Este artículo estudia el mecanismo de flotabilidad del cuarzo en presencia de almidón no modificado y colectores catiónicos. El efecto depresor del polímero natural se muestra en soluciones ...ligeramente alcalinas ó neutras,dependiendo de la concentración y largo de la cadena hidrocarbonada del colector. La interacción específica almidón-cuarzo produce un desplazamiento en el P.I.E. del mineral hacia valores más ácidos de pH. El potencial de flujo (xi ) del cuarzo, en presencia de colector y almidón se aproxima a cero según sea la concentración de colector y el valor del pH. La adsorción del almidón sobre la superficie del mineral a 25º C, señala bajas densidades de adsorción a pH 9,5 lo cual explica la elevada flotabilidad del cuarzo a dicho valor de pH , acorde con los resultados obtenidos por otros autores.
The flotation of -10 μm diameter quartz particles using dodecyltrimethylammonium bromide (DTAB), one of the typical complete ionizable collectors, was carried out at pH 5, 7.4 and 10 by varying the ...DTAB concentration in the presence of 1×10-3 mol·dm-3 KNO3 as a supporting electrolyte. The adsorption density of dodecyltrimethylammonium ions (DTA+) and zeta potential of quartz were also measured in order to analyze the flotation results. The results obtained are summarized as follows. 1. Almost complete flotation is achieved at a surface coverage of DTA+ of the order of several percent on quartz surfaces. 2. The negative zeta potential of quartz decreases with DTAB concentration and changes its sign after passing through an isoelectric point (iep) at some particular DTAB concentration depending upon the pH of the solution. By analyzing the adsorption data at the iep using Stern-Langmuir adsorption isotherm, the free energy change of specific adsorption of DTA+, ΔGsp, was obtained as follows: pH 5, -4.4 kcal·mol-1; pH 7.4, -4.7 kcal·mol-1; pH 10-5.9 kcal·mol-1. 3. The bilayer adsorption of DTA+ occurs simultaneously on top of the first monolayer formed patchwise on the surface even at low surface coverage of DTA+, whereby the quartz surfaces are made hydrophilic and flotation ceases. No flotation occurred at an adsorption density of DTA+ corresponding to θDTA+=100%(corresponding. to the first monolayer coverage of 50%) at pH 10. This contrasts with the result of dodecylammonium acetate (DAA) at pH 9.8, in which quartz showed complete flotation even at an adsorption density of DAA corresponding to a bilayer adsorption. This is in support of the capillary condensation of undissociated dodecylamine at the point of contact between fine grained quartz particles. 4. There was no significant difference in the adsorption and flotation behavior at pH 5 between DTAB and DAA.
The stability of different type nanomaterials play an important role among recent scientific and industrial challenges, including the examination of the effect of polymers, surfactants and their ...mixture on surface and electric surface properties and aggregation extent of dispersed particles, which are of utmost importance. Bentonite and its composite with different nanomaterials are frequently used for instance in environmental protection for wastewater treatment, since due to their great specific surface area they have excellent sorption properties. There are several publications in the literature for the application of bentonite in drilling muds. By using them the fluid loss can be decreased during the drilling process, the filtration of the fluid can be increased, it also improves the rheological properties and the formation damage can also be mitigated. During research the investigation and the analysis of the zeta-potential of nanoparticles and their composites at different pH and salt content can be an interesting topic. During our experiments the electric surface properties of nanomagnetite synthetized in laboratory (NM), cation exchanged bentonite from Mád (Be) and the composite particles of these particles were investigated. Hybrid particles of different compositions (9:1, 7:3, 1:1, 3:7, 1:9) were analyzed at different potassium chloride concentrations (0.1 – 0.0001 M). The surface adsorption on the surface, i.e. the change in the surface charge can be traced well by analyzing the obtained zeta-potential values. The behavior of such systems was observed in the full pH interval, thus, valuable data were obtained regarding the colloidal stability. As for the stability, different requirements may emerge in practice, there are application fields where the colloidally stable system is advantageous, on the other hand, in some cases, ceasing the stabile system is the goal. Our investigations are of high importance in terms of stability and its characterization 1.
Elektroforetický rozptyl svetla (ELS) je nová experimentálna technika umoòujúca mera spectrum elektroforetickej pohyblivosti alebo zeta (ξ) potenciálu skupiny èastíc. Toto spectrum odráa distribúciu ...náboja a èiastoène distribúciu rozmeru týchto èastíc. Avak, okrem modálnej hodnoty napr. zeta potenciálu èastíc rovnakého druhu, z ELS spektra môeme vyèíta aj niektoré ïalie charakteristiky disperzného systému. Pre vybrané binárne zmesi dobre definovaných koloidných a jemnozrnných èastíc SiO2 a SiO2 modifikovaných aminopropylom alebo hematitu (tieto zloky majú odliné charakteristiky povrchového náboja) boli z ELS spektier urèené rozsahy pH vodného prostredia pri ktorých dochádza k heterokoagulácii, heterostabilizácii a heterokoagulaèno-heterostabilitnému prechodu týchto èastíc. K úplnej heterokoagulácii dochádza ak (jediná) modálna hodnota monomodálneho ELS spectra zmesi leí medzi modálnymi hodnotami ELS spektier individulánych zloiek zmesi pri tom istom pH. Úplná heterostabilita sa naopak uplatòuje keï obidve modálne hodnoty bimodálneho ELS spectra zmesi sa zhodujú s modálnymi hodnotami ELS spektier zloiek pri rovnakom pH. Heterokoagulaèno-heterostabilitný prechod bol nakoniec identifikovaný v situácii keï pre zmes sa získalo bimodálne spectrum, avak aspoò jedna jeho modálna hodnota bola odliná od modálnej hodnoty ELS spektra niektorej zo zloiek. Takto odhadnuté charakteristiky boli potvrdené výpoètom energetickej bariéry medzi èasticami-zlokami.
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