Sequential combination of NaClO chain breakage/CuxO catalytic oxidation processes for high efficiency treatment of ultra-high concentration PVA wastewater

Polyvinyl alcohol (PVA) is a kind of refractory organic polymer with high COD and low BOD. Efficient treatment of PVA wastewater has always been a challenging subject especially for ultra-high concentration (UHC). In this paper, based on our previous work, a sequential combination process method including NaClO chain breakage followed by Cu x O activated carbon catalytic oxidation was developed to efficient treat UHC PVA wastewater. The sequential combination system was optimized by monitoring the treatment performance with different key parameters (such as oxidant dosage, Cu loading and catalyst dosage, two-stage reaction time, pH value, etc.). And the COD of PVA wastewater declined from the initial 206,240.00 mg/L to 557.78 mg/L (removal rate 99.73 %), the PVA concentration decreased from the initial 171,325.00 mg/L to 19.94 mg/L (removal rate 99.99 %) under the optimal conditions. Through the discussion of the combined processes, it was found that both chain breakage and catalytic oxidation were necessary and indispensable to achieve efficient degradation of PVA wastewater. Additionally, the free radical scavenging experiments show that the combined oxidation process was mainly controlled by the catalytic oxidation process, and followed the free radical reaction mechanism with·OH as the main oxidant. Based on this, it is recommended that subsequent researchers focus on the combined process for the treat of refractory organic wastewater.