Incorporation of silica into the goethite structure: a microscopic and spectroscopic study

Quartz and iron(hydr)oxide are reactive surface phases that are often associated with one another in soils and sediments. Despite the several studies on the coating of quartz with iron oxides, the reactivity of dissolved species(Si) leached from quartz with iron(hydr)oxides has received limited attention. In this study, goethite synthesized on quartz substrates were characterized using field emission scanning electron microscopy, X-ray diffraction(XRD), transmission electron microscopy, and Fouriertransform infrared(FT-IR) spectroscopy. The SEM characterization revealed that bundles of thin parallel aligned goethite rods were formed at p H [ 10, while large pseudohexagonal crystals of twinned goethite needles were synthesized at p H B 10 after dehydration and hydration in the alkaline media. TEM analysis showed expanded and distorted lattice spacing of the crystal structure of iron(hydr)oxide due to silica incorporation. The characterization showed that silica increased the crystallite size of the goethite and transformed its acicular texture to a larger,twinned needle structure. FT-IR and XRD analyses revealed band shifts in crystal bonds as well as new bond formations, which indicate the presence of changes in the chemical environment of Fe–O and Si–O bonds. Thus, the presence of sorbed silicates modifies the crystal and lattice structure of goethite.

Characterization of lauryl betaine foam in the Hele-Shaw cell at high foam qualities(80%-98%)

Lauryl betaine(LB)as an amphoteric surfactant carries both positive and negative charges and should be able to generate stable foam through electrostatic interaction with nanoparticles and co-surfactants.However,no previous attempts have been made to investigate the influence of nanoparticles and other co-surfactants on the stability and apparent viscosity of LBstabilized foam.In this study,a thorough investigation on the influence of silicon dioxide(SiO2)nanoparticles,alpha olefin sulfonate(AOS)and sodium dodecyl sulfate(SDS),on foam stability and apparent viscosity was carried out.The experiments were conducted with the 2D Hele-Shaw cell at high foam qualities(80%-98%).Influence of AOS on the interaction between the LB foam and oil was also investigated.Results showed that the SiO2-LB foam apparent viscosity decreased with increasing surfactant concentration from 0.1 wt%to 0.3 wt%.0.1 wt%SiO2 was the optimum concentration and increased the 0.1 wt%LB foam stability by 108.65%at 96%foam quality.In the presence of co-surfactants,the most stable foam,with the highest apparent viscosity,was generated by AOS/LB solution at a ratio of 9:1.The emulsified crude oil did not imbibe into AOS-LB foam lamellae.Instead,oil was redirected into the plateau borders where the accumulated oil drops delayed the rate of film thinning,bubble coalescence and coarsening.