Enhanced dewatering extent of sludge by Fe3O4-driven heterogeneous Fenton.

[Display omitted] • Sludge dewatering extent was enhanced after Fe 3 O 4 -activated H 2 O 2 treatment. • Enhanced mechanism of sludge dewatering by Fe 3 O 4 -activated H 2 O 2 was unveiled. • Fe 3 O 4 -activated H 2 O 2 disrupted sludge EPS and released intracellular water. • Fe 3 O 4 as skeleton builder enhanced sludge floc strength and formed new channels. Homogeneous Fenton (Fe2+/H 2 O 2) 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 Fe 3 O 4 as heterogeneous Fenton catalyst, Fe 3 O 4 -activated H 2 O 2 (Fe 3 O 4 + H 2 O 2) in this study was adopted to improve sludge deep-dewatering. Reduction efficiency of the bound water (71.3 %) after Fe 3 O 4 + H 2 O 2 treatment (after a reaction time of 30 min) were much higher than those in the Fe2++H 2 O 2 treatment. Especially, the moisture content of treated sludge cake by Fe 3 O 4 + H 2 O 2 remarkably decreased from 86.4 % to 61.3 %. Improvement mechanism of sludge dewatering after Fe 3 O 4 + H 2 O 2 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 Fe 3 O 4 + H 2 O 2 destroyed sludge extracellular polymeric substances and cell structure to release intracellular water. Furthermore, Fe 3 O 4 as a skeleton builder could reconstruct destructive sludge flocs and form new dewatering channels. Finally, low Fe leaching content and recoverability of Fe 3 O 4 effectively will decrease environmental implication. [ABSTRACT FROM AUTHOR]