Decomposition and decoloration of synthetic dyes using hot/liquid (subcritical) water.
We have studied the decomposition and decoloration of 4-(2-Hydroxynaphthylazo) benzenesulfonic acid sodium salt (AO7, acid dye) as a model for textile wastes by using a flow-type subcritical water system. The operating temperature was ranged from 180 to 374 degrees C at 10-25 MPa at a wide range of residence time. The pressure (up to 25 MPa) did not affect the decomposition reactions. AO7 completely decomposed at higher temperatures and or longer residence times. The main products from decomposition of AO7 were found to be 2-naphthalenol, phenol, 1,1'-Binaphthalene-2,2'-diol, and N-(phenylmethylene)benzenamine. In order to identify the decomposition pathways, the products were also individually treated under a batch type subcritical water conditions. We found that 2-naphthalenol underwent to further decomposition to 1,1'-Binaphthalene-2,2'-diol during the subcritical water reaction. Other decomposition products resulted from the decomposition of directly AO7. Kinetic model of the subcritical water reaction was developed by considering major products. The kinetic constants obtained from the proposed reaction pathway showed good agreement with experimental results.
Hosseini
Somayeh Daneshvar
SD
Department of Chemical Engineering, College of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai-shi, Osaka 599-8531, Japan.
Asghari
Feridoun Salak
FS
Yoshida
Hiroyuki
H
D003116:Color; D004396:Coloring Agents / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D008956:Models, Chemical; D009284:Naphthols / Q000737:chemistry; D011312:Pressure; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D004396:Coloring Agents; D009284:Naphthols; D014867:Water