Mechanochemical Preparation Of Iron-based Nanomaterials Used For Removing Organic Contaminants From Water

China is in a stage of rapid economic development,and huge quantities of wastewater are discharged from industrial production and human living activities,which contain various types of contaminants with poor biodegradability and high toxicity.These wastewater may cause serious environmental pollution,pose adverse impact on people's health and ecosystems,and hinder the sustainable development of economy if they are not effectively treated before discharge.Among most water treatment technologies,the absorption process manifests the most simple operation and higher efficiency;while advanced oxidation process?AOP?is the optimal choice to treat high-concentration and refractory organic wastewater,with which total mineralization of organic pollution comes true.The key of these two technologys is absorbents with large adsorption capacity and catalysts possessing highly efficient activity,respectively.Since the properties of non-toxicity,low-cost and peroxidase activity,iron-based nano-materials have attracted an extensive attention in environmental pollution remediation.Fe-based metal organic framework?Fe-MOFs?and the derivated iron-carbon materials usually possess high specific surface areas,large pore volumes and regulable crystal structure,which have shown great application potential in wastewater treatment as efficient absorbents and Fenton catalysts.Fe-MOFs are generally synthesized by traditional hydrothermal or solvothermal methods,which are time-consumping,hard-to-opeate and low-producing and unable to large-scale production.Mechanochemical grinding can exert methanical energies to raw materials attributed by the the extrusion,shearing and rubbing forces during grinding,which induces physical and chemical reaction of chemicals and materials.Therefore,mechanochemical method is a fast,simple,cheap and environmental-friendly technique for synthesis of nano-materials.Most importantly,this technique has the potential to large-scale prepare nanomaterials.In this paper,Fe-MOFs,Fe-MOFs load with Pd?Fe-MOF-Pd?and magnetic Fe-MOF?Fe-MOF/Fe₃O₄?absorbents were prepared via the mechanochemical grinding method;the Fe-MOFs and Fe-MOF-Pd materials were carbonized at high temperature under the protection of N₂ to obtain core/shell structured Fe@C and Fe-Pd@C Fenton-like catalysts;and a simple and efficeint method was developed to activate the used and deactivated commercial iron-carbon materials.The efficiency of the synthesized adsorbents and Fenton-like catalytic performance of Fe-C matertials was evaluated by using phenol and methyl orange?MO?as model pollutants.The detailed studies were listed below:Firstly,magnetic Fe-MOF/Fe₃O₄ composites we synthesized using mechanochemical method and characterized in detail.The obtained composites were used both as absorbents and Fenton-like catalysts to remove MO from water samples.The result indicated that Fe-MOF/Fe₃O₄ composites had strong adsorption ability to MO and could efficiently catalyze the degradation of MO in a wide solution pH range.The synergistic effect of absorption and Fenton-degradation was beneficial for the rapid and efficient elimination of MO from water.Secondly,amino functionalized Fe-MOFs loaded with Na₂PdCl₄?Fe-MOF-Pd?were synthesized with mechanochemical method.After carbonization at high temperature,core/shell structured Fe-Pd@C composites were obtained.The Fe-Pd@C composites were utilized as Fenton-like catalysts to degrade phenol in water based on microelectrolysis and Fenton reactions.The result indicated the presence of trace amount of Pd NPs in the Fe-Pd@C composites?molar ratio of Fe and Pd is 100:1?promoted phenol degradation in a wider solution pH range since Pd NPs could accelerate the transition of Fe³⁺to Fe²⁺on the surface of catalysts.The degradation efficiency of phenol in the Fe-Pd@C-H₂O₂ system was significantly higher than that in the Fe@C-H₂O₂,ZVI-H₂O₂,and commercial Fe/C-H₂O₂ systems especially at pH?5.The quchening experiments and the ESR measurement indicated hydroxyl free radicals and electrons were the leading active factors for degrading phenol.Thirdly,a simple and inexpensive activation method for used or deactivated commercial iron-carbon is explored.After pyrolysis at high temperature,iron oxides and amorphous carbon on the surface of Fe-C materials were removed,which led to the increased surface areas and strengthend absorption ability and catalytic performance of the Fe-C materials.The activited iron-carbon could catalyze the oxidative degradation of MO over a wider pH range?3.5-5.5?,and also showed good stability and reusability.In a word,high-temperature pyrolysis can improve the catalytic activity of commercial iron-carbon materials and resume the activity of the used or deactived iron-carbon materials.This technique can avoid wasting of the raw materials.This paper shows the potential application of mechanochemical method and iron-based nanomaterial in wastewater treatment.