Adsorption Of Polycyclic Aromatic Hydrocarbons Research Articles

Distribution and Potential Sources of OCPs and PAHs in Waters from the Danshui River Basin in Yichang, China.

To investigate the concentrations, spatial distribution, potential sources and mass fluxes of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in waters from the Danshui River Basin, a total of 20 water samples were collected and analyzed from a karstic river in Western Hubei of Central China. The average concentrations of total OCPs and PAHs in the river water were 4719 pg·L−1 and 26.2 ng·L−1, respectively. The characteristic ratios of different isomers and the composition analysis of individual OCPs and PAHs revealed that HCHs originated from a mixed input of technical HCHs and Lindane, DDTs were mainly from technical DDTs, and PAHs mainly originated from biomass and coal combustion. The mass flux analysis showed that PAHs had a higher emission and heavier burden than OCPs in the Danshui River Basin. OCPs and PAHs emitted from agricultural or other human activities could enter the groundwater and then be transported to the surface/river water in the karst area. The adsorption of OCPs and PAHs by particles and the sedimentation of particles could be the primary processes to intercept these pollutants in the water of the karstic river system.

Effects of organic matter on polycyclic aromatic hydrocarbons in riverine sediments affected by human activities

Organic matter (OM) is an important component of riverine environments and a major factor in the migration and transformation of hydrophobic organic substances, such as polycyclic aromatic hydrocarbons (PAHs), to sediments. We studied the distributions, sources, and correlations between PAHs and OM in sediments from the Duliujian and the Beiyun rivers in North China. Sixteen PAHs were detected in the surface sediments at total concentrations ranging from 356 to 4652 ng·g−1 dry weight, which caused a moderate to high level of pollution. The PAH distributions were significantly and positively correlated with OM (p < 0.01) and higher concentrations were detected downstream of areas affected by human activity. Petroleum, coal, and wood combustion were the main sources of PAHs in riverine sediments, and the sources of OM in sediment included terrestrial and aquatic higher plants, soil, and sewage discharge. The OM accumulated and aged along the river, with increases in the degree of aromaticity and condensation, which led to stronger adsorption of PAHs. Our results will help to promote the management and restoration of contaminated riverine sediments.

A Mini-Review for an Adsorption of Polycyclic Aromatic Hydrocarbons (PAHs) by Physical Gel

On 4 December in 2002, the mainstream source of exposure to Polycyclic Aromatic Hydrocarbons (PAHs) was defined by the Scientific Committee as food and inhaled air. Several Polycyclic Aromatic Hydrocarbons (PAHs) such as benzo[a]pyrene, chrysene, and dibenzo(a,h)anthracene in food caused the risk of human health. These are produced by the cooking processes, including combustion processes and pyrolysis sources. Certain food preparation methods like grilling, roasting, and smoking are accumulated PAHs in the sink pipes. As PAHs are toxic and carcinogenic, it raises health and environmental problems. What is the method for preventing PAHs exist in wastewater? This review article introduces a functional material, gelatin physical gels, to trap and remove the PAHs. The physical gel changes from colorless to pale yellow during the adsorption of PAHs in household wastewater. The concentration of PAHs is determined by GC-MS analysis, which decreases the potential risk of human exposure in an environment with PAHs.

Adsorption mechanism of polycyclic aromatic hydrocarbons using wood waste-derived biochar

The polycyclic aromatic hydrocarbons (PAHs) have been attracted increasing attentions due to their carcinogenicity and teratogenicity. Adsorption is widely considered one of the most potential technologies for PAHs removal. In this study, we prepared two kinds of oxygen-rich biochar derived from waste wood to investigate the PAHs adsorption performance, and the molecular simulation was used to build the 16 priority PAHs, 23 nitrated PAHs, 9 oxygenated PAHs adsorption model. The surface adsorption performance of oxygen-rich biochar significantly depends on the pyrolysis conditions. The main out-comings demonstrated that the adsorption of naphthalene (C10H8) molecules first occurred, and the optimal adsorption positions of oxygen-rich biochar strongly adhered to functional groups of carboxyl and hydroxyl. Moreover, benzene ring, -COOH, and -CH3 of biochar were the main adsorbed functional groups for PAHs adsorption. The oxygen-rich biochar had the targeted-adsorption effect on PAHs removal especially symmetrical PAHs, and the targeted-adsorption mechanism was finally proposed. The research is beneficial to guide the removal of PAHs from polluted water and mitigate the environmental pollution caused by biomass waste mismanagement, simultaneously.

Adsorption of Polycyclic Aromatic Hydrocarbons by Natural, Synthetic and Modified Clays

Polycyclic aromatic hydrocarbons (PAHs) are of major scientific concern owing to their widespread presence in environmental compartments and their potential toxicological effects on humans and biota. In this study, the adsorption capacity of natural (montmorillonite (Mt)), synthetic (Na-Mica-4), and modified (with octadecylamine and octadecyltrimethylamine (ODA-Mt, ODA-Mica-4, and ODTMA-Mt and ODTMA-Mica-4)) clays were assessed and compared for the removal of 16 PAHs. Materials were synthesized and characterized by X-Ray diffraction, Zeta potential, and Fourier-transform infrared spectroscopy. The results showed its correct preparation and the incorporation of PAHs in the structure of the clays after the adsorption tests. The proposed materials were effective PAH adsorbents, with adsorption percentages close to 100%, in particular those using Mt. Mt and Na-Mica-4 presented a better adsorption capacity than their organofunctionalized derivatives, indicating that the adsorption of PAHs may occur both in the surface part and in the interlayer. The proposed adsorbents take the advantage of being a low cost and highly effective. They can be an interesting alternative for wastewater treatment and soil remediation to prevent PAH contamination.

Rapid synthesis of graphite phase carbon nitride/zeolitic imidazolate framework-8 with hierarchical structure and its superior adsorption of polycyclic aromatic hydrocarbons from aqueous solution

Graphite phase carbon nitride (g-C3N4) incorporating zeolitic imidazolate framework-8 (ZIF-8) nanocomposite (g-C3N4 /ZIF-8) with hierarchical structure was synthesized successfully by simple and rapid in situ growth method at room temperature. The composites were used as an adsorbent of solid-phase extraction (SPE) and the superior adsorptive removal of polycyclic aromatic hydrocarbons (PAHs) for the first time. Under several optimum conditions, the g-C3N4 /ZIF-8-SPE-HPLC-FLD method show low detection limits (0.006–3.41 μg L−1) and limit of quantification (0.02–11.3 μg L−1), wide linear ranges from 0.02 to 1000 μg L−1 for all compounds, correlation coefficients (r) of more than 0.9968, and satisfying reproducibility (relative standard deviations, RSDs < 4.0% for intra-day, RSDs < 8.3% for inter-day), the spiked recoveries at two levels of 10.0, 50.0 μg L−1 were in the range of 77.4%-114% with the RSDs less than 8.66%. In addition, the g-C3N4/ZIF-8 nanocomposites demonstrated excellent enrichment ability and extraction efficiency for PAHs compared with commercial adsorbents, which might since there were strong π-π stacking force, hydrophobic interaction, hydrogen bonding, and more adsorption sites compared with other adsorbents. Finally, the g-C3N4 /ZIF-8 based SPE method was combined with high-performance liquid chromatography (HPLC) to detect fifteen PAHs in environmental water samples successfully.

Simulating yield and morphology of carbonaceous nanoparticles during fuel pyrolysis in laminar flow reactors enabled by reactive inception and aromatic adsorption

Carbon black and soot are synthesized by gas-phase pyrolysis of hydrocarbons. Inception, surface growth, and coagulation control process yield and agglomerate morphology. Here, we present a sectional population balance model (SPBM) coupled with chemistry to simulate carbon black formation by ethylene pyrolysis in laminar flow reactors. The SPBM tracks agglomerate size distribution and morphology. New particles are formed by the dimerization of polycyclic aromatic hydrocarbons (PAHs) and grow with hydrogen abstraction acetylene addition as well as the addition of PAHs on their surface. Three different dimerization models for inception and PAH adsorption are compared: irreversible, reversible, and reactive. With irreversible PAH dimerization and surface growth, more than 90% of PAH mole fraction converts to particles even at low-temperatures (T<1200 K) causing an overestimation of the primary particle number density due to non-stop new particle formation. With reversible dimerization, the mass yield is underestimated by more than a factor of 3. With reversible dimerization and surface growth followed by a chemical bond formation step (chemical dimerization/reactive model), particles form and grow mostly at high temperatures (T>1200 K); the particle size distribution, as well as the average primary particle and mobility diameters are predicted within 30% of measurements. The reactive model enhances the agglomerate morphology prediction in the low-temperature regions of the reactor and appears to be more consistent with the latest understanding of inception and surface growth.

Magnetic poly(β-cyclodextrin) combined with solubilizing agents for the rapid bioaccessibility measurement of polycyclic aromatic hydrocarbons in soils

The rapid determination of the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soils is challenging due to their slow desorption rates and the insufficient extraction efficiency of the available methods. Herein, magnetic poly(β-cyclodextrin) microparticles (Fe3O4@PCD) were combined with hydroxypropyl-β-cyclodextrin (HPCD) or methanol (MeOH) as solubilizing agents to develop a rapid and effective method for the bioaccessibility measurement of PAHs. Fe3O4@PCD was first validated for the rapid and quantitative adsorption of PAHs from MeOH and HPCD solutions. The solubilizing agents were then coupled with Fe3O4@PCD to extract PAHs from soil-water slurries, affording higher extractable fractions than the corresponding solution extraction and comparable to or higher than single Fe3O4@PCD or Tenax extraction. The desorption rates of labile PAHs could be markedly accelerated in this process, which were 1.3–12.0 times faster than those of single Fe3O4@PCD extraction. Moreover, a low HPCD concentration was sufficient to achieve a strong acceleration of the desorption rate without excessive extraction of the slow desorption fraction. Finally, a comparison with a bioaccumulation assay revealed that the combination of Fe3O4@PCD with HPCD could accurately predict the PAH concentration accumulated in earthworms in three field soil samples, indicating that the method is a time-saving and efficient procedure to measure the bioaccessibility of PAHs.

Study on the Electron Action Mechanism of Hydrogen Adsorption and Activation on Platinum Clusters with the help of Computer Software

Cyclic aromatic hydrocarbons occupy a certain proportion in the high boiling point fractions of petroleum and are difficult to convert. Hydrocracking to lighten polycyclic aromatic hydrocarbons is currently an effective way of conversion. As the first step of catalytic reaction, the adsorption of polycyclic aromatic hydrocarbons (PAHs) on the surface of catalytic materials is of great significance to the subsequent reaction process. In this paper, molecular dynamics and density functional theory (DFT) were used as research tools, and Nano-sized PT clusters were selected as adsorption models [1-3]. Firstly, the adsorption mode of H2 on Pt clusters was analyzed from the frontier orbital point of view, and the changes of electron distribution of H2 on Pt clusters from physical adsorption to chemical adsorption were compared with the help of computer software.

An experimental and numerical study of the effects of reactant temperatures on soot formation in a coflow diffusion ethylene flame

The effects of elevated reactant temperatures on soot formation in a laminar coflow ethylene flame were experimentally and numerically investigated. Ethylene flames at the reference reactant temperatures (both air and fuel), Tr, of 300K (LT), 473K (MT), 673K (HT), and 713K (UHT) were established. In the experiment, soot volume fractions (fv), primary particle diameters (dp), and soot (flame) temperatures (TF) were measured. The flames were also simulated by the CoFlame code with the Conjugate Heat Transfer (CHT) condition. The experimental results show that elevating Tr positively affects soot formation. The increase in the maximum fv is greater on the wing pathline (∼1.9 times) than on the centerline (∼1.2 times) when the adiabatic flame temperature increases by ∼100K. An analysis of the experimental and numerical data suggests that soot formation is promoted by enhanced soot surface growth. The numerical simulation reveals that PAH (polycyclic aromatic hydrocarbon) adsorption, which is a function of PAH concentration, becomes important at high Tr as its mass contribution increases from ∼50% to ∼70%. This may be attributed to early fuel pyrolysis within the fuel tube.

Adsorption of polycyclic aromatic hydrocarbons by surfactant-modified clinoptilolites for landfill leachate treatment

The authors report the potential adsorption capacities of three surfactant-modified clinoptilolites (MC)—cetylpyridinium chloride (CPC)-MC, didodecyldimethylammonium bromide (DDAB)-MC, and hexadecyltrimethylammonium bromide (HDTMA)-MC—for the removal of polycyclic aromatic hydrocarbons (PAHs) from aquatic environments and landfill leachate. A liquid–liquid extraction method was used to extract PAHs from water and GC/MS was used to analyse the PAHs. PAH accumulations on CPC-MC, DDAB-MC, and HDTMA-MC were linear over 21 successive batch adsorption tests for anthracene (708, 737, and 750 µg/g), fluoranthene (1355, 1583, and 1303 µg/g), fluorene (973, 1060, and 1147 µg/g), phenanthrene (844, 1057, and 989 µg/g), and pyrene (1343, 1569, and 1269 µg/g). The leachability after 21 successive accumulations was <2% for anthracene, <4% for fluoranthene, <3% for fluorene, <4% for pyrene, and <5% for phenanthrene for each adsorbent. PAH removals from landfill leachate for anthracene, fluoranthene, fluorene, phenanthrene, and pyrene were 97.8%, 98.6%, 95.7%, 97.0%, and 98.5% for CPC-MC and 99.0%, 99.6%, 98.0%, 99.0%, and 99.6% for DDAB-MC, respectively, meeting the fresh water quality standards established by British Columbia and the World Health Organization (WHO) for anthracene, fluoranthene, and fluorene. The molecular weight and molecular structure of PAHs and the hydrophobicity of adsorbents can fundamentally influence the PAH adsorption mechanism based on π–π stacking.

Utilization of activated carbon derived from waste plastic for decontamination of polycyclic aromatic hydrocarbons laden wastewater.

Serious environmental deterioration caused by synthetic waste plastics, and the pollution of freshwater resources are the most alarming and marked challenges of the 21st century. Therefore, immense scientific efforts are being made towards the management of waste plastics and treatment of polluted water. The current study reports on the utilization of waste polyethylene terephthalate (wPET) and waste polystyrene (wPS) for fabrication of activated carbon (AC) and its application for the removal of hazardous polycyclic aromatic hydrocarbons (PAHs) pollutants from water. AC was prepared from wPET and wPS by carbonization under a N2 atmosphere followed by chemical activation with 1 M KOH and 1 M HCl. The AC was characterized by scanning electron microscopy, surface area analysis, and Fourier transform infrared spectroscopy. Adsorption of PAHs from aqueous solutions through AC was examined by batch adsorption tests. The optimum parameters for maximum adsorption of PAHs were found to be: initial PAHs concentration 40 ppm, 2 h contact time, pH 3, 5, and 7, 50 °C temperature and adsorbent dose of 0.8 g. Kinetic and isotherm models were applied to evaluate the adsorbent capacity for PAHs adsorption. The kinetic study shows that the adsorption of these PAHs onto AC follows pseudo-second-order kinetics. The experimental results demonstrated that the Langmuir isotherm model best fitted the data. The thermodynamic factors calculated such as entropy change (ΔS°), enthalpy change (ΔS°) and free energy change (ΔG°) show that the adsorption process is non-spontaneous and endothermic in nature. Results were also compared with the efficiencies of some commercial adsorbents used in practice. This examination revealed that the novel plastic-derived AC possesses a great potential for elimination and recovery of PAH elimination from industrial wastewater.

Laboratory evaluation of PAHs removal by multi-functional green pervious concrete (MGPC) pavement

Stormwater runoff-induced polycyclic aromatic hydrocarbons (PAHs) contaminants increasingly endanger the groundwater reserve and ecosystems due to the extensive coverage of impervious pavements in urban surroundings. The multi-functional green pervious concrete (MGPC) pavement, a type of organoclay modified pervious concrete pavement, is proved to be an innovative and effective stormwater management method as well as an environmental technology for controlling the runoff both in quantity and quality. To further study the field applicability of the MGPC pavement, extensive experiments should be conducted by considering multiple variables that represent different scenarios, such as rainfall intensity, traffic flow, and traffic loads, stability, and reusability. This study conducts a laboratory-scale investigation of MGPC pavement performance on PAHs removal by varying a series of PAH initial concentrations, flow rate, and contamination cycles. The results indicated that lower initial PAHs concentration and slower flow rate promoted the PAHs removal efficiency, and the MGPC pavement still kept considerable PAHs adsorption capacity after 50 contamination cycles. The results provide important references in evaluating and designing the MGPC pavement as a stormwater management method with attenuating the runoff-induced PAHs contamination.

Modeling soot formation in laminar coflow ethylene inverse diffusion flames

A numerical study is conducted using the CoFlame code to investigate the sooting characteristics of ethylene-fueled laminar coflow inverse diffusion flames (IDFs), aiming to gain insights into the different flame structure and soot formation features between an IDF and a normal diffusion flame (NDF). The effects of oxygen mole fraction in the oxidizer stream, denoted as Oxygen Index (OI), on flame structure and soot production are studied over the OI range of 21% to 33%. The soot model parameters were chosen to produce overall reasonably good agreement between the predicted and measured in terms of soot volume fraction, mean primary particle size, and the mean number of primary particles per aggregate in both the normal and inverse configurations. A sensitivity study showed that soot nucleation and soot surface growth by PAH adsorption modeling should be considered simultaneously as a strongly coupled process through competing for polycyclic aromatic hydrocarbons (PAHs). The IDF configuration displays distinct characteristics from the NDF one in terms of flame structure as well as soot production. In IDFs soot is formed along the outer edge of reaction front, and does not cross the reaction front to the oxidizer, decoupling completely soot oxidation which leads to soot emission from the open flame tip. Modeling results indicate that in the IDF configuration the hydrogen abstraction acetylene addition (HACA) process is severely suppressed, while the adsorption of PAH molecules is dominant to soot surface growth at relatively low temperatures. Nucleation of new particles is significant all along the flame height, causing emission of young soot. IDF represents an ideal configuration to study soot surface growth by PAH adsorption. Increasing OI enhances all the soot processes, especially surface growth by PAH adsorption. Although soot oxidation rate by OH radicals is also strongly enhanced, it remains about two orders of magnitude lower than soot surface growth rate by PAH adsorption.

Sorption behavior of polycyclic aromatic hydrocarbons on biodegradable polylactic acid and various nondegradable microplastics: Model fitting and mechanism analysis

The main objective of this study was to gain more detailed knowledge of how four selected polycyclic aromatic hydrocarbons (PAHs) interact on six nondegradable types of microplastics (MPs) and one biodegradable plastic (BP) in two water matrices. The results were evaluated using the popular Freundlich and Langmuir isotherm models, as well as a new modified mathematical model. The modified mathematical model was developed to additionally elucidate the adsorption mechanism, to investigate transfer kinetics of PAHs and to predict the variation of adsorption rate and capacity as a function of time. The adsorption kinetics of selected PAHs onto MPs and biodegradable plastic were described best by the pseudo-second order kinetic model (R2 = 0.810–0.999), implying that chemisorption is possibly the adsorption mechanism. The results of the adsorption isotherm study also indicated that adsorption of PAHs on selected types of microplastics was best described by the Langmuir model, implying that adsorption of PAHs is more dominant on powdered types of MPs in both synthetic and real water matrices. On the other hand, the lowest adsorption affinity was achieved for adsorption of PAHs on polylactic acid, indicating that this type of biodegradable plastic would have significantly less impact on the transport and distribution of PAHs through environment.

Design of Hybrid PAH Nanoadsorbents by Surface Functionalization of ZrO2 Nanoparticles with Phosphonic Acids.

This study focuses on the preparation of innovative nanocomposite materials based on surface modification of commercial nano-ZrO2 optimized from Brønsted acid–base surface reactions. This surface modification was carried out by direct grafting of suitable phosphonic acids bearing a vinylic or phenylic substituent in aqueous solution. Different loading quantities of the anchoring organophosphorus compounds were applied for each materials synthesis. The resulting nanohybrids were thoroughly characterized by infrared spectroscopy (DRIFT), solid-state nuclear magnetic resonance (NMR), nitrogen adsorption-desorption (BET), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS), demonstrating the reliability and efficient tunability of the surface functionalization based on the starting Zr/P ratio. Our nanocomposite materials exhibited a high specific surface area as well as complex porosity networks with well-defined meso-pore. The as-prepared materials were investigated for the adsorption of a mixture of 16 polycyclic aromatic hydrocarbons (PAHs) at 200 ng·mL−1 in an aqueous solution. Adsorption kinetics experiments of each individual material were carried out on the prepared PAHs standard solution for a contact time of up to 6 h. Pretreatments of the adsorption test samples were performed by solid-phase extraction (SPE), and the resulting samples were analyzed using an ultrasensitive GC-orbitrap-MS system. The pseudo-first-order and the pseudo-second-order models were used to determine the kinetic data. The adsorption kinetics were best described and fitted by the pseudo-second-order kinetic model. The correlation between the nature of the substituent (vinylic or phenylic) and the parameters characterizing the adsorption process were found. In addition, an increase of PAHs adsorption rates with phosphonic acid loading was observed.

Prediction of organic compounds adsorbed by polyethylene and chlorinated polyethylene microplastics in freshwater using QSAR

Microplastics (MPs), a growing class of emerging pollutants in the environment, have attracted widespread attention due to their adsorption properties. Recent research on MPs has mainly concentrated on seawater, and little work has been conducted on freshwater. Investigating and predicting the adsorption behavior of organic pollutants by MPs are necessary in freshwater. In this study, the adsorption behavior of 13 organic chemicals by polyethylene (PE) and chlorinated polyethylene (CPE) MPs was determined under freshwater conditions. Results shows the majority of the organic chemicals exhibit no distinctive differences in their adsorption on two MPs. However, the adsorption of polycyclic aromatic hydrocarbons and chlorobenzene on CPE is obviously stronger than that on PE, and the result is a counter for two pesticides. Quantitative structure activity relationship (QSAR) analysis was performed for the prediction of adsorption capacity. A QSAR model with acceptable performance (R2 = 0.8586) was built to predict the adsorptive affinity (expressed as logKd) of organic compounds on the PE MPs via multivariable linear regression (MLR) on forty-nine determined and collected data. The octanol/water partition coefficient (logKow) and excess molar refractive index (E) play dominant roles in the model. A QSAR model with satisfactory performance (R2 = 0.9302) was also established for logKd values from CPE MPs in freshwater by using 13 adsorption data determined. The logKow and most negative charge on Cl atom (Q-max,cl) play decisive roles in the adsorption. The findings can provide a scientific basis for the risk assessment of waters contaminated by MPs and organic pollutants.

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by cellulosic aerogels during smoked pork sausage manufacture

The present study proposes a natural cellulosic adsorbent for removing polycyclic aromatic hydrocarbons (PAHs) generated during the manufacture of smoked pork sausage. Cellulose aerogels regenerated from three different solutions (NaOH/urea, LiBr, and LiOH/urea) were prepared and evaluated for adsorption of PAHs (benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene) under different smoking conditions by high-performance liquid chromatography) with fluorescence detection. The quality properties (moisture content, protein content, pH, peroxide value, microbial and sensory properties) of smoked sausages after adsorbent treatment were also noted. All the adsorbents proved suitable for the removal of PAHs. The adsorption efficacy was strongly dependent on the surface structure and pore size distribution of the cellulosic aerogels. Among the three adsorbents, the LiBr-functionalized absorbent displayed the highest adsorptive efficiency for total PAHs, without causing noticeable quality changes in pork sausages. It was concluded that functionalized cellulosic aerogels have prospects as eco-friendly adsorbents that effectively remove PAHs from smoked meat and meat products.

Adsorption of polycyclic aromatic hydrocarbons on FeOOH polymorphs: A theoretical study

In this work we studied interactions of polycyclic aromatic hydrocarbons (PAHs) with surfaces of two iron oxyhydroxide polymorphs, goethite and lepidocrocite, by means of density functional theory (DFT) method. The first focus here was to obtain adsorption energies of selected PAH molecules with the (110) goethite surface and the (010) lepidocrocite surface by performing DFT calculations with the inclusion of dispersion interactions. To this end we have performed assessment of six different methods to show their efficiency and predictability of nonbonding interactions. The second objective was to compare adsorption capability of two FeOOH polymorphs, goethite and lepidocrocite, as common minerals in several soil types and to relate obtained adsorption energies to different surface structure and topology of the most stable surfaces of both polymorphs. The goethite (110) surface has more complicated topology and three different types of OH groups compared to the lepidocrocite (010) surface formed by a plane of OH groups of the same type. For goethite, adsorption energy did not increase monotonically with the increasing molecular size of PAHs and the strongest adsorption was observed for the linearly-shaped anthracene molecule. On the other hand, adsorption of PAHs at the lepidocrocite surface increased energetically with increasing molecular weight, and the strongest adsorption was achieved for the pyrene molecule. The results showed that the goethite (110) surface is more attractive than the (010) lepidocrocite surface, which is explained by the different surface topology, and types and surface density of the OH groups.

Simultaneous extraction of diverse organic pollutants from environmental water using a magnetic covalent organic framework composite

Polycyclic aromatic hydrocarbons (PAHs), tetracyclines (TCs), and triphenylmethane dyes (TDs) are common organic pollutants, which may threat the human health or natural microbial communities. In this work, we report a novel multifunctional sorbent based on core-shell magnetic carboxylate-functionalized covalent organic frameworks composites (Fe3O4@COF–COOH) for the simultaneous adsorption of these target analytes via mixed-mode solid phase extraction. The behaviors of the synthetic composite for the adsorption of PAHs, TCs, and TDs were evaluated based on the Freundlich and Langmuir isotherm models. In combination with quantum chemistry calculations, it was found that the multiple interactions including π-π stacking, hydrogen bonding, and electrostatic attractions were existed between COF–COOH and guest molecules. The extraction parameters were optimized, and a novel simultaneous absorption-stepwise desorption (SASD) strategy for the enrichment of PAHs, TCs, and TDs was proposed. By coupling with HPLC-DAD method, the validation results revealed good linearities (R2 ≥ 0.9882) for all analytes. High sensitivity with LODs within the range of 0.003–0.008, 0.02–0.06, and 0.006–0.008 μg L−1 were obtained for PAHs, TCs, and TDs, respectively. High recoveries ranging from 93.6 to 105.8% were obtained with intra-day RSDs of 2.2–6.3% and inter-day RSDs of 3.2–6.5%. The obtained results demonstrated that the proposed SASD strategy using Fe3O4@COF–COOH as sorbents can be extended to other aqueous solutions consisting of trace multi-target analytes.