A Novel Environmental Route to Ambient Pressure Dried Thermal Insulating Silica Aerogel via Recycled Coal Gangue

Table 3

Extraction of SiO₂ after chemical activation.

Samples	Na2CO3 coal gangue (w/w)	Calcination temperature (°C)	Calcination time (hours)	Silicon yield (%)	Si/Na mol/mol
CSi-4-1	0.8	850	2	96.49 ± 1.31	1 : 1
CSi-4-2	0.9	850	2	96.47 ± 1.52	0.88 : 1
CSi-4-3	1.0	750	2	76.70 ± 1.23	0.62 : 1
CSi-4-4	1.0	800	2	95.58 ± 1.69	0.77 : 1
CSi-4-5	1.0	850	2	98.70 ± 0.56	0.80 : 1
CSi-4-6	1.0	900	2	89.02 ± 2.52	0.72 : 1
CSi-4-7	1.2	850	1	95.18 ± 3.05	0.64 : 1
CSi-4-8	1.2	850	2	99.50 ± 2.59	0.66 : 1
CSi-4-9	1.2	850	3	98.53 ± 1.52	0.66 : 1
CSi-4-10	1.2	850	4	93.64 ± 0.53	0.63 : 1
CSi-4-11	1.2	850	5	90.76 ± 0.86	0.61 : 1
CSi-4-12	1.3	850	2	98.70 ± 1.79	0.61 : 1
CSi-4-13	1.4	850	2	99.20 ± 0.92	0.57 : 1
CSi-4-14	1.5	850	2	97.28 ± 1.63	0.52 : 1
CSi-4-15	1.6	850	2	98.46 ± 2.46	0.50 : 1