Location: Integrated Cropping Systems ResearchTitle: Nitrate sorption and desorption in biochars from fast pyrolysis Author
Submitted to: Microporous and Mesoporous Materials Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2013
Publication Date: 7/11/2013
Citation: Chintala, R., Mollinedo, J., Schumacher, T.E., Malo, D.D., Papiernik, S.K., Clay, D.E., Kumar, S., Gulbrandson, D. 2013. Nitrate sorption and desorption in biochars from fast pyrolysis. Microporous and Mesoporous Materials Journal. 179:250-257. Interpretive Summary: In US agriculture, nitrogen fertilizers are routinely applied to agricultural crops. Agriculture has been implicated as a major source of nutrients (including nitrate) to surface and ground water, and as one of the causes of the hypoxic zone in the Gulf of Mexico. Nitrate removal technologies have been developed for water treatment, but controlling nitrate movement in soil would eliminate the need for remediation. We studied the potential for biochar to reduce nitrate mobility in soil. We used biochars produced as a by-product of biofuel production by microwave pyrolysis using corn stover, Ponderosa pine wood residue, and switchgrass as feedstocks. Our results demonstrate that these biochars have a high capacity to remove nitrate from soil water, depending on the surface properties of biochar, solution pH, and presence of competitive ions. Results suggest that biochars may useful as soil amendments to enhance fertilization and decrease water contamination. Scientists, engineers, and extension personnel can use this information to recommend practices to reduce water contamination by nitrogen fertilizers.
Technical Abstract: Increasing the nitrate (NO3-) sorption capacity of Midwestern US soils has the potential to reduce nitrate leaching to ground water and reduce the extent of the hypoxia zone in the Gulf of Mexico. The objective of this study was to determine the sorption and desorption capacity of non-activated and chemically activated biochars from microwave pyrolysis using selected biomass feedstocks of corn stover (Zea mays L.), Ponderosa pine wood chips (Pinus ponderosa Lawson and C. Lawson), and switchgrass (Panicum virgatum L.). Surface characteristics such as surface area and net surface charge have shown significant effects on nitrate sorption and desorption in biochars. Freundlich isotherms performed well to fit the nitrate sorption data (R2 >0.95) of biochars when compared to Langmuir isotherms. Nitrate sorption and desorption was significantly influenced by solution pH and presence of highly negative charged potential ions such as phosphate (PO43-) and sulfate (SO42-) in aqueous solution. Chemical activation with concentrated HCl had significant effect on surface characteristics of biochars and enhanced the nitrate sorption capacity. The first order model fit the nitrate desorption kinetics of biochars with a high coefficient of determination (R2 >0.95) and low standard error (SE).