Study on re-emission and stabilization of mercury in seawater flue gas desulfurization wastewater
ZHAO Hong
LEI Siyuan
LI Chengbao
TANG Ke
GUO Hao
WU Wei
MA Baolin
ZHENG Han
GUAN Jian
XU Renbo
LUO Tongda
SUN Lushi
Abstract：The seawater flue gas desulfurization(SFGD)system,as an ideal alternative to traditional limestone-based systems,effectively controls sulfur dioxide(SO2)emissions from coal-fired flue gas while also suppressing mercury(Hg)emissions.However,the reductive nature of seawater has led to concerns regarding the re-emission of mercury on a global scale.In this study,the aeration process of SFGD wastewater was simulated to investigate the effects of pH,system temperature,and the concentrations of SO32-and Cl-on the re-emission of elemental mercury(Hg0).The objective of this study was to elucidate the migration and transformation characteristics of mercury in SFGD systems.Furthermore,the study investigated the suppression mechanisms of four additives:two precipitants(Na2S,an inorganic sulfide,and TMT-15,an organic sulfide)and two oxidants(NaClO and Fenton reagent).The results demonstrated that S(Ⅳ)was the primary factor promoting Hg0 re-emission,with over 54％of Hg2+being reduced to Hg0 at an SO32-concentration of 0.05 mmol/L.Concurrently,elevated concentrations of Cl-,low temperatures,and heightened pH levels exhibited a substantial inhibitory effect on Hg0 re-emission.All four additives effectively inhibited Hg0 re-emission through different mechanisms.Na2S and TMT-15 reacted with H g2+in the liquid phase to form water-insoluble precipitates and chelates,thereby preventing reduction to Hg0.NaClO and Fenton reagent suppressed Hg0 re-emission by rapidly oxidizing Hg0 back to Hg2+and stabilizing it in the liquid phase.They also inhibited Hg2+reduction by oxidizing reductive ions in the solution.At optimal dosages,the suppression efficiencies of Na2S,TMT-15,NaClO,and Fenton reagent were 78.1％,79.9％,84.8％,and 94.2％,respectively.Compared to precipitants,oxidants such as NaClO and Fenton reagent significantly reduced the required aeration intensity,demonstrating excellent potential for application in the aeration processes of SFGD wastewater treatment.
Keywords：seawater flue gas desulfurization wastewatermercuryre-emissionadditivestabilization
Publication Date：2025-01-31
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 201-208 )