Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
150498 | Chemical Engineering Journal | 2011 | 8 Pages |
The aim of this study was to determine the effectiveness of gamma radiation to degrade cytarabine in aqueous solution. The effect of dose rate, initial cytarabine concentration, medium pH, and the presence of H2O2, Cl−, CO32−, NO3−, NO2− and organic matter was studied. Furthermore, the influence of the chemical composition of water on cytarabine degradation was evaluated by using different water matrix (ultrapure water, surface water, groundwater, and wastewater) and the variations in total organic carbon concentration and toxicity were also studied. Results show that cytarabine radiolysis fits pseudo-first order kinetics. The dose constants determined in this study ranged from 0.002 × 10−2 to 1.32 × 10−2 Gy−1, whereas the initial radiation-chemical yield ranged from 0.033 to 0.94 μmol J−1. Cytarabine degradation in the presence of Cl−, CO32−, NO3−, NO2− and humic acid showed a decrease in dose constants with the increase in present species concentration, largely due to competition of cytarabine with Cl−, CO32−, NO3−, NO2− and humic acid by the reactive species generated, mainly HO radicals. Cytarabine degradation was slightly improved by the presence of small amounts of H2O2, which acted as promoter of HO radicals. However, the dose constant decreased at high concentrations of H2O2 (concentrations above 1 mM) due to inhibition of HO radicals by recombination reactions. The effectiveness of gamma radiation was markedly reduced in wastewater due to inhibition of the reactive species by the high organic matter and anion content of the water. This study shows that it is not possible to completely mineralize organic matter in ultrapure water, surface water, groundwater, or wastewater at the radiation doses used
► Gamma radiation is an effective treatment for removing cytarabine from aqueous solutions. ► The experimental results demonstrate that cytarabine degradation takes place via oxidative pathway. ► Lower degradation rate constants are obtained in SW, GW and WW than in UW due to the presence of organic matter and HCO3− (radical scavengers).