Interfacial interactions between nitrifying bacteria and mineral carriers in aqueous media determined by contact angle measurements and thin layer wicking

Contact angle measurements enable the determination of the surface free energy on flat and smooth solid surfaces. The thin layer wicking technique permits this determination for powdered materials. Both techniques were assayed on limestone and basalt which were the materials used as supports for bacterial adhesion. The resulting surface free energy components were compared. The free energy of interaction between nitrifying bacteria and support materials in aqueous medium (∆G132) was calculated and correlated with bacterial adhesion observed in a previous study. Although the values of the polar and apolar components were not exactly the same, both techniques lead to the same conclusions in terms of the ability for bacterial adhesion.Project 01:REGII:6:96.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI - BD:9121:96

Effect of the Molecular Weight of Polyvinyl Alcohol on Some Adsorption Parameters in the Titania-Polymer Solution System

Fractions of polyvinyl alcohol (PVA) obtained by separation of the PVA samples of the mean molecular weight of 72000 and 125000 have been studied. The effect of the molecular weight of PVA, pH value and concentration of the solution on the adsorbed amount and the thickness of the adsorption layer of PVA (<5) were measured. The value of d was determined from the viscosity change of titania suspensions with adsorbed PVA in relation to the same suspensions without PVA. The volume occupied by a polyvinyl alcohol molecule at the interface region was evaluated from the adsorbed amount and the value of d. Thus calculated volume was then compared with the volume occupied by a PVA molecule in the bulk solution

Electrostatic Potentials at Solid/Liquid Interfaces

This review deals with electrostatic potentials within solid/electrolyte interfaces. The electrostatic potentials of several planes are defined and discussed: the inner surface potential affecting the state of charged surface species due to interactions with potential determining ions (Ψ0), the potential affecting the state of associated counterions (Ψβ), the potential at the onset of diffuse layer (Ψd) and the electrokinetic potential (ζ). The relevance of zero values of these potentials is also discussed and the corresponding points of zero charge are defined. Experimental methods for the measurement of the interfacial potentials are presented. The relations between potentials and surface charges are given on the basis of the Surface Complexation model. Some experimental findings are provided

Electrostatic Potentials at Solid/Liquid Interfaces

This review deals with electrostatic potentials within solid/electrolyte interfaces. The electrostatic potentials of several planes are defined and discussed: the inner surface potential affecting the state of charged surface species due to interactions with potential determining ions (Ψ0), the potential affecting the state of associated counterions (Ψβ), the potential at the onset of diffuse layer (Ψd) and the electrokinetic potential (ζ). The relevance of zero values of these potentials is also discussed and the corresponding points of zero charge are defined. Experimental methods for the measurement of the interfacial potentials are presented. The relations between potentials and surface charges are given on the basis of the Surface Complexation model. Some experimental findings are provided

Influence of Solution pH on Stability of Fumed Silica–Polyacrylic Acid Systems

The influence of polyacrlic acid (PAA) adsorption on fumed silica (SiO2) surface on suspension stability has been studied. Сhanges in the suspension stability were monitored using a Turbiscan LabExpert with a TLAb Cooler cooling module at 25oC. PAA is an anionic polymer containing carboxyl groups; therefore all the measurements were carried out at different pH 3, 6 and 9. Analysis of obtained transmission and backscattering curves and Turbiscan Stability Indexes (TSI) allowed determination of the most probable mechanism of the system stability.Вивчено вплив адсорбції поліакрилової кислоти (ПAК) на поверхні високодисперсного кремнезему (SiO2) на стабільність суспензії. Зміни стабільності суспензії спостерігались за допомогою приладу Turbiscan LabExpert із охолоджуючим модулем TLAb Cooler при 25oC. ПAК є аніонним полімером, що містить карбоксильні групи, тому всі вимірювання проводились при різних рН (3, 6 та 9). Аналіз одержаних кривих перенесення та зворотнього розсіяння, а також індексів стабільності (Turbiscan Stability Indexes (TSI)) дозволив визначити найбільш вірогідний механізм стабілізації вивчених систем.Изучено влияние адсорбции полиакриловой кислоты (ПAA) на поверхности высокодисперсного кремнезема (SiO2) на стабильность суспензии. Изменения стабильности суспензии наблюдались с помощью прибора Turbiscan LabExpert с охлаждающим модулем TLAb Cooler при 25oC. PAA является анионным полимером, содержащим карбоксильные группы, поэтому все измерения проводились при различных рН (3, 6 и 9). Анализ полученных кривых переноса и обратного рассеяния, а также индексов стабильности (Turbiscan Stability Indexes (TSI)) позволил определить наиболее вероятный механизм стабилизации изученных систем

Surface Free Energy of Textile

Opisane su pojave na graničnim površinama u mokrim procesima oplemenjivanja tekstila, od kojih su najznačajnije - kvašenje, penetracija i adsorpcija. Ove se pojave događaju u kontaktu dviju površina - kapljevine (kupelji) i krutine (tekstila), čija površinska svojstva određuju jakost međudjelovanja kruto-kapljevito. Ta su međudjelovanja rezultat slobodne površinske energije tekstila i svojstva kupelji kojom se površina tekstila obrađuje. Slobodna površinska energija nekog materijala (krutine) zbroj je energetskih doprinosa propisanih različitim površinskim interakcijama, nepolarnim Lifshitz-van der Waalsovim i polarnim kiselo-baznim interakcijama. Najčešće primjenjivana metoda određivanja slobodne površinske energije direktnim mjerenjem dodirnog kuta (kuta kvašenja) ima znatnih ograničenja kada je u pitanju tekstil, dakle, heterogena, porozna i najčešće hidrofilna površina. Metoda određivanja dodirnog kuta koristi se uglavnom na vrlo glatkim, homogenim, najčešće hidrofobnim površinama, kao što su npr. polimerne folije. Problem određivanja slobodne površinske energije na heterogenim, poroznim materijalima, slabo definirane geometrije, kao što su praškasti materijali, tekstil, keramika i sl. riješio je Chibowski polazeći od modificirane Washbornove jednadžbe koja se odnosi na mjerenje kapilarnosti poroznih materijala. U ovom radu opisan je pristup određivanju slobodne površinske energije i odgovarajućih energetskih komponenata na tekstilu, koji se temelji na eksperimentima kvašenja i penetracije nekoliko vrsta otapala, polarnih i nepolarnih na uzorcima tekstila, korištenjem aparature po Chibowskom i Holyszu.Phenomena on the interfaces in textile wet finishing processes are described: wetting, penetration and adsorption. These phenomena occur in contact of two surfaces - liquid (bath) and solid (textile) whose surface properties determine the intensity of the solid-liquid interaction. These interactions are the result of the surface free energy of textile and the property of treatment bath used for the treatment of the textile surface. The surface free energy of a material (solid) is the sum of energy contributions required by different surface interactions, non-polar Lifshitz van der Waals and polar acid-basic interactions. The mostly used method for determining the surface free energy by direct measuring the contact angle (wetting angle) contains considerable restrictions when it comes to textile, thus a heterogeneous, porous and mostly hydrophilic surface. The method of determining contact angle is used mostly on very smooth, homogeneous, mostly hydrophobic surface, such as polymer foils. The problem of determining surface free energy on heterogeneous, porous materials, which have a poorly defined geometry, such as powder materials, textile, ceramics and the like, was solved by Chibowski, starting from Washburn equation which applies to the measurement of the capillarity of porous materials. This paper describes an approach to the determination of surface free energy and corresponding energy components on the textile. It is based on the experiments of wetting and penetration of several solvents, polar and non-polar ones, on textile samples using the equipment made by Chibowski and Holysz

Adsorption of polyelectrolytes from semi-dilute solutions on an oppositely charged surface

We propose a detailed description of the structure of the layer formed by polyelectrolyte chains adsorbed onto an oppositely charged surface in the semi-dilute regime. We combine the mean-field Poisson-Boltzmann-Edwards theory and the scaling functional theory to describe the variations of the monomer concentration, the electrostatic potential, and the local grafting density with the distance to the surface. For long polymers, we find that the effective charge of the decorated surface (surface plus adsorbed polyelectrolytes) can be much larger than the bare charge of the surface at low salt concentration, thus providing an experimental route to a "supercharging" type of effect.Comment: 14 pages, 6 figure

The temperature effect on electrokinetic properties of the silica–polyvinyl alcohol (PVA) system

The influence of polyvinyl alcohol (PVA) adsorption on the structure of the diffuse layer of silica (SiO2) in the temperature range 15–35 °C was examined. The microelectrophoresis method was used in the experiments to determine the zeta potential of the solid particles in the absence and presence of the polymer. The adsorption of PVA macromolecules causes the zeta potential decrease in all investigated SiO2 systems. Moreover this, decrease is the most pronounced at the highest examined temperature. Obtained results indicate that the conformational changes of adsorbed polymer chains are responsible for changes in electrokinetic properties of silica particles. Moreover, the structure of diffuse layer on the solid surface with adsorbed polymer results from the following effects: the presence of acetate groups in PVA chains, the blockade of silica surface groups by adsorbed polymer and the shift of slipping plane due to macromolecules adsorption

Materials selection for optimum energy production by double layer expansion methods

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Power Sources. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Power Sources (2014) DOI:http://dx.doi.org/10.1016/j.jpowsour.2013.12.125The capacitive mixing procedure for energy extraction based on Double Layer Expansion (CDLE) belongs to the group of so-called CAPMIX techniques, which aim at obtaining energy from the salinity difference between fresh and sea waters. Specifically, the CDLE technique takes advantage of the voltage rise that occurs when sea water is exchanged for river water in a pair of porous electrodes which jointly behave as an electrical double layer supercapacitor. In this article, we deal with some experimental aspects that are key for optimizing the extracted energy, and have not been analyzed yet with sufficient detail. This investigation will help in evaluating those parameters which we need to be fixed in a future CDLE device. These include the charging potential, the durations of the different cycle steps, the load resistance used, and the porosity and hydrophilicity of the carbon.Departamento de Física Aplicada, Universidad de GranadaThe research leading to these results received funding from the European Union 7th Framework Programme (FP7/2007-2013) under agreement No. 256868. Further financial support from Junta de Andalucía (Spain), project PE-2008-FQM3993 is also gratefully acknowledged