Relative Insignificance of Mineral Grain Zeta Potential to Colloid Transport in Geochemically Heterogeneous Porous Media

Abstract

The role of ζ-(zeta)potential of mineral grains in the initial deposition kinetics of colloidal particles in geochemically heterogeneous porous media is investigated. Colloid deposition experiments with colloidal silica particles flowing through columns packed with chemically heterogeneous sand were carried out. Patchwise chemical heterogeneity was introduced to the granular porous medium by modifying the surface chemistry of a fraction of the quartz sand grains via reaction with aminosilane. Experimental initial colloid deposition rates and resulting collision efficiencies were compared to theoretical predictions based on the measured average ζ-potential of the chemically heterogeneous sand. It is shown that colloid deposition kinetics are controlled by the degree of patchwise chemical heterogeneity and that use of the measured ζ-potential of the granular porous medium in theoretical predictions leads to erroneous results.

Deposition of Silver Nanoparticles in Geochemically Heterogeneous Porous Media: Predicting Affinity from Surface Composition Analysis

“…As shown on figure 13, there was indeed a strong correlation (R = 0.992) between the affinity of AGNPs for the heterogeneous media and the mass percentage of the FeO---GB---HC. Similar evidence has been reported in literature for a system using a mixture of uncoated silica beads and beads that are fully coated with aminosilane (Elimelech, Nagai et al 2000) .…”

“…Although studies exist using a mixture of negatively charged uncoated quartz sands and positively charged quartz sands that are fully coated with either iron oxyhydroxide (Johnson, Sun et al 1996) or aminosilane (Elimelech, Nagai et al 2000) and the linear relationship between the attachment efficiency (α) and ratio of mixing (of the positively charged and negatively charged collectors) was proved with the aminosilane coated collectors, it might be questionable that whether such an introduction of the oppositely charged collectors can realistically represent the surface heterogeneity that often occurs locally on a single collector surface. Therefore, it might be helpful to revisit the similar problem using partially modified surface that might mimic the local heterogeneity more realistically.…”

“…Let alone the some intrinsic inadequacies of DLVO theory even in modeling the particle deposition onto a homogeneous surface, ) using DLVO theory with the ζ potential of a heterogeneous surface would introduce further problems, which has been elucidated by Elimelech et al (Elimelech, Nagai et al 2000) using a mixed porous medium composed of quartz sand (negatively charged) and silylated quartz sand (positively charged) for deposition experiments. The authors showed that the deposition kinetics was determined primarily by the extent of heterogeneity and that using ζ of the collector surface for prediction would lead to erroneous results.…”

Numerical Simulation of Fly-Ash Transport in Three Sands of Different Particle-Size Distributions Using Hydrus-1d

“…Johnsor (1999) documented that the ζ-potential (-48 to -16 mV) increased with the increasing electrolyte ionic strength (10 -5 to 10 -1 M). Elimelech et al (2000) showed that the ζ-potential (-24 to -80 mV) con-siderably decreased with increasing pH (3 to 9) for 10 -3 M NaCl used as a background electrolyte. Saprykina et al (2010) cited considerably lower absolute value of the ζ-potential (-25.4 mV at pH 7.2).…”

“…Saprykina et al (2010) cited considerably lower absolute value of the ζ-potential (-25.4 mV at pH 7.2). Grain coatings may significantly increase the ζ-potential value (even to the positive values) (Elimelech et al, 2000) and considerably influence (increase) colloid (which is negatively charged) attachment when studying colloid transport in sandy materials (Shani et al, 2008). No quartz grain coatings were expected in our study.…”