Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils

Abstract

This is the first study to evaluate the potential application of FGDG as an in situ Pb stabilizer in contaminated soils with two different compositions and to explain the underlying mechanisms. A smelter Pb contaminated soil (SM-soil), rich in ferrihydrite bound Pb (FH-Pb), cerussite and litharge with a total Pb content of 65,123mg/kg and an organic matter rich orchard soil (BO-soil), rich in FH-Pb and humic acid bound Pb with a total Pb content of 1532mg/kg were amended with 5% FGDG (w/w). We subjected the two soils to three leaching tests; toxicity characteristic leaching protocol (TCLP), synthetic precipitation leaching protocol (SPLP), kinetic batch leaching test (KBLT) and in-vitro bioaccessibility assay (IVBA) in order to evaluate the FGDG amendment on Pb stabilization. Solid residues of original and FGDG amended soil were analyzed using X-ray absorption spectroscopy (XAS) to identify changes in Pb speciation after each leaching test. The leachate Pb concentrations of FGDG amended soil were lower compared to those of in non-amended soil. The linear combination fitting analysis of XAS confirmed the formation of anglesite and leadhillite in FGDG amended soil. FGDG reduced the Pb desorption from ferrihydrite (FH), by forming FH-Pb-SO ternary complexes. FGDG decreased the Pb adsorption onto humic acid (HA) possibly due to the release of divalent cations such as Ca and Mg, which can compete with Pb to get adsorbed onto HA. The FGDG can successfully be used to remediate Pb contaminated soil. The efficiency of the treatment highly depends on the soil composition.

Sustainable effects of gypsum from desulphurization of flue gas on the reclamation of sodic soil after 17 years

“…The concentrations of all the metals in the treated plots were well below the risk control standard for soil contamination of agricultural land in China MEEPRC (Ministry of Ecology and Environment of the People's Republic of China), 2018. Similar results were reported in our previous studies (Chen et al, 2015;Zhao et al, 2018aZhao et al, , 2018b and other studies (Koralegedara et al, 2017;Sakai, Matsumoto, & Sadakata, 2004) in both laboratory soil columns and field experiments.…”

“…reported that there were only a few negative results in the treated soils, even when the treatments were applied at rates representing cumulative 80-year applications of FGD gypsum. Furthermore, Koralegedara et al (2017) demonstrated that Pb concentrations in the leachate from FGD gypsum-treated soils were T A B L E 7 Proportions of soil aggregates (≥250 μm) and non-aggregates (<250 μm) averaged across the three exchangeable sodium percentage (ESP) classes after 17 years of reclamation with gypsum from desulphurization of flue gas (FGD) less than those from untreated soils because FGD gypsum reduced the Pb desorption from ferrihydrite. The results from the present study further confirm that the use of FGD gypsum to reclaim sodic soil did not contaminate the soil after 17 years.…”

“…In addition, the impurities and heavy metals in FGD gypsum and their potentially hazardous effects on plants and water after its application to soils have been studied extensively (Chen et al, 2015;Ishak, Seaman, Sumner, & Miller, 1999;Yang et al, 2016). In general, most studies have confirmed that the use of FGD gypsum in agriculture presents a relatively small ecological risk (Briggs, Fine, Markee, & Gustin, 2014;Sakai et al, 2004;Wang et al, 2008) and even helps remove trace elements from soils (Clark et al, 2001;Koralegedara et al, 2017). As a result, FGD gypsum is now used widely to reclaim saline-sodic soils worldwide.…”

Properties and Micro-Structure Assessment of Building Materials Based on Flue Gas Desulfurisation Gypsum Modified by Cement and Industrial Waste

“…The development of industrial activities such as steel and iron manufacturing, smelt and power generation lead to the release of large quantities of flue gas desulfurisation (FGD) gypsum [1], blast furnace slag (BFS) [2], silica fume (SF) [3], and fly ash (FA) [4], which occupies much land and poses a threat to the environment if disposed in landfills. Therefore, it is a hot topic to use and recycle these industrial wastes instead of landfilling [5][6][7][8].…”

“…FGD gypsum is a by-product of power station where FGD equipment is installed to remove SO 2 from the flue gas by adding limestone/lime. The higher content of calcium sulphate dihydrate, fewer impurities, smaller and more uniform particle size, wider range of sources, better fire resistance, lower thermal expansion coefficient, lower cost and sounder insulation properties are the obvious advantages of FGD gypsum [1,[9][10][11]. It is applied widely in construction and building engineering materials nowadays, for example, as a cement-coagulation agent or raw material in the production of cement and concrete to control the hydration rate of cement and improve the early strength, or as a body of cementitious materials after calcined to prepare lightweight gypsum-based building elements [12][13][14].…”