Characteristics of amorphous silica prepared from serpentinite using various acidifying agents

This paper examines the effect of the nature of the precipitating agent (HCl, CO2 and (NH4)2CO3) on the surface area of the resulting silica powders synthesized from serpentinite after its leaching in hydrochloric acid. In order to prepare a product consisting of small discrete particles polymerized into three-dimensional networks without using additives (surfactant and/or flocculant), synthesis from nearly-saturated sodium metasilicate solution at laboratory temperature under alkaline and acid-set conditions was applied in the present work. hly acidic solution (e.g. at significant stochiometric excess of hydrochloric acid over the silicate) a regular density xerogel with a high specific surface area (541 m2 g− 1) was achieved. Through synthesis of silica gel by acidification using CO2 and (NH4)2CO3, the values 392 m2 g− 1 and 414 m2 g− 1 respectively of the specific surface area were obtained. The microporosity of silica samples precipitated by HCl was confirmed by t-methods and α-methods, whereas powders prepared using CO2 and (NH4)2CO3 were identified as being mesoporous. The mesopore size distribution calculated using the BJH method and DFT model shifted with rising pore diameter in the following order: silica precipitated by HCl, (NH4)2CO3 and CO2.