Vermiculite

About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.

Adsorption of ammonium from simulated wastewater by montmorillonite nanoclay and natural vermiculite: experimental study and simulation

Abstract: In this research, montmorillonite nanoclay (MNC) and vermiculite were used to adsorb ammonium (NH4+) from simulated wastewater. The effect of organic acids, cations, and anions on adsorption of NH4+ was also studied using batch experiments. The presence of organic acids significantly decreased the NH4+ adsorption using both adsorbents and the reduction followed the order of citric acid > malic acid > oxalic acid. The presence of cations in wastewater could decrease the adsorption of NH4+ and the ion exchange selectivity on the MNC and vermiculite followed the orders Mg > Ca ≥ K > Na and Mg > > Ca > Na > K, respectively. Adsorption of NH4+ by adsorbents in the presence of sulfate (SO4) was higher than those in the presence of phosphate (PO4) and chloride (Cl) anions. Results indicated that MNC and vermiculite had good potential for NH4+ removal depending on adsorbent dosage, pH, contact time, and initial NH4+ concentration. The effect of pH on removal of NH4+ indicated that MNC would be more appropriate as the adsorbent than vermiculite at low pH values. Kinetic analysis demonstrated that the rate-controlling step adsorption for NH4+ by MNC and vermiculite was heterogeneous chemisorption and followed the pseudo-second-order model. The desorption experiments indicated that the adsorption of NH4+ by adsorbents was not fully reversible, and the total recovery of adsorbed NH4+ for MNC and vermiculite varied in the range of 72 to 94.6% and 11.5 to 45.7%, respectively. Cation exchange model (CEM) in PHREEQC program was used to simulate NH4+ adsorption. Agreement between measured and simulated data suggested that CEM was favored in simulating adsorption of NH4+ by clay minerals. The results indicated that MNC and vermiculite have good performance as economic and nature-friendly adsorbents that can ameliorate the water and environment quality.

Surface area of vermiculite with nitrogen and carbon dioxide as adsorbates

Abstract: Surface-area studies were made on several homoionic vermiculites with both nitrogen and carbon dioxide as adsorbates. These studies show that only very slight penetration occurs between individual vermiculite platelets. This is in contrast to an earlier investigation of montmorillonite where it was found that the degree of penetration between layers is quite high, particularly for carbon dioxide, and is governed by the size and charge of the interlayer cation. The inability of these adsorbates to penetrate substantially between vermiculite platelets is due primarily to this mineral’s high surface-charge density.

Calcium: aluminium exchange equilibria in clay minerals and acid soils1

Abstract: Summary Exchange reactions between 0.0in AlCl3 solutions of different pH and Ca-saturated montmorillonite, vermiculite, illite, and soils from the Park Grass Experiment at Rothamsted and the Deerpark Experiment, Wexford, Ireland, showed that Al3+ and Al(OH)2+ were adsorbed from solutions of pH > 4.0 and Al3+ and H+ from solutions of pH < 3.0. When Al was adsorbed, the cation exchange capacity of Ca-saturated soils and clays increased. Conventional Ca: Al exchange isotherms showed that Al3+ was strongly preferred to Ca2+ on all soils and clays. The equilibrium constant for Ca: Al exchange, K, was identical for soils before and after oxidizing their organic matter and did not vary, for any exchanger, with Al-saturation or the initial pH of the AlCl3 solution. This proved the validity of the procedure used for calculating exchangeable Al3+. K values for Ca:Al exchange favoured Al3+ in the order: vermiculite > Park Grass soil > Deerpark soil > illite > montmorillonite. The influence of surface-charge densities of the clay minerals on this order is discussed and a method proposed and tested for calculating the K value of a soil from its mineralogical composition.

Layer Charge Decrease by Tetrahedral Cation Removal and Silicon Incorporation during Natural Weathering of Phlogopite to Saponite1

Abstract: A substantial layer charge decrease, from 210 to 140 meq/100 g, occurred during the natural weathering of phlogopite through vermiculite to saponite in Kansas. A comparison of the Fe²⁺ content and layer charge of the coarse fraction (72% phlogopite) and the fine fraction (71% saponite) indicated that iron oxidation cannot account for the layer charge decrease during the transformation. Control studies on iron oxidation during vermiculitization of biotites and lepidomelane did not correlate with layer charge decrease. Elemental analysis of the coarse and fine fractions revealed gains and losses of cations during the weathering of the mica flakes to fine particles. The Si⁴⁺ and Mg²⁺ increased by 2.66 and 0.84%, respectively, while Al³⁺ and total Fe³⁺ plus Fe²⁺ decreased by 0.34 and 1.21%, respectively, in the two fine fractions compared to the macroflakes. The elemental analyses also revealed the unique nature of this phlogopite which contained fewer moles of Al³⁺ than K⁺; the presence of some isomorphously substituted tetrahedral Fe³⁺ contributed 17% of the total negative layer charge. Loss of layer charge was found to be a result of the loss of isomorphically substituted tetrahedral Al³⁺ and Fe³⁺ by authigenic recrystallization with an increase in tetrahedral Si⁴⁺. In control studies, removal of isomorphously substituted tetrahedral Al³⁺ from Ontario phlogopitic vermiculite and Transvaal micaceous vermiculite by citrate chelation also resulted in an equivalent layer charge decrease.