Study On The Synergistic Mechanism In Tannic Acid-iron-based Fenton-like Syste

Water pollutants that threaten public safety and environmental health are multi-component,which determines that complex and refractory wastewater is difficult to achieve standard discharge through a single treatment method.Multi-step combined processes such as adsorption,coagulation,and advanced oxidation are often required to jointly treat various inorganic and organic pollutants.In actual operation,the multi-step combined process has a series of shortcomings such as long process flow,high investment cost,large dosage of chemicals,and difficult management,which increases the difficulty of actual wastewater treatment.The traditional Fenton process exhibits multiple effects of oxidation,coagulation,and adsorption,providing a new strategy for the treatment of multi-component pollutants.However,limited by the inconsistency of iron species and applicable p H ranges,the oxidation,coagulation,and adsorption in the traditional Fenton process cannot achieve efficient synergy in the same time and space,and the mechanism of action on different pollutants also needs to be studied urgently.Therefore,this paper proposes to construct a tannic acid-iron-based Fenton-like system for the synergistic removal of multi-component pollutants.The specific research content and results are as follows:（1）An effective TA/Fe（Ⅲ）/H₂O₂ simultaneous oxidation and coagulation process was proposed,and multi-component pollutants were simultaneously removed in a wide p H range.Under optimal conditions,the sulfamethazine（SMR）and turbidity removal efficiencies at p H=7 were 95.43%and 98.41%,respectively.The applicability was verified by treating spiked actual secondary wastewater.It showed significantly enhanced removal performance compared with PFS coagulation and classic Fenton in terms of SMR,COD,UV₂₅₄ and turbidity,which were 98.29%,57.94%,54.20%and 98.39%,respectively,without any p H adjustment.The mechanism analysis revealed that the introduction of TA can not only promote the iron redox cycle for the production of·OH,but also neutralize the charge for the generation of the porous flocs.Due to the bridging of TA,the synergy of Fenton oxidation and in-situ coagulation was achieved in a single processing unit.Finally,the synergy mechanism proposed that a four-step process sequentially proceeded during the treatment,including（1）inner sphere complexation,（2）homogeneous Fenton,（3）charge neutralization coagulation/heterogeneous Fenton,and（4）aggregation/sedimentation.（2）An effective n-CaO₂@TA-Fe simultaneous oxidation and adsorption process was proposed,which simultaneously realized the oxidative degradation of glyphosate（N-（phosphonomethyl）glycine,C₃H₈NO₅P）and the adsorption of released phosphate ions in a wide p H range.Mechanism analysis confirmed that the addition of TA can generate·OH by promoting the redox cycle of iron,and n-CaO₂@TA-Fe can confine the generated ROS（H₂O₂,·OH）on the surface of the composite material,and promote its conversion to·O₂^-and¹O₂.Under the action of ¹O₂,·O₂^-and·OH,most glyphosate can be degraded into phosphate ions by breaking C-P and C-N bonds,and then combined with Ca²⁺released by n-CaO₂ to form Ca（H₂PO₄）₂,which can be fixed on the surface of the material.