Effect of Si/Al molar ratio on the immobilization of selenium and arsenic oxyanions in geopolymer

Tian, Quanzhi; Chen, Changshuai; Wang, Meng Meng; Guo, Binglin; Zhang, Haijun; Sasaki, Keiko

doi:10.1016/j.envpol.2021.116509

Cited by 25 publications

(13 citation statements)

References 41 publications

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“…Furthermore, it is worthy to note that increasing the As V contents appears to enhance the phase transition from amorphous to crystalline (Figures 4a and S5), with the highest crystallinity of the specimen containing the maximum As V content (i.e., 0.05 wt.%). This has also been observed in previous reports 9,18 and is likely owing to the hydration inhibition of geopolymer gel by arsenate. The NaOH concentration is also observed to have a profound effect on the phase composition of the geopolymer, and Figures 4b and S6 illustrate the relationship between the NaOH concentration and the crystalline phase composition.…”

Section: Effect Of Curing Time On Ucs It Has Been Reportedsupporting

confidence: 87%

“…Besides, this geopolymer has a 28-day UCS as high as 31.88 MPa. In comparison to conventional FA-based geopolymers, 18,20,22,32 the geopolymer exhibits superior compressive strength, making it an attractive material for use in construction.…”

Section: Effect Of Fa Asv and Gy Contents On Ucs As Shown Inmentioning

confidence: 99%

“…This may attribute to the structural weakening of geopolymer gels due to the loss of structural water during the curing at elevated temperature (i.e., 65 °C), 41 and the reduction in compactness owing to the phase transitions from amorphous gels to crystalline minerals. 16,18 Nevertheless, it is apparent that when the specimen was prepared with 54 wt.% FA and 10 M NaOH, curing at 65 °C for 24 hours can endow the specimen with a 7-day UCS as high as 35.52 MPa (Figure 2b), implying that curing at elevated temperature can not only enhance the early strength of the specimen but also shorten the curing time. 44 Leaching results of As V .…”

Section: Effect Of Curing Time On Ucs It Has Been Reportedmentioning

confidence: 99%

“…as the alternative cementitious materials have received much attention and been extensively studied. 2,15,[18][19][20] Of various S/S technologies, geopolymerization of the mixture of arsenic-bearing waste and the silica-and/or alumina-rich industrial solid wastes (e.g., fly ash, red mud, mine tailing, etc.) by alkali activation has been demonstrated to be an effective alternative to immobilize arsenic into the geopolymer matrix.…”

Section: Introductionmentioning

confidence: 99%

“…by alkali activation has been demonstrated to be an effective alternative to immobilize arsenic into the geopolymer matrix. [18][19][21][22][23] Geopolymer binders derived from both the alkali activation of coal fly ash 21 and the high-energy ball milling activation of granulated lead smelting slag 22 have shown excellent ability to stabilize the municipal solid waste incinerator fly ash (MSWI FA) with high arsenic content. Recently, it was reported that red mudmetakaolin (MK) based geopolymer shows a good arsenic retention capability as well as a high compressive strength (~ 15 MPa), making it an environmentally friendly backfilling material for sustainable remediation of arsenic pollution.…”

Section: Introductionmentioning

confidence: 99%

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Arsenic(V) Immobilization in Fly Ash and Lead-Zinc Mine Tailing-based Geopolymer: Performance and Mechanism Insight

Bah

Jin

Ramos

et al. 2022

Preprint

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Global mining activities produce thousands of millions of toxic-bearing mine tailing (MT) wastes each year. Storage of the mine tailings not only encroaches upon large areas of cropland but also arouses additional ecological and environmental risks especially when the toxics (e.g., arsenic) are leached out during the stormy weather. Herein we demonstrate that geopolymerization of a mixture of the toxic-bearing mine tailings and the coal fly ash (FA) with a blending of sodium hydroxide (NaOH) and sodium silicate solution can effectively immobilize extra arsenic (As) species derived from arsenic-bearing wastes in the geopolymer specimens, which also possess high compressive strengths (e.g., > 25 MPa for specimens with 54 wt.% FA and activated with 10 M NaOH), allowing them to be further used as low-carbon, cement-free building materials. The geopolymer strength was found to depend clearly upon the NaOH concentration, the fly ash content, the arsenic content, and the curing time, with the maximum being 37.07 MPa for a specimen with 54 wt.% FA, 0.03 wt.% As activated with 10 M NaOH and cured for 28 days. Leaching tests showed that all specimens can achieve an immobilization efficiency as high as 95.4% toward As, and that the leachabilities of both As and other toxic heavy metals are far below the limits of the Chinese leaching standard for hazardous wastes (GB 5085.3 − 2007). Microstructural analyses using X-ray diffractometer (XRD), scanning electron microscopic (SEM), Fourier transform infrared (FTIR) indicate that the As species was physically encapsulated along with the formation of geopolymer gels at first, and then chemically incorporated into the crystalline phases (e.g., calcium silicate, and calcium silicate hydroxide) derived from the geopolymer gels as a result of prolonging the curing time. The developed FA/MT-based geopolymers represent a promising green material for both the remediation of As-bearing lands and the construction industry.

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Section: Effect Of Curing Time On Ucs It Has Been Reportedsupporting

confidence: 87%