenols removal from aqueous solutions by activated carbon – temperature effect of adsorption kinetics and equilibrium

The temperature dependences of adsorption equilibrium and kinetics were measured and analyzed for 2-, 3-, 4-nitrophenol removed from aqueous solutions by activated carbon. The structural and surface characteristics of the applied adsorbent were estimated by nitrogen adsorption/desorption and potentiometric titration. The adsorption equilibrium measurements were carried out at 278, 298 and 318 K. High sorption capacities were obtained, reaching even about 11, 5 and 6 mmol/g for 2-, 3- and 4-nitrophenol, respectively. The adsorption kinetics were measured at 278, 288, 298, 308, 318 and 328 K. An increase in the adsorption rate and amount was observed with increasing temperature. For analysis of the equilibrium experimental data the General Langmuir isotherm was applied, in the case of kinetic data various equations and models including first-, second-, mixed-order, their fractal analogus, and multi-exponential equations, and diffusion models were used. The thermodynamic analysis of adsorption isotherms was conducted. The surface functional groups of activated carbon and the nitrophenol adsorption mechanism, were studied by using XPS technique and the thermal analysis, moreover, the thermal stability of adsorbate-adsorbent systems was determined. The thermal analysis and XPS revealed weaker interactions of 2-nitrophenol molecules with carbon surface as a result of formation of the intramolecular hydrogen bonds, on the contrary to 3- and 4-nitrophenol which could stronger interact with the adsorbent surface groups.

Sorption studies of 4-NP onto goethite: effects of contact time, pH, concentration, ionic strength and temperature

The effects of different state variables (contact time, pH, concentration, ionic strength and temperature) were investigated on the adsorption of 4-nitrophenol (4-NP) onto goethite for its potential utilization in mitigating water pollution. The results suggested that the adsorption of 4-NP reached a quasi-steady state equilibrium at 24 h and followed pseudo-second order kinetics. The computed value of pseudo-second order rate coefficient for adsorption of 4-NP on goethite was 447.57 kg mM−1 h−1. Adsorption of 4-NP on goethite was higher when the solution pH was < pHzpc of goethite and near pKa(7.15)of 4-NP and vice versa. The effect of concentration of 4-NP on adsorption revealed the heterogeneity of sorption sites on goethite surface; highly selective sites of higher bonding energy up to sorption density of 1.42 mM kg−1 and lower selectivity sites of lesser bonding energy for sorption density above 2.07 mM kg−1. An increase in ionic strength, increased the adsorption of 4-NP on goethite but an increase in temperature decreased the adsorption. The changes in thermodynamic parameters indicated that adsorption of 4-NP was a spontaneous and exothermic reaction with an increase in the entropy of the system. Based on these results, the optimal conditions for the maximal removal of 4-NP were 6.7–7.0 pH, 0.015–0.02 ionic strength, 15 °C temperature with 1: 100 goethite (sorbent)-solution ratio.

Production of activated biochar from Luffa cylindrica and its application for adsorption of 4-Nitrophenol

Activated biochar was prepared from dried Luffa cylindrica fruits as a convenient source of carbon-rich biomass. In this regard, a commonly practiced single-step H3PO4 pretreatment and combined H3PO4 and H2SO4 treatments before and after the pyrolysis were utilized for the production of loofah-derived biochar (LB) and sulfuric acid-treated LB (SLB). These biochars were compared in terms of physicochemical characteristics and the potential for removal of 4-Nitrophenol (4NP). It was indicated that the adsorption of 4NP was more efficient on SLB compared to LB with a Langmuir maximum monolayer adsorption of 436.6 mg/g vs 265.4 mg/g at 30 °C. Thermodynamic studies demonstrated that the adsorption process was endothermic and associated with entropy increase for both biochars. BET analysis showed that the surface area of LB and SLB were 28 and 46 times as high as that of non-activated carbonized loofah, respectively. Based on the analysis of the surface functional groups by FTIR spectroscopy and N2 adsorption-desorption experiments, pore filling and hydrogen bonding were suggested as major factors contributing to the high performance of the prepared adsorbents. Other notable mechanisms for 4NP removal were π-interactions and degradation. The possibility of reusing the adsorbents and recycling the waste sulfuric acid was also investigated, demonstrating the commercial attractiveness and environmental friendliness of the produced biochars.

Preparation of magnetic double network nanocomposite hydrogel for adsorption of phenol and p-nitrophenol from aqueous solution

Collagen-(AMPS-MAA/AAm)-Fe3O4@SiO2 magnetic double-network nanocomposite hydrogel (DNNH) was synthesized through in-situ free-radical copolymerization under ultrasound-assisted condition. The pure double-network hydrogels (PDNH) and their magnetic composite structure were systematically characterized through XRD, FTIR, SEM-EDS, VSM, DTG, and tensile tests. The DNNH exhibits more powerful mechanical attributes (σf of 0.33 MPa, εf of 26.5 mm/mm) than PDNH (σf of 0.314 MPa, εf of 31 mm/mm). The adsorption process, which is influenced by multiple factors, was examined and the results of the surveys illustrated that the adsorption capacity improved with the Fe3O4 @SiO2 nanoparticles. Adsorption behavior was checked for the adsorption of phenol and 4-nitrophenol and it was found to remove about 77% and 83% of phenol and 4-nitrophenol solutions at pH 7, respectively. The applicability of kinetic and isotherm studies for the adsorption of mentioned pollutions, especially the pseudo-second-order model and Langmuir model were proved (qm = 16.52 mg/g for phenol and qm = 19.20 mg/g for 4-nitrophenol). Thermodynamic studies proposed that the adsorption of phenol and 4-nitrophenol was spontaneous and endothermic. Reusability of the prepared hydrogel in the adsorption–desorption process was simply done for successive 4 times. As a result, the prepared hydrogel is known as a suitable adsorbent for phenol and 4-nitrophenol adsorption from aqueous solutions.

Intriguing hierarchical Co@NC microflowers in situ assembled by nanoneedles: Towards enhanced reduction of nitroaromatic compounds via interfacial synergistic catalysis

Developing highly efficient and cost-effective catalyst with tuned microstructure holds great promise in the reduction of nitroaromatic compounds under mild reaction conditions. Herein, we report a new Co@NC-MF catalyst with a fascinating hierarchical flower-like architecture in situ assembled from uniform Co@NC nanoneedles, which can function as a favorable platform for the efficient reduction of nitroaromatic compounds in the presence of NaBH4. In addition with the structural advantage, the characterization and experimental results demonstrate the enormous advantage of interfacial synergistic catalysis in enhancing the catalytic performance. The outside electron-rich N-doped carbon layer as Lewis basic sites and the inside Co nanoparticles are responsible for the adsorption of 4-nitrophenol (4-NP) and generation of active hydrogen species, respectively. This work contributes to the construction of well-integrated composites with well-balanced interface synergy to boost the catalytic performance in various heterogeneous reactions.