Construction of catalytic system by FeⅢ(tpy)Cl3 complexes-activated periodate and its catalytic degradation mechanism for dyeing wastewater
Objective The dyeing wastewater poses a threat to the ecological environment.Advanced oxidation processes(AOPs)exhibit excellent oxidation efficiency in wastewater treatment.The solid-state and stability of periodate(PI)make it obtained wide attention.As a result,Pl-based AOPs are gradually gaining research and being tried for the treatment of dyeing wastewater.However,current transition metal-based activators for PI often require larger doses to obtain the desired effect,which undoubtedly increases the cost of wastewater treatment.Metal coordination complexes are applied similarly to biological enzymes,with trace and efficient application effects.This study aimed to construct a novel catalytic system by activating PI by FeⅢ(tpy)Cl3 complex to investigate its application prospects in wastewater treatment and to elucidate the catalytic mechanism.Method The catalytic degradation performance of the FeⅢ(tpy)Cl3/PI system was tested using the dye Acid Red 1(AR1)as the target pollutant.The effects of catalyst and oxidant dosage,pH,and temperature on the catalytic performance of this system were explored.Meanwhile,the catalytic mechanism of the system was investigated by capture and probe experiments.Moreover,the practical application prospects of the system were evaluated by testing the degradation efficiency of various organics and the resistance to inorganic salt ions.Results The result showed that the FeⅢ(tpy)Cl3 complexes have excellent activation effects on PI,which could remove 98％of AR1 within 15 min.More importantly,the performance of the FeⅢ(tpy)Cl3/PI system is much higher than that of the previously reported FeⅢ(tpy)Cl3/H2O2 system.Meanwhile,the test results show that the concentration of FeⅢ(tpy)Cl3 and PI has a great influence on the performance of the FeⅢ(tpy)Cl3/PI system.In detail,the degradation of AR1 in the FeⅢ(tpy)Cl3/PI system is following the pseudo-first-order kinetic model,while the rate constant of AR1 degradation increase linearly with the increase of FeⅢ(tpy)Cl3 and PI dose.Moreover,the results show that the catalytic performance of FeⅢ(tpy)Cl3/PI system is almost independent of pH and could achieve efficient degradation of the dye over a wide pH range(3-9).Also,the increase in temperature could increase the catalytic activity of the FeⅢ(tpy)Cl3/PI system and accelerate the degradation of AR1.In addition,the active species in this system were investigated using methanol,benzoquinone,and furfuryl alcohol as hydroxyl radical,superoxide radical,and singlet oxygen trapping agents,respectively,and PMSO as a probe for high-valent metal-oxo.The results of mechanism studies show that FeⅢ(tpy)Cl3/PI system includes superoxide radicals,singlet oxygen,and high-valent metal-oxo,and these active species together promote the degradation of AR1.The removal rates of sulfamethoxazole,2,4-dichlorophenol,2,4,6-trichlorophenol,and rhodamine B in the FeⅢ(tpy)Cl3/PI system are 100％,81％,89％,and 89％,respectively,indicating that the FeⅢ(tpy)Cl3/PI system is well suited for the removal of most organics.Inorganic salt ions are usually included in the actual organic wastewater.The results show that the catalytic system is not disturbed by common inorganic salt ions for the degradation of organic matter and has good prospects for practical application.Conclusion FeⅢ(tpy)Cl3 has excellent activation performance for PI,and the removal rate of AR1 is up to 98％within 15 min,which is much higher than the conventional FeⅢ(tpy)Cl3/H2O2 system.Compared with other iron-based catalysts,FeⅢ(tpy)Cl3 complexes are simple to prepare and require only minute doses to achieve efficient degradation of organic matter,which helps to reduce the economic cost of wastewater treatment.In addition,the system shows universality for the degradation of various organics,and the catalytic degradation process do not interfere with the solution pH and common inorganic salt ions,which makes this system excellent prospect for practical wastewater treatment applications.Overall,this study provides a novel PI activator and also provides an efficient method for dyeing wastewater treatment.
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