A sequential anaerobic aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated soil was used to degrade sulfonated azo dyes Orange G (OG), Amido black 10B (AB), Direct red 4BS (DR) and Congo red (CR). Under anaerobic conditions in a fixed-bed column using glucose as co-substrate, the azo dyes were reduced and amines were released by the bacterial biomass. The amines were completely mineralized in a subsequent aerobic treatment using the same isolates. The maximum degradation rate observed in the treatment system for OG was 60.9 mg/l per day (16.99 mg/g glucose utilized), for AB 571.3 mg/l per day (14.46 mg/g glucose utilized), for DR 112.5 mg/l per day (32.02 mg/g glucose utilized) and for CR 134.9 mg/l per day (38.9 mg/g glucose utilized).
Activated carbon prepared from Eichhornia was used for the adsorptive removal of Pb(II) from aqueous solution. As the raw material for the preparation of the activated carbon is an aquatic weed, the production of this carbon is expected to be economically feasible. Parameters such as agitation time, metal ion concentration, adsorbent dose and pH were studied. Adsorption equilibrium was reached in 100 min for a solution containing 15 mgdm À3 and 125 min for solutions containing 20 and 25 mgdm À3 Pb(II), respectively. Adsorption parameters were determined using both Langmuir and Freundlich isotherm models. The adsorption capacity was 16.61 mgg À1 at pH 3.0 for particle sizes of 125±180 mm. Pb(II) removal increased as the pH increased from 2 to 4 and remained constant up to pH 10.0. Desorption studies were also carried out with dilute hydrochloric acid to recover both carbon and Pb(II). Quantitative desorption of Pb(II) from carbon indicates that adsorption of metal ion is by ion exchange.
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