Synthesis of a new flocculant based on poly(acrylamide-co-(N-octyl-4-vinylpyridinium bromide)) [AM5/VP5C8Br]-application for the turbidity removal from clay suspension

The interactions between poly(acrylamide-co-(N-octyl-4-vinylpyridinium bromide)) [AM5/VP5C8Br] cationic polyelectrolyte, and clay particles in dilute aqueous suspensions are studied in the aim of adsorption and flocculation. The extents of both phenomena are significantly influenced by the ionic strength of the medium. The adsorption of the clay particles on the copolymer chains occurs initially by the hydrophobic interaction. As flocculation mechanisms, the hydrophobic interaction between copolymer chains and the clay particles appears to be principal. In this work, we have prepared a copolymer which has been characterized by conductivity, viscosity, ¹H NMR, and FT-IR spectroscopies. The copolymer dosage and pH are two of the most important experimental parameters in the coagulation/flocculation operations used for study and optimization of the wastewater treatment operations. Under optimized conditions, 97% efficiency of the turbidity elimination, with a very low flocculant concentration of 3?ppm have been achieved in order to produce drinking water with standard limits around the world (< 1 NTU). The conclusion drawn on the basis of these results is that wastewater treatment using this new copolymer [AM5/VP5C8Br] has proved to be a good flocculant in overseeing of wastewater turbidity problems.     

Effect of Shear Flow on Nanoparticles Migration near Liquid Interfaces

The effect of shear flow on spherical nanoparticles (NPs) migration near a liquid–liquid interface is studied by numerical simulation. We have implemented a compact model through which we use the diffuse interface method for modeling the two fluids and the molecular dynamics method for the simulation of the motion of NPs. Two different cases regarding the state of the two fluids when introducing the NPs are investigated. First, we introduce the NPs randomly into the medium of the two immiscible liquids that are already separated, and the interface is formed between them. For this case, it is shown that before applying any shear flow, 30% of NPs are driven to the interface under the effect of the drag force resulting from the composition gradient between the two fluids at the interface. However, this percentage is increased to reach 66% under the effect of shear defined by a Péclet number Pe = 0.316. In this study, different shear rates are investigated in addition to different shearing times, and we show that both factors have a crucial effect regarding the migration of the NPs toward the interfacial region. In particular, a small shear rate applied for a long time will have approximately the same effect as a greater shear rate applied for a shorter time. In the second studied case, we introduce the NPs into the mixture of two fluids that are already mixed and before phase separation so that the NPs are introduced into the homogenous medium of the two fluids. For this case, we show that in the absence of shear, almost all NPs migrate to the interface during phase separation, whereas shearing has a negative result, mainly because it affects the phase separation.     

3-Methyl-3a,4-Dihydro-3H-Thiochromeno[4,3-c]isoxazol

Abstract  The crystal structure of the title compound, C₁₁H₁₁NOS, was determined by an X-ray diffraction analysis. The compound crystallizes in the monoclinic space group P2₁/c with cell parameters a = 10.533(2) ?, b = 12.7826(19) ?, c = 7.6491(17) ?, β = 107.997(17)^°, V = 979.5(3) ?³ and Z = 4. The S containing heterocycle adopts a sofa conformation, whereas the 5-membered ring adopts an envelope conformation. The crystal packing is characterized by weak C–H···N contacts and π-stacking interactions. Graphical Abstract  The title compound, 3-methyl-3a,4-dihydro-3H-thiochromeno[4,3-c]isoxazol was synthesized by an 1,3 dipolar cycloaddition reaction and its crystal structure determined. Single crystal X-ray diffraction analysis reveals that the aromatic 6-membered ring is planar, whereas the ring containing the S atom adopts a sofa conformation and the 5-membered ring an envelope conformation. The methyl group is in an equatorial position.      

Na1.72Mn3.28(AsO4)3

The single crystal of sodium manganese arsenate (1.72/3.28/12), Na_1.72Mn_3.28(AsO₄)₃, used for analysis was prepared by solid‐state reaction at 1073 K. The compound crystallizes in the monoclinic system in space group C2/c. The structure consists of a complex network of edge‐sharing MnO₆ octahedral chains, linked together by AsO₄ tetrahedra, forming two distinct channels, one containing Na⁺ cations and the other occupied statistically by Mn⁺ and Na⁺ cations.     

Dual fluorescence of 4-N,N-dimethylaminopyridine. Role of hydrogen-bonded complex in the ground state

A correlation is shown between the appearance of the dual fluorescence of 4-N,N-dimethylaminopyridine (DMAP) solutions and the formation of hydrogen-bonded of complexes in the ground state. A comparative absorption study between pyridine, N,N-dimethylaniline and DMAP shows that the hydrogen-bonded complex is situated on the amino nitrogen of DMAP. A “pretwisted” conformation of DMAP in the ground state isassumed due to this hydrogen-bonded complex. Simulations by intermolecular interaction calculations and spectroscopic calculations (CNDO/s) confrim the “twisting” influence of water molecules (and/or any other hydrogen bonding) on the amine in the ground state. This “pretwisting” in the ground state by hydrogen bonding is common in many other aromatic amines. Moreover, the deforming role of hydrogen bonding in the ground state seems to be a general phenomenon in flexible aromatic molecules.     

Novel green strategy to improve the hydrophobicity of cellulose nanocrystals and the interfacial elasticity of Pickering emulsions

The development of Pickering emulsions as ecologically correct stabilized with bio-based material by substituting synthetic petroleum-derived tensoactives assumed a very attractive level, representing the current guideline of the global market for homecare industry, food and beverage applications. In this wor, cellulose nanocrystals (CNCs), a hierarchically advanced biomaterial, were produced to stabilize innovative emulsions formulated with western soapberry Sapindus saponaria L. oil (SO). Besides, green surfactants (triterpene saponins extracted from S. saponaria L. pericarp; SAP) were also investigated to stabilize the oil/water interface. The synergistic combination between cellulose nanowhiskers and the bioactive glycosides has never been reported in the literature. Dynamic interfacial tensions of SAP and SO were firstly investigated, and their capacity to form a plastic membrane at oil/water interface was revealed. Response surface methodology (RSM) was employed to study the influence of the binary systems (CNC:SAP) on the stability of emulsified systems, such as size and zeta potential. In addition, a new calculation was proposed to determine the coverage of the oil droplets formed by the mixture of cellulose crystallites and natural surfactants. The optimal nanoemulsion composition was determined to be 60 w/w (%) of water, 23.905 w/w % of SO, 5 w/w % of CNC and 8.095 w/w% of SAP to produce of smallest droplet (165.1 nm) combined with higher zeta potential module (?46.7 mV). Results highlight the potential of Sapindus saponins and cellulose nanowhiskers for efficient producing label-friendly nanoemulsions applicable for drug, cosmeceutical or edible delivery systems.

Graphical abstract

     

Complex Formation of Acetic Acid with Ca(II) and Mg(II) Under Physiological Conditions

Potentiometric titrations of aqueous acetic acid alone and in the presence of Ca(II) or Mg(II) ions have been carried out under physiological conditions at the temperature 37 °C and ionic strength 0.15 mol⋅dm⁻³ (NaCl) at different ligand-to-metal ratios. Changes in pH were monitored with a glass electrode calibrated daily in terms of the hydrogen ion concentrations. Titration data within the pH range 2.5 to 6.6 were analyzed to determine stability constants using the SUPERQUAD program. Different combinations of complexes were considered during the calculation procedure for both systems, but evidence was found only for mononuclear ML and ML₂ species. Speciation calculations based on the corresponding constants were then used to simulate the species’ distributions.     

Strontium dicobalt orthophosphate

In crystalline SrCo₂(PO₄)₂; triclinicP¯1,M _r =395.4,a=5.014(2),b=8.639(4),c=9.691(1)Å,a=118.04(3),=75.09(4), =86.90(4)°,V=350.4(3)ų,Z=2,D _calc=3.747 g cm^–3, MoK=0.71069 Å,=12.49 mm^–1,F(000)=372,T=298 K,R=4.1% for 1190 obs. reflections; Co²⁺ and PO ₄ ^3– ions are found on planes parallel to (001). Co²⁺ occupies sites of four- and five-(trigonal bipyramidal) coordination with average Co-O distances, 1.948(8) and 2.087(8) Å, respectively. The blue color of solid is due to the tetrahedral coordination geometry of the four-coordinate copper atoms.