Preparation of halloysite-derived mesoporous silica nanotube with enlarged specific surface area for enhanced dye adsorption

Surface Improvement of Halloysite Nanotubes

“…For the S0 sample, the BET surface area and the total pore volume were recorded at 59.04 m 2 /gm and 0.26 cm 3 /g, respectively. The results of S0 are in agreement with other findings [26]. As the treatment of HNTs is conducted by adding SDS, PVA, and MA at 5, 7, and 10%, the BET surface area decreased to 40.13 m 2 /gm (about a 30% decrease) for S05, and then moderately increased to 54.68 m 2 /gm, almost approaching the level of S0.…”

“…Recently, two publications, Shu et al [26] and Gaaz et al [27], both in press, have shown that the specific surface area was improved to new frontiers, as far as 608 m 2 /g and 306 m 2 /g, by treating HNTs with alkali solution, followed by acid etching, respectively. Briefly, esterification is obtained via PVA-MA crosslinking [28,29].…”

Template-free Synthesis of Mesoporous Silica with High Specific Surface Area from Natural Halloysite and Its Application in Methylene Blue Adsorption

“…All the acid-treated samples are amorphous ( Fig. 2) and composed of mainly SiO 2 (above 95%) and traces of Al Table 3) reaches up to 767 m 2 /g, which is much superior to those of the halloysite-derived nanoporous silica in literatures (below 608 m 2 /g) [7][8][9][10]15] . The N 2 adsorption-desorption isotherms (insert in Fig.…”

“…Beyond 4 h, the sample became crystalline zeolite LTA (PDF 73-2340), which is a type of sodium aluminosilicate crystal. The Si-O-Al network of calcined halloysite is supposed to be etched by concentrated OH  and react with Na + to form new sodium aluminosilicate framework during alkali-hydrothermal treatment [10] . The long-enough treatment (above 4 h) leaded to the formation of zeolite LTA crystals.…”

“…Shu, et al [9] found that pre-calcining halloysite could activate the tubewall framework, and then, acid-etching resulted in mesoporous silica nanotube with enlarged SSA of 415 m 2 /g. In order to further improve SSA, Shu, et al [10] introduced a short-term NaOH treat-ment on the pre-calcined halloysite, and then etched it with acid, producing mesoporous silica nanotubes with SSA as high as 608 m 2 /g. Nevertheless, the SSA is still limited compared to those of the mesoporous silica fabricated by the traditional template methods (700 m 2 /g-1000 m 2 /g) for FDU-1 [11] , SBA-15 [12] , KIT-6 [13] .…”