Characterisation of sewage sludge-derived adsorbents for H2S removal. Part 2: Surface and pore structural evolution in chemical activation

Abstract

This paper presents results of chemical activation of sewage sludge, a waste material generated in sewage treatment processes, to produce an adsorbent for H₂S removal. Dewatered sewage sludge samples were subjected to chemical treatment by sulfuric acid and zinc chloride at various molar concentrations and were then pyrolysed in inert gas atmosphere at various temperatures for different hold times. Resulting adsorbents were characterised in terms of BET surface area, micropore area and pore size/volume distributions. In this study, it was shown that pyrolysis temperature and activation chemicals used significantly affect the surface area development and pore structure evolution. Solution molar concentration of the activating agent is a particularly important factor. H₂S adsorption tests were carried out on the derived adsorbents using a thermogravimetric analyser. Experimental results demonstrate that sewage sludge, a waste material in abundant supply at virtually no cost, is a viable source of activated adsorbents. Its potential use for odour control is reinforced by the need to find environmentally safe disposal alternatives for sewage sludge. From both economics and environmental perspectives, these experimental results warrant further efforts, perhaps in terms of large scale manufacturing and testing.