A Comparative Study of Cod Removal from Wastewater Using Biochar and Activated Carbon from Hardwood and Pine Tree

摘要

Production of large scale commercial carbon-products essentially requires examination of various feed stocks, manufacturing process/steps and the performance of the product to remove the target pollutant. This study evaluates the removal performance of Chemical Oxygen Demand (COD) from municipal wastewater using biochar and activated carbons (having different activation levels) produced from hardwood and pine tree. First, biochars were produced from hardwood (chips and pellets) and pine (pellets) by pyrolysis process at 850 °F. The biochars were then physically (steam) activated at 1500 °F with different activation (residence) times. The iodine numbers (IN) of biochar from hardwood chips, hardwood pellets and pine pellets were determined to be 76 mg/g, 128 mg/g and 121 mg/g respectively. On the other hand, the iodine numbers (IN) of activated carbon from hardwood chips, hardwood pellets and pine pellets were determined to be 1001 mg/g, 878 mg/g and 826 mg/g respectively, indicating significant activation level. Batch kinetic experiments and isotherm studies were performed to evaluate the effect of activation of biochars (i.e. activated carbons) on COD removal. Batch kinetic studies showed that the biochars were not effective at all in removing COD and even released COD. However, activated carbon produced from these biochars showed excellent COD removal in all cases. The results showed that up to 47% COD removal can be achieved with a target dosage 300 mg/L (with 30-minute reaction time) using the activated carbon (with IN of 1001 mg/g) from hardwood chips. The equilibrium data represented by Freundlich isotherm model also supported the above result showing the enhanced performance of this activated carbon (from hardwood chips) compared to the other carbon products for COD removal.