A novel advanced oxidation process to degrade organic pollutants in wastewater: microwave-activated persulfate oxidation.
This article, for the first time, provides a novel advanced oxidation process based on sulfate radical (SO4*-) to degrade organic pollutants in wastewater: microwave (MW)-activated persulfate oxidation (APO) with or without active carbon (AC). Azo dye acid Orange 7 (AO7) is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 (up to 1000 mg/L) is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion (up to 0.50 mol/L), the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 (500 mg/L) is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 (484 nm), during MW-APO, two bands in the ultraviolet region (228 nm and 310 nm) are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO4*- is identified with quenching studies using specific alcohols. Both SO4*- and *OH could degrade AO7, but SO4*- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.
Yang
Shiying
S
Key Laboratory of Marine Environment & Ecology, Ministry of Education, Qingdao 266100, China. shiningpup@hotmail.com
Wang
Ping
P
Yang
Xin
X
Wei
Guang
G
Zhang
Wenyi
W
Shan
Liang
L
D002606:Charcoal / Q000737:chemistry; D008872:Microwaves; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
D013431:Sulfates; D002606:Charcoal