Kinetic Studies of Cs+ and Sr2+ Ion Exchange Using Clinoptilolite in Static Columns and an Agitated Tubular Reactor (ATR)

Abstract

Natural clinoptilolite was studied to assess its performance in removing caesium and strontium ions, using both static columns and an agitated tube reactor (ATR) for process intensification. Kinetic breakthrough curves were fitted using the Thomas and Modified Dose Response (MDR) models. In the static columns, the clinoptilolite adsorption capacity (qe) for 200 ppm ion concentrations was found to be ~171 and 16 mg/g for caesium and strontium, respectively, highlighting the poor material ability to exchange strontium. Reducing the concentration of strontium to 100 ppm, however, led to a higher strontium qe of ~48 mg/g (close to the maximum adsorption capacity). Conversely, halving the column residence time to 15 min decreased the qe for 100 ppm strontium solutions to 13–14 mg/g. All the kinetic breakthrough data correlated well with the maximum adsorption capacities found in previous batch studies, where, in particular, the influence of concentration on the slow uptake kinetics of strontium was evidenced. For the ATR studies, two column lengths were investigated (of 25 and 34 cm) with the clinoptilolite embedded directly into the agitator bar. The 34 cm-length system significantly outperformed the static vertical columns, where the adsorption capacity and breakthrough time were enhanced by ~30%, which was assumed to be due to the heightened kinetics from shear mixing. Critically, the increase in performance was achieved with a relative process flow rate over twice that of the static columns.

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

“…In the latter case, a small, or irregular particle size would be a lesser concern, as the contact solution can simply percolate through the adsorbent bed [75]. The adsorbent and contact solution could be agitated as a slurry [76], as is practiced at the UK Enhanced Actinide Removal Plant, although this increases mechanical complexity. This scenario being the case, an important factor in an experimental setup is the ratio of adsorbent mass to solution volume, to provide high efficiency but also a sufficiently low resulting iodine concentration.…”

Process intensification of dendritic fibrous nanospheres of silica (DFNS) via continuous flow: a scalable and sustainable alternative to the conventional batch synthesis

“…61 The ATR is a commercially successful reactor in industries known to handle solid slurries and suspensions in addition to gas-liquid and solid-liquid-gas processes. [62][63][64][65][66][67] The unique tube-and-agitator design 68,69 has been proven to effectively circumvent pressure drops when connecting two or more reactors in series, thus enabling kilo-scale production with high throughput. Owing to these advantages, we decided to employ this scale-up tool for demonstrating the telescoped flow synthesis for the high-throughput production of DFNS.…”

Equilibrium Isotherms and Kinetic Effects during the Adsorption of Pb(II) on Titanosilicates Compared with Natural Zeolite Clinoptilolite

“…According to the general empirical formula of CPT-(Na,Mg,K,Ca) 3-6 (Si 30 Al 6 )O 72 •20H 2 O)-the TEC is between 2.4 and 2.64 meq/g [29,30], and the typical values for the Si/Al ratio are between 4 and 5.3 [61,73]. The typical TEC values for Na-K-ETS-4-(NaK) 9 Ti 5 Si 12 O 38 OH•12H 2 O-varies between 5.54 and 6.39 meq/g [19,23], and those for GTS-1-(Na) 3 Ti 4 O 4 (SiO 4 ) 3 •4H 2 O-are around 6.65 meq/g [74]. The Si/Ti ratios in Na-ETS-4 and GTS-1 are 2.4 [75] and 0.75 [39,76], respectively.…”

“…The adsorption, separation, and ion-exchange properties of zeolites stem from their distinctive three-dimensional porous framework structure [17]. Natural zeolites such as clinoptilolite (CPT) [18,19] and chabazite (CHZ) [20] are extensively studied because of their natural abundance and low cost of procurement, making them economically suitable for large-scale application in agriculture [21][22][23], construction [24,25], as molecular sieves [26], and in the field of environmental preservation [27][28][29][30][31][32][33][34][35]. The vast majority of the studies on natural zeolites are concentrated on their application as adsorbents in water and wastewater treatment, for the removal of heavy metals and organic pollutants (e.g., dyes, ammonia, aniline, etc.)…”