Clay and Zeolite-Clay Based Monoliths as Adsorbents for the Hg(II) Removal from the Aqueous Solutions

Abstract

Clay and zeolite-clay-based monoliths (ZCBM and CBM) were used as mercury removal adsorbents in aqueous solutions. Clay and zeolite-clay-based monoliths (40 holes in 18 mm diameter) were obtained by extruding the material with water. This research aimed to investigate and compare the capacities and kinetics of two adsorbents, zeolite-clay, and clay-based monoliths, to identify the most effective adsorbent in adsorbing mercury(II) ions. The ZCBM and CBM crystal structures were characterized using a scanning electron microscope, Brunauer–Emmett–Teller (BET) theory, and an X-ray diffractometer. The effect of contact time (40, 80, 120, 160, 200, and 240 minutes), adsorbent doses (1 and 2 mg/L), as well as initial concentrations (1–5 mg/L) were variables evaluated. The most effective adsorbent is identified by selecting the highest adsorption efficiency. These equilibrium experimental data and the adsorption kinetics were investigated in a batch-type reactor. Data of equilibrium were examined with the Freundlich, Langmuir, and BET isotherm models by observing the lowest sum of squares (SSE) value. This Langmuir isotherm model indicated the most significant fit to the adsorption data of both adsorbents. To examine the kinetic data, the pseudo-first-order and pseudo-second-order adsorption kinetic models were implemented. This adsorption kinetic characterization using both ZCBM and CBM was well displayed by the pseudo-first-order model. Even though the maximum equilibrium adsorption capacity was 0.167 mg/g for ZCBM, but SSE value showed that CBM was the adsorbent with the highest adsorption efficiency, namely 72.3%. Therefore, CBM becomes the most effective adsorbent for mercury removal from water.

Keywords

• adsorption
• clay
• isotherm
• mercury
• monolith