Table 2.
Characteristics of bleaching earth.
P1 | P2 | P3 | P4 | P5 | P6 | P7 | |
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Mineral | Attapulgite clay | Attapulgite clay | Attapulgite clay | Magnesian bentonite | Magnesian bentonite | Magnesian bentonite | Kerolite-hydrated magnesium silicate |
Modified | Physically activated | pH-modified | Not modified | Not modified | Not modified | Acid-modified | Chemically modified |
pH | 8.0 | 3.2 | 8.0 | 8.5 | 10.0 | 6.5 | 6.0 |
Density (kg/m3) | 0.41 | 0.51 | 0.47 | 0.60 | 0.60 | 0.60 | 0.55 |
Composition (%) | |||||||
SiO2 | 55–60 | 58.8 | 56.1 | 63.1 | 53.5 | ||
Al2O3 | 2.5 | 5.3 | 5.7 | 8.3 | 4.0 | ||
Fe2O3 | 12–14 | 1.4 | 1.6 | 1.9 | 1.5 | ||
MgO | 18–21 | 23.0 | 23.6 | 23.0 | 30.5 | ||
CaO | 0.5–1.0 | 2.1 | 2.7 | 2.6 | 0.7 | ||
Na2O | 0.05–0.25 | - | - | - | 0.3 |