Decontamination of a natural multicomponent aqueous liquid waste by titania photocatalysis
The aerobic photocatalytic degradation of municipal dump-site leachate at 300 K has been carried out in a pilot-scale bubble column reactor. The leachate feed is a complex mixture of various organics and nitrogenous compounds. Runs were performed over a 48-hour period at atmospheric pressure. Compositional analysis of aliquots from the reactor revealed simultaneous total organic carbon removal and conversion of uric compounds to ammoniacal species as evidenced by time-on-stream pH increase. A Langmuir-Hinshelwood kinetic model with a unimolecular rate-determining step and a strong adsorption constant (41.6 M−1) adequately described the TOC reduction rate while NH4+ ions production rate attained a maximum around a TOC concentration of 35mM suggesting competitive adsorption between the precursors for the two parallel reactions. Reaction rates exhibited linear dependency on light intensity up to 10−4 Einstein s−1 and thereafter levelled off.
Keywords: titania photocatalysis, leachate, slurry bubble column reactor, municipal solid waste, aqueous liquid waste, waste decontamination, aerobic degradation, kinetic modelling, total organic carbon, TOC removal