"Soft and rigid" dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate

Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiols (1, 2-ethanedithiol (ED) or 4, 4'-biphenyldithiol) to create the thiol (-SH) groups on polymer surface. This "short" dithiols are expected to be fixed via one of -SH groups to radicals created by the plasma treatment on the PET surface. "Free" -SH groups are allowed to interact with Au nanoparticles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrokinetic analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the modified PET were studied by atomic force microscopy (AFM). The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on the modified surface only in the case of biphenyldithiol pretreatment. The possible explanation is that the "flexible" molecule of ethanedithiol is bounded to the activated PET surface with both -SH groups. On the contrary, the "rigid" molecule of biphenyldithiol is bounded via only one -SH group to the modified PET surface and the second one remains "free" for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface

A review on development and application of plant-based bioflocculants and grafted bioflocculants

Flocculation is extensively employed for clarification through sedimentation. Application of eco-friendly plant-based bioflocculants in wastewater treatment has attracted significant attention lately with high removal capability in terms of solids, turbidity, color, and dye. However, moderate flocculating property and short shelf life restrict their development. To enhance the flocculating ability, natural polysaccharides derived from plants are chemically modified by inclusion of synthetic, nonbiodegradable monomers (e.g., acrylamide) onto their backbone to produce grafted bioflocculants. This review is aimed to provide an overview of the development and flocculating efficiencies of plant-based bioflocculants and grafted bioflocculants for the first time. Furthermore, the processing methods, flocculation mechanism, and the current challenges are discussed. All the reported studies about plant-derived bioflocculants are conducted under lab-scale conditions in wastewater treatment. Hence, the possibility to apply natural bioflocculants in food and beverage, mineral, paper and pulp, and oleo-chemical and biodiesel industries is discussed and evaluated

Flocculation efficiency of reacetylated water soluble chitosan versus commercial chitosan

In this work, the flocculation efficiency of reacetylated chitosans were compared with those of commercially available chitosans. The flocculation properties were investigated in dispersion of clay by means of turbidity measurements, colloid titration and measurements of the floc size. Reacetylated chitosan dissolves in deionized water without any additives and exhibits good flocculation properties like a wider flocculation window but a higher amount of polymer. For commercial chitosan lower amounts of polymer were required for the flocculation of clay dispersion. Flocculation with commercial chitosan is possible even in basic range

Modification of Black Film Hydration by Infrared Irradiation

URL: http://www-spht.cea.fr/articles/S03/024 Contrôle de l'hydratation d'un film noir par infrarougeInternational audienceWe report the behavior of Newton and Common Black Films (NBF and CBF respectively) irradiated by a low power infrared source, for different kinds of surfactant. During irradiation, the film structure is continuously investigated by means of X-ray reflectivity. The irradiation reduces the film thickness by extracting water from the central core. Different processes are involved: evaporation of bonded water molecules through the aliphatic medium in the NBF and thermo-osmotic flow of liquid water in the CBF. In all cases the process is reversible when the irradiation is stopped

Cationic flocculants carrying hydrophobic functionalities: Applications for solid/liquid separation

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size

Formation of polyelectrolyte complexes in a polycarboxybetaine/weak polyanion system

Polycarboxybetaines - polymers containing a substituted ammonium moiety and a carboxylate group in every monomer units - show in aqueous solutions a pH-dependent intramolecular charge interactions. Here, we show that despite of this intramolecular charge effect mixing positively charge polycarboxybetaine and oppositely charged poly(maleic acid-co-propene) can yield polyelectrolyte complexes (PEC). Dynamic light scattering and viscometry has proved formation of highly swollen PEC nanoparticles with sizes in the range of 5-8 nm at n-/n+ ratio from 0.6 to 1.0. Significant difference in charge densities and molecular dimensions in the solution were suggested as the main reasons for deviation from 1:1 PEC stoichiometry