Details

Autor(en) / Beteiligte

• Hsu, Che-Jung
• Chen, Yun-Hsin
• Hsi, Hsing-Cheng

Titel

Adsorption of aqueous Hg2+ and inhibition of Hg0 re-emission from actual seawater flue gas desulfurization wastewater by using sulfurized activated carbon and NaClO

Ist Teil von

• The Science of the total environment, 2020-04, Vol.711, p.135172-135172, Article 135172

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2020

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• [Display omitted] •Sulfurized activated carbon shows good Hg removal in seawater FGD system.•Hg adsorption by sulfurized activated carbon slightly increased at pH 7 and 8.•Hg adsorption by sulfurized activated carbon in seawater is endothermic.•Pseudo-second-order adsorption may be rate-limiting for Hg2+ adsorption.•Addition of NaClO reduced the Hg2+ removal yet inhibited Hg0 re-emission. The potential impacts of seawater flue gas desulfurization (SFGD) process used in coal-fired power plants have been greatly concerned because the wastewater containing Hg is directly discharged into the ocean environment without proper treatment. Furthermore, the re-emission of Hg as Hg0 to the atmosphere from SFGD wastewater caused by the reduction of aqueous Hg2+ has also been observed. This study investigated the dependence of Hg2+ adsorption behavior for sulfurized activated carbon (SAC) in actual SFGD wastewater on various influencing factors, including initial Hg2+ concentration, solution pH, contact time, temperature, and the addition of oxidant (sodium hypochlorite, NaClO). SAC exhibited greater Hg2+ adsorption than raw activated carbon at an initial Hg2+ concentration of more than 4,723 ng L−1. The Hg2+ removal efficiency of SAC was slightly larger at pH 7.0 and 8.0 than that at pH within 2.0–6.0. Hg2+ adsorption on SAC was well correlated with the linear adsorption model. Kinetic analysis results indicate that pseudo-second-order adsorption may serve as the rate-limiting reaction of Hg2+ adsorption on SAC. Thermodynamic analyses confirmed the endothermic and spontaneous adsorption behavior of Hg2+ on SAC in the seawater environment. Notably, the addition of NaClO significantly reduced the Hg2+ removal efficiency when SAC was used as the adsorbent. Nevertheless, NaClO addition also inhibited the reduction reaction of Hg2+ to Hg0 by forming strong HgCl complexes, which decreased the risk of Hg0 reemitted into the atmosphere via a SFGD system.