Immobilization of antimony waste slag by applying geopolymerization and stabilization/solidification technologies

Figures & data

Table 1. Chemical composition of the AWS and the additives used (% w/w, dry basis)

Compound	Unit	AWS	Portland cement	Fly ash	Clay	Gypsum	Blast furnace slag
SiO2	%	42.49	20.50	51.84	49.77	0.31	38.2
Al2O3	%	6.06	5.14	24.68	14.99	0.18	13.7
Fe2O3	%	3.22	3.28	10.78	11.04	0.06	0.99
CaO	%	29.13	63.51	4.65	7.12	37.38	32.65
MgO	%	1.43	0.86	2.68	2.11	0.54	7.76
SO3	%	0.70	2.69	1.01	0.27	49.18	1.50
Na2O	%	0.146	0.35	0.24	1.84	0.00	0.43
K2O	%	1.22	0.72	2.46	1.33	0.02	0.97
Loss on ignition	%	0.0	2.97	0.70	10.72	11.00	0.00
pH		11.80	11.10	8.00	8.27	11.34	1.50

Figure 1. Properties of the AWS studied. (a) The As and Sb leaching results of the AWS and ground AWS (G.AWS). (b) Acid neutralization capacity of the AWS.

Table 2. Leaching test results of the AWS according to the EU waste acceptance criteria

Compound	Test result	Unit	Limit value for hazardous-waste landfills	Limit value for non-hazardous-waste landfills	Limit value for inert waste landfills	Test method
Arsenic	0.01	mg/L	2.5	0.2	0.05	EN 12457-4 ISO 17294-2
Barium	0.47	mg/L	30	10	2	EN 12457-4 ISO 17294-2
Cadmium	<0.0005	mg/L	0.5	0.1	0.004	EN 12457-4 ISO 17294-2
Total chromium	<0.001	mg/L	7	1	0.05	EN 12457-4 ISO 17294-2
Copper	<0.01	mg/L	10	5	0.2	EN 12457-4 ISO 17294-2
Mercury	0.005	mg/L	0.2	0.02	0.001	EN 12457-4 ISO 17294-2
Molybdenum	0.3	mg/L	3	1	0.05	EN 12457-4 ISO 17294-2
Nickel	0.12	mg/L	4	1	0.04	EN 12457-4 ISO 17294-2
Lead	<0.01	mg/L	5	1	0.05	EN 12457-4 ISO 17294-2
Antimony	0.20	mg/L	0.5	0.07	0.006	EN 12457-4 ISO 17294-2
Selenium	0.016	mg/L	0.7	0.05	0.01	EN 12457-4 ISO 17294-2
Zinc	<0.015	mg/L	20	5	0.4	EN 12457-4 ISO 17294-2
Chlorine	23	mg/L	2500	1500	80	EN 12457-4 SM 4500 Cl^−:C
Fluorine	2.35	mg/L	50	15	1	EN 12457-4 SM 4500 F^−:D
Sulfate	850	mg/L	5000	2000	100	EN 12457-4 SM 4500 SO4^2-:E
Phenol index	<0.1	mg/L	—	—	100	EN 12457-4 ISO 6439 (1990)
Dissolved organic carbon (DOC)	12.5	mg/L	100	80	50	EN 12457-4 EN 1484 (1997)
Total dissolved solids	4977	mg/L	10000	6000	400	EN 12457-4 SM 2540:C
Total organic carbon	0.35	%	6%	5%	30000	EN 13137 (2001)
BTEX (benzene, toluene, ethylbenzene, xylene)	<0.1	mg/kg	—	—	6	ISO 22155 (2005)
PCBs (total)	<0.1	mg/kg	—	—	1	ISO 10382 (2002) (GC-ECD)
Mineral oils and derivatives	382	mg/kg	—	—	500	EN 14039 (2004)

Table 3. Content of the S/S samples

	Activator/liquid
Sample content*	NaSil NaOH	8 M NaOH	Water
Portland cement	+	+	+
Fly ash + Portland cement	+	+	+
Fly ash	+	+	+
Fly ash + Portland cement + clay	+		+
Fly ash + Portland cement + gypsum	+		+
Fly ash + Portland cement + blast furnace slag	+		+
Fly ash + clay + gypsum	+		+
Portland cement + clay + gypsum	+		+
Fly ash + clay + blast furnace slag	+		+
Portland cement + clay + blast furnace slag	+		+

Notes: *Twenty-three types of samples were prepared by using NaSil NaOH or 8 M NaOH or water. Each sample was prepared in triplicate.

Figure 2. The UCS and leaching (As and Sb) results of the samples prepared by using NaSil NaOH, 8 M NaOH, and water as activators, and Portland cement and fly ash as additives.

Figure 3. The acid neutralization capacity of the samples prepared by using NaSil NaOH, 8 M NaOH, and water as activators, and Portland cement and fly ash as additives.

Figure 4. The UCS and leaching (As and Sb) results of the samples prepared by using NaSil NaOH and water as activators, and Portland cement, fly ash, clay, gypsum, and blast furnace slag as additives. (a) NaSil NaOH as activator. (b) Water as activator.