Activated carbon from soybean hulls

This thesis relates to a process for making activated carbon from soybean hulls. Activated carbon is capable of adsorbing and/or filtering contaminants from drinking water and further providing an excellent adsorptive medium for removing contaminants from industrial waste water streams. It is expected that the char from the soybean hulls would be competitive in terms of adsorptive and regeneration capabilities with activated carbon obtained from other sources, such as coconut shells. Although soybean hulls can be utilized as an animal feed or as a soil builder, it would be more profitable to convert it to activated carbon which in the marketplace costs ~$ 1.10/lb in ton quantities. Once regenerated, activated carbon brings ~$.70/lb. The soybean hulls were first washed with distilled water to remove dirt and other water soluble organic and inorganic compounds which are present on, or among, the hulls and then were dried in an oven. They were then placed in a lab scale furnace having a gas input port, an exhaust output port and a thermocouple insert. The outport port was connected to a cold trap (immersed in liquid nitrogen) to collect the liquid byproducts. The hulls were then carbonized at selected temperatures (300-500°C) and time periods under a continuous flow of inert gas. The charred hulls were then activated in flowing CO2 at temperatures of 600-800°C for selected time periods. The effects of the processing parameters, temperatures, activation time, and activation gas flow rates on the properties of the processed hulls were determined. Adsorption properties were determined by using the instrument Quantachrome Autosorb 1-C. The data was analysed using Minitab, a statistical software. A linear regression of the full quadratic model was performed to optimize the variables for maximum surface area --Abstract, page iii