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A new one-pot synthesis method optimized by a 23 experimental design was developed to prepare a biosorbent, sugarcane bagasse cellulose succinate pyromellitate (SBSPy), for the removal of Cu(II) and Zn(II) from single-component aqueous solutions, in batch and continuous modes. The bi-functionalization of the biosorbent with ligands of different chemical structures increased its selectivity, improving its performance for removing pollutants from contaminated water. The succinate moiety favored Cu(II) adsorption, while the pyromellitate moiety favored Zn(II) adsorption. Sugarcane bagasse (SB) and SBSPy were characterized using several techniques. Analysis by 13C Multi-CP SS NMR and FTIR revealed the best order of addition of each anhydride that maximized the chemical modification of SB. The maximum adsorption capacities of SBSPy for Cu(II) and Zn(II), in batch mode, were 1.19 and 0.95 mmol g-1, respectively. Homogeneous surface diffusion, intraparticle diffusion, and Boyd models were used to determine the steps involved in the adsorption process. Isothermal titration calorimetry was used to assess changes in enthalpy of adsorption as a function of SBSPy surface coverage. Fixed-bed column adsorption of Cu(II) and Zn(II) was performed in three cycles, showing that SBSPy has potential to be used in water treatment. Breakthrough curves were well fitted by the Thomas and Bohart-Adams models. [ABSTRACT FROM AUTHOR]

Abstract: This work developed a new and efficient method of extracting and separating Co(II), Ni(II) and Cd(II) in aqueous two-phase systems (ATPS) composed of triblock copolymer (L64)+Na2C4H4O6 +water and L64+Li2SO4 +water using the hydrophobic extractant 1-nitroso-2-naphtol, which complexes the metal ions and partitions in the triblock copolymer micelles in the ATPS top phase. Metal extraction from the salt-rich phase to the copolymer – rich phase is strongly affected by the fine-tuning of the following parameters: amount of added extractant, type of electrolyte, pH, and tie-line length. Excellent separation factors (S i,j) between the metals were obtained at pH = 3.00 (S Co,Cd = 1550 and S Ni,Cd = 16,700) and pH = 1.00 (S Co,Ni = 826). In the interference study, Co(II) was selectivity extracted in the top phase in the presence of Ni(II) and Cd(II) in a concentration of up to 20 times the cobalt level in the system. [Copyright &y& Elsevier]

A bioadsorbent (CEDA) capable of adsorbing As(V) and Cu(II) simultaneously was prepared by tosylation of microcrystalline cellulose (MC) and nucleophilic substitution of the tosyl group by ethylenediamine. MC, tosyl cellulose, and CEDA were characterized by elemental C, H, N, and S analysis, infrared spectroscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The adsorption of As(V) and Cu(II) on CEDA was evaluated as a function of solution pH, contact time, and initial solute concentration. The maximum adsorption capacities of CEDA for As(V) and Cu(II) were 1.62 and 1.09 mmol g−1, respectively. The interactions of As(V) and Cu(II) with CEDA were elucidated using thermodynamic parameters, molecular quantum mechanics calculations, and experiments with ion exchange of Cd(II) by Cu(II), and As(V) by SO 4 2−. Adsorption enthalpies were determined as a function of surface coverage of the CEDA, using isothermal titration calorimetry, with Δ ads H ° values of −32.24 ± 0.07 and −93 ± 2 kJ mol−1 obtained for As(V) and Cu(II), respectively. The potential to reuse CEDA was evaluated and the interference of other ions in the adsorption of As(V) and Cu(II) was investigated. Multi-component experiments showed that Cd(II), Co(II), Ni(II), and Pb(II) did not interfere in the adsorption of Cu(II), while SO 4 2− inhibited As(V) adsorption. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Sugarcane bagasse cellulose mixed ester succinate phthalate (SBSPh) was synthesized by a novel one-pot reaction method. The effects of temperature, time and mole fraction of succinic anhydride (χ SA) on the responses weight gain (wg), number of carboxylic acid groups (n T,COOH), and adsorption capacity (q) of Co2+ and Ni2+ were evaluated by a 23 experimental design. The chemical structure of the material was elucidated by Fourier transform infrared, 13C Multiple Cross-Polarization solid-state NMR spectroscopy and 1H NMR relaxometry. The best SBSPh synthesis condition (100 °C, 11 h, χ SA of 0.2) yielded a wg of 59.1%, n T,COOH of 3.41 mmol g−1, and values of q Co 2+ and q Ni 2+ of 0.348 and 0.346 mmol g−1, respectively. The Sips model fitted better the equilibrium data, and the maximum adsorption capacities (pH 5.75 and 25 °C) estimated by this model were 0.62 and 0.53 mmol g−1 for Co2+ and Ni2+, respectively. The Δ ads H ° values estimated by isothermal titration calorimetry were 8.43 and 7.79 kJ mol−1 for Co2+ and Ni2+, respectively. Desorption and re-adsorption efficiencies were evaluated by a 22 experimental design, which showed that SBSPh adsorbent can be recovered and reused without significant loss of adsorption capacity. [ABSTRACT FROM AUTHOR]

In the second part of this series of studies, the monocomponent adsorption of Cu 2+ , Co 2+ and Ni 2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2 2 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed ( Q max ), efficiency of the adsorption process ( EAP ), and effective use of the bed ( H ). The higher Q max for Cu 2+ , Co 2+ and Ni 2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (Δ ads H °) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of Δ ads H ° were in the range of 3.0–6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption ( E des ) and re-adsorption ( E re-ads ) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E des and E re-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale. [ABSTRACT FROM AUTHOR]

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g −1 at pH 4.5, and 1.734 and 1.230 mmol g −1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol −1 , indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions. [ABSTRACT FROM AUTHOR]

In the third part of this series of studies, the adsorption of the basic textile dyes auramine-O (AO) and safranin-T (ST) on a carboxylated cellulose derivative (CTA) were evaluated in mono- and bi-component spiked aqueous solutions. Adsorption studies were developed as a function of solution pH, contact time, and initial dye concentration. Adsorption kinetic data were modeled by monocomponent kinetic models of pseudo-first- (PFO), pseudo-second-order (PSO), intraparticle diffusion, and Boyd, while the competitive kinetic model of Corsel was used to model bicomponent kinetic data. Monocomponent adsorption equilibrium data were modeled by the Langmuir, Sips, Fowler-Guggenhein, Hill de-Boer, and Konda models, while the IAST and RAST models were used to model bicomponent equilibrium data. Monocomponent maximum adsorption capacities for AO and ST at pH 4.5 were 2.841 and 3.691 mmol g −1 , and at pH 7.0 were 5.443 and 4.074 mmol g −1 , respectively. Bicomponent maximum adsorption capacities for AO and ST at pH 7.0 were 1.230 and 3.728 mmol g −1 . Adsorption enthalpy changes (Δ ads H ) were obtained using isothermal titration calorimetry. The values of Δ ads H ranged from −18.83 to −5.60 kJ mol −1 , suggesting that physisorption controlled the adsorption process. Desorption and re-adsorption of CTA was also evaluated. [ABSTRACT FROM AUTHOR]

Aqueous two-phase systems (ATPSs) are strategic liquid-liquid systems for extraction and purification of compounds. However, only a few studies have evaluated the thermodynamic parameters that allow comprehension of the partition process of different molecules. Here, we investigated the chymosin (Chy) partitioning behavior in macromolecule + salt + water ATPSs by obtaining the partition coefficient ( ), Gibbs free energy change of transfererence ( ), enthalpy change of transference ( ), and entropy change of transference ( ), at infinite dilution, and their dependence on the ATPS properties. Chy transfer from the bottom to the top phase of the ATPS was enthalpically driven, with -4.84 kJ mol-1 < < -170.34 kJ mol-1 and -11.69 J mol-1 K-1 < < -558.95 J mol-1 K-1 characterizing an enthalpy-entropy compensation process; -1.36 kJ mol-1 < < -3.77 kJ mol-1. became more negative as the tie-line length increased, showing that specific macromolecule-Chy interactions determine the enzyme concentration in the top phase. The nature of the cation/anion, hydrophobic/hydrophilic balance of the top phase, and macromolecule molar mass influence the intermolecular interaction between Chy and top phase components, changing the enzyme partition behavior. Negative parameters were attributed to the Chy transfer from a higher (bottom phase) to the lower (top phase) configurational entropy region. [ABSTRACT FROM AUTHOR]

Partitioning behavior of the whey proteins a-lactalbumin (α-la) and β-lactoglobulin (β-lg) in aqueous two-phase systems prepared with poly ethylene glycol (PEG) and sodium polyacrilate (NaPA) was investigated as a function of pH and polymer concentrations. It was observed that α-la concentrated in the PEG phase while β-lg concentrated in the NaPA phase. Response surface methodology was applied to optimize protein partitioning and to achieve the best conditions for their fractionation. Thermodynamic analysis based on isothermal titration microcalorimetry indicated that the partitioning of α-la was accompanied by endothermic heat and was entropically driven, while β-lg partitioning was accompanied by exothermic heat and was enthalpically driven at low polymer concentrations and entropically driven at high polymer concentrations. Purification and yield parameters were determined using fresh whey and the results allowed for conclusion of the great applicability of this new system for α-la and β-lg fractionation. [ABSTRACT FROM AUTHOR]

Highlights: [•] A green and low cost technique for metal separation was discovered. [•] Aqueous two-phase system (ATPS) is predominantly composed by water. [•] ATPS is an efficient substitute for liquid-liquid extraction using organic solvent. [•] Excellent separation factor for Cu and Zn was obtained. [Copyright &y& Elsevier]

Abstract: Magnesium aluminum layered double hydroxide (LDH) was synthesized by the co-precipitation method followed by calcination. The resulting materials were characterized by X-ray diffraction (PXRD) and attenuated total reflectance with Fourier transform infrared spectroscopy (FTIR/ATR) and simultaneous thermogravimetric analysis/differential scanning calorimetry coupled to mass spectrometry (TGA–DSC–MS). Calcined and non-calcined LDHs were used as adsorbents to remove azo dye Acid Green 68:1 in an aqueous solution. Adsorption experiment results indicated that calcined LDH possesses greater adsorption capacity (154.8mgg−1) than non-calcined LDH (99.1mgg−1). Isotherms showed that adsorption of the dye was more consistent with the Langmuir model. Kinetic experiments of calcined LDH adsorption showed that for low concentration (50, 100 and 200mgL−1), the system reached the adsorption equilibrium in 1, 2, and 4h, and for higher concentration after 10h. The best kinetic model was the pseudo-second order. Adsorption studies also showed that the capacity for adsorption of the dye by calcinated LDH does not significantly diminish with pH level variation. [Copyright &y& Elsevier]

The present study includes measurements of the phase composition, density, and refractive index of aqueous two-phase systems of poly(ethylene oxide) 1500 (PEO1500) + sodium thiosulfate + H2O at (283.15, 298.15, and 313.15) K. With the experimental results obtained, phase diagrams were established, and the influence of temperature on the densities, binodal position, and refractive index values was analyzed and discussed. The experimental tie-lines were described using the Othmer–Tobias correlation. The experimental aqueous two-phase system data were correlated with the nonrandom two-liquid (NRTL) thermodynamic model for the activity coefficients; the results were considered excellent according to a global root-mean-square deviation of 0.97 %. [ABSTRACT FROM AUTHOR]

Preferential solvation participate in various supramolecular self-assembly processes, whose thermodynamic properties can be modulated by the addition of ionic liquids (ILs). However, the effects of these liquids on the thermodynamics of the host-guest complexation process remain unexplored. In this study, the thermodynamic properties of the complexation between 1-dodecylpyridinium cations (C 12 Py+) and β-cyclodextrin (βCD) species in aqueous solutions with different concentrations of 1-alkyl-3-methylimidazolium halides (C n mimX) were investigated by isothermal titration calorimetry. In water, C 12 Py+ and βCD form a 1:1 inclusion complex, which is enthalpically (Δ H i c o = −9.2 ± 0.1 kJ mol−1) and entropically (T Δ S i c o = 16.1 ± 0.2 kJ mol−1) favorable. However, in IL aqueous solutions, all the βCD―C 12 Py+ thermodynamic parameters of the complexation change and this IL effect is dependent on the carbon chain length of C n mim+ cations. ILs with shorter alkyl chains (C n mim+, n ≤ 4) decreases the system entropy, while ILs with longer alkyl chains (C n mim+, n ≥ 6) reduce the enthalpy values. These effects are attributed to i) preferential solvation of surfactant tails by ILs; ii) ability of the ILs to modify the 3D water structure and iii) inclusion of IL molecules into the inner cavities of βCD. [ABSTRACT FROM AUTHOR]