Low Energy Mesoporous Silica Recovery from a Nigerian Kaolinite …
89
Preparation of Mesoporous Silica
The activated metakaolin (MK) was magnetically stirred, then mixed with 100 ml
aqueous acids solution. The leaching temperature was controlled at 60, 80 or 100 °C,
with varying acid concentration and solid-to-liquid ratio. Finally, the resultant solid
was filtered off, washed with deionized water and dried at 60 °C overnight [4–6].
Results and Discussion
Characterization of the Calcined Kaolinite and Porous Product
The calcined kaolinite maintains similar chemical composition with raw Share kaolinite (Al 2 Si 2 O 5 [OH] 4 ) (Nigeria) as examined by XRF majorly contains 48.83 wt.%
SiO 2, 41.5 wt.% Al 2 O 3 ; 1.59 wt.% Fe 2 O 3 and 1.56 wt.% K 2 O while other components were in trace quantities. The XRD confirmed the composition to be made up of
quartz (96-900-5018) and traces of accessory minerals such as magnetite (Fe 24 O 32 :
96-900-9770, usually it is Fe 3 O 4 ). The micrograph studies revealed the calcined
sample shared similar flaky particles as the raw kaolinite. The chemical composition
of the solid products at optimized showed that the products are silica dominated. The
metal oxides content was reduced after acid activation, except for SiO 2 as well as
silica module (SiO 2 /Al 2 O 3 ). The results also affirm the possible occurrence of cationexchange reactions during acid leaching. The XRD of the product was detected to be
amorphous and is composed mainly of silica (Fig. 1), well characterized with broad
halo peak.
The nitrogen adsorption–desorption isotherms are detailed in Table 1. The results
showed that leached product was nanoporous with specific surface area (S BET ) of up to
45.23 m
2 /g for hydrochloric acid leaching. Also, leached products are characterized
Fig. 1 XRD patterns of the HCl-product. (Color figure online)
89
Preparation of Mesoporous Silica
The activated metakaolin (MK) was magnetically stirred, then mixed with 100 ml
aqueous acids solution. The leaching temperature was controlled at 60, 80 or 100 °C,
with varying acid concentration and solid-to-liquid ratio. Finally, the resultant solid
was filtered off, washed with deionized water and dried at 60 °C overnight [4–6].
Results and Discussion
Characterization of the Calcined Kaolinite and Porous Product
The calcined kaolinite maintains similar chemical composition with raw Share kaolinite (Al 2 Si 2 O 5 [OH] 4 ) (Nigeria) as examined by XRF majorly contains 48.83 wt.%
SiO 2, 41.5 wt.% Al 2 O 3 ; 1.59 wt.% Fe 2 O 3 and 1.56 wt.% K 2 O while other components were in trace quantities. The XRD confirmed the composition to be made up of
quartz (96-900-5018) and traces of accessory minerals such as magnetite (Fe 24 O 32 :
96-900-9770, usually it is Fe 3 O 4 ). The micrograph studies revealed the calcined
sample shared similar flaky particles as the raw kaolinite. The chemical composition
of the solid products at optimized showed that the products are silica dominated. The
metal oxides content was reduced after acid activation, except for SiO 2 as well as
silica module (SiO 2 /Al 2 O 3 ). The results also affirm the possible occurrence of cationexchange reactions during acid leaching. The XRD of the product was detected to be
amorphous and is composed mainly of silica (Fig. 1), well characterized with broad
halo peak.
The nitrogen adsorption–desorption isotherms are detailed in Table 1. The results
showed that leached product was nanoporous with specific surface area (S BET ) of up to
45.23 m
2 /g for hydrochloric acid leaching. Also, leached products are characterized
Fig. 1 XRD patterns of the HCl-product. (Color figure online)