Enhanced dewatering extent of sludge by Fe 3 O 4 -driven heterogeneous Fenton.

Homogeneous Fenton (Fe2+ /H2 O2 ) serves as a high-efficiency conditioning method for sludge dewatering due to the generation of strong oxidizing hydroxyl radicals (OH). However, high dose of ferric salts produces iron-rich dewatered sludge and decrease sludge organic matters, which will not be conducive to the subsequent disposal and reutilization. Considering advantages of Fe3 O4 as heterogeneous Fenton catalyst, Fe3 O4 -activated H2 O2 (Fe3 O4  + H2 O2 ) in this study was adopted to improve sludge deep-dewatering. Reduction efficiency of the bound water (71.3 %) after Fe3 O4  + H2 O2 treatment (after a reaction time of 30 min) were much higher than those in the Fe2+ +H2 O2 treatment. Especially, the moisture content of treated sludge cake by Fe3 O4  + H2 O2 remarkably decreased from 86.4 % to 61.3 %. Improvement mechanism of sludge dewatering after Fe3 O4  + H2 O2 treatment mainly included electrostatic neutralization, reactive radical oxidation, and skeleton building by analysis of contribution factors. The generation of H+ in acidification could neutralize the negatively charged compounds to promote sludge hydrophobicity. Meanwhile reactive radicals generated from Fe3 O4  + H2 O2 destroyed sludge extracellular polymeric substances and cell structure to release intracellular water. Furthermore, Fe3 O4 as a skeleton builder could reconstruct destructive sludge flocs and form new dewatering channels. Finally, low Fe leaching content and recoverability of Fe3 O4 effectively will decrease environmental implication.