Adsorption behavior of a tri-functionalized imprinted resin with high selectivity for 5-sulfosalicylic acid: Batch experiments and DFT calculation

Enhancement of adsorption of cyanobacteria, Microcystisa aeruginosaby bacterial-based compounds

In the present study, algicidal bacteria cultivated in an aqueous medium were utilized as a surface modification agent to develop an efficient adsorbent for the removal of Microcystis aeruginosa. The modification considerably enhanced M. aeruginosa cell removal efficiency. Moreover, the introduction of bio-compounds ensured specificity in the removal of M. aeruginosa. Additionally, the cyanotoxin release and acute toxicity tests demonstrated that the adsorption process using the developed adsorbent is environmentally safe. Furthermore, the practical feasibility of the adsorptive removal of M. aeruginosa was confirmed through cell removal tests performed using the developed adsorbent in a scaled-up reactor (50 L and 10 tons). In these tests, the effects of the adsorbent application type, water temperature, and initial cell concentration on the M. aeruginosa removal efficiency were evaluated. The results of this study provide novel insights into the valorization strategy of biological algicides repurposed as adsorbents, and provide practical operational data for effective M. aeruginosa removal in scaled-up conditions.

Rational design of molecularly imprinted electrochemical sensor based on Nb2C-MWCNTs heterostructures for highly sensitive and selective detection of Ochratoxin a

Developing an efficient method for screening Ochratoxin A (OTA) in agriculture products is vital to ensure food safety and human health. However, the complex food matrix seriously affects the sensitivity and accuracy. To address this issue, we designed a novel molecularly imprinted polymer (MIP) electrochemical sensor based on multiwalled carbon nanotube-modified niobium carbide (Nb2C-MWCNTs) with the aid of the density functional theory (DFT). In this design, a glassy carbon electrode (GCE) was first modified by Nb2C-MWCNTs heterostructure. Afterward, the MIP layer was prepared, with ortho-toluidine as a functional monomer selected via DFT and OTA acting as a template on the surface of Nb2C-MWCNTs/GCE using in-situ electropolymerization. Electrochemical tests and physical characterization revealed that Nb2C-MWCNTs improved the sensor's active surface area and electron transmission capacity. Nb2C-MWCNTs had a good synergistic effect on MIP, endowing the sensor with high sensitivity and specific recognition of OTA in complex food matrix systems. The MIP sensor showed a wide linear range from 0.04 to 10.0 μM with a limit of detection (LOD) of 3.6 nM. Moreover, it presented good repeatability and stability for its highly antifouling effect on OTA. In real sample analysis, the recoveries, ranging from 89.77% to 103.70%, agreed well with the results obtained by HPLC methods, suggesting the sensor has good accuracy and high potential in practical applications.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π-π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Study on adsorption of salicylic acid and sulfosalicylic acid by MOF-sodium alginate gel beads obtained in a green way

A composite (ZS-UiO-66-NH2) zirconium crosslinked sodium alginate gel beads (ZS)-metal-organic skeleton (UiO-66-NH2) were prepared in this study through in-situ growth under simple, green and mild conditions for removal of the salicylic acid (SA) and sulfosalicylic acid (SSA) from water. The physicochemical properties of ZS-UiO-66-NH2 were characterized using various analytical methods. The influencing factors in the adsorption process including pH of solution, amount of adsorbent, coexisting ions, adsorption time, reaction temperature and equilibrium concentration of SA/SSA were performed in batch adsorption. The experimental results indicated that ZS-UiO-66-NH2 had high stability and could achieve efficient adsorption of SA/SSA in broad pH range (2-9) and salinity (0-0.2 mol·L-1). SA and SSA adsorbed on the composite at 293 K reached high values of 193 and 167 mg·g-1 from Langmuir model, respectively. Kinetic and isotherm studies demonstrated that the adsorption processes were mainly multilayer heterogeneous chemisorption. Thermodynamic data manifested that the two processes were exothermic and spontaneous with increasing entropy. ZS-UiO-66-NH2 can effectively remove SA/SSA from simulated wastewater under different pH and can be reused after elution with a NaHCO3 solution (5 mmol·L-1). The ZS-UiO-66-NH2 composite has great potential for removing SA/SSA from actual water bodies.

Regulating steric hindrance in difunctionalized porous aromatic frameworks for the selective separation of Pb(II)

Efficient and selective removal of Pb(II) from wastewater with complex matrix remains a challenging task. Porous aromatic frameworks (PAFs) with predesigned functional building blocks provide a favorable platform for the selective separation of Pb(II). Herein, the bifunctional SPAFs with the introduction of -OH and -SO3H were synthesized through rationally optimizing their steric hindrance. As a result, the SPAF-0.75 exhibits favorable adsorption capacity of Pb(II) (212.34 mg g-1), which is 22 times larger than pristine framework. Competition experiment indicates that SPAF-0.75 possess the selective removal of Pb(II) without interfering from co-existing metal ions. The removal rate of SPAF-0.75 still retain at 100% after six successive cycles. The DFT calculation illustrates that -OH and -SO3H are co-participate in the process of capturing Pb(II), revealing SPAF-0.75 preferred removal of Pb(II) owing to the lowest adsorption energy (ΔEab = -3.99 eV). This study extend the understanding of the structure-property relationship and facilitate new possibilities for PAFs.

Controlled synthesis of Fe3O4/MnO2 (3 1 0)/ZIF-67 composite with enhanced synergetic effects for the highly selective and efficient adsorption of Cu (II) from simulated copperplating effluents

This study designed a composite material with internal synergistic effects among multiple components to achieve highly selective adsorption of Cu (II). Through controlled synthesis, the Fe3O4/MnO2(3 1 0)/ZIF-67 composite was successfully fabricated, leading to significant improvement in adsorption selectivity, capacity, and adsorption rate. The experimental results showed that the composite is of outstanding selectivity in the adsorption of Cu (II), with a partition coefficient K of Cu (II) that was 2.2-5.3 times higher than that of other coexisting ions. Moreover, the composite exhibited a remarkable adsorption capacity of 1261.0 mg g-1 and a fast adsorption rate of 840.7 mg g-1 h-1 at 298 K. Additionally, its magnetic property facilitated easy separation from wastewater, thereby enhancing its potential for commercial applications. The synergetic effect mechanism was analyzed through characterizations and DFT calculations. Furthermore, the recyclability of the composite was investigated, which showed that after seven cycles, the adsorption efficiency remained at 85% of its initial efficiency. It can be concluded that Fe3O4/MnO2(3 1 0)/ZIF-67 has potential to address challenges posed by heavy metal pollution in copperplating effluents.

Screening of MnO2 with desired facet and its behavior in highly selective adsorption of aqueous Pb (II): Theoretical and experimental studies

In this study, Density Functional Theory (DFT) calculations and experimental methods were used to evaluate MnO₂ with 5 different facets for their selective adsorption of Pb (II) from wastewater containing Cd (II), Cu (II), Pb (II), and Zn (II). The DFT calculations were used to screen the selective adsorption capability of the facets and demonstrated that the MnO₂ (3 1 0) facet has an excellent performance in selective adsorption of Pb (II) among all facets. The validity of DFT calculations was verified by comparing with the experimental results. MnO₂ with different facets was prepared in a controlled manner and the characterizations confirmed that the lattice indices of the fabricated MnO₂ have the desired facets. Adsorption performance experiments illustrated a high adsorption capacity (320.0 mg/g) on the (3 1 0) facet MnO₂. The selectivity of adsorption of Pb (II) was 3-32 times greater than that of the other coexisting ions, i.e., Cd (II), Cu (II), and Zn (II)), which is consistent with results of the DFT calculations. Furthermore, DFT calculations of the adsorption energy, charge density difference, and projected density of states (PDOS) showed that the adsorption of Pb (II) on the MnO₂ (3 1 0) facet is non-activated chemisorption. This study shows that it is feasible to use DFT calculations to quickly screen suitable adsorbents for environmental applications.

Highly defective copper-based metal-organic frameworks for the efficient adsorption and detection of organophosphorus pesticides: An experimental and computational investigation

Organophosphorus pesticide (OP) residues pose a serious threat to human health, motivating the search for novel adsorbents and detection methods. Herein, defective copper-based metal organic frameworks (Cu-MOFs) were synthesized by the reaction of Cu²⁺ ions and 1,3,5-benzenetricarboxylate linkers in the presence of acetic acid. As the amount of acetic acid increased, the crystallization kinetics and morphology of the Cu-MOFs changed, leading to mesoporous Cu-MOFs with many large surface pores (defects). Adsorption studies of OPs revealed the defective Cu-MOFs showed faster pesticide adsorption kinetics and higher pesticide adsorption capacities. Density functional theory calculations showed that pesticide adsorption in the Cu-MOFs was mainly electrostatic. A dispersive solid phase extraction method was developed based on a defective Cu-MOF-6 for rapidly extracting pesticides from food samples. The method allowed pesticide detection over a wide linear concentration range, low limits of detection (0.0067-0.0164 µg L^-1) and good recoveries in pesticide-spiked samples (81.03-109.55%).

Equilibria of semi-volatile isothiazolinones between air and glass surfaces measured by gas chromatography and Raman spectroscopy

Trace amounts of semi-volatile organic compounds (SVOCs) of the two isothiazolinones of 2-methylisothiazol-3(2H)-one (MIT) and 2-octyl-4-isothiazolin-3-one (OIT) were detected both in the air and on glass surfaces. Equilibria of SVOCs between air and glass were examined by solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS). Surface to air distribution ratios of K_sa for MIT and OIT were determined to be 5.10 m and 281.74 m, respectively, suggesting more abundant MIT in the gas phase by a factor of ∼55. In addition, a facile method of silver nanocube (AgNC)-assisted surface-enhanced Raman scattering (SERS) has been developed for the rapid and sensitive detection of MIT and OIT on glass surfaces. According to MIT and OIT concentration-correlated SERS intensities of Raman peaks at ∼1585 cm^-1 and ∼1125 cm^-1, respectively. Their calibration curves have been obtained in the concentration ranges between 10^-3 to 10^-10 M and 10^-3 to 10^-11 M with their linearity of 0.9986 and 0.9989 for MIT and OIT, respectively. The limits of detection (LODs) of the two isothiazolinones were estimated at 10^-10 M, and 10^-11 M for MIT and OIT, respectively. Our results indicate that AgNC-assisted SERS spectra are a rapid and high-ultrasensitive method for the quantification of MIT and OIT in practical applications. The development of analytical methods and determination of the Ksa value obtained in this study can be applied to the prediction of the exposure to MIT and OIT from various chemical products and dynamic behaviors to assess human health risks in indoor environments.

Synthesis, evaluation of drug delivery potential, and the quantum chemical investigation on a molecular imprinted polymer for quetiapine antipsychotic; a joint experimental and density functional theory study

In this project, the quetiapine drug was used as the template for synthesis of a molecular imprinted polymer (MIP). The polymerization approach for preparation of this composite was precipitation, where methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), and 2,2-azobisissobutyronitrile (AIBN) were used as the functional monomer, the cross-linker, and the initiator, respectively. Scanning electron microscopy (SEM) showed that the diameter of the nanoparticles is about 70 nm. The adsorption rates of quetiapine to the MIP host were evaluated at different pHs, and the results showed that the highest adsorption values were obtained at pH = 7. Moreover, the kinetics of the adsorption process was detected to follow the Langmuir isotherm (R² = 0.9926) and the pseudo-second-order kinetics (R² = 0.9937). The results confirmed the high capability of the synthesized MIPs as pharmaceutical carriers for quetiapine. Furthermore, the kinetics of the drug release from the MIP follows the Higuchi model at the pHs of 5.8–6.8 and the Korsmeyer–Peppas model at the pHs of 1.2–5. Finally, in light of the density functional theory (DFT)-based quantum chemical descriptors, the polymer–quetiapine drug complex was designed and investigated. The results showed that there is a strong interaction between the host (polymer) and the guest (drug) due to several hydrogen bonds and other intermolecular (polar) interactions.

Adsorptive removal of sulfosalicylic acid from aqueous medium by iron(III)-loaded magnetic chitosan/graphene oxide

In this study, an iron(III)-loaded magnetic chitosan/graphene oxide composite (Fe-MCG) was synthesized and applied for the adsorptive removal of sulfosalicylic acid (SSA) in aqueous solution. The results obtained from the application of various characterization techniques such as scanning electron microscopy (SEM), vibrating-sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS) prove the successful formation of the composite with enhanced microstructure and superparamagnetic properties. The adsorption capacity of Fe-MCG towards SSA via batch mode reaches up to 135 mg/g at 293 K. The adsorption of SSA onto Fe-MCG is driven by monolayer adsorption with the chemical and physical adsorption processes both playing active roles. The Langmuir isotherm and pseudo-second-order kinetic models were observed to best describe the equilibrium adsorption and kinetic processes, respectively. The values obtained for the associated thermodynamic parameters confirm that the adsorptive process is spontaneous, exothermic and entropy-increasing. The efficacy and reusability of the spent Fe-MCG was studied using 0.01 mol/L NaOH solution. The kinetic process for the desorption of SSA from Fe-MCG is well described by the pseudo-second-order kinetic model. Based on the experimental results and XPS analysis, the underlying mechanisms for the uptake of SSA onto Fe-MCG involve electrostatic forces, complexation, π-π stacking, and hydrogen bonding. Overall, the excellent features of Fe-MCG enhance its potential as an adsorbent for the sequestration of SSA in environmental media.

Novel dual-template molecular imprinted electrochemical sensor for simultaneous detection of CA and TPH based on peanut twin-like NiFe2O4/CoFe2O4/NCDs nanospheres: Fabrication, application and DFT theoretical study

Hollow peanut-shaped NiFe₂O₄/CoFe₂O₄ twinned nano-spherical shell composite materials have interconnected electron channels and excellent electrochemical performance, which prompted the use of this unique spatial structure to fabricate efficient electrochemical sensors. In this work, N-doped carbon dots (NCDs) incorporated into magnetic NiFe₂O₄/CoFe₂O₄ nanoparticle shell (NiFe₂O₄/CoFe₂O₄/NCDs) modified glassy carbon electrode (GCE) was applied to construct a dual-template molecularly imprinted polymer (MIP) based electrochemistry sensor (NiFe₂O₄/CoFe₂O₄/NCDs/MIP/GCE) for the simultaneous detection of catechin (CA) and theophylline (TPH). MIP was fabricated by an in-situ electrochemical polymerization strategy based on the theoretical exploration and density functional theory (DFT) computer directional simulation to screen out the optimal functional monomer (L-arginine) and the optimal ratio between the dual template molecules (CA and TPH) and functional monomer. The materials were characterized by SEM, TEM, XRD, XPS, and TGA. Besides, electron binding energy, binding constant, and imprinting factor were investigated. With the optimal conditions, the proposed electrochemical dual detection system showed outstanding analytical performance for the simultaneous sensing of CA and TPH, with an ultralow detection limit (LOD, S/N = 3) of 1.3 nM for CA in 0.01-1 μM (R² = 0.9956) and 1-50 μM (R² = 0.9928), as well as a LOD of 20.0 nM for TPH in the linear range of 0.1-100 μM (R² = 0.9939), respectively. Also, the selectivity and anti-interference performances of the fabricated sensor were performed by differential pulse voltammetry and chronoamperometry, and successfully detected the analyte from tea drinks and human urine samples with the recovery rates ranging from 98.22% to 104.76% and relative standard deviations (RSD) were 1.19%-3.81%, demonstrated the sensor has excellent stability, repeatability, and reproducibility, which paves the way for other platforms to use this nanomaterial for the detection of antioxidant in the filed food safety.