Adsorption Of Aromatic Compounds Research Articles

Layered Silicates Exhibiting MOF-Like Gate-Opening Behaviors in Liquid-Phase Adsorptions: Experimental and Theoretical Investigations.

Layered silicates, including clay minerals, can be used as liquid-phase adsorbents in many important applications. However, because their two-dimensional interlayer space is narrow and not entirely opened due to the presence of interlayer species, guest species are forced to penetrate while expanding the interlayer space, which limits their adsorption performances compared with microporous materials such as MOFs and zeolites. Herein, as reported for the adsorption of gaseous species on flexible MOFs, we report a layered silicate that exhibits gate-opening adsorption in liquid phases. This layered silicate, synthesized via dilute acid treatment of the parent sodium-type, exhibits an abrupt increase in the basal spacing (layer thickness + interlayer space) to reach a plateau even at an earlier stage of benzoic acid adsorption from acetonitrile, whereas a typical layered silicate, magadiite, exhibits a gradual increase in the basal spacing as adsorption progress under identical conditions. The layered silicate shows an excellent adsorption capacity and rate for benzoic acid uptake from acetonitrile, which is considerably higher than that of magadiite. With comprehensive adsorption tests using different adsorbates and solvents, we propose that the layered silicate has zeolite-like but distorted, flexible open microchannels within each layer, and the intralayer microchannels can effectively and rapidly accommodate the solvent (acetonitrile) molecules, which are capable of expanding the framework to initiate the adsorption of aromatic compounds. The density function theory calculation revealed the adsorption mechanism, where the layered silicate accommodates acetonitrile in the intralayer microchannel followed by the interlayer space, and the former selectively plays a role as the adsorption site of aromatic compounds via exchange with acetonitrile.

Effect of biochar structure on the selective adsorption of heavy components in bio‐oil

AbstractIn this study, biochars with different structures were prepared through HNO3 oxidation and secondary pyrolysis to study the relationship between the structure of biochar and its selectivity for the adsorption of light and heavy aromatics in bio‐oil. The results showed that the adsorption rates of biochar with different structures ranged from 2.90 to 4.00 g bio‐oil per g biochar. The influence of pore structure was dominant, followed by the influence of O‐containing functional groups and the degree of graphitization. The higher the adsorption capacity of biochar for bio‐oil, the smaller the concentrations of the light aromatic model compounds in the absorbed bio‐oil (ABO). Among the five light aromatics, biochar has the best adsorption selectivity for dihydroxybiphenyl and the worst for eugenol and propyl phenol. This is attributed to the diphenyl ring structure of dihydroxybiphenyl, which makes it more susceptible to adsorption, and other light model compounds only have one benzene ring. In summary, biochar demonstrates better adsorption selectivity for heavy aromatics than light aromatics. The more developed the pore structure is, the more enriched O‐containing functional groups are, and the higher the graphitization degree of biochar is, the better the selective adsorption of aromatic compounds in bio‐oil.

Mesoporous materials functionalized with polyaniline for the removal of the phenol from the aqueous solution

The functionalization of mesoporous solids with polyaniline (PANI) is explored as an alternative for the adsorption of phenol. It investigates the impact of the nature of the surface (homogeneous SBA-15 vs. heterogeneous Bone Char, BC) on adsorption efficiency. The results highlight that incorporating PANI into mesoporous materials intensifies π-π interactions, thereby enhancing the adsorption of aromatic compounds like phenol for SBA-15:SBA-15/PANI in a ratio of 1:2.3, and for BC:BC/PANI in a ratio of 1:1.8. The PANI functionalization decrease the surface area of the SBA-15 and BC in 32.9% and 57% respectively, but interaction and chemical properties of the composites allow increase the phenol adsorption. The phenol adsorption on SBA-15, Char, SBA-15/PANI, and BC/PANI follows the pseudo second-order kinetic with R2 = 0.994 and intraparticle diffusion. The maximum adsorption capacity was estimated to be SBA-15 (121.8 mg g−1), SBA-15/PANI (283.8 mg g−1), BC (21.59 mg g−1), and BC/PANI 38.59 mg g−1), this means that PANI allows exceeding the adsorption capacities than the original adsorbents.

Hydrophilicity of Organically Modified Montmorillonite and Effect on Benzene Adsorption by the Molecular Dynamics Method.

Interlayer modification of layered materials with organocations has been known to endow the nanocomposite with hydrophobicity, and adsorption of aromatic compounds in the aqueous phase has been investigated for decades by using montmorillonite, a representative layered clay mineral, as the host material. Usage of the organocation has been believed to be effective due to the π-π interaction with the aromatic adsorbate, the presence of which is not verified spectroscopically in the water-immersed state. Considering that the organocation is generally regarded as a pillar to keep the interlayer space, the interaction between the organocation and adsorbate has not yet been clarified sufficiently. In the present study, we revealed the role of the organocation by the molecular dynamics method, where tetramethylammonium (TMA) and trimethylphenylammonium (TMPA) ions were selected as the representative and simple organocations, and benzene was the adsorbate to exclude the effect of the substitution group. Both H2O and benzene molecules were introduced in the interlayer of TMA- or TMPA-modified montmorillonite to model the water-immersed adsorption structure. It was found that H2O is preferentially distributed on the clay surface, followed by the center of the interlayer when the amount of H2O is large. In the adsorption model, benzene was vertically adsorbed on the clay surface. Radial distribution function analysis revealed that benzene is distributed around both the methyl and the phenyl groups in the TMA and TMPA cations, but the orientation of the phenyl ring is not consistent with that of benzene. Thus, benzene was found not to form the π-π interaction in montmorillonite modified with the TMPA cations in the water-immersed state. Furthermore, the surface was partly covered with the phenyl group in the TMPA cation, decreasing the adsorption area. Therefore, the experimental suggestion that benzene is adsorbed on the clay surface was reproduced by our simulation, and the interaction between the organocation and benzene and surface occupancy should be paid attention to maximize the adsorption property.

Thermodynamic Characteristics and Selectivity of the Liquid-Phase Adsorption of Aromatic Compounds on Hypercrosslinked Polystyrene Networks with Ultimate-High Crosslinking Densities by Data of Liquid Chromatography.

This study delves into the thermodynamics of liquid-phase adsorption on hypercrosslinked polystyrene networks (HPSNs), widely recognized for their distinct structure and properties. Despite the considerable progress in HPSN synthesis and characterization, gaps persist regarding the chromatographic retention mechanism, thermodynamics of adsorption, and their impact on the adsorption selectivity, especially in the case of networks with ultra-high crosslinking densities (up to 500%). Utilizing high-performance liquid chromatography (HPLC), we have explored, for the first time, the thermodynamic intricacies of liquid-phase adsorption onto HPSNs crosslinked in the entire range of the crosslinking degree from 100 to 500%. Our findings reveal the dependences of thermodynamic characteristics and selectivity of adsorption on the crosslinking degree, textural features, and liquid-phase composition in the region of extremely low adsorbent surface coverages (Henry's range). We have detected that, in the case of HPSNs, the dependence of the thermodynamic characteristics of adsorption on the liquid-phase composition is different than for classical HPLC stationary phases. Moreover, we scrutinize the impact of the molecular structure of the studied aromatic compounds on the thermodynamic characteristics and selectivity of the liquid-phase adsorption on HPSNs. Investigating liquid-phase adsorption selectivity, we demonstrate the pivotal role of π-π interactions in separating aromatic compounds on HPSNs. Eventually, we unveil that the thermodynamic characteristics of adsorption peculiarly depend on the crosslinking degree due to the profound impact of the crosslinking on the electronic density in benzene rings in HPSNs, whereas the separation throughput peaks for the polymer with a 500% crosslinking degree, attributed to its exceptionally rigid network structure, moderate swelling and micropore volume, and minimum specific surface area.

π–π stack driven competitive /complementary adsorption of aromatic compounds on MIL-53(Al)

In this study, the selective adsorption of aromatic compounds on mesoporous MIL-53(Al) was investigated, and followed the order: Biphenyl (Biph) > Triclosan (TCS) > Bisphenol A (BPA) > Pyrogallol (Pyro) > Catechol (Cate) > Phenol (Phen), and exhibited high selectivity toward TCS in binary compounds. In addition to hydrophobicity and hydrogen bonding, π–π interaction/stacking predominated, and more evidently with double benzene rings. TCS-containing halogens could increase π interaction on the benzene rings via forming Cl–π stacking with MIL-53(Al). Moreover, site energy distribution confirmed that complementary adsorption mainly occurred in the Phen/TCS system, as evidenced by ΔQpri (the decreased solid-phase TCS concentration of the primary adsorbate) < Qsec (the solid-phase concentrations of the competitor (Phen)). In contrast, competitive sorption occurred in the BPA/TCS and Biph/TCS systems within 30 min due to ΔQpri = Qsec, followed by substitution adsorption in the BPA/TCS system, but not for the Biph/TCS system, likely attributed to the magnitude of energy gaps (Eg) and bond energy of TCS (1.80 eV, 362 kJ/mol) fallen between BPA (1.74 eV, 332 kJ/mol) and Biph (1.99 eV, 518 kJ/mol) according to the density-functional theory of Gaussian models. Biph with a more stable electronic homeostasis than TCS lead to the occurrence of substitution adsorption in the TCS/BPA system, but not in the TCS/Biph system. This study provides insight into the mechanisms of different aromatic compounds on MIL-53(Al).

Insights into the abiotic fragmentation of biodegradable mulches under accelerated weathering conditions

Biodegradable mulches (BMs) can be tilled into soils to mitigate disposal and environmental problems. However, the content of biodegradable microplastics (BMPs) would increase with the addition of biodegradable macroplastics (BMaPs). The fragmented particles have a strong affinity to soil pollutants, having the potential to transfer via the terrestrial food web in an agroecosystem. Based on the spectral analysis and particle size analysis, this study explored the physicochemical characteristics of weathered BMaPs and BMP-derived dissolved organic matter (DOMBMP). Ultraviolet (UV) irradiation reduced the mechanical strength of BMaPs and induced oxygenated functional groups, thus increasing surface roughness and hydrophilicity. This promoted the adsorption of aromatic compounds and heavy metals from soils to BMPs. After entering the water environment, the pH of the solution with DOMBMP decreased, whereas the concentration of dissolved organic carbon (DOC) increased. Compared with paper mulch, bioplastic mulch contributed a higher amount of DOMBMP, such as aromatic structure-containing chemicals and carboxylic acids, to the water environment but released fewer and smaller plastic particles. The findings from this study can help manage environmental risks and determine disposal strategies after the use of mulching.

Effect of Poly(vinyl alcohol) on Catalytic Performance of Al-Pillared Clay in Alkylation of Aromatic Hydrocarbons with Olefins

It is vital to design and synthesize efficient catalysts for removing olefins from aromatics and prolonging reaction time. The catalytic properties of pillared clay for olefin removal from aromatic compounds can be enhanced noticeably by grafting organic polymer molecules due to modification of the clay porosity in the pillaring reaction. In the present work, a series of catalysts are prepared by pillaring raw bentonite and acid-treated bentonite with aluminum and poly(vinyl alcohol) (PVA) intercalation. Prepared samples are evaluated in the olefin removal process and characterized by X-ray diffraction patterns (XRD), temperature-programmed desorption (TPD) of NH3, and nitrogen adsorption–desorption isotherms. The BET results reveal that the pillaring reaction in an aqueous solution of PVA increases the clay’s surface area to greater than 200 m2.g–1. The pore volume of alumina-pillared acid-activated clay (Al-PAAC) is enhanced from 0.278 to 0.321 and 0.416 cm3.g–1 at the PVA concentrations of 30 and 50 wt %, respectively. The samples modified with PVA, as a precursor in the pillaring reaction, show an enhanced catalytic activity compared to the other samples due to a higher number of active sites. The olefin conversion of the pillared sample remains above 50% in the presence of 50 wt % PVA for more than 26 h. Furthermore, PVA could facilitate the reactant’s access to the active acid sites in the interlayer of the pillared clay. The adsorption of aromatic compounds and olefins by the pillared samples follows the intraparticle diffusion kinetic model. In addition, the Langmuir model fits the adsorption isotherm data well.

Estimation of Adsorbed Amounts in Organoclay by Machine Learning.

Adsorption properties of organoclay have been investigated for decades focusing on the morphology and physicochemical properties of two-dimensional interlayers. Experimental studies have previously revealed that the adsorption mechanisms depend on the molecular species of the organocation and adsorbate, making it difficult to estimate the adsorbed amount without experiments. Considering that the adsorption of aromatic compounds has been reported by using various clays, organocations, and adsorbates, machine learning is a promising method to overcome the difficulty. In the present study, we collected adsorption data from the literature and constructed models to estimate the adsorbed amount of the organoclay by random forest regression. The composition of the clay, molecular descriptors of the organocation and adsorbate obtained by the RDKit, and experimental conditions were used as the explanatory variables. Simple model construction by using all the experimental data resulted in low R 2 and a mean absolute error. This problem was solved by the correction of the adsorbed amount data by the Langmuir or Freundlich equation and the following model construction at various equilibrium concentrations. The plots of the adsorbed amount estimated by the latter model were located close to the corresponding adsorption isotherm, while that by the former was not. Thus, it was revealed that the adsorbed amount was estimated quantitatively without understanding the adsorption mechanisms individually. Feature importance analysis also revealed that the combination of the organocation and adsorbate is important at high equilibrium concentrations, while the clay should be selected carefully as the concentration gets lower. Our results give an insight into the rational design of the organoclay including the synthesis and adsorption properties.

Revisit the adsorption of aromatic compounds on graphene oxide: Roles of oxidized debris

The latest structural model of graphene oxide (GO) consists of two parts: large sheet of lightly oxidized graphene (FG) and small highly oxidized debris (ODs) in the form of “GO = FG + ODs”. Given the new model, this study focused on the roles of ODs played in the adsorption of aromatic compounds on GO. Firstly, π-conjugation, hydrophobicity, and surfaces charges of GO were examined to reveal how ODs stripping affected the surface property. Then, microscopic adsorption process was captured to reveal the behaviour of ODs during the adsorption process. Finally, isothermal and kinetics experiments were carried out to explore the effects of ODs striping on adsorption capacity and adsorption rate of GO. The results showed that ODs play key roles during the adsorption process and serves as important adsorption sites towards aromatic compounds. The adsorption was enhanced upon the significant stripping of ODs and was mainly attributed to the weakened electrostatic repulsion, increased π-π interaction, and increased hydrophobic interaction between GO and the aromatic compounds. Therefore, ODs should be considered during the development of GO-based environmental nanomaterials for applications.

Effect of Tube Diameters and Functional Groups on Adsorption and Suspension Behaviors of Carbon Nanotubes in Presence of Humic Acid

The adsorption and suspension behaviors of carbon nanotubes (CNTs) in the water environment determine the geochemical cycle and ecological risk of CNTs and the compounds attached to them. In this study, CNTs were selected as the research object, and the effect of tube diameters and functional groups (multiwall CNTs (MWNTs) and hydroxylated MWNTs (HMWNTs)) on the adsorption and suspension behaviors of the CNTs in the presence of humic acid (HA) was systematically analyzed. The results indicate that HA adsorption decreased with the increase in the solution pH, and the adsorption amount and rate were negatively correlated with the tube diameter of the CNTs. The surface hydroxylation of the CNTs prevented the adsorption of HA, and the maximum adsorption amounts on the MWNTs and HMWNTs were 195.95 and 74.74 mg g−1, respectively. HA had an important effect on the suspension of the CNTs, especially for the surface hydroxylation, and the suspension of the CNTs increased with the increase in the tube diameter. The characteristics of the CNTs prior to and after adsorbing HA were characterized by transmission electron microscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. The results indicate that surface hydroxylation of the CNTs increased the adsorption of aromatic compounds, and that the CNTs with a smaller diameter and a larger specific surface area had a disordered carbon accumulation microstructure and many defects, where the adsorption of part of the HA would cover the defects on the CNTs’ surface. Density functional theory (DFT) calculations demonstrated that HA was more easily adsorbed on the CNTs without surface hydroxylation. This investigation is helpful in providing a theoretical basis for the scientific management of the production and application of CNTs, and the scientific assessment of their geochemical cycle and ecological risk.

Adsorptive Separation of Aromatic Compounds from Alkanes by π-π Interactions in a Carbazole-Based Conjugated Microporous Polymer.

Separation of aromatic/alkane mixtures of similar size and properties is critical for the chemical industry as conventional thermal separation is a high-cost and an energy-intensive process. Adsorptive separation based on porous materials is a prospective and economical technology as well as a suitable alternative to the energy-inefficient heat-driven separation process. With this in mind, we design and synthesize a novel microporous polymer (termed CMP-S-1) with a conjugated aromatic skeleton as a porous adsorbent for aromatic/alkane separation. CMP-S-1 possesses high aromatic adsorption selectivity in two representative separation systems (benzene vs cyclohexane and 3-methylthiophene vs n-octane) based on a vapor adsorption experiment and an ideal adsorbed solution theory simulation. The instant adsorption rate, adsorption energy calculations, and liquid fixed-bed breakthrough experiments give convincing demonstrations on the preferential selective adsorption of aromatic compounds over alkanes in CMP-S-1. The strong π-π interaction between aromatics and the naphthalene ring is considered as the main reason for the strong affinity of aromatic compounds in the CMP-S-1 skeleton. The remarkable aromatic/alkane separation performance of CMP-S-1 verifies the important influence of the π-conjugation interaction in the conjugated porous polymer for the low-energy consumption adsorption separation process.

Impact of the Preparation Procedure on the Performance of the Microporous HKUST-1 Metal-Organic Framework in the Liquid-Phase Separation of Aromatic Compounds.

To date, metal-organic frameworks (MOFs) have been recognized as promising solid phases in high-performance liquid chromatography (HPLC). This research aimed to elucidate the role of the physico-chemical characteristics of the microporous HKUST-1 metal-organic framework in its operation as a selective adsorbent in HPLC. For this, the HKUST-1 samples were prepared by microwave-assisted synthesis and a solvothermal procedure. According to the chromatographic examinations, the HKUST-1 material synthesized in the microwave fields shows an efficient performance in the selective adsorption of aromatic compounds with different functionalities. This study revealed a significant impact of the preparation procedure on the mechanism of the liquid-phase adsorption on the HKUST adsorbents under conditions of the HPLC. An effect of the elution solvent with the different coordination ability to the Cu2+ sites in the HKUST-1 structure on the adsorption selectivity was observed.

PH-Dependent adsorption of aromatic compounds on graphene oxide: An experimental, molecular dynamics simulation and density functional theory investigation

This work provides a comprehensive understanding for the pH-dependent adsorption of aromatic compounds (ACs) on graphene oxide (GO). Isothermal and kinetics experiments indicated both adsorption capacity and adsorption rate were suppressed at higher pH, and the mechanisms were revealed by molecular dynamics simulations and density functional theory calculations. More specifically, π-π, hydrogen bond, vdWs, and water-mediated steric hindrance interactions were examined to reveal how pH affected the adsorption capacity, and microscopic dynamic adsorption process was captured to reveal how pH affected the adsorption rate. Results showed the reduced adsorption capacity at higher pH was mediated by increased electrostatic repulsion, weakened π-π interaction, and increased water-mediated steric hindrance. The pH-dependent behaviour of GO was responsible for the effect of pH on adsorption rate. Self-aggregation of GO at lower pH helped to capture ACs and created more favourable adsorption sites. Upon the adsorption of ACs on GO, GO/water/AC/water/GO sandwich-like structure formed, which was also mediated by solution pH. Overall, pH affects the adsorption of ACs on GO by regulating driving forces, adsorption process, and the configuration property of GOAC complex.

Record Complexity in the Polycatenation of Three Porous Hydrogen-Bonded Organic Frameworks with Stepwise Adsorption Behaviors.

Hydrogen-bonded organic frameworks (HOFs) show great potential in many applications, but few structure-property correlations have been explored in this field. In this work, we report that self-assembly of a rigid and planar ligand gives rise to flat hexagonal honeycomb motifs which are extended into undulated two-dimensional (2D) layers and finally generate three polycatenated HOFs with record complexity. This kind of undulation is absent in the 2D layers built from a very similar but nonplanar ligand, indicating that a slight torsion of ligand produces overwhelming structural change. This change delivers materials with unique stepwise adsorption behaviors under a certain pressure originating from the movement between mutually interwoven hexagonal networks. Meanwhile, high chemical stability, phase transformation, and preferential adsorption of aromatic compounds were observed in these HOFs. The results presented in this work would help us to understand the self-assembly behaviors of HOFs and shed light on the rational design of HOF materials for practical applications.

Adsorption-enhanced catalytic wet peroxide oxidation of aromatic compounds on ionothermally synthesised copper-doped magnetite magnetic nanoparticles

Environmental contextAromatic compounds are major organic pollutants that are hard to clean up by either adsorption or biological treatment processes. We synthesised Cu-doped Fe3O4 magnetic nanoparticles and showed that they efficiently degrade various aromatic compounds with H2O2 under mild conditions. This active and stabile heterogeneous Fenton-like catalyst has the potential for various environmental applications. AbstractMagnetite magnetic nanoparticles (Fe3O4 MNPs) have great potential in environmental remediation owing to the intrinsic peroxidase-like activity, which is unfortunately not strong enough to activate H2O2 for practical applications. Herein, Cu-doped Fe3O4 MNPs (Fe2.88Cu0.12O4) were ionothermally synthesised and demonstrated as a highly efficient and stable heterogeneous Fenton-like catalyst for the catalytic wet peroxide oxidation of aromatic compounds with H2O2 at pH ~7 and 25°C. Theoretical calculations found that the interaction between aromatic compounds (e.g. orange G) and Cu2+ through a terminal end-on binding mode with moderate strength was favourable to enhance their adsorption on Fe2.88Cu0.12O4. In addition, copper dopants increased the decomposition rate of H2O2 at 25°C about four-fold (0.584h−1 on Fe2.88Cu0.12O4 versus 0.153h−1 on Fe3O4), which is attributed to efficient redox cycling of iron and copper ions for synergistic activation of H2O2. Copper-enhanced adsorption of aromatic compounds, together with synergistic activation of H2O2 by surface iron and copper active sites, explained the higher catalytic activity of Fe2.88Cu0.12O4. This study provided new insight for improving the catalytic performance of magnetite-based heterogeneous catalysts for various environmental and biomedical applications.

Adsorption of aromatic compounds by biochar: influence of the type of tropical biomass precursor

Biomasses have been used as adsorbents since they are inexpensive and can offer excellent performance in adsorption of pollutants and in water remediation. To increase their performance, thermal decomposition of biomass under oxygen-limited conditions to produce biochar has attracted increasing attention. The properties of biochar are affected by the preparation temperature and the type of biomass used. This work investigates the influence of the type of precursor tropical biomass used to prepare biochar with a high capacity for the adsorption of some polycyclic aromatic hydrocarbons (PAHs) in aqueous solution. Biochars prepared from coconut waste, elephant grass, orange waste, and guava waste were studied, and the adsorption behaviors were correlated to the chemical characteristics of the materials. The type of precursor tropical biomass determined the adsorption of PAHs by the biochars, being governed by π–π interactions, with those prepared using biomass with high lignin content showing better adsorption.

Direct Evidence for Temporal Molecular Fractionation of Dissolved Organic Matter at the Iron Oxyhydroxide Interface.

While the importance of organic matter adsorption onto reactive iron-bearing mineral surfaces to carbon stabilization in soils and sediments has been well-established, fundamental understanding of how compounds assemble at the mineral interface remains elusive. Organic matter is thought to layer sequentially onto the mineral surface, forming molecular architecture stratified by bond strength and compound polarity. However, prominent complexation models lack experimental backing, despite the role of such architecture in fractionated, compound-dependent persistence of organic matter and modulating future perturbations in mineral stabilization capacity. Here, we use kinetic assays and ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry under high temporal frequency to directly detect the molecular partitioning of organic matter onto an iron oxyhydroxide during adsorption. We observed three sequential intervals of discrete molecular composition throughout the adsorption reaction, in which rapid primary adsorption of aromatic compounds was followed by secondary lignin-like and tertiary aliphatic compounds. These findings, paired with observed differential fractionation along formulas nitrogen and oxygen content and decreasing selective sorption with reaction time, support "zonal" assembly models. This work presents direct detection of sequential molecular assembly of organic matter at the mineral interface, an important yet abstruse regulator of carbon stabilization and composition across temporal and spatial scales.

Hyper-cross-linked polymers functionalized with primary amine and its efficient adsorption of salicylic acid from aqueous solution

Chemically functionalized hyper-cross-linked polymers (HCLPs) are desired for efficient adsorption of aromatic compounds. Herein primary amine (–NH2) was indirectly functionalized on the HCLPs and the aniline-modified HCLPs namely An-HCLP was assessed by adsorption of salicylic acid from aqueous solution. The results indicated that 2.24 mmol·g−1 of –NH2 groups were uploaded and they are greatly beneficial for the adsorption, the enthalpy change was figured out to be −35.27 kJ·mol−1, and multiple interactions including acid-base interaction and hydrogen bonding are the main driving forces. Moreover, An-HCLP owned hierarchical porosity with continuous micropores and mesopores, which endowed them with fast kinetic adsorption, 55 min is sufficient for the adsorption attaining equilibrium, and the pseudo-second-order rate equation describes the kinetic very well with the kinetic constant (k2) of 1.266 × 10−3 g·mg−1·min−1.

Green synthesis of o-hydroxyazobenzene porous organic polymer for efficient adsorption of aromatic compounds

This work presents a simple and eco-friendly synthetic approach to fabricate a novel o-hydroxyazobenzene porous organic polymer (HAzo-POP) by diazo-coupling of 2,6-diaminoanthraquinone with m-trihydroxybenzene in aqueous solution. The prepared HAzo-POP possesses good stability and high adsorption capability towards aromatic organic pollutants due to its porous nature, highly conjugated structure and strong hydrogen bonding ability. The HAzo-POP was successfully used for the solid-phase extraction of phenylurea herbicides from six real samples prior to high performance liquid chromatography with ultraviolet detection. The analytical method showed good linearity in the range of 0.5-160.0 ng g−1 for celery, lettuce and tomato samples, and 0.4–160.0 ng mL−1 for milk, soybean milk and juice samples, with low limits of detection in the range from 0.05 to 0.30 ng g−1 (or mL−1). The HAzo-POP has a promising application potential for the adsorption of more aromatic organic compounds.