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• An effective activator of persulfate was obtained based on natural clinoptilolite. • Modified zeolite + heat synergistic activation can achieve rapid degradation. • The synergistic mechanism of degradation based on radicals has been revealed. • The activator showed good performance in three consecutive cycles. 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. [ABSTRACT FROM AUTHOR]

• 2-Methoxyphenol can be efficiently degraded by thermal or alkali activated Na 2 S 2 O 8. • Rapid degradation can be achieved by thermal-alkali synergistic activation. • Degradation intensification mechanism based on radicals has been revealed. Both thermal and alkali are effective means of persulfate (PS) activation, and the synergistic effect of them should achieve a great degradation result. It is evaluated for treating coal chemistry industry wastewater because the by-product produced in the process is sulfate, which is pre-existing in the wastewater. With thermal and alkali synergistic activation, the application of the response surface method revealed the effects of temperature, pH and concentration of persulfate on the degradation ratio of 2-methoxyphenol (MOP, a typical contaminant in coal chemical industry wastewater) and their interactions. The results showed that the degradation rate of the contaminant was temperature and pH dependent, while chloride (Cl−) and sulfate (SO 4 2−) ions had no obvious negative effect. The degradation ratio could be enhanced with higher activation temperature and pH (7–12). The faster degradation could be achieved by thermal-alkali synergistic activation, and the degradation ratio of 88.4% and 93.8% could be achieved at pH = 12 within 10 min and 20 min, respectively. Electron spin resonance (ESR) spectra and free radical scavenging experiments indicated that MOP degradation was achieved by the oxidation of both sulfate radical (SO 4 −) and hydroxyl radical (OH) at pH = 6, and only by OH at pH = 12. In addition, the radical reaction was intense under thermal-alkali synergistic activation of PS, while the quenching reaction was ineffective. [ABSTRACT FROM AUTHOR]