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Treatment of Industrial Wastewater Utilizing Standalone and Integrated Advanced Oxidation Processes
Published in Maulin P. Shah, Sweta Parimita Bera, Günay Yıldız Töre, Advanced Oxidation Processes for Wastewater Treatment, 2022
Pranjal P. Das, Piyal Mondal, Mihir K. Purkait
Pérez-Estrada et al. (2005) [55] examined the decomposition of diclofenac in aqueous solution by the application of the photo-Fenton process. The result indicated a degradation efficiency of 50% and 100% by Fenton and photo-Fenton process, respectively. Moreover, treatment of 2-chlorophenol by Fenton and photo-Fenton process led to 60% and 100% removal after 30 min of reaction time respectively. The study also reported an increase in mineralization efficiency during the Fenton process from 10% to 95% with the application of ultraviolet radiation in the system for both diclofenac and 2-chlorophenol. Thus, the collaborative effect of combining Fenton with ultraviolet radiation enhanced the overall degradation efficiency of the process. Nevertheless, the homogeneous photo-Fenton process consist of a very firm acidic pH range, apart from generating secondary contaminants like Fe2+ ions, and as such requires an extra removal system. Consequently, several heterogeneous catalysts (activated carbons, clays, zeolites and aluminas) have been extensively developed for both Fenton and photo-Fenton processes with properties such as cost effectiveness, long-term stability and photocatalytic activity. In heterogeneous photo-Fenton oxidation, the treatment can be carried out at neutral pH and room temperature and does not require neutralization of effluents after the operation. Palas et al. (2017) [56] applied both ultraviolet and visible light radiation to analyze its effect on the catalytic activity of LaCuO3 during the photo-Fenton treatment of tartrazine (food dye) in aqueous solution. The influence of catalyst loading, solution pH, H2O2 concentration and irradiation source on the degradation of tartrazine and decolorization efficiency was investigated. The study reported a decolorization and tartrazine degradation efficiency of 83.9% and 46.6% respectively for visible light irradiation, whereas the degradation efficiency significantly increases to 90.2% for color and 64.4% for tartrazine during the utilization of UV irradiation. Thus, it was concluded that the prepared perovskite catalysts showed satisfactory results under both UV and visible light irradiation.
Restricted substances for textiles
Published in Textile Progress, 2022
Arun Kumar Patra, Siva Rama Kumar Pariti
Chemically, chlorophenols are aromatic ring structures consisting of the benzene ring, -OH group and atom(s) of chlorine. They include mono-, di-, tri-, tetra- and penta-chlorinated phenols (CP, DCP, TCP, TTCP and PCP respectively). Along with the 19 possible isomers, chloroderivatives of methyl- and ethyl-phenols are also considered to be chlorophenols (Ivanciuc, Ivanciuc, & Douglas, 2006). These synthetic organic compounds are obtained by chlorinating phenol or hydrolysing chlorobenzenes. All chlorophenols are solid at room temperature except 2-chlorophenol (2-CP) which is a liquid. The aqueous solubility of chlorophenols is low, but the sodium or potassium salts of chlorophenols are significantly more soluble than the parent compounds. The acidity of chlorophenols increases as the number of chlorine substitutions increases. The n-octanol/water partition coefficients (Kow) of chlorophenols increase with chlorination, indicating a propensity for the higher chlorophenols to bio-accumulate (Chiou, Schmedding, & Manes,2005). For instance, the mono chloro compound 2-CP with Log Kow value of 2.17 has a solubility of 28.5 g/L in water while PCP having a higher Log Kow of 5.01 is sparingly soluble (0.014 g/L) (Olaniran & Igbinosa, 2011). Structures of some of the commercially-important chlorophenols are given below (Igbinosa et al., 2013) (Figure 10).