Sustainable utilization of rice husk waste for preparation of ordered nanostructured mesoporous silica and mesoporous carbon: Characterization and adsorption performance

Rice husk has a high heating value, making it an attractive source of renewable energy. Rice husk ash (RHA) forms after the combustion of rice husk to heat energy. The recovery and reuse of RHA is a sustainable strategy in a circular economy. In this research, RHA was used as the raw material for the preparation of mesoporous silica, Santa Barbara Amorphous (SBA-15). Ordered mesoporous carbon, carbons mesostructured from Korea-3 (CMK3), was synthesized utilizing SBA-15 as a template by injecting it with sucrose. According to transmission electron microscopy (TEM) images, both SBA-15 and CMK-3 consisted of high order and hexagonal arrays of mesopores. SBA-15 and CMK-3 contained large pore volumes of 1.260 and 1.185 cm3/g, high surface areas of 820 and 1005 m2/g, and uniform pore sizes of 6.41 and 3.44 nm, respectively. The amino-groups were successfully grafted on the SBA-15 surface. The amino-modified SBA-15 and CMK-3 revealed excellent adsorption of tannic acid. The effects of adsorption conditions, namely the solution temperature, adsorbent dosage, solution pH, and initial tannic acid concentration, were examined. Amino-modified SBA-15 and CMK-3 exhibited maximum adsorption capacities of 278.9 and 488.9 mg/g, respectively. Thermodynamic parameters were also investigated. The results indicated that the tannic acid adsorption was an exothermic process. Kinetic behaviors and adsorption equilibrium optimally matched the pseudo-second-order model and Langmuir isotherm. Overall, recovered RHA was useful in the preparation of mesoporous adsorbents for removing chemicals containing tannic acid from liquid waste.

Automated summary

This study utilized recovered rice husk ash (RHA) to prepare mesoporous silica and mesostructured carbon materials for the removal of chemicals containing tannic acid from liquid waste. The amino-modified SBA-15 and CMK-3 exhibited excellent adsorption capacity, with the adsorption process being exothermic. Kinetic and equilibrium adsorption behaviors were found to fit well with the pseudo-second-order model and Langmuir isotherm.