Removal of AOX in Activated Sludge of Industrial Chemical Dyestuff with Bimetallic Pd/Fe Particles

Pd/Fe bimetallic particles were synthesized by chemical deposition and used to remove absorbable organic halogens (AOX) in the activated sludge of a chemical dyestuff wastewater treatment plant. Bath experiments demonstrated that the Pd/Fe bimetallic particles could effectively remove AOX. It indicated several factors, such as Pd loading, the amount of Pd/Fe used, initial activated sludge pH, and reaction time, which could affect the removal effect. The results showed that increasing the Pd content in Pd/Fe particles, from 0.01 to 0.05 wt %, significantly increased the removal efficiency of AOX in activated sludge. The Pd/Fe particles had a much higher removal efficiency of AOX in the activated sludge than bare Fe particles. A slightly acidic condition with a Pd content of 0.05% and 10 g/L of Pd/Fe was beneficial to the process of removing AOX in activated sludge. In detail, the removal efficiency of AOX in the activated sludge could reach 50.7% after 15 days of reaction with 10 g/L of Pd/Fe (Pd loading 0.05 wt %) and at an initial pH of 6.0 during the experiments. It also showed that the control samples without Fe0 and Fe/Pd additions only removed 7.9% of AOX under the same conditions. Meanwhile, the concentrations of AOX in the supernatant of activated sludge were lower than the initial AOX concentration in the supernatant during the activated sludge remediation with Pd/Fe bimetallic particles. The results indicated that the AOX removal from the activated sludge matrix might be mainly due to the Pd/Fe bimetallic particles, and not just by phase transfer.