TY - JOUR
T1 - Ozonation of spent reactive dye-baths
T2 - Effect of HCO-3/CO23- alkalinity
AU - Alaton, Idil Arslan
AU - Kornmüller, Anja
AU - Jekel, Martin R.
PY - 2002/8
Y1 - 2002/8
N2 - The effect of carb onate and bicarbonate alkalinity (soda ash buffer as 5,180 mg/L HCO-3 alkalinity at pH 7 and as 5,100 mg/L CO23- alkalinity at pH 12) on the ozonation of reactive vinylsulphone dyestuffs in a simulated spent dye-bath has been studied at varying pHs. Adsorbable organic halogen (AOX) formation due to the high chloride content of the effluent and detoxification, which was evaluated in terms of the relative toxicity index Itox determined from the ED50 values for the marine photobacteria Vibrio fischeri, were also evaluated. Highest total organic carbon (56%), chemical oxygen demand (44%), and UV254 (77%) removals were achieved at pH 7 in the presence of HCO-3 alkalinity. The fastest decolorization was observed for the case pH 2, the first order decolorization rate constant found as k620=0.16 min-1, closely followed by the pH 12 case with soda ash (k620=0.12 min-1) case. No positive correlation was evident between AOX, whose maximum value (=1.3 mg/L) appeared after 40 min ozonation at pH 7 and decreased to 0.54 mg/L after 120 min treatment, and Itox, which decreased to 0.16 at t=50 min and increased rapidly thereafter. The Itox values were more related to color abatement kinetics. The maximum relative toxicity index of Itox=0.83 occurred after 120 min. It was also established that the presence of alkalinity in the spent reactive dye-bath had no negative impact on the oxidation rates. In contrast, its absence seriously inhibited treatment efficiency. It is speculated that, with added soda ash, the carbonate radicals HCO3· and CO3·-, which are more stable and selective than OH., were produced and promoted the oxidation process.
AB - The effect of carb onate and bicarbonate alkalinity (soda ash buffer as 5,180 mg/L HCO-3 alkalinity at pH 7 and as 5,100 mg/L CO23- alkalinity at pH 12) on the ozonation of reactive vinylsulphone dyestuffs in a simulated spent dye-bath has been studied at varying pHs. Adsorbable organic halogen (AOX) formation due to the high chloride content of the effluent and detoxification, which was evaluated in terms of the relative toxicity index Itox determined from the ED50 values for the marine photobacteria Vibrio fischeri, were also evaluated. Highest total organic carbon (56%), chemical oxygen demand (44%), and UV254 (77%) removals were achieved at pH 7 in the presence of HCO-3 alkalinity. The fastest decolorization was observed for the case pH 2, the first order decolorization rate constant found as k620=0.16 min-1, closely followed by the pH 12 case with soda ash (k620=0.12 min-1) case. No positive correlation was evident between AOX, whose maximum value (=1.3 mg/L) appeared after 40 min ozonation at pH 7 and decreased to 0.54 mg/L after 120 min treatment, and Itox, which decreased to 0.16 at t=50 min and increased rapidly thereafter. The Itox values were more related to color abatement kinetics. The maximum relative toxicity index of Itox=0.83 occurred after 120 min. It was also established that the presence of alkalinity in the spent reactive dye-bath had no negative impact on the oxidation rates. In contrast, its absence seriously inhibited treatment efficiency. It is speculated that, with added soda ash, the carbonate radicals HCO3· and CO3·-, which are more stable and selective than OH., were produced and promoted the oxidation process.
KW - Alkalinity
KW - Dyes
KW - Ozonation
KW - Textiles
UR - http://www.scopus.com/inward/record.url?scp=0036684703&partnerID=8YFLogxK
U2 - 10.1061/(ASCE)0733-9372(2002)128:8(689)
DO - 10.1061/(ASCE)0733-9372(2002)128:8(689)
M3 - Article
AN - SCOPUS:0036684703
SN - 0733-9372
VL - 128
SP - 689
EP - 696
JO - Journal of Environmental Engineering (United States)
JF - Journal of Environmental Engineering (United States)
IS - 8
ER -