Laboratory Tests of Biochars as Absorbents for Use in Recovery or Containment of Marine Crude Oil Spills

摘要

Absorption capacity of biochar for crude oil and the mineralization potential of the absorbed oil in seawater werendetermined in laboratory-scale experiments. Texas, South Louisiana, or Qua-Iboe (Nigeria) crude oils werencontacted with each of four commercial hardwood biochars and six synthesized biochars in seawater from thenGulf of Mexico and Long Island Sound (U.S.). Synthesized biochars were made from maplewood anoxically atndifferent heat treatment temperatures (HTT) from 300u0002C to 700u0002C. Oil absorption capacity of the biocharsndetermined in dip tests using oil on seawater ranged from 3.6 to 6.3 g/g. Oil-imbibed biochar particles werenbuoyant. Seawater enhanced absorption capacity in relation to the H/C ratio. Oil was less effectively absorbed innthe form of weathered water-in-oil microemulsion (‘‘chocolate mousse’’) than in as-received form. Absorptionncapacity peaked at HTT about 400u0002C and correlated poorly with %C, H/C ratio, O/C ratio, surface area, andnporosity. It is proposed that swelling, in addition to macropore filling is responsible for the high capacities ofnbiochar. In biometer tests, CO2 evolution from subcapacity levels of Texas crude in biochar suspended innseawater was stimulated relative to oil in the absence of biochar in three tests; whereas, stimulation in a fourthntest was not statistically significant. Thus, biochar may prime biodegradation by providing a favorable solidnsupport and an interstitial reservoir of hydrocarbons for degrader biofilms. While less absorptive than manynexperimental high-tech absorbents, biochar may serve as an inexpensive alternative for recovery of marine oilnspills in a form suitable as a fuel or as an aid to natural attenuation.