Optimization of a novel setup for an on-line study of elemental mercury adsorption by cold-vapor atomic absorption spectrometry

ABSTRACT

The objective of this work was developing a simple and stable time-based on-line setup for assessing the potential of mercury [Hg] vapor adsorption of the commercial sorbents used in air sampling and control operation followed by cold vapor atomic absorption spectrometry [CVAAS]. A special designed separation chamber was used where reduction of the injected Hg [II] solution took place. Purge gas passes through this chamber resulting to a prompt release of mercury vapor, purging into the adsorbent that regulated at the desired adsorption temperature. After sorbent saturation, in order to study the adsorption parameters of sorbents [activated carbon and bone char] such as breakthrough time [BTT], and adsorptive capacity, mercury gas stream was passed through the sorbents, directly transport to the CVAAS. Preliminary experiments concerning the reductant solution showed that SnCl[2] offers higher stability than NaBH[4]. Around the loading range 0.125-2.5 ml min-1 of 100 micro g l[-1] Hg[II] solution, a linear calibration curve with the equation peak area=0.134; loading flow=-0.017 and a correlation coefficient r=0.996 was obtained, and the detection limit was improved up to c[L]=1micro g l[-1]. The relative standard deviation of five measurements of lowest flow loading of Hg [II] was RSD=2.8%. The significant differences were observed in the breakthrough time and mercury adsorptive capacity between activated carbon and bone char [P=0.010]. This novel setup is suitable for an on-line study of elemental mercury adsorption, determination of breakthrough time and adsorption capacity, and because of its stable performance during all experiments; it can be applied to the time based studies