BackgroundPaint laden with polychlorinated biphenyls (PCBs) often acts as a point source for environmental contamination. It is advantageous to address contaminated paint before the PCBs transport to surrounding media; however, current disposal methods of painted material introduce a variety of complications. Previous work demonstrates that PCBs can be broken down at ambient temperatures and pressures through a degradation process involving magnesium metal and acidified ethanol. This report is an extension of that work by describing the development of a delivery system for said reaction in preparation for a field test. Two treatment options including the Activated Metal Treatment System (AMTS) and the Non-Metal Treatment System (NMTS) remove and degrade PCBs from painted surfaces.FindingsAMTS decreased the Aroclor® concentration of a solution by more than 97% within 120 minutes and the Aroclor® concentration of industrial paint chips by up to 98% over three weeks. After removing up to 76% of PCBs on a painted surface after seven days, NMTS also removed trace amounts of PCBs in the paint’s concrete substrate. The evaporation rate of the solvent (ethanol) from the treatment system was reduced when the application area was increased. The solvent system’s ability to remove more than 90% of PCBs was maintained after losing 36% of its mass to solvent evaporation.ConclusionsThe delivery systems, AMTS and NMTS, are able to support the hydrodechlorination reaction necessary for PCB degradation and are therefore attractive options for further studies regarding the remediation of contaminated painted surfaces.
A heterogenous catalytic system consisting of mechanically alloyed Mg/Pd particles has been used to degrade the peroxide explosive, triacetone triperoxide (TATP). The degradation of the TATP with the Mg/Pd particles (half life of 1.2 Â 10 1 min) was compared to the degradation with microscale Mg particles (half life of 1.7 Â 10 3 min) and 10% Pd on activated carbon (half life of 8.7 Â 10 2 min). Combining the Mg and Pd on carbon (Pd/C) through a mechanical alloying process is shown to produce reactive particles that can be used to degrade TATP. The major product of the degradation of TATP with mechanically alloyed Mg/Pd particles was acetone. A material balance for carbon was also calculated for the degradation reaction with 94 AE 5% (mean AE standard deviation) of the TATP carbons accounted for in the production of acetone.
Dimensional analysis is traditionally one of the first topics covered in a general chemistry course. Chemists use dimensional analysis as a tool to keep track of units and guide them through calculations. Although unit conversions are taught in a variety of subjects over several grade levels, many students have not mastered this topic by the time they enter college. To properly equip beginning chemistry students, a collaborative active-learning activity was developed. This article describes the activity and reports data of the effects it had on students’ performance in a first-semester general chemistry course at a large research institution.
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