Preparation Of Co-Ni-based Layered Double Hydroxides Composites And Their Degradation Behavior Of PPCPs

PPCPs are a kind of emerging organic pollutants discovered at the end of the 20th century,whose components have strong ecological toxicity,pseudo-persistence,polarity and biological activity.While benefiting human beings,these substances are also continuously introduced into the environmental water body,bringing potential threats to human health and ecological environment.Therefore,there is an urgent need for an efficient method to deal with PPCPs.Compared with the traditional Fenton oxidation technology,the advanced oxidation technology based onhas better selectivity,wider p H range and higher redox potential.LDHs is an ideal catalyst for activating PMS to degrade pollutants because of its unique double-layer metal structure,relatively large specific surface area and high porosity.In this paper,according to the properties and characteristics of LDHs materials,cobalt-nickel-based LDHs composites were designed and prepared,which can be used to efficiently activate PMS to degrade PPCPs in water.The main results are as follows:（1）Co-Ni LDH was synthesized by one-step hydrothermal method,and the oxide（Co-Ni LDO）was calcined to activate PMS to degrade tetracycline（TC）.In the process of degradation of TC in Co-Ni LDO/PMS system,the catalyst showed excellent catalytic performance for pollutants.Co-Ni LDO is rich in O_V and has high specific surface area.In the reaction volume of 50 m L,30 mg/L TC was removed completely in 60 min without adjusting the p H value of 0.1 g/L Co-Ni LDO,1.6 m M PMS.Through the detection of degradation intermediates,the possible degradation pathway and the reaction mechanism dominated by O_V in TC degradation system were proposed.¹O₂ plays a decisive role in the degradation system,while,andplay a secondary role.At the same time,Co-Ni LDO/PMS system has strong ability to resist the interference of anions and shows high reuse efficiency.After 5 cycles,the degradation efficiency of TC is still higher than 92%.This study provides an effective way for the removal of TC,and provides a new clue to introduce O_V into the system of activated PMS to degrade organic pollutants to improve the performance of the catalyst.（2）Using metal-organic framework as template,magnetic hollow nano-core-shell material Fe₃O₄@Co-Ni LDH was prepared by simple ultrasonic method,and PMS was activated to degrade FAV,and good catalytic effect was obtained.Under the condition of uncontrolled p H value,PMS concentration of 0.7 m M and catalyst dosage of 0.05 g/L,the degradation efficiency of FAV with an initial concentration of 40 mg/L of 100 m L can reach 92.7%in 30 min.The results of electron paramagnetic resonance（EPR）and radical quenching experiments show that ¹O₂ plays a major role in the degradation system of Fe₃O₄@Co-Ni LDH/PMS/FAV,and the redox cycle of O_V and Co²⁺/Co³⁺on the surface of Fe₃O₄@Co-Ni LDH is very important for the activation of PMS.In addition,the reaction mechanism and possible degradation pathway of the degradation system were also proposed.Fe₃O₄@Co-Ni LDH has good magnetic recovery performance,and Fe₃O₄@Co-Ni LDH catalyst shows excellent recyclability in circulation experiments,so it has a good application prospect for the degradation of wastewater containing antiviral drugs.（3）Using Fe₃O₄@ZIF-67 as precursor,Fe₃O₄@Co-Ni LDH magnetic hollow core-shell catalyst was synthesized by hydrothermal method,and Fe₃O₄@Co-Ni LDO was obtained after calcination to activate PMS to degrade 3-TC.The experimental conditions remain unchanged,under the condition of Fe₃O₄@Co₃O₄ as catalyst,the degradation efficiency of 3-TC is 49.8%;while when Fe₃O₄@Co-Ni LDO-3 is used as catalyst,the degradation efficiency of 3-TC is greatly improved,and 3-TC is completely degraded within 40 min.The experimental results show that the Fe₃O₄@Co-Ni LDO catalyst synthesized under a certain ratio of Co/Ni can accelerate the electron transport rate and redox rate through the synergistic effect between Co and Ni,which shows higher catalytic efficiency than that of single metal oxidative degradation of 3-TC.The degradation mechanism was determined by quenching experiment,EPR analysis and electrochemistry,and the intermediates in the degradation process were determined.The results show that cobalt-nickel-based LDOs/PMS has application potential in efficient degradation of 3-TC and other PPCPs.