Fabrication of a Nanoporous Silica Hydrogel by Cross-Linking of SiO₂–H₃BO₃–Hexadecyltrimethoxysilane for Excellent Adsorption of Azo Dyes from Wastewater

Abstract

This study reports a novel cross-linking approach to fabricate the hydrothermally neutralized silica hydrogel of SiO2–H3BO3–hexadecyltrimethoxysilane by grafting alkylsilane groups onto the nanoporous silica. The synthesized silica hydrogel possessed a large specific surface area of 51.3 m2g–1 and showed excellent dye adsorption capability of cationic dyes in neutral (pH 7) and alkaline (pH 9) medium from wastewater. The colloidal electrokinetic potential analysis revealed that the outstanding adsorption efficiency of cationic dyes over anionic dyes strongly relies on the surface charge of the hydrogels. Moreover, the hydrophobic interactions between the dye molecules and the hydrogels were studied, and it was found that the dye adsorption performance can be tuned by altering the concentration of hydrophobic reagents of the hydrogel. The dye adsorption mechanism was established, and the kinetic study suggested that the adsorption is a pseudo-second-order reaction. Adsorption isotherms at various equilibrium conditions fitted well with the Langmuir isotherm. Therefore, this strongly supports the promising and practical application of the prepared silica hydrogel. The recyclability of the hydrogel was studied, and it showed 90% adsorption efficiency by the regenerated gel up to 6 cycles, which has a high potential in wastewater treatment.

Nanolayer-Constructed TiO(OH)2 Microstructures for the Efficiently Selective Removal of Cationic Dyes via an Electrostatic Interaction and Adsorption Mechanism

“…The large surface area can increase the available adsorption sites and thus improve the adsorption of dyes in aqueous solution. 35,36 The morphological feature composed of the stacked nanolayers indicates that the prepared nanolayer-constructed TiO(OH) 2 microstructures likely possess a large surface area. The nitrogen adsorption−desorption isotherm of the nanolayer-constructed TiO(OH) 2 microstructures tested at 77 K is presented in Figure 2a.…”

“…Therefore, the SEM images demonstrate that the prepared nanolayer-constructed TiO­(OH) 2 microstructures possess large surface areas. The large surface area can increase the available adsorption sites and thus improve the adsorption of dyes in aqueous solution. , …”

Synthesis of Sodium Carboxymethyl Cellulose/Poly(acrylic acid) Microgels via Visible-Light-Triggered Polymerization as a Self-Sedimentary Cationic Basic Dye Adsorbent

“…Studies have shown that dyes are toxic to aquatic organisms and potentially mutagenic and carcinogenic to humans. , Therefore, it is necessary to remove dyes efficiently from wastewater. To date, conventional approaches for treating dye wastewater include catalytic degradation, biodegradation, ionic exchange, membrane separation, flocculation–sedimentation, and adsorption. , Among these, adsorption is a simple, efficient, low-cost, and versatile method. − …”

3D Interlayer Slidable Multilayer Nano-Graphene Oxide Acrylate Crosslinked Tough Hydrogel

“…Among them, nanoparticles are regarded as rigid sites with functional ability and mechanical energy dissipation ability via adsorption–desorption of polymer chains. Examples include silver, TiO 2 , hydroxyapatite, silicate, − and so forth. (2) one-dimensional nanotubes or nanofibers.…”