Photodechlorination of Aroclor 1254 in a Pilot-Scale Flow through Photoreactor

Abstract

A novel pilot-scale flow through photoreactor has been designed with the intent to apply it in the field. The photoreactor uses a new plastic coil, instead of the conventional quartz tube. The photoreactor consists of six ultraviolet ͑UV͒ lamps with five around the coil and one at the center. Laboratory investigations were conducted using the photoreactor to treat neat Aroclor 1254 in alkaline isopropanol ͑IPA͒. The photoreaction is fast and efficient, even though the UV transmittances of the three plastic tubes investigated were lower than that of quartz. The reaction kinetics of the practical mixtures are explored. An analysis of five different constituent congeners of Aroclor 1254 indicated that higher congeners dechlorinate producing some of the lower ones, which are subsequently dechlorinated. The dechlorination of Aroclor 1254 was faster when water was added to the alkaline IPA-Aroclor solution.

Photocatalytic dechlorination of PCB 138 using leuco-methylene blue and visible light; reaction conditions and mechanisms

“…To confirm the mechanism of the reaction, a similar experiment was performed using red (660 nm) and blue (436 nm) (LEDs) and PCB 77 (3,3 ,4, in the presence of TEA. The results are presented in Fig.…”

“…The quantum yield of the reaction for dechlorination of Aroclor 1254 is reported to be as high as >30, which is very promising for developing a practical method for remediation of PCB, e.g. in contaminated soil [3].…”

Reductive Dechlorination of PCBs Using Photocatalyzed UV Light

“…1. It seems that dechlorination at 350 nm is more efficient than at 254 nm 2. This may be due to the role of platinum promoting charge separation.…”

“…Rapid photocatalytic dechlorination of PCB, using TiO 2 and 350‐nm light has been found to be feasible. The process is competitive with the known 254‐nm chain reaction in basic IPA 1, 2 which is promising for practical application 3. The processes at the TiO 2 surface, shown in Eqs.…”

“…Photochemical dechlorination of PCBs in alkaline 2‐propanol (IPA) using 254‐nm UV light leads to complete dechlorination within a short period of time. The chemistry of dechlorination is a chain reaction, that has a quantum yield >1 1, 2. As this is an efficient photolytic reaction with no chemicals being further required, it is an attractive option for scaling the technology to field use 3.…”