Hierarchically porous SiO₂/C hollow microspheres: a highly efficient adsorbent for Congo Red removal

Abstract

Hierarchically porous SiO 2 /C hollow microspheres (HPSCHMs) were synthesized by a hydrothermal and NaOH-etching combined route. The adsorption performance of the prepared HPSCHMs was investigated to remove Congo Red (CR) in aqueous solution. The results show that the synthesized composite possesses a hollow microspherical structure with hierarchical pores and a diameter of about 100-200 nm, and its surface area is up to 1154 m 2 g À1. This material exhibits a remarkable adsorption performance for CR in solution, and its maximum adsorption amount for CR can reach up to 2512 mg g À1 . It shows faster adsorption and much higher adsorption capacity than the commercial AC and gAl 2 O 3 samples under the same conditions. The studies of the kinetics and thermodynamics indicate that the adsorption of CR on the PHSCHM sample obeys the pseudo-second order model well and belongs to physisorption. The adsorption activation energy is about 7.72 kJ mol À1 . In view of the hierarchically meso-macroporous structure, large surface area and pore volume, the HPSCHM material could be a promising adsorbent for removal of pollutants, and it could also be used as a catalyst support.

The synergetic effect of a structure-engineered mesoporous SiO2–ZnO composite for doxycycline adsorption

“…Recently, remarkable progress has been achieved in the field of adsorption on metal oxides. 23–25 However, the adsorption performance of these was hindered by their low surface area due to particle aggregation. 26–28 In general, there are two main strategies to increase the surface area and accessible to active adsorption sites thus enhancing the adsorption properties of metal oxides.…”

Green and Facile Synthesis of Porous SiO2@C Adsorbents from Rice Husk: Preparation, Characterization, and Their Application in Removal of Reactive Red 120 in Aqueous Solution

“…e e e max max e (9) where q e is the adsorption capacity of RR120 (mg g −1 ), q max is the maximum adsorption capacity, C e is the equilibrium concentration, n, k, K, a, b, A, and B are constant parameters for the isotherm equations, q D−R is the D−R maximum adsorption capacity of the RR120 (mg g −1 ), and ε is the Polanyi potential given by the equation below…”

“…Fortunately, rice husk contains both essential C and Si; thus, it is beneficial for the fabrication of nanocomposites containing SiO 2 and C, which can be employed as a great anode material for lithium-ion batteries or an effective adsorbent for the removal of pollutants in aqueous solutions. − Consequently, intensive efforts have been made in exploiting rice husk as a low-cost source for synthesizing SiO 2 /C composites or carbon/Si-based materials. The methods include a sol–gel technique combined with mechanical milling, steam activation, hydrothermal coupling with a NaOH etching route, calcination cooperating with a magnesiothermic reduction reaction, calcination of the pyrolyzed rice husk in a NaOH solution, , and post-heat treatment processes before hydrolysis of tetraethyl orthosilicate to form SiO 2 shells on organic sphere templates followed by calcination in the air . Actually, these as-mentioned methods have been successfully employed for synthesizing SiO 2 /C nanocomposites or carbon/Si-based materials.…”

“…9−20 Consequently, intensive efforts have been made in exploiting rice husk as a low-cost source for synthesizing SiO 2 /C composites or carbon/Si-based materials. The methods include a sol−gel technique combined with mechanical milling, 21 steam activation, 22 hydrothermal coupling with a NaOH etching route, 9 calcination cooperating with a magnesiothermic reduction reaction, 7 calcination of the pyrolyzed rice husk in a NaOH solution, 22,23 and post-heat treatment processes before hydrolysis of tetraethyl orthosilicate to form SiO 2 shells on organic sphere templates followed by calcination in the air. 24 Actually, these as-mentioned methods have been successfully employed for synthesizing SiO 2 /C nanocomposites 25 or carbon/Si-based materials.…”

Facile Synthesis of Cu-Zn Binary Oxide Coupled Cadmium Tungstate (Cu-ZnBO-Cp-CT) with Enhanced Performance of Dye Adsorption

“…The adsorption equilibrium capacity of SiO 2 /C was higher than Cu-ZnBO-Cp-CT but required high CR concentration and contact time. Moreover, as per the preparation step, SiO 2 /C was costlier than Cu-ZnBO-Cp-CT [32].…”