Decolourisation of dyes and dyehouse effluent in a bubble‐column reactor by heterogeneous catalytic ozonation

Abstract

The decolourisation of aqueous solutions of dyes by ozonation with various heterogeneous catalysts using a bubble-column reactor was investigated. The catalysts studied were hydrated alumina, activated carbon and ferric oxide supported on silica. The optimum catalyst concentration and pH for decolourisation were determined in each case. Hydrated alumina and silica-supported ferric oxide showed excellent catalytic activity under acidic conditions, whereas activated carbon was found to be effective under both acidic and alkaline conditions. In addition to studying the effect on individual dyes, tests were carried out on effluent from a commercial dyeing unit. The reaction kinetics in the presence of various catalysts were also monitored.

Decolorization of C.I. Reactive Red 2 by catalytic ozonation processes

“…(10)-(15)) [15,18,26,39] and O 3 /MnO 2 systems (Eqs. (16)- (20)) [15][16][17]40]. Dye + OH • → products Mn(II) can react with O 3 to produce hydrous manganese oxide (Mn(OH 2 )) in situ, which subsequently attacks the pollutant molecules and accelerates degradation [11].…”

Ozonation of humic acid in water

“…These groups could either be formed on the HA molecules or be acidic compounds that split from HA molecules as a result of the oxidation. Synchronously, pH is usually considered as an important parameter of the ozonation kinetics of organic substances, 21,22 hence HA ozonation in phosphate buffer (pH 7) was further investigated. Results showed that the HA ozonation in buffer solution agreed with the pseudo-first-order equation, as can be seen in Fig.…”

Effect of magnetic catalysts on the kinetic behaviour of Reactive Black 5 decomposition by an O3/H2O2 process

“…The RB5 solution was scanned by a spectrophotometer (Metertech, SP-830, Taiwan) from 320 nm to 900 nm, and the optical absorption curve plotted. Decolourization of RB5 was determined using the characteristic peak absorbance (598 nm), a similar method was reported for detecting the dyes 7 and RB5 mineralization was determined by results of a TOC analyzer (Tekmar, Dohrmann Phoenix 8000, USA). The Zeta potential of the magnetic catalyst (SiO 2 /Fe 3 O 4 ) in the aqueous phase was measured using a Zetasizer Nano Instrument (Nano ZS, Red badge ZEN 3600, UK) with the solution pH adjusted between 2 and 7.5 by adding NaOH and HCl.…”

“…1 -3 These studies show that industrialscale AOPs for water and waste-water treatment have been developed for the oxidation of various refractory and hazardous organics in the presence of oxidants such as UV/H 2 7 allow faster removal of organic pollutants because such catalysts improve the oxidizing power of O 3 and thus significantly reduce the cost of the ozonation process. The use of ozone coupled with effective, inexpensive, and non-toxic mobilized/immobilized heterogeneous catalysts for the treatment of waste-water has been reported.…”

“…The use of ozone coupled with effective, inexpensive, and non-toxic mobilized/immobilized heterogeneous catalysts for the treatment of waste-water has been reported. 7,8 Catalytic ozonation with metal oxides can proceed through two pathways: (a) enhancing OH· generation from aqueous ozone; 6,9 and (b) forming surface complexes between the carboxylic groups of the pollutants and the surface metal sites of the catalyst, which renders the coordinated pollutants more reactive towards molecular ozone. 5 Typically, catalytic ozonation is conducted in a suspension of submicrometre size particles 2,5 and therefore requires an additional separation step to remove the catalyst from the treated water.…”