TiO2 nanofibre assisted photocatalytic degradation of reactive blue 19 dye from aqueous solution.

The photocatalytic degradation of Reactive Blue 19 (RB19) dye has been studied using TiO2 nanofibre as the photocatalyst in aqueous solution under UV irradiation. Titanium dioxide nanofibre was prepared using a templating method with tetraisopropylorthotitanate as a precursor. The experiments were carried out in the presence of the TiO2 nanofibre, and the effects of pH and electron acceptors on the degradation process were investigated. In order to observe the quality of the aqueous solution, chemical oxygen demand (COD) measurements were also carried out before and after the treatments. The photocatalytic decomposition of RB19 was most efficient in acidic solution. With the addition of hydrogen peroxide and potassium persulphate, as electron acceptors, into illuminated TiO2 nanofibre suspensions, a synergistic effect was observed leading to an enhancement of the decolorization. From experimental results, under the condition of 1 g TiO2 nanofibre l(-1), pH 3, and UVC light irradiation, decolorization would be complete in two hours. A significant decrease in the COD values was observed, which clearly indicates that the photocatalytic method offers good potential for the removal of RB19 from aqueous solution. The kinetic of photocatalytic removal of RB19 followed the Langmuir-Hinshelwood model. These results suggest that TiO2 nanofibres with UV photocatalysis can be envisaged as a method for the treatment of coloured wastewaters, in particular in textile industries.

Posttreatment of upflow anaerobic sludge blanket-treated industrial wastewater by a rotating biological contactor.

The performance of a rotating biological contactor (RBC) for posttreatment of the slaughterhouse effluent from an upflow anaerobic sludge blanket (UASB) reactor was investigated in this study. The 280-L, six-stage RBC pilot plant was operated at different organic loading rates (OLRs) and biodisk speeds. The overall removal efficiencies for soluble biochemical oxygen demand (SBOD), total biochemical oxygen demand (TBOD), and total chemical oxygen demand (TCOD) decreased with increasing OLRs. Disk rotational speed did not have a significant effect on performance in the range studied. The results showed that satisfactory posttreatment to meet regulatory requirements for agricultural purposes (effluent biochemical oxygen demand of 100 mg/L) can be achieved at an OLR of 5.3 +/- 2.9 g SBOD x m(-2) x d(-1), with an SBOD removal efficiency of 85 +/- 3%. Most of the organics were removed in the first three stages, with minimal contribution from the remaining stages of the RBC reactor. There was a decrease in SBOD removal efficiency to 74 +/- 3% at an OLR value of 17.8 +/- 2.1 g SBOD x m(-2) x d(-1). The results for elimination capacity indicated a linear relationship with first-stage OLRs without any signs of limitation at the range of loading rates investigated in this study. However, average first-stage elimination capacity rates of 4.8 and 3.8 g x m(-2) x d(-1) at OLR values of 17.8 and 11 g SBOD x m(-2) x d(-1) were relatively lower than previous studies of RBC performance using domestic or industrial wastewater without anaerobic pretreatment. It was suggested that the lower elimination capacity rates were due to the fact that a smaller fraction of UASB effluent was biodegradable as reflected in TBOD/TCOD ratios of 0.47 +/- 0.04.