Evaluation of Zeolite as a Potential Reactive Medium in a Permeable Reactive Barrier (PRB): Batch and Column Studies

Abstract

The purpose of this work is to evaluate the capacity of a natural zeolite to be used as a reactive material in a permeable reactive barrier (PRB) to remove inorganic contaminants from groundwater. To this aim, zeolite samples were subjected to characterization tests, column experiments, batch tests and a flushing process to evaluate the adsorption and desorption capacities of the zeolite. In the column experiments, the samples were subjected to eight successive cycles involving the percolation of a potassium aqueous solution (1500 mg/L) and a subsequent flushing process with water. Batch tests were conducted by mixing 20 g of zeolite with 100 mL of single-element aqueous solutions of K and Zn with concentrations of 200 mg/L. The results indicate that the zeolite rock is composed predominantly of clinoptilolite species and has a Si/Al ratio of 6.8, a high cationic exchange capacity (CEC) of 180 cmolc/kg and a high K+ adsorption rate with a removal efficiency of 78%. The adsorption isotherms of the zeolite follow the Langmuir model and are well fit by a pseudo-second-order kinetic model showing a high correlation coefficient (r2 > 0.999) for both K+ and Zn2+ cations. Additionally, the contaminant transport parameters for K+ ions (Rd = 24.9; Dh = 1.32 × 10–2 cm2/s and α = 1.42) reveal that the zeolite is resistant to the dispersion of ions in the barrier, indicating that the material has advantageous characteristics for use in a PRB. However, the flushing process of the material is not efficient, indicating that the appropriate use of the zeolite is in clean-up systems in which the adsorbent material can be exchanged after losing its efficiency as a reactive barrier.

Exploring the Properties of Micronized Natural Zeolitic Volcanic Tuff as Cosmetic Ingredient

“…Generally, the Si/Al ratio is theoretically related to the CEC value. Zeolites with lower Si/Al ratio have higher CEC values [ 28 ]. As it can be seen, the Si/Al of MZ S1 was 5.20 and its CEC value was 1.60 meq/q, while the Si/Al and CEC value of RZ S1 was 4.89 and 1.18 meq/q, respectively.…”

Suitability Zoning for Sustainable Drainage Systems (SuDSs): Application in a Basin in Southern Brazil

“…Regarding the groundwater level and rockhead depth combined with the permeability, porosity, and storage capacity characteristics of geological material, units 1 and 2 had potential for a wide range of SuDS types, while unit 3 had a more restricted potential. Notably, the most favorable infiltration conditions were presented by unit 2, but this unit also had the greatest potential for groundwater contamination, and it is advisable to adopt systems that allow the use of horizontal permeable reactive barriers in accordance with the guidelines presented in [47,48]. Units 1 and 3 had water interfaces that could affect the efficiency of infiltration-based systems; these interfaces were higher in unit 3 than in unit 1.…”

“…Conversely, geological materials have high erodibility and low cohesion, which favors the instability of excavated slopes. It is recommended that the systems be implemented with protection measures, such as permeable reactive barriers, as proposed by [47,48]. Thus, the installation of systems with a lower runoff accumulation magnitude should be prioritized, as they allow better control of possible contaminants and the area affected by infiltration, in addition to reducing installation costs.…”

Testing Zeolite and Palygorskite as a Potential Medium for Ammonium Recovery and Brewery Wastewater Treatment

“…The choice of solvents for desorption and regeneration tests was guided by the existing literature [34,35]. The aim of desorption with deionized water is to evaluate the ability of the adsorbent particles to release ions with the flow of a natural solvent, thereby preventing the introduction of a new element and consequently avoiding the contamination of the area with a new chemical product [36]. On the other hand, research has indicated that the use of HCl 0.1 N is the most effective eluent for regenerating these materials [37].…”