removal of 2,4-dichlorophenoxyacetic acid from water and organic by-product minimization by catalytic ozonation

2,4-dichlorophenoxyacetic acid (2,4-dcpa acid) is a toxic herbicide. earlier studies to remove 2,4-dcpa acid from water used expensive and/or toxic reagents, resulting in the formation of toxic organic by-products (org-bps). this study evaluates the removal of 2,4-dcpa acid from aqueous media using uncatalysed and catalytic ozonation with fe doped with ni and co respectively. mixed metal oxides of ni and co loaded on fe respectively, prepared by co-precipitation and physical mixing were used as catalyst for ozone facilitated oxidation degradation of 2,4-dcpa acid. their surface properties were determined by employing sem, bet and nh3-tpd. hplc, ic and toc data were used for quantifying substrate and oxidation products. conversion of 2,4-dcpa acid increased from 38% in acidic water to 73% in basic water, however, only 26% of the total carbon was removed and 9.5% in the form of org-bps. with 7:3 fe:ni (co-ppt) catalyst (surface area 253 m2 g−1; particle size 236 nm), 97% of pollutant was converted. most importantly, 92% of carbon was removed and org-bp formation was minimized to 1.5%. with 7:3 fe:ni (mixed) catalyst (surface area 12 m2 g−1; particle size 1274 nm), 68% of 2,4-dcpa acid was converted, while 23% of toc was removed, however, 66% of org-bp’s still remained. in uncatalysed ozonation degradation of 2,4-dcpa acid improved with the increase in hydroxide ion concentration. ozonation in presence of 7:3 fe:ni (co-ppt) catalyst resulted in highest activity for dechlorination, toc removal and org-bp minimization, thus improving the quality of contaminated water.