Functionalization of carbon silica composites via in-pore synthesis of active sites for NH $$_3$$ 3 and SO $$_2$$ 2 adsorption

Abstract

To enhance the gas adsorption of toxic industrial chemicals such as NH\(_3\) and SO\(_2\), a biphasic carbon silica composite (CSC) is functionalized with combinations of potassium carbonate or potassium phosphate and various metal chlorides with divalent cations. A precipitation reaction occurs within the pores of the CSC between non-monovalent cations and anions to create essentially insoluble active sites. The adsorption capacities of these functionalized materials are measured at atmospheric pressure and low concentrations of NH\(_3\) and SO\(_2\). Along with capacity performance, the synthesized materials are characterized using X-ray diffraction, porosimetry and pH measurements to analyze the structure, the incorporation, and the effects of impregnation upon functionalization. Results show that successful incorporation of all insoluble precipitates enhances adsorption capacities compared to impregnant-free substrates. Furthermore, characterization results show reduced pore volumes and surface areas of functionalized materials with structural integrity maintained. Both NH\(_3\) and SO\(_2\) adsorption can be improved via dual salt functionalization of metal chlorides with potassium salts which form insoluble precipitates on CSC and MCM-41 adsorbent materials. In order to target both adsorbates effectively, the incorporation of K\(_2\)CO\(_3\) and ZnCl\(_2\) to form ZnCO\(_3\) provides the highest adsorption capacities for both NH\(_3\) and SO\(_2\).