Development of montmorillonite-supported nano CaO2 for enhanced dewatering of waste-activated sludge by synergistic effects of filtration aid and peroxidation

Nanosized CaO 2 was first synthesized using montmorillonite clay layers as templates for combining the positive effects of filtration aid and peroxidation on the dewatering of waste-activated sludge (WAS). Exchangeable Ca 2+ compensating for negative charges of montmorillonite reacted with the added H 2 O 2 , affording nano CaO 2 on the surface or in the interlayer regions of montmorillonite (montmorillonite-supported nano CaO 2 , MMT-nano CaO 2 ). The catalytic capacity of montmorillonite for generating OH from nano CaO 2 was verified by electron paramagnetic resonance (EPR), therefore, the radical oxidation induced by MMT-nano CaO 2 can destruct the floc structure of WAS with the omission of Fe(II), the conventionally used catalyst for Fenton reaction. As a result, the reduction in specific resistance of filtration (SRF) by 62.2% was achieved with the MMT-nano CaO 2 dosage of 100   mg/g dry solid (DS) and the weakly acidic pH of 5. OH led to the reduction of hydrophilic protein in extracellular polymeric substances (EPS), and the swelling behavior of montmorillonite contributed to the formation of a porous structure as draining medium for water withdrawing. The above factors were the dominant mechanisms for enhancing dewatering performance.