Mesoporous hexagonal and cubic aluminosilica adsorbents for toxic nitroanilines from water

Abstract

In the present study, ordered mesocage hexagonal P6mm and cubic Pm3n aluminosilica nanoadsorbents with monolith-like morphology and micro-, meso-, and macro-pores were fabricated using a simple, reproducible, direct synthesis. Our results suggest that the aluminosilica nanoadsorbents attained the ordering and uniform hexagonal and cubic pores even at the high Si/Al ratio of 4. The acidity of nanoadsorbents significantly based on the amount of aluminum species in the walls of the silica pore framework. Aluminosilica nanoadsorbents were used as a removal of environmentally toxic aromatic amines, namely p-nitroaniline (p-NA), from wastewater. The loading amount of Bronsted acid sites, mesostructural geometries, and multi-directional pores (3D) of the aluminosilica adsorbents played a key factor in the enhancement of the coverage adsorbent surfaces and intraparticle diffusion of adsorbate molecules onto the network surfaces and into the pore architectures of monoliths. Significantly, we developed theoretical models to explain the 3D microscopic geometry and the pore orientation of aluminosilica monoliths. A key component of the nanoadsorbents is the ability to create revisable p-NA adsorption systems with multiple reuse cycles. However, simple treatment using an acidic aqueous solution was found to remove effectively the p-NA and to form “p-NA-free” pore surfaces without any mesostructural damage.