Acid Mine Drainage Treatment Assisted by Lignite-derived Humic Substances: Metal Removal and Speciation Modelling
William E. Olds[1],[2], Daniel C.W. Tsang 1,[3],*, Paul Weber2
Supplementary Materials
Table S1. Target pH for rapid metal removal of as various metal hydroxides
Table S2. Stability constants for complexation by humic substances
Figure S1. Mixing regimes for the dosing of humic substances: (a) BTP scenario and (b) MSS scenario.
Figure S2. Solution pH of AMD up to seven days after CaCO3 dosing.
Figure S3. Metal concentrations of AMD after CaCO3 neutralization with addition of humic substances.
Figure S4. Speciation of residual metals in AMD after CaCO3 neutralization with addition of 100 mg L-1 of SEHA.
Figure S5. Speciation at different sites of humic substances.
Table S1. Target pH for rapid metal removal of as various metal hydroxides
Metal / pH* / Stability Constant of Metal Hydroxide Precipitation*Fe3+ / 3.5-4.3 / 39.5
Al3+ / 4.9-5.2 / 33.5
Pb2+ / 6.3 / 15.3
Cu2+ / 6.8-7.2 / 19.3
Zn2+ / 8.2-8.4 / 15.5
Ni2+ / 9.3 / 17.2
Fe2+ / 9.5 / 15.1
Cd2+ / 9.7-9.8 / 14.3
Adapted from Morel (1983); Kelly (1988); and Younger et al. (2002).
TableS2.Stability constants for complexation by functional groups of humic substances
Humic Acid / Fulvic AcidCarboxylic / Phenolic / Carboxylic / Phenolic
Fe3+ / 3.5 / 17.5 / 6.0 / 36
Al3+ / -1.05 / 8.89 / -4.11 / 12.16
Pb2+ / 1.25 / 4.84 / -1.16 / 6.92
Cu2+ / 2.23 / 6.85 / 0.26 / 8.26
Zn2+ / 0.11 / 2.39 / -3.84 / -0.73
Ni2+ / -0.26 / 1.0 / -2.07 / 2.03
Cd2+ / -0.2 / 2.37 / -0.97 / 0.50
Adapted from Milne et al. (2003).
Figure S1. Mixing regimes for the dosing of humic substances: (a) BTP scenario and (b) MSS scenario.[Based on the field scenarios, the BTP neutralization dose was defined as the amount of Ca(OH)2 required to raise the pH of AMD to 7, which was 845 mg L-1 (as CaCO3) as determined by jar test. This suggested a Ca(OH)2 neutralization efficiency of 96%, when compared to 815 mg L-1 (as CaCO3) of NaOH as determined by titration. In view of turbulent stream mixing and slow dissolution kinetics of CaCO3 at circum-neutral pH, the MSS neutralization dose was defined as the amount of CaCO3 required to raise the pH of AMD to 6 after one hour mixing at 100 rpm, which was 1800 mg L-1 (as CaCO3) as determined by jar test. This represented a low CaCO3 neutralization efficiency of 42%, which was within the reported range of 30-70% (Trumm, 2010)]
Figure S2. Solution pH of AMD up to seven days after CaCO3 dosing.
Figure S3. Metal concentrations of AMD after CaCO3 neutralization with addition of humic substances: (a) Ni; (b) Zn; (c) Cu; (d) Cd; and (e) Pb (error bar represents standard deviation, n ≥ 2).
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Figure S4. Speciation of residual metals in AMD after CaCO3 neutralization with addition of 100 mg L-1 of SEHA.
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Figure S5. Speciation at different sites of humic substances: (a) electrostatic fulvic and humic sites; (b) fulvic carboxylic and phenolic sites; and (c) humic carboxylic and phenolic sites (notes: (6)Me+2D(aq) - fulvic electrostatically bound; (7)Me+2D(aq) - humic electrostatically bound; HA1-Me(6)(aq) - fulvic carboxylic; HA2-Me(6)(aq) - fulvic phenolic; HA1-Me(7)(aq) - humic carboxylic; HA2-Me(7)(aq) - humic phenolic).
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1Department of Civil and Natural Resources Engineering, University of Canterbury, Christchurch 8140, New Zealand.
2Solid Energy New Zealand Ltd,Private Bag 1303, Christchurch, New Zealand.
3Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
* Corresponding author (email: , phone: 852-2766-6072; fax: 852-2334-6389).