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In the context of depollution and textile wastewater treatment, the sorption-based processes are good candidates to achieve the efficient removal of such toxics substances as dyes. In the present study, the exchange−adsorption from aqueous solutions of three azoic dyes, Methyl Orange (MO), Orange II (OII), and Orange G (OG), onto Mg−Al−LDH−NO 3 layered double hydroxides (LDH, molar Mg:Al ratio of 2) was investigated through monitoring all retained and removed species in combination with direct calorimetry and X-ray diffraction measurements. Kinetic curves, determined for several initial concentrations of the three dyes, indicated that the process was fast (between 60 and 100 min) and followed the pseudo-second order model in line with the passage of the removed dye through a chemisorption stage, thus constituting the ratelimiting step. Dye adsorption isotherms (H2-type) showed some differences in the maximum adsorption quantity (5.5 mmol g −1 , MO; 2.7 mmol g −1 , OII; 1.7 mmol g −1 , OG), consistent with anionic exchange capacity and adsorption on the external surface, depending on the cross-sectional area of the dye species and with their hydrophobic− hydrophilic character. The uptake of sodium cations as a function of the dye type and the surface coverage ratio pointed that the counterions can either stay in solution or be adsorbed to neutralize the free −SO 3 − moieties or other anionic species in the interlayer space. The cumulative enthalpy of displacement was negative in conformity with the exothermic character of the overall process. The intercalation of dye anions into the interlayer space of LDH materials led to its expansion with various distances being dependent both on the dye type and on the overall exchange balance. The latter included also the desorption of nitrates as well as the presence of carbonate species within the interlayer space, due to exchange in open systems exposed to the ambient atmosphere.

Different continuous flow processes allow the production of LDHs particles with controlled size and morphology or individual nanosheets, and of LDH-based hybrids and nanocomposites. Continuous flow method Microreactor Static methodMetal salt solution Alkaline solution BatchLDH particle diameter Volume (%) LDH particle diameter Volume (%) Metal salt solution Alkaline solution Synthesis of layered double hydroxides through continuous flow processes: A review

Aqueous suspensions of highly stable Mg/Al layered double hydroxide (LDH) nanoparticles were obtained via a direct and fully colloidal route using asymmetric poly(acrylic acid)-b-poly(acrylamide) (PAA-b-PAM) double hydrophilic block copolymers (DHBCs) as growth and stabilizing agents. We showed that hybrid polyion complex (HPIC) micelles constituted of almost only Al(3+) were first formed when mixing solutions of Mg(2+) and Al(3+) cations and PAA3000-b-PAM10000 due to the preferential complexation of the trivalent cations. Then mineralization performed by progressive hydroxylation with NaOH transformed the simple DHBC/Al(3+) HPIC micelles into DHBC/aluminum hydroxide colloids, in which Mg(2+) ions were progressively introduced upon further hydroxylation leading to the Mg-Al LDH phase. The whole process of LDH formation occurred then within the confined environment of the aqueous complex colloids. The hydrodynamic diameter of the DHBC/LDH colloids could be controlled: it decreased from 530 nm down to 60 nm when the metal complexing ratio R (R = AA/(Mg + Al)) increased from 0.27 to 1. This was accompanied by a decrease of the average size of individual LDH particles as R increased (for example from 35 nm at R = 0.27 down to 17 nm at R = 0.33), together with a progressive favored intercalation of polyacrylate rather than chloride ions in the interlayer space of the LDH phase. The DHBC/LDH colloids have interesting properties for biomedical applications, that is, high colloidal stability as a function of time, stability in phosphate buffered saline solution, as well as the required size distribution for sterilization by filtration. Therefore, they could be used as colloidal drug delivery systems, especially for hydrosoluble negatively charged drugs.

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Two organosolv lignins extracted during pilot runs of the Fabiola process were analyzed, fractionated and chemically modified with ethylene carbonate (EC) to produce building blocks suitable for polymer synthesis. Isolation of low dispersity fractions relied on the partial solubility of the lignins in organic solvents. Lignins solubility was first evaluated and analyzed with Hansen and Kamlet-Taft solubility parameters, showing a good correlation with the solvents dipolarity/polarizability parameter π*. The results were then used to select a sequence of solvents able to fractionate the lignins into low dispersity fractions of increasing molar masses, which were analyzed by 31 P NMR, SEC and DSC. The lignins were then reacted with EC, to convert the phenolic OH groups into primary aliphatic OH groups. The reactivity of the organosolv lignins was high, and milder reaction conditions than previously reported were sufficient to fully convert the phenolic OH groups. A gradual reduction in reactivity with increasing molar mass was evidenced and attributed to reduced solubility of high molar mass fragments in EC. Undesirable crosslinking side reactions were evidenced by SEC, but were efficiently limited thanks to a fine control of the reaction conditions, helping to maximize the benefits of the developed lignin modification with EC.

The controlled growth of cyano-bridged coordination polymers was developed by using layered double hydroxides (LDH) as bidimensional host structures. A series of nanocomposites [B0.66Al0.33(OH)2]0.33+/[MFe(CN)6]− (B = Mg, Ni; M = Ni, Co) were obtained by step-by-step coordination of hexacyanoferrate building blocks and bivalent metal ions into the interlayer domain of the matrix. The obtained nanocomposites were studied by infrared (IR), UV−vis spectroscopy, X-ray diffraction, and magnetic measurements, which reveal the presence of cyano-bridged coordination polymers [MFe(CN)6]− intercalated into the LDH. [MFe(CN)6]− confined into diamagnetic [Mg0.66Al0.33(OH)2]0.33+ and magnetic [Ni0.66Al0.33(OH)2]0.33+ LDH layers show the presence of a spin-glass behavior in which the magnetic parameters depend on the nature of both the confined coordination polymer and the LDH host.

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