High-efficiency carbamazepine degradation using a Ni/Co-LDH as the peroxymonosulfate activator: Performance, mechanism and degradation pathway

In this study, Ni/Co layered double hydroxide (Ni/Co-LDH) with uniform flake structure was synthesized successfully as an effective activator in the carbamazepine (CBZ) degradation by peroxymonosulfate (PMS). Our results indicated that Ni/Co-LDH possessed a high specific surface area (72.9942 m2/g) and exhibited great activation performance, in which 100% CBZ removal could be achieved within 300 s under neutral conditions with 5 mg/L Ni/Co-LDH and 0.3 mmol/L PMS. In addition, the crystal structure and morphology of the prepared Ni/Co-LDH kept unchanged during degradation cycles. X-ray photoelectron spectroscopy (XPS) analysis and free radical identification experiment speculated that the cycle of Ni2+/Ni3+ and Co2+/Co3+ on Ni/Co-LDH surface were responsible for efficient HO•/SO4•− generation from PMS. Based on identified products through high resolution mass spectrometry (HR-MS), it was proposed that the degradation pathway of CBZ was a heterozygous process involving deamidation, hydroxylation and electron transfer. The ECOSAR calculation results indicated the toxicity of some products was still at very toxic level, thus certain attention should be paid to the toxicity of intermediates in the process of treating pollutants in water.