title: Destruction of methyl bromide sorbed to activated carbon by thiosulfate or electrolysis.
abstract: Methyl bromide (CH3Br) is widely used as a fumigant for postharvest and quarantine applications for agricultural products at port facilities due to the short treatment period required, but it is vented from fumigation chambers to the atmosphere after its use. Due to the potential contributions of CH3Br to stratospheric ozone depletion, technologies for the capture and degradation of the CH3Br are needed to enable its continued use. Although granular activated carbon (GAC) has been used for CH3Br capture and thiosulfate has been used for destruction of CH3Br in aqueous solution, this research explored techniques for direct destruction of CH3Br sorbed to GAC. Submerging the GAC in an aqueous thiosulfate solution achieved debromination of CH3Br while sorbed to the GAC, but it required molar concentrations of thiosulfate because of the high CH3Br loading and produced substantial concentrations of methyl thiosulfate. Submergence of the GAC in water and use of the GAC as the cathode of an electrolysis unit also debrominated sorbed CH3Br. The reaction appeared to involve a one-electron transfer, producing methyl radicals that incorporated into the GAC. Destruction rates increased with decreasing applied voltage down to ∼-1.2 V vs the standard hydrogen electrode. Cycling experiments conducted at -0.77 V indicated that >80% debromination of CH3Br was achieved over ∼ 30 h with ∼ 100% Coulombic efficiency. Sorptive capacity and degradation efficiency were maintained over at least 3 cycles. Capture of CH3Br fumes from fumigation chambers onto GAC, and electrolytic destruction of the sorbed CH3Br could mitigate the negative impacts of CH3Br usage pending the development of suitable replacement fumigants.
authors: †Department of Civil and Environmental Engineering, University of Nevada, Reno, Nevada 89557, United States.
authors: Yu
authors: Y
authors: Yang
authors: ‡Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, California 94305, United States.
authors: Yuanqing
authors: Y
authors: Li
authors: §San Joaquin Valley Agricultural Sciences Center, USDA-ARS, 9611 South Riverbend Avenue, Parlier, California 93648, United States.
authors: Spencer S
authors: SS
authors: Walse
authors: ‡Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, California 94305, United States.
authors: William A
authors: WA
authors: Mitch
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D000397:Air Pollution / Q000517:prevention & control*; D002606:Charcoal / Q000737:chemistry*; D004566:Electrodes; D004572:Electrolysis; D005651:Fumigation; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D010084:Oxidation-Reduction; D013885:Thiosulfates / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D006842:Hydrocarbons, Brominated; D013885:Thiosulfates; D002606:Charcoal; C005218:methyl bromide