Nanoscale Fe(0) particles for pentachlorophenol removal from aqueous solution: temperature effect and particles transformation.
Pentachlorophenol (PCP), as an important contaminant which was toxic and intractable, has received extensive attention. In this paper, the temperature effect during the transformation of PCP using nanoscale Fe(0) particles was studied, and the transformation processes of PCP and iron particles was explained. The results revealed that the removal processes of PCP followed pseudo first-order kinetics. The scale of dechlorination to the transformation of PCP increased with the increase of temperature, though the transformation rate decreased after reacting for 2 h under the experimental condition. However, the initial apparent transformation rate constants were calculated to be 0.312-0.536 h(-1) at the temperature of 20-50 degrees C, which showed an increase of transformation rate along with the increase of temperature. And the surface-area-normalized rate constants were calculated to be 9.50 x 10-3-1.63 x 10-2 L . h-1 . m-2. The experimental activation energy was calculated to be 15.0 kJ x mol(-1) from these rate constants using Arrhenius equation. A phenomenon observed at 50 degrees C indicated that more than one chlorine atom was removed from PCP and suggested β-elimination might be the major pathway for transformation. Sorption experiments showed that the sorption process on the surface of particles could be ignored in the kinetics and thermodynamics models. The changes of morphologies of nanoparticles before and after reaction indicated the transformation process of iron particles, and could be used to explain the changes of activity of nanoparticles. Magnetite (Fe3O4) and/or maghemite (Fe2O3) and lepidocrocite (γ-FeOOH) were corrosion products of iron. And along with the increase of temperature, the increased intensity of XRD peaks revealed the related a better crystallizing.
Rong
R
Cheng
Xiang
X
Zheng
Peng
P
Liu
Jian-Long
JL
Wang
D007700:Kinetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D010416:Pentachlorophenol / Q000737:chemistry / Q000302:isolation & purification*; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification
D058185:Magnetite Nanoparticles; D014874:Water Pollutants, Chemical; D010416:Pentachlorophenol