Functionalization of Shirasu-balloons Surface for Removal of Cadmium Ions from Contaminated Soil

Abstract

Microspheres of aluminosilicate glass from volcanic sediment, whose surface was modified with functional groups, Shirasu-balloons (SB) were investigated as an adsorbent to remove cadmium ion from the contaminated soil. The introduction of thiol group (-SH) on the surface of SB enabled to adsorb cadmium ion, meanwhile the introduction of an alkyl group (-ODS) made the surface of SB hydrophobic, consequently increased the mechanical strength of SB. Those adsorbents could float up on the water surface after adsorption process. The prepared adsorbent was characterized by FTIR spectrophotometer, elemental analysis and optical microscope for photographic images. The adsorption of cadmium ions on the adsorbent was investigated by comparing the results by a plain SB with those by thiol-functionalized SB. The adsorption maximum for cadmium ion was 3.75 mg/g for SH-SB and 2.62 mg/g for SH-ODS-SB, respectively. The adsorption of cadmium ions on the functionalized SH-SB and SH-ODS-SB was fitted well to the Langmuir isotherm equation. After shaking time for 24 hours, the recovering ratios of the absorbents from soil were 73 wt% for SH-SB and 98 wt% for SH-ODS-SB absorbents. In addition, the kinetic and adsorption-desorption properties of the adsorbent were also discussed.

Adsorption of Carbon Dioxide on Shirasu‐based Materials

“…It has been reported that the Shirasu‐based materials can adsorb ions [44–46] and compounds [47,48] . On the other hands, surface modification of Shirasu‐based materials were effective ways to improve their adsorption capacities of the chemical species [44,45,47,48] . We have also identified the effect of surface modification of a Shirasu‐based material via various pretreatment procedures (solution treatment and calcination) on improving its surface acidity and promoting a chemical reaction in the presence of acids [49] .…”

“…[47,48] On the other hands, surface modification of Shirasu-based materials were effective ways to improve their adsorption capacities of the chemical species. [44,45,47,48] We have also identified the effect of surface modification of a Shirasu-based material via various pretreatment procedures (solution treatment and calcination) on improving its surface acidity and promoting a chemical reaction in the presence of acids. [49] While, it has been reported that adsorption capacities of carbon dioxide of zeolites were improved by increasing their acidity.…”

“…The materials are also expected to exhibit similar adsorption functions as zeolites because Shirasu‐based materials mainly included silica and alumina which were also included in zeolites. It has been reported that the Shirasu‐based materials can adsorb ions [44–46] and compounds [47,48] . On the other hands, surface modification of Shirasu‐based materials were effective ways to improve their adsorption capacities of the chemical species [44,45,47,48] .…”