Carbonization of sewage sludge as an adsorbent for organic pollutants

Abstract

Abstract Sewage sludge (SS) is an inevitable byproduct that is generated in large amounts in the sewage treatment process. It has been regarded as an ecological burden due to its high pathogenic microorganisms and odor emissions. As a carbon-rich material, SS has the potential of carbonaceous adsorbents for the removal of organic pollutants. Physical and chemical activation were conducted to enhance their porosity and surface area. Carbon dioxide and steam were usually used as physical activation reagents while the KOH, NaOH, ZnCl2, H2SO4, etc., were chemical activation reagents. A nitrogen adsorption-desorption curve and a scanning electron microscope (SEM) were conducted to investigate the pore structure characteristics. The sludge-derived adsorbents are widely applied in removing organic pollutants from aqueous and atmosphere. The microporosity leading to the van der Waals force is one factor contributing to the adsorption mechanism. Besides, the adsorption mechanisms depend on the characteristics of adsorbents and adsorbates. The original characteristics of sludge determined the adsorption property. The silicon oxide in sludge carbon played complexation to - COOH group of the benzoic acid, leading to preferable adsorption ability. Partition adsorption is also ascribed to the adsorption of the hydrophobic surface of sludge carbon to the hydrophobic organic pollutants such as toluene and p-chlorophenol. Granular sludge carbon is also developed as an adsorbent for the removal of organic pollutants, considering its efficient recovery and separation. Special hollow-like and hollow spherical sludge carbon were prepared for the adsorption of dye in batch and column experiments. Thus, the carbonization of sludge into carbonaceous production could be a promising method for resource utilization of sludge as well as sludge disposal treatment.