Comparison of Activated Carbon and Pyrolyzed Biomass for Removal of Humic Acid From Aqueous Solution

Abstract

The pyrolysis of sewage sludge (SS) and olive mill waste (OMW) was carried out under nitrogen atmosphere and analyzed thermogravimetric and scanning electron microscopy micrographs. Removal capacity of pyrolyzed cokes was measured by humic acid solution. Humic substances can react with chlorine to produce carcinogens in drinking water. Activated carbon can be used as an effective treatment method to remove humic substances from water to prior to disinfection by chlorination. Olive mill waste, an agricultural byproduct and sewage sludge were used to produce acti- vated carbon by pyrolysis with the addition of zinc chloride to enhance the reaction. Activated carbon was also produced using olive mill waste and sewage sludge. Both of them were compared to a commercially-available activated carbon product. Optimum pyrolysis conditions and concentration of the activating agent were identified. The equilibrium parame- ter model of the Freundlich isotherm and Langmuir isotherm was applied to the adsorption data, and the efficiency of py- rolyzed coke was determined. Activated carbon produced from olive waste material had a lower specific surface area (437.92 m 2 /g) than activated carbon produced from sewage sludge (814.48 m 2 /g). While both of these were lower than the surface area of a commercially activated carbon, the latter fell within the expected range of commercial products, thus suggesting an effective means of producing activated carbon while reducing sewage waste disposal costs. Municipal and industrial plants in Turkey, and other countries, consume large volumes of water for various pur- poses. The water quality that is required for a plant varies with the specific purpose, and so the quality of water that is discharged from a plant. Increasing demands on existing water supplies place pressure on wastewater facilities to adequately treat and release large amounts of water. The quality of natural waters varies with source (e.g., groundwa- ter aquifer or surface water body), but all waters contain some minerals, trace elements and organic substances, and are treated to different levels of purity depending upon their intended use. Humic substances are abundant organic compounds found in sediment, soil and even in rocks that are formed from the decay of organic molecules from vegetation, ani- mals, and microbes. Not surprisingly, coal, which is formed when plant material is compressed under extreme pressure in a low-oxygen environment, can be high in humic substances. Water, flowing through coal seams, can accumulate and carry humic substances to groundwater sources and surface water bodies. The nature of these substances can vary widely, but in general they can be defined as acidic, hydro- philic and complex materials, including humic acids, fulvic acids and humins. Humic acids are common in natural wa- ters and pose no risk to humans or animals in their unaltered states.