The Effect of Dissolved Humic Acids on Aluminosilicate Formation and Associated Carbon Sequestration

Table 2

Speciation of Al and Si in 0.5, 0.75, and 1.0 mM Al; 0.5 mM Si solutions with 0 (Al-Si) and 6 mg/L (Al-Si-DOC) as calculated using Visual MINTEQ ver 2.53 with the Thermo.vdb database¹.

Al-Si	Si species percent		Al species percent
[Al] mM	H4SiO4^0	AlH3SiO4^2+		Al(OH)2^+	Al(OH)3^0	Al(OH)4^−	AlOH^2+	Al^3+	Al3(OH)4^5+	AlH3SiO4^2+
0.5	98.1	1.8		48.9	23.0	14.6	9.0	0.9	1.6	1.8
0.75	96.9	3.1		48.5	20.5	11.8	10.2	1.2	5.3	2.1
1	96.0	4.0		46.0	19.0	11.0	10.1	1.3	10.0	2.0
Al-Si-DOC	Si species percent		Al species percent									mM
[Al] mM	H4SiO4^0	AlH3SiO4^2+		Al(OH)2^+	Al(OH)3^0	Al(OH)4^−	AlOH^2+	Al^3+	Al3(OH)4^5+	AlH3SiO4^2+	Al-HA	Al-HA	C
0.5	98.1	1.9		47.2	21.1	12.6	9.2	1.0	1.6	1.9	5.3	0.026	0.052
0.75	96.9	3.1		47.2	19.1	10.6	10.4	1.3	5.3	2.1	3.5	0.027	0.053
1	95.9	4.0		45.0	18.0	10.1	10.2	1.3	10.0	2.0	2.7	0.027	0.053

¹Source of thermodynamic data for aqueous species: Al hydrolysis species [20]; AlH₃SiO₄²⁺ [21]; Al₃(OH)₄⁵⁺ [22]. Organic complexation was calculated using the Stockholm Humic Model [16].