Comparative studies of mineralization and detoxification of Mordant Black 17 in aqueous solution by UV light induced Mn+/H2O2 and Mn+/S2O82− systems

Abstract

The present study reports a process for simultaneous mineralization and detoxification of Mordant Black 17 with high electrical energy efficiency. Hydrogen peroxide and ammonium persulphate (APS) were used for the generation of hydroxyl and sulphate radicals using UV light (λ = 254 nm) and Fe and Ag ions as catalysts. The detoxification and energy efficiency of various processes were measured by monitoring growth inhibition of Escherichia coli and Electrical Energy per Order (EE/O) applicable for low concentration contaminants respectively. Systems catalyzed by Fe are more energy efficient and possess higher mineralization and detoxification efficiency than that of Ag. The concentration of the catalysts and oxidants were found to strongly influence the EE/O of the systems. The most cost efficient processes for simultaneous mineralization and detoxification are Fe/APS/UV at pH 3.00 and Fe/HO/UV at pH 3.00 and 5.78. The upper limit concentration of Fe is fixed at 0.01 mM for complete detoxification. The treated solutions start detoxifying at this concentration, above which they remain more toxic than the original dye solution irrespective of the extent of mineralization. On the contrary, no such limit could be established for Ag systems for complete detoxification even after 91% mineralization.

The Removal of Binary Mixture of Dyes by Heterogeneous Fenton Oxidation: Kinetics, Product Identification and Toxicity Assessment

“…The first method is based on the E. coli growth inhibition (metabolic inhibition) bioassay. 7,24 Luria Bertani (LB) agar, LB broth and ampicillin used in the toxicity assessment study were acquired from Himedia, India. The lyophilised luminescent bacteria, A. fischeri used for the toxicity assessment by light loss assay was supplied by Modern Water Inc, USA.…”

“…( 7)). 37 (7) The effect of pH on decolorisation in n-Fe 2 O 3 /SPS system was established by carrying out the reaction at pH…”

“…Advanced Oxidation Processes (AOPs), which involve in situ generation of hydroxyl radicals, have achieved the above goals to a great extent. [2][3][4] The oldest AOPs, involving activation of hydrogen peroxide (HP) and sodium persulphate (SPS) to generate hydroxyl and sulphate radicals [5][6][7] using Fe 2+ as a catalyst, are popularly known as Fenton (Fe 2+ /HP) and Fenton-type process (Fe 2+ /SPS) (Eqs.…”

“…19 On the contrary, there are instances of increased toxicity of the solutions even when Fenton and Fenton-type processes achieve mineralisation to the extent of >90%. 7,20 Therefore, it is essential to test the toxicity of industrial wastewater after treatment, after a complete mineralisation is achieved. Some authors have used Aliivibrio fischeri and some Escherichia coli for the toxicity assessment.…”