Enhancing Arsenic Solidification/Stabilisation Efficiency of Metallurgical Slag-Based Green Mining Fill and Its Structure Analysis

Abstract

To dispose of arsenic-containing tailings with low carbon and high efficiency, sodium sulphate (Na2SO4), sodium hydroxide (NaOH), calcium nitrate Ca(NO3)2 and calcium hydroxide Ca(OH)2 were independently added to metallurgical slag-based binder (MSB) solidification/stabilisation (S/S)-treated tailings (MSTs) to enhance the MST arsenic S/S performance. Results showed that only Ca(OH)2 could increase the unconfined compressive strength of MST from 16.3 to 20.49 MPa and decrease the leachate As concentration from 31 μg/L to below 10 μg/L. Na3AsO4·12H2O and NaAsO2 were used to prepare pure MSB paste for mechanism analysis. The results of microstructure analyses showed the high specific surface area and amorphous properties of calcium–sodium aluminosilicate hydrate facilitated the adsorption or solid-solution formation of As(V) and As(III). As(V) formed an inner-sphere complex in ettringite, whereas As(III) formed an outer-sphere complex, and the relatively larger size and charge of As(V) compared with SO42− restrict substitution inside channels without affecting the ettringite structure under high loading of As(V). The added Ca(OH)2 promoted the hydration reaction of MSBs and facilitated the formation of a Ca–As(V) precipitate with low solubility, from Ca4(OH)2(AsO4)2·4H2O (Ksp = 10−27.49) to Ca5(AsO4)3(OH) (Ksp = 10−40.12). This work is beneficial for the application of cement-free MSB in the S/S process.

Study on Solidification and Stabilization of Antimony-Containing Tailings with Metallurgical Slag-Based Binders

“…The feature at 977 cm −1 is the antisymmetric Si-O(Al) stretching vibration which is characteristic of C-S-H gel. The bands at 513 cm −1 and 451 cm −1 are caused by the out-of-plane banding vibration and in-plane bending vibration of Si-O, respectively [ 14 , 29 , 30 , 31 ]. The only difference between MSB-Sb and MSB was that the absorption peaks related to C-S-H gel in MSB-Sb shifted to the wavelet numbers.…”

“…However, the production of cement is accompanied by the large CO 2 emission, yielding the high cost and limiting the use of the final product [ 8 ]. To reduce carbon emissions and to make it possible to absorb a large amount of metallurgical solid waste, blast furnace slag (BFS), steel slag (SS), and flue gas desulfurized gypsum (FGDG) were proposed as cementing binders [ 14 , 15 , 16 ]. In the hydration process, BFS provides potentially active silicon–oxygen and aluminum–oxygen tetraheda, SS is a source of alkaline substances, and FGDG ensures sulfate ions [ 17 , 18 ].…”

“…At present, most research aimed at evaluating the environmental friendliness of S/S materials and the leaching characteristics of heavy metals using different leaching methods [ 4 , 19 ]. According to our previous research, the metallurgical slag-cementing binders effectively limits the leaching concentration of As and Sb, and the dominant leaching mechanism for Sb is diffusion [ 14 , 15 , 20 ]. In addition, in our previous research, the solidification mechanism of As was confirmed [ 21 , 22 ].…”

Green Low-Carbon Technology for Metalliferous Minerals

“…The first paper, by Gao et al [1], provides an experimental study for the disposal of arsenic-containing tailings with low carbon and high efficiency. In their research, sodium sulphate (Na 2 SO 4 ), sodium hydroxide (NaOH), calcium nitrate Ca(NO 3 ) 2, and calcium hydroxide Ca(OH) 2 were independently added to metallurgical slag-based binder (MSB) solidification/stabilisation (S/S)-treated tailings (MSTs) to enhance the MST arsenic S/S performance.…”