Efficient degradation of 2-methoxyphenol using heterogeneous-homogeneous synergistic activated persulfate with modified clinoptilolite + heat

Abstract An easily obtainable and cheap activator was obtained with natural clinoptilolite, which was easy to be modified with a ferrous sulfate solution. The modification can greatly improve the Fe/C ratio of the zeolite surface without changing the typical porous structure of natural clinoptilolite. The modified zeolite can activate sodium persulfate to degrade 2-methoxyphenol (MOP, a typical organic contaminant in salty wastewater), and has a heterogeneous-homogeneous synergistic effect accompanying heat. The mechanism investigation shows the activation of single modified zeolite is more complex at normal temperature (25 °C), and many types of free radicals are involved in the degradation through multiple pathways. Rapid degradation of MOP can be achieved with the synergistic effect of the modified clinoptilolite + heat, and the degradation ratio reaches 95.0% in 10 min caused by the generation of more sulfate- and superoxide radicals. Comparing with the effect of the directly activated persulfate process by ferrous sulfate, a better degradation effect could be obtained with active substance slowly released by the modified zeolite. And adding thermal activation can further increase the activation rate and utilization of oxidants. Finally, better mineralization efficiency achieves, and the total organic carbon (TOC) removal ratio with synergistic activation is about 5 times that of a single activation by modified zeolite within 20 min. In addition, the activator shows good activated performance in three consecutive cycles. The MOP degradation ratio using M80-zeolite, reducing by 21.8% at 10 min in the third use, could be recovered to 95.0% with the original modified method.