Dual-membrane assisted heterogeneous Fenton for pulp wastewater treatment

Heterogeneous Fenton process is mainly used to degrade wastewater COD. Compared to traditional Fenton process, heterogeneous Fenton can avoid the generation of iron sludge, while the utilization rate of H₂O₂ still need to be improved. In this work, two type of ceramic membranes assisted heterogeneous Fenton process were proposed. One membrane was used as H₂O₂ distributor, while another was used for separating and recycling the catalyst. Different catalysts and their COD degradation performance were investigated first. The adding dose and rate of H₂O₂ and permeate flux were optimized subsequently. The stability of the catalytic and the membrane fouling condition were finally evaluated. The results revealed that cubic Cu₂O possessed the best COD degradation performance. When the reaction conditions were that Cu₂O (1 g•L^-1), H₂O₂ dosage (0.8 ml•L^-1), wastewater permeability (137 L•m^-2•h^-1) and reaction temperature(30℃), the COD degradation amount of RO(Ⅰ)-RO(Ⅳ) were 11, 130, 291 and 417 mg•L^-1. The utilization rate of H₂O₂ for RO(Ⅰ)-RO(Ⅳ) were 9%, 106%, 232% and 334%, the utilization efficiency of H₂O₂ exceeded 100% means there are chlorine free radicals play a role in COD degradation. The COD degradation amount increased linearly with increasing of Cl^- concentration. The COD degradation rate had an increasing tendency with the decreasing of the permeability of separation membrane. In the 360 min reaction process, Cu₂O catalyst may form a reversible cake layer on the surface of the membrane distributor. However, this cake layer has scarcely effect on the permeation resistance. The COD degradation were greater than 65% stably. Moreover, with the increase of conductivity in pulp wastewater, catalysts would become instability with more of Cu ion dissolution. In heterogeneous Fenton process, ceramic membrane can enhance the treatment efficiency to pulp waste water, which performed in increasing of the utilization rate of H₂O₂ and improving the stability in continuous operation process.