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[Display omitted] In the adsorption process of functionalized layered double hydroxide (LDH) to target pollutants it, is essential to investigate the role of functional groups. In this work, 2‑mercaptoethane sulfonic acid (MS) was used as an intercalation modifier to prepare functionalized NiFe-LDH by solvothermal method. The interfacial interaction between the functional groups and the NiFe-LDH surface was studied via molecular dynamics simulation. During the intercalation process, the more negatively charged sulfonic acid group tends to self-assemble electrostatically with the LDH laminate, while the sulfhydryl group is involved in complexing heavy metal ions. The adsorption experiments showed that the adsorption performance of the adsorbent for the three ions of Cd2+, Mn2+, and Co2+ at 298.15 K was 266.16 mg/g, 175.60 mg/g, and 106.56 mg/g, respectively, which were 10 times, 8.7 times, and 4.9 times higher than that of unmodified NiFe-LDH. Meanwhile, Multiwfn wavefunction analysis combined Visual Molecular Dynamics (VMD) was applied to analyze and visualize the reaction active sites & the interactions between MS and NiFe-LDH, and the complexation of the functional group of MS with metal ions, to insight the role of the functional groups in MS molecule, and to reveal the cause that the adsorption capacity of modified NiFe-LDH for heavy metals greatly improves from the view of atoms. [ABSTRACT FROM AUTHOR]

Previous researches investigated the adsorption properties and mechanism of clay minerals on antibiotic pharmaceuticals and personal care products (PPCPs) via batch adsorption experiments and X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) characterization, but many PPCPs exhibit different ionization states under different pH conditions; the research on the microscopic mechanism of different ionized PPCPs species adsorbed by clay minerals is very scarce. In this work, as a typical PPCPs contaminant, the common tetracycline (TC) was chosen as the study target; the adsorption micro mechanism of montmorillonite (MMT) on different TC species in aqueous solution was explored in details. Especially outstanding, for the first time, with the help of Multiwfn wavefunction program, quantitative analysis of molecular surface analysis and basin analysis were applied to quantitatively investigate the electrostatic interaction between MMT and different TC species, the possible positions of lone pair electrons. Independent gradient model (IGM) analysis and Hirshfeld surface analysis including local surface analysis were integrated to visualize the binding sites, interaction types, and relative strength between MMT and TC+/− or TC+/2− species, which can insight into the interaction essence from the microscopic perspective at the atomic level. [ABSTRACT FROM AUTHOR]

Abstract Herein, we reported the adsorption and desorption of Pb(II) on l -lysine modified montmorillonite (L-Mt) with molecular dynamics simulation. l -lysine (Lys) modified montmorillonite (L-Mt) was prepared, characterized by various analytical techniques, and the simulation studies were performed to evaluate the interlayer structure and interaction properties of l -lysine and L-Mt. The results of X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectrum suggested that Lys+ was intercalated into the interlayer of Na-montmorillonite (Na Mt) successfully. The batch adsorption experiments were implemented to study the adsorption capacity of Pb(II) on L-Mt in water. The maximum adsorption capacity of Pb(II) on the L-Mt (up to 43.3 mmol/100 g) were considerably higher than that on Na Mt (up to 15.3 mmol/100 g), at room temperature. The adsorption isotherms of both, L-Mt and Na Mt can fit the Langmuir isotherm. The adsorption experiments showed that Pb(II) removal efficiency of L-Mt is better than Na Mt in acidic solution. The simulation results revealed the micro-mechanism of Lys+ inserted into the interlayer gallery of Na Mt. It can be deduced that lysine interacted with montmorillonite surface mainly through the protonated side-chain amino group rather than through the protonated main-chain amino group or deprotonated carboxyl group. These consequences are expected to elucidate the adsorption mechanisms occurring at the water/clay minerals interface at atom level, providing significant insight into the adsorption and retention of Pb(II) on L-Mt composite, and lead to relevant engineering applications while treating heavy metals of wastewater. Graphical abstract Unlabelled Image Highlights • l -lysine modified montmorillonite (L-Mt) has higher adsorption capacity for Pb(II) than Na Mt. Their maximum adsorption capacity is 43.3 mmol/100 g and 15.3 mmol/100 g, respectively. • L-Mt is more efficient on the retention of Pb(II) than Na Mt. When pH 3.0, the desorption ratio of Pb(II) is 16.08% and 58.31%, respectively. • The microstructure and interaction between lysine and Na Mt has been revealed by molecular dynamic simulation. [ABSTRACT FROM AUTHOR]

Amino trimethylposphonate(ATMP) functionalized HAP were synthesized with different ATMP addition (0, 5%, 10%, 15%) and the adsorption performance towards Pb2+ and Cd2+ were studied in an aqueous solution. Under the optimum condition, HAP with ATMP addition of 10% (10AT-HAP) displayed the most efficient adsorption performance with the adsorption capacity of 1458.79 mg/g and 321.26 mg/g towards Pb2+ and Cd2+, respectively, which improved 76% and 92% than that of the artificially prepared HAP in the laboratory, respectively. For both heavy metal ions, the adsorption mechanism also included ion exchange and surface complexation, in which the surface complexation played a predominant role. In addition, XRD showed that a new crystal phase was formed after Pb2+ adsorption, while no new phase appeared after Cd2+ adsorption, indicating that the adsorption mechanism of Pb2+ involved dissolution-precipitation. The fitting results of adsorption isotherm and kinetics showed that the adsorption of Pb2+ and Cd2+ on HAP and 10AT-HAP were well fitted by the Langmuir isotherm model and Pseudo-second model. Moreover, Multiwfn wavefunction program based on density functional theory (DFT) was applied to deeply probe and vividly visualize the interaction sites, interaction types, interaction strength and the essence of interactions between HAP and ATMP or ATMP-HAP composite and heavy metal ions. [Display omitted] • The adsorption capacity of 10AT-HAP on Pb2+ and Cd2+ reached 1458.79 and 321.26 mg/g. • The adsorption mechanisms were revealed by experiment and Multiwfn program. • ATMP formed ternary complex with HAP and heavy metal ions. • The oxygen atoms of the phosphate groups of ATMP played a major complexation role. [ABSTRACT FROM AUTHOR]

Two gemini surfactants propylbis (dodecyldimethyl) ammonium chloride (12−3−12) and propylbis (octadecyldimethyl) ammonium chloride (18–3-18) with different chain lengths were used to modify Ca- montmorillonite (Ca-Mt). XRD results showed that the arrangement of surfactants was mainly paraffin-type and with additional minor lateral-bilayer in the interlayer space of montmorillonite. Batch adsorption tests indicated that the modified organo-montmorillonite (G 12 -Mt and G 18 -Mt) had better removal effect on three benzotriazole emerging contaminants (ECs) than that of original Ca-Mt, and the sequence of adsorption capacity was 1-Hydroxybenzotriazole (OHBTA) > benzotriazole (BTA) >5-methylbenzotriazole (TTA). Molecular dynamics simulation was carried out to reveal the arrangement, conformation and behavior of Gemini surfactants in the interlayer of Mt. at atomic level. The results suggested that one of the two long alkyl chains was erected in a paraffin-type arrangement, the other long alkyl chain accompanying with the positively charged N head groups & the propyl spacer were parallel to the Mt. (001) plane and was fixed near the top and bottom surfaces with the arrangement of lateral-bilayer, which was agreement with the XRD data. BTA molecules located at the aggregate organic phase formed by the alkyl chain, while Cl− ions preferred to appear in the middle area of the interlayer of montmorillonite. Meanwhile, Multiwfn wavefunction program was applied to quantitatively analysis the molecular surface area in different electrostatic potential (ESP) intervals, the ESP minimum & maximum values on the three ECs molecular vdW surface, integrating with color-filled ESP planar maps and VMD program to insight the electrostatic interaction and magnitude order between Gemini surfactants modified Ca-Mt and three pollutants. The adsorption mechanisms of Gemini surfactants modified Mt. to three benzotriazole emerging contaminants involved electrostatic interaction and hydrophobic partitioning effect. [Display omitted] • ESP distribution was used to quantitatively assess the electrostatic interaction. • MD simulation was used to reveal the dynamics of interlayer species. • The adsorption effects of different gemini surfactants modified Mts were compared. • The adsorption micromechanisms were uncovered. [ABSTRACT FROM AUTHOR]

The corresponding adsorption mechanism of the adsorbent in the process of adsorbing phosphate. As shown, three adsorption mechanisms of the adsorbent in the process of adsorbing phosphate: 1: The combination of PO 4 3− and La3+ produces LaPO 4 with smaller Ksp. 2: H 2 PO 4 − and HPO 4 2− enters the interlayer through a substitution reaction with OH− between the LDH layers to realize the adsorption of phosphate. 3: The electrostatic mutual attraction between quercetin and phosphate realizes the adsorption of phosphate. [Display omitted] Severe water eutrophication due to large releases of phosphorus has become a worldwide environmental problem. Adsorption active sites is less of traditional adsorbents in the phosphorus removal process resulting in low removal efficiency, so the new high-efficiency phosphorus removal adsorbents become an effective way to solve the problem. In this work, quercetin modified MnFe layered double hydrotalcite three-dimensional composites structures encapsulated by lanthanum (La(III)) nanoparticles (QLa@MnFe-LDH) were successfully prepared by a classical hydrothermal method. The results of the adsorption experiments show that La(III) nanosphere-encapsulated MnFe-LDH provides a more adequate binding site for phosphate adsorption. The adsorption performance of QLa@MnFe-LDH for phosphate was outstanding, the maximum adsorption capacity was 346.5 mg/g at 298.15 K, which was 300 % higher than that of MnFe-LDH. Moreover, QLa@MnFe-LDH retained its high adsorption capacity (>315.5 mg/g) over a wide range of pH (4.0 ∼ 7.0). The active sites of the reactions were predicted by Multiwfn and Visual Molecular Dynamics (VMD), and novel visualization studies of weak interactions were applied to theoretical studies. The modified MnFe-LDH encapsulated by La nanospheres has a strong adsorption capacity for phosphate adsorption. Therefore, the modified QLa@MnFe-LDH was expected to become an effective adsorption material for phosphorus removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel ampholytic surfactant was firstly used to modify acidified Na-Mt. • Cationic panthenol modified Na-AMt had a higher adsorption capacity to two pollutants. • The arrangement of different components in the interlayer of Mt was revealed. • The bonding characteristics and dynamic behavior of different species were explored. • The electrostatic interaction and hydrophobic partitioning were demonstrated. A novel ampholytic surfactant (cationic panthenol, CP) modified montmorillonite (CPMMt) was firstly prepared and investigated its removal effect and mechanism for a class of emerging pollutants such as benzothiazole (BTH) and 2-hydroxybenzothiazole (2-OH-BTH) in water. Batch experiments were conducted to probe the effects of various conditions on the adsorption. The results showed CPMMt-1.0 had greater adsorption performance for BTH and 2-OH-BTH than Na-AMt (acidified Na-Mt), and the maximum equilibrium adsorption capacities of CPMMt-1.0 for BTH and 2-OH-BTH were three times that of Na-AMt. Zeta potential analysis, the effect experiments of solution pH combined with Multiwfn wave function program were carried out to inspect the electrostatic interaction. Furthermore, molecular dynamics simulation was applied to investigate the dynamics behavior of cationic panthenol (CP) and BTH or 2-OH-BTH in the interlamellar of montmorillonite. The results demonstrated that CP molecules presented a lateral bilayer structure, which was in good agreement with XRD experimental data, and the interaction between BTH and the surface of montmorillonite was stronger than that of 2-OH-BTH, which implies that the CPMMt-1.0 had better adsorption performance for BTH than 2-OH-BTH, which was consistent with the experimental results. The adsorption mechanism involved electrostatic interaction and hydrophobic partitioning. [ABSTRACT FROM AUTHOR]

Benzyldimethylhexadecylammonium chloride (HDBAC) modified montmorillonite was synthesized and the compounds were used for the adsorption of diclofenac sodium (DCF) and ibuprofen (IBU). The adsorption effect was the best when the best dosage of the HDBAC was 1.6 CEC (cation exchange capacity). The adsorption capacity (q e) of H-Mt-1.6 for DCF and IBU was 125.55 mg/g and 81.64 mg/g, respectively. The q e of Ca-Mt for DCF and IBU was 54.02 mg/g and 13.14 mg/g, respectively. H-Mt-1.6 had higher adsorption effect than Ca-Mt. The adsorption process of H-Mt-1.6 on DCF followed the Langmuir adsorption model and the adsorption process of IBU followed the Freundlich adsorption model. The equilibrium could be reached after 120 min. The adsorption process of H-Mt-1.6 on DCF and IBU followed a pseudo-second-order kinetic model. The adsorption on DCF was endothermic, while adsorption on IBU was exothermic. [Display omitted] [ABSTRACT FROM AUTHOR]

• Montmorillonite was modified with green and environment-friendly Histidine salt. • His-Mt is proved to be a high-efficiency adsorbent for removal of heavy metal ions. • Maximum adsorption capacity for Pb(II) and Cu(II) with His-Mt is 107.73 mg/g and 30.72 mg/g. • Ion exchange is main mechanism by Na-Mt by forming Pb(CO 3) 2 or Cu(OH) 2. A novel nanocomposite of sodium montmorillonite with L-Histidine (His-Mt), was prepared to remove Pb(II) and Cu(II) from aqueous media. The resulting nanocomposites were characterized by XRD, FT-IR, BET, SEM, TG/DTG, XPS techniques. All characterizations confirmed the anchoring of L-Histidine to Na-Mt, and the packing sequence of His in the interlayer gallery may form a monolayer structure. The His salt obtained a skewed orientation compared to the silicate surface. The single/ co-adsorption of Cu(II) and Pb(II) by pure and modified i.e. Na-Mt and His-Mt were carried out by batch adsorption experiments. The maximum adsorption capacity (q max) of Pb(II) and Cu(II) by Na-Mt and modified His-Mt was 89.08 mg/g, 23.93 mg/g, and 107.73 mg/g, 30.72 mg/g, correspondingly. The pseudo-second-order model (kinetic model) and Langmuir model (isotherm model) well-matched with the adsorption process. The data analysis showed it was an endothermic, favorable and spontaneous process, Cu(II) and Pb(II) showed competitive adsorption in the co-adsorption system. Na-Mt adsorbed M(II) ions by ion exchange mechanism, while M(II) formed complexes with histidine and were adsorbed in the interlayer region or the surface of His-Mt. [ABSTRACT FROM AUTHOR]

• A green and environment-friendly modifier was used to prepare Met-Mt. • The mechanism of adsorption by Met-Mt was studied by ESP and ALIE analysis. • Met-Mt exhibits excellent performance for removal of Pb2+. A novel and platelike nanomaterial of methionine-montmorillonite composite was successfully prepared and applied to the adsorption of lead ions in aqueous. The application of a series of characterization methods, such as XRD, FT-IR, BET, TG/DTG, SEM revealed the morphology, structure and physicochemical properties of the nanocomposites and confirmed the anchoring effect of methionine on Na-Mt. Furthermore, it has been demonstrated that the filling arrangement of methionine in the interlayer channel can be oriented along the y-axis or the z-axis or inclined to the silicate surface to form a single layer structure. Under optimized experimental conditions, Met-Mt-0.8 composites were verified to be the most effective adsorbent for Pb2+ ion along with a maximum adsorption capacity of 117.79 mg/g, significantly higher than that of Na-Mt (101.11 mg/g). Gaussian program and Multiwfn program were united to take a sight on the microscopic adsorption mechanism of Met-Mt and Pb2+, concluding that methionine formed a complex with lead ions and facilitated them to lock in the montmorillonite layer. Moreover, methionine is ligated with Pb2+ by oxygen atom on C-OH in the carboxyl group. [ABSTRACT FROM AUTHOR]

Sodium lignosulfonate (Na-LS) was used to modified montmorillonite to form lignosulfonate-montmorillonite (LS-MMT). The as-prepared samples were characterized by various equipment to analyze the surface morphology and structure of the pure and reformed samples. The adsorption capability (q e , mg/g) of LS-MMT or Ca/Na-MMT for Pb(II) and Cu(II) at different reaction intervals, the concentration of metal ions, temperature, and pH were studied by batch adsorption experiments. The results revealed that LS-MMT displayed a higher adsorption capacity than Ca/Na-MMT. The pH of solutions had a great influence on the q e of the two adsorbents, and the q e was slightly enhanced with temperature increasing. The isotherm and kinetic experiments studies indicated that the adsorption of heavy metal on LS-MMT or Ca/Na-MMT fit well with the Langmuir model and pseudo-second-order kinetic model. The competitive adsorption showed that LS-MMT had a stronger affinity for Pb(II) than Cu(II), which was different from Ca/Na-MMT. Additionally, the desorption experiment showed that LS-MMT had a stronger ability to lock heavy metal ions than Ca/Na-MMT in an acidic environment with pH ranging from 3 to 5. Unlabelled Image • Lignin is a non-toxic natural polymer comprising many functional groups, i.e. carboxy, phenol, hydroxyl and methoxy groups. • The results revealed that LS-MMT displayed a higher adsorption capacity than Ca/Na-MMT. • The isotherm and kinetic experiments fit well with the Langmuir model and pseudo-second-order kinetic model. • The competitive adsorption showed that LS-MMT had a stronger affinity to Pb(II) than Cu(II). • LS-MMT had a stronger ability to lock heavy metal ions in an acidic environment with a pH range from 3 to 5. [ABSTRACT FROM AUTHOR]

[Display omitted] The tunable porous structure of metal organic frameworks (MOFs) plays a crucial role in determining their adsorption performance. In this study, we developed and employed a strategy involving monocarboxylic acid assistance to synthesize a series of zirconium-based MOFs (UiO-66-F 4) for the removal of aqueous phthalic acid esters (PAEs). The adsorption mechanisms were investigated by combining batch experiments, characterization and theoretical simulation. By adjusting the affecting factors (i.e., initial concentration, pH values, temperature, contact time and interfering substance), the adsorption behavior was confirmed as a spontaneous and exothermic chemisorption process. The Langmuir model provided a good fit, and the maximum expected adsorption capacity of di- n -butyl phthalate (DnBP) on UiO-66-F 4 (PA) was calculated to be 530.42 mg·g−1. Besides, through carrying out the molecular dynamics (MD) simulation, the multistage adsorption process in the form of DnBP clusters was revealed on a microcosmic scale. The independent gradient model (IGM) method showed the types of weak interactions of inter-fragments or between DnBP and UiO-66-F 4. Furthermore, the synthesized UiO-66-F 4 displayed excellent removal efficiency (>96 % after 5 cycles), satisfactory chemical stability and reusability in the regeneration process. Hence, the modulated UiO-66-F 4 will be regarded as a promising adsorbent for PAEs separation. This work will provide referential significance in tunable MOFs development and actual applications of PAEs removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • "Pre-embedded seed then growth" ensures the stability of the adsorbent structure. • Co-doping of dual-functional components exhibits effective synergistic adsorption. • Theoretical calculations of ligand exchange and hydrogen bonding mechanisms. • Adsorbents that degrade after adsorbing phosphates have fertilizer effect. • Proposing a closed-loop design from waste utilization to treatment and final reuse. Recovering and reusing of phosphorus (P) in wastewater is the optimal solution to address mineral shortages and eutrophication. Here, the layered double hydroxides (LDHs) grown on wood-derived aerogels (WAs) were prepared after screening the powdered precursors and named La/MgFe-LDH(LS)@WAs. The intricate pore structure and surface morphology of the WAs formed a fibrous network with ultra-low density, good strength and elasticity, allowing for uniform loading. The sample exhibited excellent adsorption capacity of 139.5 mg P/g at pH 4.0, and over 100.0 mg P/g within a wide pH range (3.0–8.0). Thomas and Yoon-Nelson models could effectively describe the dynamic adsorption process. Microscopic morphology and textural characteristics of the samples were characterized and molecular dynamics (MD) simulations and theoretical calculations based on density functional theory (DFT) were used to study the interaction mechanisms. The coordination bonds and weak interactions between the active component LS and La(OH) 3 with phosphates were characterized using interaction region indicator (IRI) and independent gradient model based on Hirshfeld molecular density partitioning (IGMH) methods. The atomic δg index mapped to the molecular structure vividly illustrated the maximum contribution of hydroxyl hydrogen to phosphate deprotonation oxygen in inter-fragment interactions on LS. Combining the formation of Me-O-P bonds characterized by X-ray photoelectron spectroscopy (XPS), the mechanism involves weak interactions (hydrogen bond) and chemical adsorption via ligand exchange. High removal efficiency was demonstrated in real wastewater. A method for waste reuse was also proposed. Plant cultivation experiments showed that La/MgFe-LDH(LS)@WAs could sustain wheat growth with slowly degrade and maintain high phosphate availability. The composite shows potential for water restoration, waste treatment, and value-added conversion in the production of controlled-release fertilizers. [ABSTRACT FROM AUTHOR]

Many studies have proved that montmorillonite (Mt) has good adsorption properties for some antibiotic pharmaceuticals, but the detailed research on the microscopic sorption mechanism is very limited from the atomic level. In the present work, Mt was chosen as an adsorbent for common emerging contaminant-ciprofloxacin (CIP) to investigate the essence of the interaction between Mt and different CIP species at different pH. X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR) characterization after adsorption under different pH were utilized to explore the difference of adsorption mechanism with the changed pH. Especially outstanding, for the first time, Molecular dynamics simulation (MD) was carried out to investigate the arrangement and dynamic behavior of cationic CIP in the interlayer of Mt, Multiwfn wave function analysis program was performed to quantitatively analyze the molecular surface electrostatic potential (ESP) distribution of different CIP species to evaluate the electrostatic interaction. Furthermore, for the first time, Hirshfeld surface analysis and independent gradient model (IGM) analysis were applied to probe and visualize the interaction sits between Mt and CIP zwitterion(CIP+/−) or CIP anion (CIP-), which can reveal the adsorption mechanism of Mt for CIP+/− and CIP- from the atomic level microscopic perspective. [ABSTRACT FROM AUTHOR]

• Ternary core-shell CS@PANI@LDH composite was synthesized and characterized. • The maximum adsorption capacity of CS@PANI@LDH was 618.16 mg/g for DCF. • Multiwfn, Chimera, VMD, and IGM were combined to reveal the adsorption mechanism. • Deduced binding mechanism was electrostatic, hydrogen bonding, and π–π interaction. The efficient removal of Diclofenac sodium (DCF), a nonsteroidal anti-inflammatory drug, has attracted more and more attention. In this work, ternary core-shell CS@PANI@LDH composite was synthesized via the in-situ growth of Mg/Al layered double hydroxide plates onto polyaniline-wrapped carbon sphere and applied for DCF removal. Various influence factors like concentration, pH, time, temperature, and background electrolytes were systematically investigated. The maximum adsorption capacity was 618.16 mg/g. Besides, after 5 regeneration cycles, CS@PANI@LDH still retained high adsorption capacity. The adsorption mechanism was investigated by Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) characterization analyses. Simultaneously, the Multiwfn program combined the Chimera program was applied to calculate and visualize the localized orbit locator (LOL) of π electrons in DCF− molecule, which explored the π electronic structure and conjugation characteristics of DCF− molecule. Moreover, the Independent Gradient Model (IGM) analysis based on pro-molecular density revealed the interaction sites and interaction strength between DCF and LDH. The adsorption mechanism could be explained through electrostatic interaction and hydrogen bonding between LDH and DCF, π-π interaction between DCF and PANI. It was the synergistic effects of different interactions that improved the adsorption of DCF by CS@PANI@LDH composite. [ABSTRACT FROM AUTHOR]

The carboxymethyl-chitosan-montmorillonite (CMC-MMT) organic-inorganic hybrid material was applied to adsorb Pb(II) and Congo red (CR) anionic dye from aqueous solution. Molecular dynamics(MD) simulation was carried out to reveal the mechanism of CMC hybrid MMT. The results suggested that CMC has been adsorbed on the interlayer space and surface of MMT, hydrogen bonds had been formed between hydroxyl & carboxyl groups of CMC with the surface of MMT, Van der Waals interaction was also existed, while amino groups of CMC hadn't obvious interaction with the surface of MMT. Batch experiments were executed to investigate the adsorption effect of CMC-MMT was compared with Na-MMT and CMC. The results showed that CMC-MMT exhibited the higher adsorption capacity than Na-MMT and CMC, The OH and COOH or NH 2 groups of CMC chains may serve as electrostatic interaction active sites and coordination sites, which improved the adsorption performance of CMC-MMT on Pb(II)，and the insertion of CMC enlarged the inter-layer space of MMT, resulting in more surface active sites in the CMC-MMT hybrid composite, which increased the adsorption of organic pollutant CR. The kinetic and isotherm studies indicated that the pseudo-second-order and the Langmuir model well described the adsorption equilibrium of Pb(II) and CR on CMC-MMT. Unlabelled Image • Molecular dynamics (MD) simulation was carried out to reveal the mechanism of carboxymethyl chitosan (CMC) hybrid montmorillonite (MMT). • The hydroxyl groups of CMC molecules interacted most strongly with MMT by hydrogen bond and van der Waals forces, the carboxyl groups had a weak hydrogen bond with the surface of MMT, and the effect of the amino groups was not obvious. • CMC-MMT organic-inorganic hybrid composite exhibited the higher adsorption capacity on Pb(II) and Congo Red (CR) than Na-MMT and CMC alone. • The insertion of CMC enlarged the inter-layer space of MMT, resulting in more surface active sites in the CMC-MMT hybrid composite, which increased the adsorption of organic pollutant CR. • The OH and COOH or NH2 groups of CMC chains may serve as electrostatic interaction active sites and coordination sites, which improved the adsorption performance of CMC-MMT on Pb(II) [ABSTRACT FROM AUTHOR]

Polyaniline (PANi)-clay hybrids are an important class of materials in the field of catalysis and adsorption. Owing to their unique structural properties such as self-assembly with functional materials, intercalation and surface functionalization, they have demonstrated to be more efficient candidates for environmental remediation than clay or polyaniline taken separately. Here, we report on the synthesis of phytic acid-doped PANI@montmorillonite (P-PANi@Mt) composite material via radical polymerization by varying the amount of Mt in the composite material. The formation of functional groups is detected by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and Raman analysis, which is consistent with the anchoring of phytic acid into PANi chains. Furthermore, the BET measurements revealed that the incorporation of Mt reduced the specific surface area of P-PANi-Mt hybrid due to the coating of Mt surface by P-PANi. The obtained materials were assessed for their capacity to adsorb copper (II) ions in aqueous media. Under optimized experimental conditions, P-PANi and P-PANi@Mt1 composites were found to be the most effective materials for Cu2+ ion capture with adsorption capacities of 66.6 mg g−1 and 87 mg g−1, respectively. By increasing the amount of montmorillonite in the composite, the adsorption capacity decreased substantially. This result could be explained by the tendency of clay particles to aggregate in the PANi matrix and therefore hinder the availability of active sites. The adsorption isotherm processes fit well with the Langmuir model and the enhanced adsorption process was ascribed to the existence of plenty of phosphoric acid groups doped to PANi-coated on Mt layers. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel adsorbent of UiO-66-NH 2 @Mg(OH) 2 was prepared and characterized. • The adsorption capacity was improved significantly after modification. • Adsorption behavior and mechanism of phosphate on UNM were explored. • Multiwfn wave function methods were applied to interpret the adsorption mechanisms. • Phosphate was successfully recovered by the struvite-based method. Two serious challenges of water eutrophication and phosphorus resources exhaustion make the P recovery imperative. In this work, a novel phosphate adsorbent UiO-66-NH 2 @Mg(OH) 2 (UNM) has been synthesized by the in-situ growth of magnesium hydroxide nanosheets around UiO-66-NH 2. The batch adsorption experiments were carried out by controlling the single variate (such as pH, initial concentration, contact time, temperature and interfering anions) to explore the adsorption behaviors. And the adsorption dynamics and isotherms fit well with the pseudo-second-order (PSO) and Langmuir models, combined with the thermodynamics results, indicating a spontaneous and endothermic monolayer chemisorption process. Besides, the maximum phosphate adsorption capacity of UNM was calculated as 408.07 mg/g (≈130.39 mg P/g) at pH = 6.0, T = 298 K. A series of characterizations (XRD, FT-IR, SEM, EDS, BET, TGA, XPS, ICP-MS et. al) and quantum chemical analysis methods (ESP, ALIE and Hirshfeld surface) was applied to predict the reactive sites. The possible mechanism can be deduced as two continuous steps: the physical attraction by weak interactions and the chemical adsorption with an ion-exchange mechanism. The UNM also presented high removal efficiency in the environmental water samples and showed satisfactory reusability and excellent chemical stability in the recycling process. From the desorption effluents, we successfully recycled the struvite with 14.31% P content. Therefore, the UNM will be regarded as a promising phosphate adsorbent in practice and this work will provide inspiration and guidance for the design and preparation of high-efficiency P-removal adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defect content and particle size of MOF-808 can be tuned using iron nitrate. • The modulating MOF-808 can achieve effective removal and recovery of phosphate. • Adsorption mechanisms involve electrostatic attractions and ligand exchange. In this work, a facile and green method is applied to synthesize hydrophilic MOF-808(Zr) and modulate its defect content and particle size using different amounts of iron nitrate (denoted as F) to obtain serial XF-MOF-808 ("X" implied the dosage of used F). The development of additional adsorption sites and the fine-tune of pore and particle size based on MOF-808 significantly improved phosphate adsorption performance. In particular, the 0.5F-MOF-808 shows excellent adsorption capacity (305.5 mg/g) and rapid diffusion rate (37.51 mg/g·min0.5) for phosphate at 298 K and initial pH = 6.5, outperforming pristine MOF-808 and most previously reported adsorbents. 0.5F-MOF-808 possesses a wide pH tolerance, outstanding reusability and excellent selectivity for phosphate adsorption from simulated wastewater, verified in environmental implication and regeneration experiments. Phosphate loaded on the adsorbent can be converted to struvite for agricultural fertilizer via a simple crystallization process. Compared to MOF-808, the exceptional sorption performance of 0.5F-MOF-808 is supported by decreased internal diffusion limitation, enlarged pore size and the development of new adsorption sites, which can be proved by advanced characterizations and batch adsorption experiments. This work presents a promising modification strategy of MOF materials for phosphate adsorption and recovery. [ABSTRACT FROM AUTHOR]

• Adsorption mechanism is elucidated by experimental and theoretical methods. • The Interface FF is introduced into Forcite module to study adsorption behavior. • Adsorption sites in PBTC are revealed by quantitative analysis on vdW surface. • Adsorption interactions are vividly shown by IGM and Hirshfeld surface analyses. • Hydrogen bond interaction may be the main force for the adsorption process. Two clay minerals, kaolinite (Kaol) and montmorillonite (Mt) with different crystal structures were chosen to investigate the comparative adsorption of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) through batch control experiments and theoretical studies. The systematical isotherm and kinetic studies agreed with Langmuir model and pseudo-second-order model, confirming a monolayer and chemisorption interaction process, respectively. The maximum removal capacities of Kaol and Mt for PBTC were 72.297 mg/g and 121.163 mg/g at pH=3.0 and T=298 K, respectively. Furthermore, the adsorption mechanisms were investigated by molecular dynamic (MD) simulations and density functional theory (DFT). The Interface force field (IFF) was firstly introduced into Materials Studio package to explore the microscopic mechanism of clay mineral interface. The dynamics behaviors verified that the oxygen (O) atom of carboxyl group has stronger affinity at the external surface of Mt, which consistent with the experimental data well. For DFT calculations, quantitative analysis around molecular van der Waals (vdW) surface was adopted to predict reactive sites for the electrophilic reaction. Independent Gradient Model (IGM) and Hirshfeld surface analyses in Multiwfn indicated that the high adsorption effect mainly attributes to hydrogen bond action. These findings improve our ability to explore the related properties occurring at the interface of different clay minerals. [ABSTRACT FROM AUTHOR]