The discharge of dye-containing effluents into the aquatic environment represents a source of aesthetic pollution with associated negative effects. Photocatalytic degradation has been identified as a suitable means of treating these effluents. In this study, the potential of a locally sourced material, periwinkle shell ash (PSA), has been explored as an effective photocatalyst for the photocatalytic decolourisation of tartrazine in aqueous solution. The efficiency of the photocatalyst was evaluated by investigating the effects of operational variables such as irradiation time, initial dye concentration and catalyst loading on the extent of decolourisation. The results show that the optimum levels of the variables were 50 minutes, 30 mg/L and 5 g/L for irradiation time, initial dye concentration and catalyst loading respectively. The pseudo first order and the Langmuir-Hinshelwood kinetic models were able to sufficiently describe the kinetics of the process. The diffusion mechanism was described by the intra-particle diffusion model while the adsorption equilibrium was described by the Langmuir isotherm equation. The results obtained indicate that PSA can be used as an effective photocatalyst for the removal of tartrazine from aqueous solution.
This work investigated the removal efficiency of Congo red dye (CRD) from aqueous solution using chitosan prepared from the biomass of Penicillium chrysogenum Thom. CRD is a benzidine -based anionic diazo dye known to be carcinogenic at low concentration. Chitosan was prepared from the mycelium of P. chrysogenum through the process of deproteination and deacetylation; and the chitosan was characterised using Fourier transform infrared spectroscopy (FT-IR) analysis through which the degree of deacetylation (DD) was estimated. Adsorption study was carried out in a slurry batch system at ambient temperature (28 ± 1 o C). The percentage yield of chitosan from the fungus was 12.2% while 82.4% DD was achieved. The FT-IR spectrum showed that chitosan contained amide carbonyl band as a measure of N-acetyl group, alkyl groups and hydroxyl groups; the spectrum of P. chrysogenum-based chitosan corresponded to the pattern of the commercial chitosan used as control. The commercial and P. chrysogenum-based chitosan attained decolourisation efficiency of 95.2% and 84.6% respectively, which gives the indication that chitosan from P. chrysogenum biomass, can effectively remove CRD from aqueous solution.
Landfill is a potential microbial hub of hydrocarbon (HC) degrading bacterial population owing to nutrient availability and continuous enrichment by organic materials. The degradation and dioxygenase activity of Carnobacterium gallinarum and Enterococcus faecalis isolated from landfill soil in Benin City was investigated. Soil samples were collected from a Government approved landfill in Benin City at a depth of 0 to 10 cm. Standard microbiological and molecular methods were followed for the isolation and characterization of bacterial population. Bacterial isolates were standardized for degradation using spectrophotometer optical density (OD) 0.08 at 600 nm (equivalent to 1×108cfu/ml). The gas chromatography with flame ionization detector (GC-FID) method was used to determine the total petroleum hydrocarbon (TPH) of waste engine oil (WEO) containing samples. The spectrophotometric methods were used for the assay of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) activity. The result of the 16S rRNA analyses of the bacterial isolates confirmed the identity of Carnobacterium gallinarum as 98.71 % and Enterococcus faecalis as 100 %. The degradation profile of Carnobacterium gallinarum and Enterococcus faecalis at varied concentrations (20, 40, 60, 80 and 100 mg/L) of WEO showed significant decline in optical density (OD) values from day 1 to day 7. The decline in OD is an indication of utilization of Polycyclic Aromatic Hydrocarbons (PAHs) present in the WEO. The result of the gas Chromatography with Flame Ionization Detector (GC-FID analyses) of degraded WEO containing samples revealed the absence of low molecular weight and high molecular weight PAHs after the 7-days degradation study. The presence of HC degrading enzyme in the bacterial isolates was confirmed by the production of C12O and C23O as a result of the formation of cis, cis muconic acid and 2-hydroxymuconic semi-aldehyde respectively. This study revealed that the landfill soil is a potential natural microcosm for WEO degrading bacteria and possesses biologically active HC degrading bacteria population such as Carnobacterium gallinarum and Enterococcus faecalis.
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