Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2011
Publication Date: 3/17/2011
Citation: Sun, K., Ro, K.S., Guo, M., Novak, J.M., Mashayekhi, H., Xing, B. 2011. Sorption of bisphenol A, 17a-ethinyl estradiol and phenanthrene on thermally and hydrothermally produced biochars. Bioresource Technology. 102:5757-5763. Interpretive Summary: Biochars are a charcoal–like product made as a co-product during the biofuel manufacturing process. They have the potential to serve as a sorption media for organic pollutants. Their ability to sorb pollutants, however, can vary due to difference in feedstock and production practices. For example, two biochars were produced using a thermal pyrolytic process while the other two were produced using hydrothermal procedures. Characterizing the thermal and hydrothermal produced biochars using spectroscopic techniques revealed that there were large differences in chemical and structural properties. We speculated that the suitability of the 4 biochars to sorb the pollutants would vary due to chemical and structural differences. To test this speculation, a series of laboratory sorption studies were conducted to quantify the amount of pollutant sorbed by each biochar. Three organic pollutants were selected as model compounds. They were reacted with the four different biochars, and after a period of time, the quantity of organic pollutants sorbed was quantified. The quantity of pollutant sorbed by each biochar was determined. These values were then linked to each biochar's chemical and structural characteristics. We found that the four biochars were effective at sorbing the three model organic pollutants; however, the hydrothermal-produced biochar was a better sprption media. Further studies are needed to clarify the relationship between the structural characteristics of each biochar with more types of organic pollutants.
Technical Abstract: In this study, organic contaminant removal potential of biochars made from various agricultural residuals was investigated through sorption experiments. The model pollutants include endocrine disrupting chemicals (EDCs) such as common estrogenic compounds, bisphenol A (BPA) and 17a-ethinyl estradiol (EE2), and a polycyclic aromatic hydrocarbon, phenanthrene (Phen). Two thermal biochars were made from pyrolyzing poultry litter and wheat straw at 400ºC for 2 to 7 hrs. Two hydrothermal biochars were made by carbonizing poultry litter and swine solids in water at 250ºC under autogenic pressure for 20 hrs. The thermal biochars were composed mostly of aromatic moieties while hydrothermal biochars were composed of diverse functional groups. Because of the diverse functional groups associated with hydrothermal biochars, sorption capacities for polar estrogenic compounds were significantly higher than that of thermal biochars. The sorption capacities for nonpolar Phen were similar for both thermal and hydrothermal biochars. This study demonstrated that hydrothmeral biochar could absorb a wide spectrum of both polar and non-polar organic contaminants than thermally produced biochars.