Illite Suspensions Research Articles

Proton Effects on Quaternary Cation Exchange and Flocculation of Silver Hill Illite

AbstractThe investigation of quaternary cation exchange and flocculation in dilute suspensions of illite with mixed Na‐K‐Ca‐Mg perchlorate solutions was extended to consider the effect of aqueous protons. The exchange reactions and flocculation of Silver Hill illite at inial pH (pHi) = 6 or 8, three total perchlorate concentrations (9, 5, or 2 molc m−3), and varying initial Na/Ca or Na/Mg ratios in the aqueous solution phase were studied. It was found that pHi had little or no effect on exchangeable cation selectivity or total adsorbed metal charge. The degree of flocculation, as described by the percentage light transmission through the illite suspensions, was found to be highly pHi dependent. The effect of pHi was greatest in the 5 molc m−3 perchlorate background, where, at an exchangeable bivalent charge fraction near 0.3, the suspension was almost completely flocculated at pHi = 6 but dispersed at pHi = 8. Overall, at a given exchangeable bivalent charge fraction, the illite suspensions became less flocculated, and showed greater sensitivity to exchangeable Ca vs. Mg, as pHi increased from 6 to 8. Changes in pHi thus produced colloidal effects just the inverse of changes in the total perchlorate concentration. Analysis of the pH dependence of the light‐transmission data suggested that the mechanism of illite flocculation was affected greatly by the adsorption‐desorption reactions of a small number of protons on the edge surfaces of suspended particles.

Experimental study of the filtration of clays by the oyster Crassostrea gigas (Thunberg): Adjustment of particle size for best retention

Pure clay suspensions of kaolinite, montmorillonite and illite were mixed for filtration by the oyster Crassostrea gigas (Thunberg). During the experiment, the water temperature, salinity and organic content of the suspended matter were stable. Differences in total biodeposition (faeces plus pseudofaeces) depended on the size of the suspended particles. The suspension characterized by particles smaller than 2.5 μm (illite) was not efficiently retained. Aggregates larger than 5 μm (montmorillonite) were rejected as pseudofaeces without ingestion. The retention rate was stimulated by addding a suspension (kaolinite) which adjusts the mode of the particle size distribution to a value between 3 and 4 μm. This adjustment not only increased retention efficiency, as estimated by the ratio faeces + pseudofaeces available suspended matter , but also facilitated ingestion. The efficiency of ingestion of suspended particles, defined as the ratio pseudofaeces faeces , was not controlled by the oysters if the particles were too small or too large. Intestinal transit took one hour. Organic enrichment occurred in the total biodeposits (faeces + pseudofaeces), equivalent to a loss of energy of 0.98 J h −1 per gram of oyster dry tissue. No changes were observed by X-ray analysis or by scanning for clay minerals in the faeces.

Colloidal stabilization of clays by asphaltenes in hydrocarbon media

Clay/asphaltene interactions play an important role in the separation of fine particles from petroleum and synthetic liquid hydrocarbon fuels. Asphaltenes, the polar fraction of hydrocarbon fuels, adsorb on clay minerals such as illite; adsorption is rapid, energetically strong, and mostly irreversible. Adsorbed asphaltenes enhance stability of illite suspensions. Although stability is found even at low surface coverages, the settling rate decreases monotonically with an increase in the adsorption density. The colloidal stability of asphaltenes-coated illite particles in hydrocarbon media is due to a combination of electrostatic and steric repulsive forces.

Partitioning Behavior of Insecticides in Soil‐Water Systems: I. Adsorbent Concentration Effects

AbstractAdsorption studies were conducted to determine whether adsorbent concentration (soil‐solution ratio) affected insecticide adsorption by soils and clays. Adsorption isotherms were obtained for several insecticides in Bondhead sandy loam and Ca‐saturated illite suspensions using adsorbent concentrations that were varied over several orders of magnitude. There was no evidence that altering adsorbent concentration exerted any influence on partitioning of insecticides between the adsorbent and solution phases. The centrifugation process, which in effect greatly increased adsorbent concentration at the bottom of the centrifugation tube, did not change the partitioning of the insecticides between the two phases. Dieldrin (1,2,3,4,10,10‐hexachloro‐exo‐6,7‐epoxyl, 4,4a,5,6,7,8,8a‐octahydro‐1,4‐endo,exo‐5,8‐dimethanophthalene), unlike the other insecticides, exhibited strong concentration‐dependent adsorption by glass surfaces, which invalidated the use of the normal “blank” (no adsorbent) sample for determining the initial solute concentration. Since glass adsorption appeared quite irreversible in aqueous solution, a sequential blank/sample adsorption technique was adopted whereby the stock solution was initially equilibrated in the glass bottle, then a small aliquot was removed for analysis before adding the adsorbent for its equilibration period. This technique produced consistent adsorption data that showed no evidence of being influenced by adsorbent concentration.

Sodium/Calcium Exchange in Montmorillonite and Illite Suspensions

AbstractThe effect of salt concentration and exchanger composition on Na/Ca exchange in montmorillonite and illite suspensions (0.02 to 0.08 g clay/g water) was studied, where the equivalent fraction of exchangeable Ca, ECa, ranged from 0.6 to 1. A theoretical evaluation based on double‐layer theory for montmorillonite indicates that the formation of tactoids and internal surfaces at the Ca3+ end of the exchange isotherm can cause the Vanselow selectivity coefficient, KV, to depend on exchangeable cation composition and total electrolyte concentration. Whereas for montmorillonite, KV increased with ECa (0.6 < ECa < 1), as predicted for internal surfaces, the reverse was true for illite, where external surfaces predominate. Likewise, for a given Na adsorption ratio, dilution of the equilibrium solution for illite (0.6 < ECa < 1) and for montmorillonite (ECa ≃ 0.6) decreased KV as predicted for external surfaces.The average Gapon selectivity coefficient for the montmorillonite (0.011) and illite clays (0.023) with ECa ≤ 0.8, suggests that the value for soils, (0.0148) reflects their mixed mineralogy.

Flocculation Value and Gel Structure of Sodium/Calcium Montmorillonite and Illite Suspensions

AbstractThe flocculation value, the minimum salt concentration which causes flocculation within 24 hours, was determined for mixtures of Na‐ and Ca‐montmorillonite (API‐25) and Fithian illite (API‐35). The equivalent fraction of exchangeable Na+, ENa, varied from 0 to 1. We prepared Na/Ca clay suspensions by adding the appropriate amounts of homoionic dry clays to a series of Na/Ca chloride solutions (0.2 to 80 molc m−8; 0.2 to 80 meq liter−1) with appropriate sodium adsorption ratio and shaking the mixture for 1 hour. The flocculation value of Ca‐montmorillonite (0.25 molo m−3) increased rapidly with small amounts of exchangeable Na+: the flocculation value for an ENa of 0, 0.2, 0.4, and 1 was 0.25, 6, 9, and 12 molc m−3, respectively. The flocculation values for Ca‐ and Na‐illite were 0.25 and 55 molo m−3, respectively, and increased linearly with ENa. Van der Waals attraction forces are mainly responsible for flocculation of Ca‐montmorillonite and illite systems. Edge‐to‐face attraction is dominant in flocculating Na‐montmorillonite. The large effect of small amounts of exchangeable Na+ in montmorillonite suspensions results from demixing of exchangeable ions whereby Na+ is the predominant cation on the external surfaces when ENa < 0.20.

The Release of Aluminum from Aluminosilicate Minerals. II. Acid-Base Potentiometric Titrations

AbstractAcidified suspensions of Al-saturated kaolinite, montmorillonite, mica, illite, and biotite in 10−3 M NaNO3 were potentiometrically titrated with 0.1 N NaOH and 0.1 N HNO3 in succession in a CO2-free nitrogen atmosphere. The resulting curves were compared with those for Al(NO3)3 solutions of similar Al concentration in the supernatant solution and corrected for Al in the entrained solution in the clay.Base titrations of Al ions adsorbed on all the minerals, except montmorillonite, showed two pH inflections separated by a buffering range. With montmorillonite, there were three pH inflections similar to those for Al in solution. The first inflections in the titration of suspensions occurred at lower pHs and were less pronounced than for Al in solution. These represent the titration of H3O+ sorbed during the pretreatment. The buffering by adsorbed Al ions is also less than that by Al in solution.The OH− used up by adsorbed Al ions between the first and last inflections was equal to, or slightly greater than, the CEC of the minerals, except for mica where it was more than twice the CEC, because new interlayer surfaces were formed during the acid pretreatment. Acid titration curves of Al ions in the adsorbed and solution states showed hysteresis when related to the base titration curves. The use of two titration speeds (3 and 0.3 pH units/hr) only slightly affected the titration curves of the minerals suggesting that the observed effects were not caused by lack of equilibrium with added base or acid.

Effect of coagulation and restabilization on the microflotation of illite

Investigated was the application of the foam separation technique of microflotation to the clarification of illite suspensions. Aluminum sulfate served as the coagulant and anionic and cationic collector surfactants were examined using a batch flotation system. Restabilization of the clay by hydrolyzed aluminum species prevented its removal by the cationic collector. The anionic collector was most effective in the pH ranges of aluminum hydroxide precipitation.

Interactions of pH‐Dependent and Permanent Charges of Clays: I. Use of Specific Ion Electrodes for Measuring Ca and Rb Activities in Bentonite and Illite Suspensions

Interactions of pH‐Dependent and Permanent Charges of Clays: I. Use of Specific Ion Electrodes for Measuring Ca and Rb Activities in Bentonite and Illite Suspensions

Interactions of pH‐Dependent and Permanent Charges of Clays: II. Calcium and Rb Bonding to Bentonite and Illite Suspensions—Clay‐Phase Retention

Panther Creek bentonite and Fithian illite suspensions were reciprocally saturated with Ca and Rb. 45Ca and 86Rb were added as tracers for Ca and Rb, respectively. Increments of H-clay were added as a source of (i) permanent charges for adsorbing Ca and Rb, and (ii) H ions for inactivation of pH-dependent charges. Fifty-milliliter volumes of clay suspensions were membrane-equilibrated with similar volumes of water. Three-component systems of bentonite, illite, and dialyzate were also equilibrated. After equilibration, assay of Ca and Rb was made in each phase. Except where Rb fixation occurred, decreasing the Ca and increasing the Rb saturations (decreasing Ca/Rb ratio) shifted Ca from pH-dependent to permanent charges, causing increased bonding and thus increased retention of Ca by the clays. Similarly, decreased Ca/Rb ratio increased the number of Rb ions adsorbed to permanent charges causing increased percentage retention. Rubidium fixation by illite markedly increased percentage Rb retained and decreased Ca retained. When pH-dependent charges were inactivated by addition of H, retention of both cations increased and became uniform at all Ca/Rb ratios. The distribution of ions in the three-component systems was predictable from the results of the two-phase systems.

Interactions of pH‐Dependent and Permanent Charges of Clays: III. Calcium and Rb Activities versus Soybean Root Uptake from Bentonite and Illite Suspensions

Panther Creek bentonite and Fithian illite suspensions were reciprocally saturated with Ca and Rb. 45Ca and 86Rb were added as tracers for Ca and Rb, respectively. Increments of H-clay were added to aliquots of the Ca-Rb saturated clays to progressively decrease the base saturation of the clays. After equilibration, the activities of Ca and Rb were measured in the clay suspensions with the Orion divalent and the Beckman monovalent electrodes. Uptake of Ca and Rb by excised soybean roots was determined from the radioactivity of each tracer. Decreased Ca saturation (increased Rb) shifted Ca ions from pH-dependent to permanent charges causing increased bonding and thus decreased Ca activities, fractions active, and root uptake. Except where specific ion bonding effects interfered, increased Rb saturation increased Rb activities and uptake—even though Rb fractions active were decreased, due to greater permanent charge bonding. With the same exception, additions of H-clays equilvalent to pH-dependent cation exchange capacity minimized Ca and Rb uptake as well as their activities and fractions active. Thus activity data generally correlated closely with uptake data, except where there were good reasons for this not to occur.

Compression Studies of Illite Suspensions

AbstractIt can be shown that the classical Gouy‐Chapman theory of the electric double layer formed on planar surfaces provides and acceptable means of predicting the “osmotic” pressure of clay suspensions for various particle spacings and electrolyte contents.A compression apparatus was designed for the measurement of the swelling pressures of clay suspensions over the range 0.1 to 100 atm. The results obtained with this apparatus for a number of illite samples are consistent with those predicted by theory.Consideration of the implications of these experiments for the mechanism of flocculation favors the following conclusions: (1) The attractive forces acting between clay particles in flocculated suspensions are probably a simple Coulombic attraction between negative and positive sites on the respective particles; (2) Van der Waal's forces are of no consequence in flocculation phenomena in the suspensions studied; (3) The energy of flocculation is small and cannot contribute significantly to the resistance of aggregates to mechanical breakdown.