The development of synthetic methods to obtain high value-added mesoporous Al-MCM-41 from a low-cost silicon-aluminum source with low toxicity is an active research topic in solid waste resource utilization. In particular, the controlled synthesis of MCM-41 with a two-level pore distribution is a challenging task. In this work, the synthesis of unimodal and bimodal mesoporous Al-MCM-41s was achieved using acids with different degrees of ionization from coal gasification fine residue (CGFR) as bulk solid waste generated by the coal gasification process. We determined that the degree of acid ionization affected the self-assembly of inorganic/organic species as well as condensation processes, resulting in some changes of the hexagonal mesoscopic structure. The unimodal mesoporous Al-MCM-41 with acetic acid HAc and bimodal mesoporous Al-MCM-41s with an inorganic acid environment (HCl, HNO3 or H2SO4) could be effectively prepared in a controllable manner by the silicon and aluminum source obtained at alkali dissolution time 6 h and crystallization conditions at pH 10.5 and 383 K in 72 h. Moreover, the synthesis of Al-MCM-41-HAc with different SiO2/Al2O3 molar ratios (18-89) could also be realized by different alkali dissolution times. And alkali dissolution time (2-24 h) and the crystallization conditions (pH 4.5-11.5, temperatures 373-393 K, and time 48-96 h) also affected the formation of unimodal and bimodal mesoporous Al-MCM-41-HAc. In addition, the maximum adsorption amount onto bimodal mesoporous Al-MCM-41-H2SO4 (476.19 mg g-1 at 308 K) was larger than that onto unimodal mesoporous Al-MCM-41-HAc (243.90 mg g-1 at 303 K). The mesoporous Al-MCM-41s showed good stability.
Keywords: Adsorption; Bimodal mesopores Al-MCM-41; Coal gasification fine residue; Crystal violet; Self-assembly.
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