In-situ copper impregnation by chemical activation with CuCl2 and its application to SO2 and H2S capture by activated carbons

Abstract

H2S and SO2 are toxic compounds that are part of the main air pollutants. They can also induce corrosion and are responsible for acidic rain. Among the methods for their capture, adsorption on copper impregnated activated carbons is one of the most efficient. The latter are generally obtained in a two-step process, consisting of the preparation of the activated carbon and then its impregnation with copper. The aim of this work is to elaborate an efficient adsorbent of H2S and SO2 in one single step. This goal is reached by an in-situ impregnation of copper using an original technique based on chemical activation using CuCl2 as activating agent which, as far as we know, was not used before in this role, i.e. as the main activating agent. The carbonisation was carried out to 800 °C either in N2 or CO2. The obtained materials have a BET surface area of around 400 m2/g and a copper content by weight of about 20%. They were tested successfully against SO2 and H2S by breakthrough measurements. In fact, they showed better results than an activated carbon prepared by chemical activation with ZnCl2 (SBET 1600 m2/g). Thermogravimetric analysis before and after breakthrough tests allowed the proposition of possible mechanisms for the retention of H2S and SO2 on the prepared materials. This new one step preparation method using CuCl2 would permit a gain of time and energy for obtaining efficient activated carbons intended to capture SO2 and H2S.