Removal Of Organophosphorus From Water By Zero-Valent Iron-Based Composites

The massive use of phosphonate in the industry has led to high concentrations of total phosphorus in wastewater,and how to economically and efficiently remove phosphonate from wastewater is a challenge in developing deep phosphorus removal technologies.Zero-valent iron（Fe⁰）is inexpensive and has a low reduction potential,which could produce a variety of iron corrosion products in water for efficient phosphorus removal.However,the passivation problems lead to low utilization.In this study,we propose to construct micron-scale Fe⁰@Fe Ox composites by ball milling and modulate the structure and quantity of Fe⁰ surface iron oxides to screen the optimal Fe⁰@Fe Ox for efficient phosphorus removal.On this basis,a batch of Fe⁰/Fe₃O₄ particles was prepared by the pre-oxidation method and used to construct Fe⁰/Fe₃O₄/Fe（II）system to investigate its process parameters for efficient organophosphate removal,and to elaborate the reaction process and removal mechanism of organophosphate at the solid-liquid interface with the help of various technical means.The main research results are as follows.（1）Ball-milled Fe⁰/Fe₃O₄ and Fe⁰/Fe₂O₃ particles were prepared by mechanical ball milling,and the optimal conditions for the preparation of the two composites were screened in terms of three aspects:ball milling time,rotational speed,and the ratio of zero-valent iron to iron oxide.The removal of organic phosphorus from water was compared between the two under different influencing factors.The results showed that the ball milling process had a better strengthening effect on the Fe⁰/Fe₂O₃ composite,which greatly improved the efficiency of zero-valent iron in the removal of organic phosphorus under alkaline conditions.The removal of organic phosphorus by ball-milled Fe⁰/Fe₂O₃ particles was always better than that of ball-milled Fe⁰/Fe₃O₄ particles at different p H.During the phosphonate removal process,a part of the phosphonate was oxidized to orthophosphate,which can be attributed to the breakage of C-P of organophosphorus due to Fe（III）in solution.（2）A batch of Fe⁰/Fe₃O₄ was prepared by Fe²⁺/O₂ pre-corrosion method,and the optimal conditions for the preparation of Fe⁰/Fe₃O₄ were screened in terms of three aspects:pre-oxidation time,Fe²⁺concentration and dissolved oxygen concentration.And based on this,Fe²⁺was added to the contaminant solution,thus the Fe⁰/Fe₃O₄/Fe2+system was constructed.The effect of the system on the removal of HEDP from the solution was investigated.The results showed that Fe0,Fe₃O₄ and Fe²⁺in the system had a synergistic effect on the removal of organophosphorus.The coexisting ions in the solution all had a facilitative effect on the removal of organophosphorus by the Fe⁰/Fe₃O₄/Fe²⁺system.The added Fe²⁺played a key role in the process of phosphorus removal in this system.（3）This study will provide theoretical support for the application of new iron-based materials in the field of deep phosphorus removal.