Results in Engineering (Sep 2024)
Aqueous benzene, toluene, ethylbenzene and xylene (BTEX) removal using core-shell structure activated carbon ball as a permeable reactive barrier material
Abstract
Permeable reactive barriers (PRBs) are passive and sustainable treatment systems for remediating the diffusion of contaminant plumes in groundwater. Several conventional reactive materials such as activated carbon (AC) have long been used as reactive media for PRBs. AC, which is known for its high adsorption capability and cost-effectiveness, is commonly used to remove multiple pollutants from groundwater. Unfortunately, among the reactive materials, AC can fill in the barrier and pose practical problems, such as a pressure drop, solid losses during handling, and safe disposal of filled sorbents, because of its low particle strength. In this study, AC balls were prepared using zeolite as the core and powdered AC, quartz, and calcite as the shell. AC ball with excellent mechanical strength and high permeability properties in the form of a core–shell layer is a good alternative to conventional reactive materials. The adsorption characteristics of benzene, toluene, ethylbenzene, and p-xylene (BTEX) from solutions using AC balls were investigated. The adsorption equilibrium is in the order of X > E > T > B. The adsorption capacity for B (4.90 mg/g), T (3.37 mg/g), E (1.16 mg/g) and X (0.46 mg/g) were observed at solution pH = 7. To validate the proposed models, batch experiments indicated that the pseudo-2nd-order (11.61 and 10.54 mg/g) and Langmuir models (8.81 and 5.27 mg/g) were the most suitable for describing the kinetics and equilibrium of benzene and toluene, respectively. Regeneration experiments were performed using chemical extraction (methanol) and microwave (MW) heating. When the AC ball was reused six times, the removal efficiency for benzene was maintained above 81 % using methanol, whereas that for benzene was increased to 91 % using MW. A series of experiments revealed that AC balls have considerable reusability. The AC ball can be effectively used as a medium for the removal of benzene in a continuous flow system such as column and sandbox. Based on these results, AC balls are a potential reactive medium for field-scale PRB practical remediation applications.
