Influence of magnetic field on Cr(VI) adsorption capability of given anaerobic sludge

To provide beneficial guide for the application of the magnetic field in the bio-treatment of the Cr(VI)-contained wastewater, sludge samples from the control bio-system A (absent of magnetic field) and the contrast bio-system B (present of magnetic field) were used to adsorb the synthetic wastewater with 100 mg l(-1) Cr(VI). Influences of two adsorption modes, single adsorption and once continuous adsorption, on the Cr(VI) adsorption capacities of both sludge samples were compared. And the influence of regeneration on the Cr(VI) adsorption capacities were also studied. The results of adsorption experiments showed that the Cr(VI) adsorption capacities of the first single adsorption for sludge sample A and B were pretty nearly, which were 9.79 and 9.93 mg, respectively. And after 5 single adsorption periods, the total Cr(VI) adsorption capacity and efficiency of the sample B were 25.88 and 55.66 mg Cr(VI) g(-1)VSS, while those of the control were 14.95 and 33.98 mg Cr(VI) g(-1)VSS, respectively. For the sludge sample A and B after a single adsorption, both functions of regeneration were remarkable. But after 13 cycles of the single adsorption-regeneration, the Cr(VI) adsorption capacity and efficiency of the sample B were 110.15 and 189.91 mg Cr(VI) g(-1)VSS, while those of the control were 70.89 and 140.38 mg Cr(VI) g(-1)VSS, respectively. Though the Cr(VI) adsorption capacity of a once continuous adsorption period was more than that of a single adsorption period obviously, the Cr(VI) removal rates of the sludge sample A and B in the third period of once continuous adsorption-regeneration were only 8.12 and 33.51%, respectively. It was concluded that the weak magnetic field did improve the Cr(VI) bio-removal efficiency and the sludge stability, the batch treatment was an ideal operation mode for the bio-treatment of the Cr(VI)-contained wastewater, as compared with the continuous operation mode, but regeneration and enough sludge content were two necessary conditions to ensure the efficiency of batch treatment.