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[Display omitted] The high binding affinity of iron(oxyhydr)oxides for phosphate has recently been used in medicine to treat hyperphosphatemia, an abnormally elevated phosphate concentration in the blood. For iron(oxyhydr)oxide nanoparticles, the composition of the organic shell has a more significant influence on their interaction with phosphate than is often assumed. This study shows different mechanisms in phosphate binding, using the example of two similar new phosphate-binding agents. We characterized the phosphate-binding behavior of two iron(oxyhydr)oxide-based nanomaterials with similar composition and particle properties and investigated their binding mechanisms by spectroscopic methods. For the often prescribed Velphoro, we demonstrated a phosphate binding capacity of>210 mg/g. A similar active ingredient named C–PAM binds over 573 mg/g. Spectroscopic measurements highlighted differences in the binding mechanism. While Velphoro binds phosphate via surface complexation independent of pH and adsorbent concentration, C–PAM shows a strong concentration dependence. At low concentrations, phosphate is bound via complexation reactions. The iron(oxyhydr)oxide structure was dissolved at higher phosphate concentrations and formed various iron phosphate species. The substances behave differently upon interaction with phosphate, although being very similar in composition and crystal structure. Thus, we demonstrated a crucial influence of the ligands in the shell on the binding mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] Nanoscale zero-valent iron (nZVI)-based composites have been widely utilized in environmental cleanup due to their low cost, high adsorption performance and strong redox activity. Herein, removal mechanism of U(VI) on nZVI/clay composites was demonstrated by batch, XPS and modeling techniques. The batch experiments showed that nZVI/clay composites exhibited the high removal capacity (88.90 mg/g at pH 4.0) and good regeneration towards U(VI) from aqueous solution. The adsorbed U(VI) was mostly reduced to U(IV) by nZVI/clay composites according to XPS analysis. The removal process of U(VI) on nZVI/clay composites was satisfactorily fitted by surface complexation modeling using strong and weak sites, indicating the high chemisorption of U(VI) on nZVI/clay composites. However, the fitting results underestimated U(VI) adsorption at pH 7.0–9.0 due to the reduction of U(VI) into U(IV), whereas the overestimation of U(VI) at pH 4.0–6.0 could be attributed to fewer surface complexation reaction involved. These findings are crucial for the application of nZVI-based composites for the highly efficient removal of radionuclides in actual environmental remediation. [ABSTRACT FROM AUTHOR]

The material with high adsorption capacity and selectivity is essential for recovering rare earth elements (REE S) from ammonium (NH 4 +-N)-rich wastewater. Although the emerging metal-organic framework (MOF) has gained intensive attention in REE S recovery, there are scientific difficulties unsolved regarding restricted adsorption capacity and selectivity, hindering its extensive engineering applications. In this work, a diethylenetriamine pentaacetic (DTPA)-modified MOF material (MIL-101(Cr)-NH-DTPA) was prepared through an amidation reaction. The MIL-101(Cr)-NH-DTPA showed enhanced adsorption capacity for La(III) (69.78 mg g−1), Eu(III) (103.01 mg g−1) and Er(III) (83.41 mg g−1). The adsorption isotherm and physical chemistry of materials indicated that the adsorption of REEs with MIL-101(Cr)-NH-DTPA was achieved via complexation instead of electrostatic adsorption. Such complexation reaction was principally governed by -COOH instead of -NH 2 or -NO 2. Meanwhile, the resulting material remained in its superior activity even after five cycles. Such a constructed adsorbent also exhibited excellent selective adsorption activity for La(III), Eu(III), and Er(III), with removal efficiency reaching 70% in NH 4 +-N concentrations ranging from 100 to 1500 mg L−1. This work offers underlying guidelines for exploitation an adsorbent for REEs recovery from wastewater. • A DTPA modified MIL-101(Cr)-NH 2 adsorbent was prepared through amidation reaction. • The adsorption of REEs was principally governed by -COOH instead of -NH 2 or -NO 2. • The -COOH was a bifunctional group for chelating REEs and reducing surface charge. • The resulting material could selectively recover REEs from ammonium-rich wastewater. [ABSTRACT FROM AUTHOR]

The removal of tetracycline antibiotics using adsorbents is becoming an environmentally friendly and cost-effective method. This study systematically analyzed the stability, structure, morphology, and chemical properties of various adsorbents. Batch adsorption experiments (pH, time, temperature, tetracycline concentration, and adsorbent dosage) were conducted to compare the adsorption capacity of the six adsorbents (biochar, activated carbon, montmorillonite, zeolite, chitosan, and polymerized aluminum chloride) for tetracycline removal. The results indicated that montmorillonite had the highest adsorption efficiency, followed by biochar, with chitosan showing the lowest efficiency. At an adsorbent dose of 25 g/L and an initial tetracycline concentration of 120 mg/L, the removal rates of tetracycline by montmorillonite, biochar, and chitosan were 97.6%, 69.3%, and 12.2%, respectively. Furthermore, the removal rate of tetracycline by biochar, following the response surface methodology optimal mode, increased by 5.5%. The Elovich model was better suited to explain the adsorption process of tetracycline compared to the conventional pseudo-first kinetic model and second-order kinetic model. The isothermal adsorption model suggested that both chemisorption and physisorption occurred in all removal processes, in which chemisorption dominated. Tetracycline was efficiently adsorbed through the combined effects of pore filling, electrostatic attraction, π-π interactions, and complexation reactions of surface functional groups. Additionally, montmorillonite demonstrated superior performance as an adsorbent for tetracycline removal from swine wastewater compared to the other adsorbents studied. [Display omitted] • A comparison of the adsorption capacity of adsorbents under laboratory conditions. • Montmorillonite exhibits a greater capacity for tetracycline. • Chemisorption was the main mechanism for the adsorption of tetracycline. • RSM can optimize adsorption parameters. • Adsorbents can efficiently remove tetracycline from swine wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel mathematical model combining kinetics and surface complexation reactions is developed. • Flowing water alters Si binding mechanisms onto α-FeOOH. • Si monomeric species occupy no more than ~ 22% of the reactive OH groups on goethite. • Surface oligomerization/polymerization is a rate-limited process in column. • Stepwise polymerization of silicate is crucial to adequately predicting the reactive transport of quinolones. Although silicates are the most common anions in aquatic systems, little is known on the roles they play on the transport of emerging contaminants, such as antibiotics. Using dynamic column experiments, we revealed the controls of Si loadings on goethite (α-FeOOH) coated sands on the transport of a widely used quinolone antibiotic, here focusing on Nalidixic Acid (NA). We find that dynamic flow-through conditions (Darcy velocities of 2.98 cm/h and 14.92 cm/h) sustain monomeric Si species with loadings of up to ~ 0.8 Si/nm2 but that oligomeric species can form at the goethite surfaces under static (batch, no-flow conditions). While these monomeric species occupy no more than ~ 22% of the reactive OH groups on goethite, they can effectively suppress NA binding, and therefore enhance NA mobility in dynamic conditions. NA can also bind on goethite when it is simultaneously injected with high concentrations of Si (2000 µM), yet it becomes progressively replaced by Si over time. Combining kinetics and surface complexation modeling, we present a new transport model to account for the stepwise polymerization of Si on goethite and NA transport. Our findings show that dissolved Si, common to natural surface waters, can play a determining role on the surface speciation and transport of antibiotics in the environment. [ABSTRACT FROM AUTHOR]

Zoogloea sp. MFQ7 achieved excellent denitrification of 91.71% at ferrous to manganous ratio (Fe/Mn) of 3:7, pH of 6.5, nitrate concentration of 25 mg L−1 and carbon to nitrogen ratio of 1.5. As the Fe/Mn ratio increasd, the efficiency of nitrate removal gradually decreased, indicating that strain MFQ7 had a higher affinity for Mn2+ than Fe2+. In situ generated biogenic Fe–Mn oxides (BFMO) contained many iron-manganese oxides (MnO 2 , Mn 3 O 4 , FeO(OH), Fe 2 O 3 , and Fe 3 O 4) as well as reactive functional groups, which play an significant part in tetracycline (TC) and cadmium (Cd2+) adsorption. The adsorption of TC and Cd2+ by BFMO can better fit the pseudo-second-order and Langmuir models. In addition, multiple characterization results of before and after adsorption indicated that the removal mechanism of BFMO on TC and Cd2+ was probably surface complexation adsorption and redox reactions. [Display omitted] • Strain MFQ7 exhibited excellent denitrification with ferrous and manganous. • Different ferrous to manganous ratios had a large effect on denitrification. • Bioprecipitation were mainly consist of MnO 2 , Mn 3 O 4 , FeO(OH), Fe 2 O 3 , and Fe 3 O 4. • The adsorption mechanism was probably surface complexation and redox reactions. [ABSTRACT FROM AUTHOR]

• Replacing MeOH with AN leads to decrease/increase in the exothermicity formation of [AgPy]+/[AgPy 2 ]+. • Changes in Δ tr H 0(r 1)/Δ tr H 0(r 2) are due mainly to a contribution from starting reagents/reaction products resolvation. • Ions and ligand solvation gives opposite contributions in the thermodynamic characteristics of complex formation reactions. • Solvation effects [Δ tr H 0([AgPy]+) – Δ tr H 0(Py)] and Δ tr H 0(Ag+) are proportional to each other with a coefficient k. • For pairs of «amphoteric – basic» solvents, a correlation between their physicochemical properties and k values was found. In this study, the enthalpies of stepwise complexation reactions between silver(I) ions and pyridine in methanol–acetonitrile mixed solvents (MeOH-AN, with molar fractions of AN varying from 0 to 1) were determined by the calorimetric method at 298.15 K. The analysis of the solvation contributions of the reactants to the alterations in the thermodynamic characteristics associated with the formation of [AgPy]+ and [AgPy 2 ]+ complexes as the solvent composition transitions, i.e. from methanol to its mixtures with acetonitrile (MeOH → χ AN), from methanol to its mixtures with N,N -dimethylformamide (MeOH → χ DMF) and from acetonitrile to its mixtures with dimethyl sulfoxide (AN → χ DMSO) was carried out. The research methodology was based on the provisions of the solvation-thermodynamic approach, based on the relationship between changes in the thermodynamic characteristics of the reactions of complex formation and solvation of reagents with a change in the composition of the solvent. [ABSTRACT FROM AUTHOR]

Heavy metal stabilization is an effective method to treat chromium in tannery sludge. Here we show that mainly investigated NaH 2 PO 4 (MSP) and organic matter (OM) to stabilize chromium in tannery sludge. The experimental investigation revealed that the addition of montmorillonite (MMT) and MSP samples showed a significant increase in the percentage of reducible and oxidizable Cr in the former compared to the samples with the addition of MMT. This is attributed to the formation of Cr–O bond, which allows the MSP to undergo an inner-sphere complexation reaction with the metal oxide of Cr via ligand exchange. Significantly, the MSP moiety adsorbs on the surface of OM through monodentate, which increases the adsorption sites of OM for Cr6+ and promotes the reduction of Cr6+ to Cr3+. Moreover, PO 4 3− reacts with Cr3+ to produce CrPO 4 precipitation, thus reducing the free Cr3+ content. Finally, DFT calculations confirmed that a ternary system is formed between PO 4 3−, OM, and Cr, and the binding energy is negative, which indicated that PO 4 3− could co-stabilize Cr with OM. [Display omitted] • Stabilization of Cr by MSP is achieved through ligand exchange. • MSP amplifies the adsorption sites of OM and promotes the reduction of Cr6+. • PO 4 3− from the dissociation of MSP reacts with Cr3+ to form CrPO 4 precipitate. • Results from DFT indicate the presence of PO 4 3−, OM, and Cr in a ternary system. [ABSTRACT FROM AUTHOR]

The simultaneous presence of heavy metals and surfactants in runoff induces complexation and ecological harm during migration. However, interactions between these pollutants are often overlooked in past studies. Thus, investigating heavy metal-surfactant complexes in runoff is imperative. In this work, Cu (II) and sodium dodecyl sulfate (SDS) were selected to investigate the interaction between heavy metals and surfactants due to the higher detected frequency in runoff. Through 1H NMR and FTIR observation of hydrogen atom nuclear displacement and functional group displacement of SDS, the change of SDS and Cu (II) complexation was obtained, and then the complexation form of Cu (II) and SDS was verified. The results showed that solution pH values and ionic strength had significant effects on the complexation of Cu (II). When the pH values increase from 3.0 to 6.0, the complexation efficiency of SDS with Cu (II) increased by 12.12% at low concentration of SDS, which may be attributed to the excessive protonation in the aqueous solution at acidic condition. The increase of ionic strength would inhibit the complexation reaction efficiency by 19.57% and finally reached the platform with concentration of NaNO 3 was 0.10 mmol/L, which was mainly due to the competitive relationship between Na (I) and Cu (II). As a general filtering material in stormwater treatment measures, natural zeolite could affect the interaction between SDS and Cu (II) greatly. After the addition of SDS, the content of free Cu (II) in the zeolite-SDS-Cu (II) three-phase mixed system was significantly reduced, indicating that SDS had a positive effect on the removal of Cu (II) from runoff. This study is of great significance for investigating the migration and transformation mechanism of SDS and Cu (II) in the future and studying the control technology of storm runoff pollution. [Display omitted] • The complexation characteristics of (SDS) and Cu (II) in runoff was investigated. • pH value and ionic strength showed influence on the complexation reaction between Cu (II) and SDS. • Natural zeolite could eliminate SDS-Cu (II) complex and improved removal efficiency of Cu (II). • The complexation mechanism and environmental implications were examined in stormwater runoff. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The isothermal titration calorimetry was applied to the complexation of humic acid, which was isolated from deep groundwater. • The complexation thermodynamic quantities of humic acid with copper (II) ions and uranyl (VI) ions were determined. • The unique complexation character of deep groundwater humic acid was revealed by reaction thermodynamics. • Determination of complexation enthalpy of in situ humic substances is helpful for the prediction of radionuclides migration. Abstract Although the thermodynamic quantities (Gibbs free energy, reaction enthalpy, and entropy) of the complexation of humic acid are necessary for the discussion of the reaction thermodynamics, their accurate determination, especially concerning dissolved humic acid in deep groundwater, has not been carried out. In this study, a combination of potentiometry and calorimetry was used for the determination of the thermodynamic values of complexation of typical humic acid and groundwater humic acid, which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe humic acid was independent of the pH of the bulk solution, whereas that of typical humic acid was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe humic acid is negligible because of its relatively small molecular size. In addition, the effect of the heterogeneity of Horonobe humic acid was not significant. Moreover, the complexation enthalpy of Horonobe humic acid was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe humic acid was not affected by the functional group heterogeneity. Consequently, the unique complexation mechanism of Horonobe humic acid was revealed based on the determined thermodynamic quantities. The migration of radionuclides in the deep underground environment must be affected by these characteristics; thus, the accurate determination of thermodynamic quantities of in situ humic substances is very helpful for the safety assessment of geological disposal, when disposal sites for radioactive waste are chosen. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Selective adsorption and regeneration of adsorbents are great challenges for fluoride removal in drinking water. In this study, a NiAl-layered metal oxide (NiAl-LMO) electrode was successfully prepared and used as an electro-adsorption electrode. With its structural memory effect for anions and high specific capacitance of 575 F·g−1, the NiAl-LMO electrode exhibits capacitive deionization performance. The maximum adsorption capacity of F− by the electrode reached 49.28 mg/g, which was 4 times that of Cl− and 2 times that of SO 4 2−, respectively. The good selectivity for F− electrosorption was ascribed to the high electronegativity of F− and the complexation between F− and hydroxyl aluminum groups. The electrode material has good stability and can be regenerated easily by applying a reverse voltage. After 10 cycles, the F− adsorption rate by the NiAl-LMO electrode was 94. 4% of the initial adsorption rate. The applied voltage enhanced the selectivity of F− adsorption by the NiAl-LMO electrode, and this electrosorption process was mainly dominated by electrical double layer adsorption. Under the conditions of 1.0 V and pH 7, the electrode showed a maximum adsorption efficiency of 73.5%. [ABSTRACT FROM AUTHOR]

Graphical abstract Enhanced extraction of rare earths by using ionic liquids originate from the synergism of Hofmeister bias and the complexation behavior of salt anions. Abstract Separation and recycling of rare-earths using ionic liquids as extractant are becoming a promising approach to replace traditional volatile organic solvents in recent years. Generally, the addition of some special salts could improve the extraction efficiency of rare-earths by numerous non-functional ionic liquids. However, knowledge behind the nature of the salt effect is limited. Here, we found that the enhancement in the extraction of rare-earth ions, Pr3+ ions, using non-functional ionic liquid, [A336][NO 3 ] (Tricaprylmethylammonium nitrate) was driven by the synergism of Hofmeister bias and complexation behaviors of salt anions with Pr3+ ions. Molecular dynamic simulations offered a new insight into the interaction mechanism of the ionic liquid with Pr3+ ions at liquid/liquid interface. It was revealed that salt anions could perform as a bridge to connect Pr3+ ions and the ionic liquid, so that promoted the extraction of Pr3+ ions. Therefore, the strong complexation ability of salt anions with Pr3+ ions and poor hydration of salt anions faciliated the transport of Pr3+ ions across liquid/liquid interface. [ABSTRACT FROM AUTHOR]

Abstract Humic acid (HA) has a major influence on the environmental fate of metal ions due to its heterogeneity in chemical compositions, structure and functional groups. In this study, we investigated the effect of humic acid (HA) with different molecular weight (Mw) on the bioavailability of Pb for a representative algae- Chlorella pyrenoidosa. The results showed that HA with larger Mw had stronger inhibitory effects on the bioavailability of Pb to algae, and the biosorption capacity of Pb decreased with increasing Mw, which is in accordance with the variations of complexation capacities of Pb for HA fraction. In addition, we found that HA with Mw lower than 10 kDa could increase the biosorption capacity of Pb. The considerable differences among the Mw fractions on Pb biosorption were mainly attributed to their properties and corresponding complexation capacities. Phenolic groups were responsible for the variations of binding capacities among different Mw fractions, and it could also better explain the bioaccumulation of Pb to the membranes of algae. By using NICA-Donnan model, we found that over 60% of Pb ions were bound by HAs through specific binding, and the formation of Pb-HAs complex were non-bioavailable to algae, which was proved by the considerably decreasing percentage of internalized Pb. This study provided further insight into the bioavailability of Pb to algae as influenced by the complexation of HA with metal ion such as Pb. Graphical abstract fx1 Highlights • Phenolic groups of HAs were responsible for the variations of binding capacities. • The sorption of Pb by C. pyrenoidosa was positively correlated with HA properties. • HA with Mw larger than 10 kDa could ameliorate the toxicity of Pb. • The high contribution of specific binding result in biologically unavailable of Pb. [ABSTRACT FROM AUTHOR]

Abstract New Mn(II)-thioantimonate compounds [Mn(NH 3) 6 ] 2 [{Mn(NH 3) 3 } 2 (μ 3 -SbS 4) 2 ]Cl 2 (1), [Mn(NH 3) 6 ][{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]·2H 2 O (2), [Mn(NH 3) 6 ][{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 ] (3), and [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n (4) were prepared in different hydrazine solution under solvothermal conditions. In 1 , the tetrahedral SbS 4 unit acts as a tridentate bridging ligand to connect the [Mn(NH 3) 3 ]2+ units into a 2-D lamellar anion [Mn(NH 3) 3 (μ 3 -SbS 4)2−] n containing 12-membered Mn 3 Sb 3 S 6 heterorings. Two SbS 4 ligands join two [Mn(NH 3) 4 ]2+ units with monodentate μ-1κ1 S 1: 2κ1 S 1 bridging mode, forming a binuclear [{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]2− anion in 2. In 3 , the SbS 4 ligand links [Mn 2 (μ-N 2 H 4) 2 ] units with tridentate bridging mode, to form a 1-D [{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 2−] n chain-like anion. Octahedral [Mn(NH 3) 6 ]2+ complex cation acts as the counter ion in compounds 1 – 3. In 4 , the Mn(N 2 H 4) units are interconnected into a neutral infinite [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n chain by μ-SbS 3 and μ-N 2 H 4 bridging ligands. The trigonal pyramidal SbS 3 unit adopts a tridentate bridging coordination mode μ-1κ2 S 1, S 2:2κ2 S 1, S 3. Compounds 1 – 4 exhibit tunable semiconducting band gaps varying in the range of 2.38–2.55 eV. Compounds 1 and 2 display higher photocatalytic activity in the degradation of crystal violet than in the degradation of methyl orange under visible light irradiation. Graphical abstract Mn(II)-thioantimonate [Mn(NH 3) 6 ] 2 [{Mn(NH 3) 3 } 2 (μ 3 -SbS 4) 2 ]Cl 2 (1), [Mn(NH 3) 6 ][{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]·2H 2 O (2), [Mn(NH 3) 6 ][{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 ] (3), and [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n (4) were prepared in different hydrazine solution under solvothermal conditions. fx1 Highlights • Mn(II) complexes with SbS 4 and SbS 3 ligands were synthesized by solvothermal method. • Four new coordination modes for the SbS 4 and SbS 3 ligands are obtained in 1 – 4. • 1 and 2 perform catalytic activity in the photodegradation of CV. [ABSTRACT FROM AUTHOR]

In this study, we developed and validated a three-dimensional fluorescence method for the determination of ethylenediamine tetraacetic acid disodium salt (EDTA-2Na) in pickles and canned mixed congee by forming a ternary fluorescent complex of zirconium-quercetin-EDTA. The complexation reaction conditions and fluorescence scanning parameters were optimized. During the fluorescent complexation reaction, reagent NH 3 and anhydrous ethanol were used to enhance the fluorescence intensity. The analysis of EDTA-2Na by fluorescence scanning was accomplished within 3 min. Under these conditions, satisfactory linearities were obtained (R2 ≥ 0.99) with limit of detection (LOD) of 0.19 µg mL-1. The recoveries were 79.8–113.2%, with relative standard deviations (RSD) below 9.7%. The relative error of fluorescence compared with HPLC-DAD detection was less than 13.5%, indicating that the results of both methods were consistent. Thus, a convenient and accurate method was established to analyze EDTA-2Na in pickles and canned mixed congee, providing a new option to rapidly monitor EDTA-2Na in foods for ensuring food safety. [Display omitted] • A new and rapid 3D fluorescence method was developed for analyzing EDTA-2Na. • Zirconium-quercetin-EDTA complexation and fluorescence scanning were optimized. • 3D fluorescence results were validated by HPLC. • The method was applied to different pickles and canned mixed congee samples. • The method provides support for monitoring the use of EDTA-2Na in foods. [ABSTRACT FROM AUTHOR]

The chloride transport properties of cement-based materials are determined via the physicochemical interactions between the pore solution and the cement hydrates. Herein, a thermodynamic model based on surface complexation reactions and dissolution/precipitation reactions was established to investigate the essential physicochemical interactions. The effects of chloride concentration, temperature, and saturation degree (the ratio of water volume to pore volume) on the physicochemical interactions were studied in detail using the resulting thermodynamic model. The published experimental results indicate that the resulting thermodynamic model accurately reflects the adsorption capacity of cement hydrates for chloride ions. Thus, this thermodynamic model can be coupled to the transport equations to achieve the durable designs for new reinforced concrete structures (RCSs) or to predict the service life of existing RCSs. It can also optimize corrosion control strategies for RCSs based on the thermodynamics and kinetics of the material. [ABSTRACT FROM AUTHOR]

The goal of this work was to understand the key factors determining the DNA compacting capacity of single-chained cationic surfactants. Fluorescence, zeta potential, circular dichroism, gel electrophoresis and AFM measurements were carried out in order to study the condensation of the nucleic acid resulting from the formation of the surfactant-DNA complexes. The apparent equilibrium binding constant of the surfactants to the nucleic acid, K app , estimated from the experimental results obtained in the ethidium bromide competitive binding experiments, can be considered directly related to the ability of a given surfactant as a DNA compacting agent. The plot of ln(K app ) vs. ln(cmc), cmc being the critical micelle concentration, for all the bromide and chloride surfactants studied, was found to be a reasonably good linear correlation. This result shows that hydrophobic interactions mainly control the surfactant DNA compaction efficiency. [ABSTRACT FROM AUTHOR]

The thermodynamics of the interaction of the acridine derivative quinacrine with tRNA Phe was studied using isothermal titration calorimetry. The binding was monophasic and exothermic. At (298.15 ± 0.01) K the equilibrium constant was calculated to be (1.76 ± 0.70)·10 5  M −1 . The binding stoichiometry was (0.15 ± 0.04). The binding was predominantly enthalpy driven (Δ H o  = −28.39 ± 0.60 kJ·mol −1 ). Salt dependent ITC studies followed by dissection of the standard molar Gibbs energy change showed that the binding reaction was driven by both polyelectrolytic and non-polyelectrolytic forces with the non-polyelectrolytic forces being dominant. Temperature dependent ITC studies showed that the binding became increasingly enthalpy driven with rise in temperature. The binding was characterized by negative standard molar heat capacity change and enthalpy-entropy compensation behaviour. [ABSTRACT FROM AUTHOR]

The chiral selectivity of β-cyclodextrin (β-CD) in the water/hexane (3.0% THF) two-phase system is studied with chromatography and interfacial tension measurements. Chromatography using silica gel impregnated with aqueous β-CD as the stationary phase reveals that the chiral selectivity of this system is higher than that predicted from the β-CD complexation that occurs in bulk water. The retention of the solutes and chiral selectivity can be explained by the adsorption of β-CD at the interface between the aqueous phase (AP) and hexane (3.0% THF) phase. The interfacial tension measurements suggest that β-CD molecules forms a monolayer at this interface. The interfacial complexation constants are larger than the corresponding bulk water constants by at least one order of magnitude. The β-CD molecules adsorbed at the interface are preferably oriented for the formation of inclusion complexes, and thereby solute molecules are directly accommodated in the CD cavity at the interface without partitioning into the AP. The present chromatography-based method probes the interfacial phenomena that are not accessible by other methods. Hence, the liquid/liquid interface is a new field for molecular recognition that does not occur in bulk solution phases. [ABSTRACT FROM AUTHOR]

The interaction of α -cyclodextrin ( α -CD) with ten ionic surfactants (S) in water was systematically examined using isothermal titration calorimetry. The S comprised cationic and anionic head groups while the hydrocarbon alkyl chain length varied from eight to fourteen carbon atoms. The heat data were measured at five temperatures ranging from 283.15 K to 318.15 K and were treated simultaneously allowing the estimation of a thermodynamically consistent temperature dependence of the equilibrium constant, as well as the enthalpy and heat capacity for the sequential formation of the [ α -CD · S] and the [ α -CD 2 ·S] inclusion complexes. All attempts to fit the data assuming that only [ α -CD · S] complexes are present failed. It was found that the thermodynamic footprint of the [ α -CD · S] complexes does not depend importantly on the head group, while the formation and stabilization of the [ α -CD 2 ·S] complexes is strongly influenced by the chemical nature of the polar head group. Several contributions to the thermodynamic parameters are discussed in detail. Among the studied surfactants, the decyl- and octylsulfates were identified as those with a predominant content of [ α -CD 2 ·S] complexes and hence they are promising candidates to form viscoelastic films at the liquid/air interface, as it was found previously for the dodecylsulfate surfactant. [ABSTRACT FROM AUTHOR]

Isosaccharinic acid is a cellulose degradation product that can form in low-level nuclear waste repositories and is known to form strong complexes with many elements, including actinides, disposed of in these repositories. We 1) reviewed the available data for deprotonation and lactonisation constants of isosaccharinic acid, and the isosaccharinate binding constants for Ca, Fe(III), Th, U(IV), U(VI), Np(IV), Pu(IV), and Am(III), 2) summarized complexation constant values for predicting actinide behavior in geologic repositories in the presence of isosaccharinate, and 3) outlined additional studies to acquire reliable thermodynamic data where the available data are inadequate. [ABSTRACT FROM AUTHOR]

To gain insight on the role of mixed solvents on the thermodynamic driving forces for the complexation between trivalent f-elements and organic ligands, solution phase thermodynamic parameters were determined for Eu(III) complexation with 2-hydroxyisobutyric acid (HIBA) and 2-aminoisobutyric acid (AIBA) in mixed methanol (MeOH)-water and N,N-dimethylformamide (DMF)-water solvents. Included in this study were the determination of mixed solvent autoprotolysis constants (pK s ) as well as the thermodynamic formation constants: log β, ΔG, ΔH, and ΔS, for ligand protonation and Eu(III)-ligand complexation utilizing potentiometry and calorimetry techniques. The results presented are conditional thermodynamic values determined at an ionic strength of 1.0 M NaClO 4 and a temperature of 298 K. It was found that moving from an aqueous solution to a binary aqueous-organic solvent affected all solution equilibria to some degree and that the extent of change depended on both the type of mixed solvent and the ligand in each study. The ability to understand and predict these changes in thermodynamic values as a function of solvent composition provides important information about the chemistry of the trivalent f-elements. [ABSTRACT FROM AUTHOR]

The present study devoted to description of efficient removal of radioactive UO 2 2+ ions (U(IV)) via complexation with Arsenazo III (ARS III) accelerated by ultrasound-assisted adsorption onto the Au-NPs supported on carbon nanotubes (Au-NPs-CNTs), which were characterized by conventional techniques such as FESEM, EDS and XRD. Central composite design (CCD) employed to model contribution of parameters viz. pH (2.5–8.5), adsorbent mass (5–25 mg), UO 2 2+ concentration (5–25 mg L −1 ) and sonication time (1–5 min) onto response. The predicted results optimum conditions corresponding achievement of maximum UO 2 2+ removal efficiency are pH 5.5, 20 mg of Au-NPs-CNTs, is highly applicability for removal of more than 98% of 25 mg L −1 of UO 2 2+ following 5 min sonication. Through analysis of corresponding results based on evaluation according to UO 2 2+ concentration were found significantly affect responds. ANOVA analysis revealed a high R 2 (0.9950) & AP (51.79) and low SD (0.6078) & CV% (0.6703) values of regression model equation which completely ensure accuracy of the quadratic model. Langmuir isotherm model was applicable for description of adsorption data with maximum monolayer adsorption capacity of 133.3 mg g −1 at 25 °C and pH 5.5. Dubinin–Radushkevich (D–R) isotherm model based on mean sorption energy (E) reveal high contribution of physisorption (1.17–3.78 kJ mol −1 ) on adsorption process. Moreover, Pseudo-second-order kinetic model delivered a better correlation for the experimental data in comparison to the pseudo-first-order kinetic model and intraparticle diffusion mechanism. [ABSTRACT FROM AUTHOR]

Thermodynamics of the U(VI) complexation with picolinic acid (HL) was investigated under constant ionic strength (1.05 mol·kg −1 NaClO 4 ) with multiple techniques, including potentiometry, spectrophotometry and calorimetry. Three stepwise complexes, UO 2 L + , UO 2 L 2 (aq) and UO 2 L 3 − , were identified, and their formation constants were determined by potentiometric titrations at 283–313 K. The spectrophotometric work at 298 K further demonstrated the formation of these three complexes. By calorimetric titrations, stepwise enthalpies of the complexation at 298 K were determined to be Δ H 11 = −(3.43 ± 0.24) kJ·mol −1 , Δ H 12 = −(3.3 ± 0.6) kJ·mol −1 , and Δ H 13 = 9.4 ± 0.6 kJ·mol −1 . A formation of the 1:1 and 1:2 complexes is driven by both enthalpy and entropy, but the formation of the 1:3 complex by entropy only. The thermodynamic parameters also suggest that in the 1:1 and 1:2 complexes, picolinate coordinates to U(VI) through the chelation mode, i.e., one carboxylate oxygen and an aromatic nitrogen bind to the U(VI) atom. [ABSTRACT FROM AUTHOR]

Ultrasound irradiation, cloud point and adsorption methods were coupled to develop a new technique for the simultaneous removal of Cd(II), Ni(II), Pb(II) and Cu(II) ions after their complexation with ( E )-4-((2-hydroxybenzylidene) amino) naphthalene-1-sulfonic acid (HBANSA). In order to reduce cost and improve practicability of process, chitosan gel (CSG) composited with bismuth(III) phosphate/iron(III) phosphate nanoparticles (CSG-BiPO 4 /FePO 4 ) were hydrothermally synthesized followed by their characterization using FE-SEM, EDS and XRD analysis. The operational parameters such as metal ions concentration, CSG-BiPO 4 /FePO 4 mass, sonication time and temperature were investigated and optimized using central composite design (CCD). In addition, the possible significant correlation between these variables and removal efficiency was studied from which the maximum efficiencies were obtained at 5.57 mg/L, 51.49 °C, 0.018 g and 10.73 min corresponding to metal ions concentration, temperature, CSG-BiPO 4 /FePO 4 and sonication time, respectively. Moreover, at these conditions, the removal percentages of the Cd(II), Ni(II), Pb(II) and Cu(II) ions were found to be 96.24, 93.73, 95.55 and 97.47, respectively. After applying various isotherms, the Langmuir isotherm model was found to be most appropriate model for describing and fitting the experimental equilibrium data and thus maximum mono-layer adsorption capacities of 8.61, 8.54, 8.65 and 8.62 mg g −1 were obtained for Cd(II), Pb(II), Cu(II) and Ni(II) ions, respectively. The study of kinetics showed well applicability of pseudo second order kinetic model with maximum mass transfer rate in adsorption process. [ABSTRACT FROM AUTHOR]

Hypothesis Complexation between Methyl orange and polycations involves multiple interactions dictated by molecular structure, composition (D/P), pH and ionic strength. The effect of ionic strength is considered a generic effect. By step-wise construction of complexes, we expect to gain insight in the nature of interactions and whether displacement by competing ions is a generic effect. Experiments We step-wise constructed complexes of methyl orange with two model polycations, whilst recording visible light spectra, size and electrophoretic mobility in buffered solution. MO organization was derived from discrete spectral changes, whereas complexes were described in terms of size and zeta-potential data. Spectral data were used to study the effect of competing ions, both potassium halides and polyanions, using a manual titration method. Findings Spectral and size data reveal a complex stoichiometry of D/P = 2.2 and 4.6 for poly(ethylenimine hydrochloride)(PEI) and poly(di allyldimethyl amine hydrochloride) PDADMAC, respectively. Contrary to PEI-MO, the formation of PDADMAC-MO complexes is driven by hydrophobic rather than electrostatic interactions. Organization of PDADMAC-MO complexes also shows a strong dependency on the order of construction and polycation concentration. Displacement of MO by halides shows no effect of ion size for PEI, whereas Hofmeister series ordering was found for PDADMAC. The displacement by polyanions is shown to be charge-stoichiometric. [ABSTRACT FROM AUTHOR]

The density measurements have been carried out for ternary aqueous solutions containing a fixed concentration (∼0.1 mol·kg −1 ) of α-cyclodextrin (α-CD) and varying concentrations (∼0.003 to ∼0.21 mol·kg −1 ) of some local anesthetical drugs, namely procaine hydrochloride (PC·HCl), lidocaine hydrochloride monohydrate (LC·HCl) and tetracaine hydrochloride (TC·HCl) at 298.15 K. The density data are used to determine apparent molar volumes of the drug molecules in ternary solutions at finite concentrations ( ϕ V ) as well at infinitely dilute solutions ( ϕ V 0 ). Following the methods developed by Høiland et al. as well by Jolicoeur et al. and using the infinite dilution volume values for the drugs in ternary and binary solutions and incorporating the equilibrium constant values for the complexation between α-CD and drugs, volume changes due to encapsulation or complexation have been estimated. It is observed that all the studied hydrochlorides exhibit high positive volume change due to complexation. The results are discussed in terms of host-guest interaction and structural specificity of guest molecules. [ABSTRACT FROM AUTHOR]

The toxicity and carcinogenicity of Cr(VI) makes it a major threat to the health of animals and people. However, how to efficiently remove Cr(VI) still faces important challenges. In this study, a new metal-free polypyrrole-red phosphorus (PPy-RP) composite is successfully synthesized by in-situ oxidation polymerization for Cr(VI) removal from wastewater. The maximum adsorption capacity (q m) of Cr(VI) on PPy-RP-1 is 513.2 mg/g when the pH value is 2, which is far superior to RP nanosheets (207.8 mg/g) and PPy (294.9 mg/g). The improved q m can be ascribe to the good dispersion and increased specific surface area of PPy-RP adsorbent. Encouragingly, PPy-RP adsorbent still exhibits excellent stability after 7 cycles tests without a significant decline in removal efficiency, and remain above 81.4%. Based on the fittings of adsorption isotherms and kinetics, the process conforms to the pseudo-first-order kinetic model and the single-layer adsorption of the Langmuir model with an R2 value of 0.98533. The adsorption process is chemical and monolayer. The experimental result demonstrates that the PPy-RP can efficient removal Cr(VI) by electrostatic attraction and complexation reaction (formation of N–Cr(VI) bond) through the PPy on the surface. The results of this study indicate that PPy-RP is a promising adsorbent to remove the Cr(IV). [Display omitted] • In situ polymerization method was used to synthesize the PPy-RP adsorbent. • The maximum adsorption capacity of PPy-RP-1 for Cr (Ⅵ) reached 513.2 mg/g. • The RP successfully prevented agglomeration of the PPy in aqueous solutions. • The mechanism of adsorption combined with reduction has been ascertained. [ABSTRACT FROM AUTHOR]

Histone deacetylases (HDACs) catalyze the hydrolysis of acetylated lysine side chains in histone and non-histone proteins, and play a critical role in the regulation of many biological processes, including cell differentiation, proliferation, senescence, and apoptosis. Aberrant HDAC activity is associated with cancer, making these enzymes important targets for drug design. In general, HDAC inhibitors (HDACi) block the proliferation of tumor cells by inducing cell differentiation, cell cycle arrest, and/or apoptosis, and comprise some of the leading therapies in cancer treatments. To date, four HDACi have been FDA approved for the treatment of cancers: suberoylanilide hydroxamic acid (SAHA, Vorinostat, Zolinza®), romidepsin (FK228, Istodax®), belinostat (Beleodaq®), and panobinostat (Farydak®). Most current inhibitors are pan-HDACi, and non-selectively target a number of HDAC isoforms. Six previously reported HDACi were rationally designed, however, to target a unique sub-pocket found only in HDAC8. While these inhibitors were indeed potent against HDAC8, and even demonstrated specificity for HDAC8 over HDACs 1 and 6, there were no structural data to confirm the mode of binding. Here we report the X-ray crystal structure of Compound 6 complexed with HDAC8 to 1.98 Å resolution. We also describe the use of molecular docking studies to explore the binding interactions of the other 5 related HDACi. Our studies confirm that the HDACi induce the formation of and bind in the HDAC8-specific subpocket, offering insights into isoform-specific inhibition. [ABSTRACT FROM AUTHOR]

The Experimental thermodynamic equilibrium ( p K a values) and stability (log β ) constants of vanadium and platinum binary and mixed ligand complexes involving naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid were determined at 310.15 K in 0.16 mol·dm −3 KCl aqueous solutions using pH-potentiometric technique and by means of two estimation models (HYPERQUAD 2008 and Bjerrum–Calvin). The theoretical calculations of overall protonation and stability constants of the metal complex species in solution were predicted as the free energy change associated with the ligand protonation, and metal ion–ligand complex formation equilibria (species solvation/de-solvation) using ab initio and density function theory (DFT) calculations. The usage of the experimental potentiometry technique and theoretical predictions provides a complete picture of the microscopic equilibria of the studied systems (vanadium/platinum–naringenin–phenolic acid). Specifically, this theoretically DFT predications would be useful to determine the most real protonation constants of the studied bioligands in which the binding sites changes due to the ligand protonation/deprotonation equilibria. Also, the complexing capacities of vanadium and platinum towards naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid in solutions were evaluated and discussed. From the determined experimental stability constants of different metal complex species, the concentration distribution diagrams of the various metal ion complex species in solution was estimated using HySS 2009 software. [ABSTRACT FROM AUTHOR]

Ternary mutual diffusion coefficients ( D 11 , D 22 , D 12 and D 21 ) measured by the Taylor dispersion method are reported for aqueous solutions of levodopa (L-dopa) (1) in the presence of 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD) (2) at 25 °C and 37 °C and concentrations up to 0.005 mol · dm −3 . The effects of HP-β-CD (HP-β-CD) on the transport of L-dopa are assessed by comparing the binary diffusion coefficient of aqueous L-dopa solutions with the main diffusion coefficient ( D 11 ) measured for ternary {L-dopa (1) + HP-β-CD (2)} solutions. 1 H NMR spectroscopy suggests no significant complexation between HP-β-CD and L-dopa. However, coupled diffusion of L-dopa and HP-β-CD occurs, as indicated by non-zero values of the cross-diffusion coefficients, D 12 and D 21 . HP-β-CD concentration gradients produce significant co-current coupled flows of L-dopa. [ABSTRACT FROM AUTHOR]

The interaction of proflavine with tRNA phe was studied using isothermal titration calorimetry to gain insights into thermodynamics of the binding reaction. Isothermal titration calorimetric studies revealed the association to be exothermic and favored by both negative enthalpy and positive entropy changes. The equilibrium constant for the complexation process was calculated to be (2.85 ± 0.09) 10 5 M −1 at T = 293.15 K. The equilibrium constant decreased with increasing temperature suggesting that the complexation is less favored at higher temperatures. The standard molar enthalpic contribution enhanced in magnitude while the standard molar entropic contribution decreased with increasing temperature. The complexation was further characterized by negative standard molar heat capacity and (enthalpy + entropy) compensation. Salt dependent ITC studies and parsing of the standard molar Gibbs energy revealed that the complexation process was largely dominated by non-polyelectrolytic forces which remained almost unaltered at all the salt concentrations studied. [ABSTRACT FROM AUTHOR]

Zinc deficiency is now recognized as one of the most severe problems of human malnutrition world-wide. Lactose being a reducing sugar is able to chelate zinc and reduce the reactivity of zinc with other food components. Therefore, a process for the preparation of lactose–zinc complex has been standardized in the present work. Level of zinc salt was optimized on the basis of maximum binding ability of lactose to chelate zinc. The microstructure of lactose–zinc complex revealed that the size of the lactose crystals decreased and formed noticeable aggregates upon complexation. Sensory scores of milk fortified with zinc salt were significantly lower (P < 0.05) than milk fortified with lactose–zinc complex during storage. The heat coagulation time (HCT) of milk fortified with lactose–zinc complex was comparable with control and exhibited Type A curve with HCT-pH maxima at acidic side of natural pH. Milk fortified with lactose–zinc complex showed non-significant differences in physicochemical properties (such as pH, acidity, viscosity, HMF and TBA) than control milk during storage upto 7 days. Milk fortified with lactose–zinc complex showed significantly (P < 0.05) higher in vitro bioavailability than unfortified (control) and zinc salt fortified milk. [ABSTRACT FROM AUTHOR]

Polymeric lanthanide complexes with thiostannate and polyamine mixed ligands, [Ln(peha)(μ–SnS 4 H)] n [Ln=La ( 1a ), Nd ( 1b )] and [{Ln(tepa)(μ–OH)} 2 (μ–Sn 2 S 6 )] n nH 2 O [Ln=Nd ( 2a ), Sm ( 2b ), Gd ( 2c ), Dy ( 2d )] (peha=pentaethylenehexamine, tepa=tetraethylenepentamine) were respectively prepared in peha and tepa coordinative solvents by the solvothermal methods. In 1a and 1b , the Ln 3+ ions are coordinated by a hexadentate peha ligand forming [Ln(peha)] 3+ units. The [SnS 4 H] 3− anion chelates a [Ln(peha)] 3+ unit via two S atoms and coordinates to another [Ln(peha)] 3+ unit via the third S atom. As a result, the [Ln(peha)] 3+ units are connected into coordination polymers [Ln(peha)(μ–SnS 4 H)] n by an unprecedented tridentate μ–η 1 ,η 2 –SnS 4 H bridging ligands. In 2a – 2d , the Ln 3+ ions are coordinated by a pentadentate tepa ligand, and two [Ln(tepa)] 3+ units are joined by two μ–OH bridges to form a binuclear [{Ln(tepa)(μ–OH)} 2 ] 4+ unit. Behaving as a bidentate μ–η 1 , η 1 –Sn 2 S 6 bridging ligand, the Sn 2 S 6 unit connects [{Ln(tepa)(μ–OH)} 2 ] 4+ units into a neutral coordination polymer [{Ln(tepa)(μ–OH)} 2 (μ–Sn 2 S 6 )] n via the trans S atoms. The Ln 3+ ions are in distorted monocapped square antiprismatic and bicapped trigonal prismatic environments in [{Ln(peha)(μ–SnS 4 H)] n and [{Ln(tepa)(μ–OH)} 2 (μ–Sn 2 S 6 )] n , respectively. The denticities of ethylene polyamine play an important role on the formation and complexation of the thiostannate in the presence of lanthanide ions. Compounds 1a – 2d show well-defined absorption edges with band gaps between 2.81 and 3.15 eV. [ABSTRACT FROM AUTHOR]

(Liquid + liquid) extraction of ethylbenzene from n -octane by using tetrabutylammonium bromide-based deep eutectic solvents (DESs) containing pyridine, ethylene glycol, or a mixture of both complexing agents was investigated at 25 °C and atmospheric pressure. The performance of each DES was determined from the distribution ratio and selectivity values calculated using experimental (liquid + liquid) equilibrium data of the ternary systems ethylbenzene + n -octane + DESs. The DES with only ethylene glycol had a high selectivity but a low distribution ratio, whereas the DES with only pyridine had a high distribution ratio but a low selectivity. For the other DESs, adding pyridine increased the distribution ratio, and increasing the molar ratio of ethylene glycol increased the selectivity. Generally, whenever the selectivity increased, the distribution ratio decreased, and vice versa. The nonrandom two-liquid model was used to correlate the experimental data, and the average root mean square deviation (RMSD) between correlated and experimental tie lines was 1.4%. Moreover, the Conductor-like Screening Model for Real Solvents was successfully used to predict the ternary tie lines for the studied systems with an average RMSD of 3.7%. [ABSTRACT FROM AUTHOR]

The complexation of Ni(II) and Fe(III) with nicotinamide in aqueous ethanol and aqueous dimethyl sulfoxide was directly studied by calorimetry at T = 298.15 K and ionic strength value 0.25 (NaClO 4 ). The results of thermochemical study were discussed using solvation-thermodynamic approach basing on the accounting of reagents solvation. The absence of contact ion pairing between Ni 2+ and ClO 4 - was observed by IR-spectroscopy at ionic strength value 0.25. Nicotinamide was found to replace the water molecule within cation coordination sphere by means of UV–Vis spectroscopy. [ABSTRACT FROM AUTHOR]

The sorption of Inositol hexaphosphate (IP 6 ) onto gibbsite was investigated using a combination of adsorption experiments, 31 P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP 6 sorption decreased with increasing pH. At pH 6, IP 6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. 31 P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, −6, −13 and −21 ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and 31 P MAS NMR data, IP 6 sorption to gibbsite was modeled with an extended constant capacitance model (ECCM). The adsorption reactions that best described the sorption of IP 6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex: AlOH + IP 6 12 - + 5 H + ↔ Al ( IP 6 H 4 ) 7 - + H 2 O 3 AlOH + IP 6 12 - + 6 H + ↔ Al 3 ( IP 6 H 3 ) 6 - + 3 H 2 O 2 AlOH + IP 6 12 - + 4 H + ↔ ( AlOH 2 ) 2 2 + ( IP 6 H 2 ) 10 - The inner-sphere complex involving three surface sites may be considered to be equivalent to a surface precipitate. Thermodynamic parameters were obtained from equilibrium constants derived from surface complexation modeling. Enthalpies for the formation of inner-sphere surface complexes were endothermic, while the enthalpy for the outer-sphere complex was exothermic. The entropies for the proposed sorption reactions were large and positive suggesting that changes in solvation of species play a major role in driving the sorption process. [ABSTRACT FROM AUTHOR]

The equilibrium constants of the 1:1 NpO 2 + /benzoate complex were determined by spectrophotometric titrations at variable temperatures ( T = 283 to 343 K) and the ionic strength of 1.05 mol · kg −1 . The enthalpy of complexation at T = 298 K was determined by microcalorimetric titrations. Similar to other monocarboxylates, benzoate forms a weak complex with NpO 2 + and the complexation is strengthened as the temperature is increased. The complexation is endothermic and is entropy-driven. The enhancement of the complexation at elevated temperatures is primarily attributed to the increasingly larger entropy gain when the water molecules are released from the highly-ordered solvation spheres of NpO 2 + and benzoate to the bulk solvent where the degree of disorder is higher at higher temperatures. The spectroscopic features of the Np(V)/benzoate system, including the effect of temperature on the absorption bands, are discussed in terms of ligand field splitting and a thermal expansion mechanism. [ABSTRACT FROM AUTHOR]

The behavior in aqueous solution of the doubly-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate-)-g-poly(N-isopropylacry-lamide)-g-poly(N,N-dimethylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM, was compared to that of the single-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate)-g-poly(N-isopropylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM. The investigation through turbidimetry, pyrene fluorescence probing, viscometry and dynamic light scattering revealed that the existence of the hydrophilic poly(N,N-dimethylacrylamide), PDMAM, side chains in the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM did not perturb the thermoresponsiveness of the poly(N-isopropylacrylamide), PNIPAM, side chains, but favoured the stabilization in water of the core-corona nanoparticles, formed upon heating the aqueous solution above the Lower Critical Solution Temperature (LCST) of PNIPAM chains. In a similar manner, the complexes formed between the cationic surfactant N,N,N,N-dodecyltrimethylammonium chloride, DTAC, and the oppositely charged backbone of the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM were stabilized in water by the PDMAM side chains. Thus, phase separation was prevented upon heating the aqueous solution above LCST. Moreover, the ¹H NMR study revealed that the fraction of PNIPAM chains forming solid-like aggregates at high temperature increased substantially in the presence of DTAC, as a consequence of the net charge decrease of the backbone due to the polymer/DTAC complexation. [ABSTRACT FROM AUTHOR]

The controlled assembly of oppositely charged polysaccharides led to colloids stable in physiological media, capable of encapsulating a molecular drug and of sorbing proteins at their interface. Two types of particles were obtained: both chitosan-dextran sulfate (CS-DS) and chitosan-heparin (CS-HP) stable over 30days in PBS at 25 and 37°C. At gastric pH 1.2, these particles remained stable over 3days, enough for a stomach transit. The structural analysis by small angle X-ray scattering (SAXS) showed that CS-DS surface was semi-rough and chains inside particle exhibited rod-like conformation. Moreover, the particle interfaces could efficiently be functionalized with anti-OVA or anti-α4β7 antibodies, in PBS, with the conservation of the antibody bioactivity over at least 8days. Finally, during the assembly process, a molecular model drug, AMP, could be encapsulated with a loading efficiency up to 72% for CS-DS particles and 66% for CS-HP. All these data establish that the controlled assembly process under equilibrium conditions lead to colloids well suited for the targeted nanodelivery of drugs. [ABSTRACT FROM AUTHOR]

Mercury (Hg) compounds are widely distributed toxic environmental and industrial pollutants and they may bring danger to growth and development of aquatic organisms. The distribution of Hg species in the 3 percent NaCl solution was calculated using the chemical equilibrium model Visual MINTEQ, which demonstrated that Hg was mainly complexed by chlorides in the pH range 5.0–9.0 and the proportions of HgCl4 2−, HgCl3 − and HgCl2(aq) reached to 95 percent of total Hg. Then the effects of cations (Ca2+, Mg2+, K+ and H+), anions (HCO3 −, NO3 −, SO4 2− and HPO4 2−) and complexing agents (ethylene diamine tetraacetic acid (EDTA) and dissolved organic matter (DOM)) on Hg toxicity to Photobacterium phosphoreum were evaluated in standardized 15min acute toxicity tests. The significant increase of 6.3-fold in EC50 data with increasing pH was observed over the tested pH range of 5.0–8.0, which suggested the possible competition between hydroxyl and the negatively charged chloro-complex. By contrast, it was found that major cations (Ca2+, Mg2+ and K+) have little effect on Hg toxicity to P. phosphoreum. An interesting finding was that the addition of HPO4 2− significantly increased Hg toxicity, which may imply that the addition of phosphate increased the soluble Hg–chloro complex species. Additions of complexing agents (EDTA and DOM) into the exposure water increased Hg bioavailability via complexation of Hg. Finally, a model which incorporated the effect of pH, HPO4 2−, HCO3 −, SO4 2− and DOM on Hg toxicity was developed to predict acute Hg toxicity for P. phosphoreum, which may be a useful tool in setting realistic water quality criteria for different types of water. [Copyright &y& Elsevier]

Highlights: [•] The thermodynamic parameters of the formed complexes have been reported. [•] Application of cyclodextrins markedly enhanced aqueous solubility of acyclovir derivative. [•] Enhanced solubility of 6-Ph-O-Me-TACV is caused by insertion of aromatic part of drug molecule into cyclodextrin cavity. [•] The stability constants of the complexes (51-313) allowed for easy release and transfer of the drugs in body fluids. [•] Partition coefficients between 1-octanol and aqueous buffered cyclodextrin solutions have been reported. [ABSTRACT FROM AUTHOR]

Highlights: [•] Surface complexation model developed for predicting Hg(II) adsorption onto goethite. [•] New method developed for describing a goethite sample’s surface heterogeneity. [•] Developed approach to quantify carbonate contamination in solid–solution systems. [•] Model proved capable of predicting Hg(II) adsorption over all conditions tested. [ABSTRACT FROM AUTHOR]

Highlights: [•] Surface speciation of U(VI) on maghemite at liquid–solid interface. [•] U(VI) is predominantly bound to maghemite via outer sphere complexes. [•] Formation of ternary surface complexes probed by online monitoring. [•] Different type of U(VI) complexation on maghemite and ferrihydrite is revealed. [Copyright &y& Elsevier]

Abstract: Plant products are rich in minerals, e.g. iron, as well as in phenolic acids, e.g. gallic acid (GA). GA contains a galloyl group leading to complexation with iron, and thus decreasing the bioavailability of iron. As complexation of GA–iron seems to be pH-dependent, lactic acid fermentation could be a technique to improve the bioavailability of iron. On the other hand different lactobacillus strains are able to metabolize GA into pyrogallol (PYR). In this study, the influence of pH and microbial conversion of GA on iron complexation during fermentation with Lactobacillus plantarum and Lactobacillus collinoides was investigated. PYR was detected as the only conversion product of GA. At the end of the fermentations, a decreased pH to 5 and 5.7 for L. plantarum and L. collinoides respectively was measured. Based on the colour change during fermentation and based on the spectrophotometric analysis with standards, complexation between iron and GA or PYR was established. From the results, it could be concluded that the effect of pH on complexation was more pronounced compared to the microbial conversion of GA. Based on these results, L. plantarum is an efficient bacteria to destabilize the formed complexes which could lead to an improved bioavailability of iron. [Copyright &y& Elsevier]

Highlights: [•] Surface conductivity can diminish the electrophoretic mobility of SiO2 nanoparticles. [•] Electrophoretic mobility can be corrected of surface conductivity. [•] Surface complexation models allow surface conductivity estimation. [•] Surface conductivity explains the low apparent zeta potential of SiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Excited states of TP+@CB[n] inclusion complexes interact with Fe2+. [•] No ternary TP+@CB[n] complexes with Fe2+ in aqueous solutions were observed. [•] The quenching rate constants of TP+ triplet excited states decreases in CB[n]. [ABSTRACT FROM AUTHOR]

Highlights: [•] Chitosan (Ch) complexation with surface active ionic liquids (ILs). [•] Nature of interactions driving complexation in various concentration regimes of surfactant. [•] Detailed physicochemical and imaging study of Ch-ILs systems. [•] Comparison of interactions of Ch-ILs vs. Ch-surfactants (conventional). [•] Synthesis and characterization of Ch nanoparticles with assistance of ILs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Isotherm modeling predicted multilayer complexation for Sb(V) on red earth soils. [•] Bidentate mononuclear and binuclear complexes formation was predicted by SCM. [•] Sb(V) sorption peaked at pH 4 and pH dependence was not observed for Sb(III). [•] Spectroscopic and modeling data revealed Fe O Sb for inner sphere complexation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pure iron was used as substrate for study of mussel adhesive protein adsorption. [•] Multianalytical in situ studies of the protein film forming and complexation. [•] Spectroscopy analysis was assisted by ab initial computational modeling. [•] Details of the film formation, structure, property, and compaction mechanism. [•] Tri-catechol/Fe3+ complexation leads to compaction of the surface protein film. [ABSTRACT FROM AUTHOR]