Red Mud-derived Zero Valent Iron For The Removal Of 4-CP And Cr(Ⅵ) In Water

Water is an important resource for life on Earth,and clean water is essential for humans and ecosystems.In the past few decades,the continuous population growth,rapid industrialization,intensification of urbanization and improper use of natural resources have had a negative impact on the aquatic environment,such as organic pollutants and heavy metal ions and other pollutants entering the aquatic environment in large quantities,due to their high toxicity,bioaccumulation,persistence and trigenicity(mutagenic,teratogenic and carcinogenic),seriously threatening human health.The zero-valent iron material in the iron system has the characteristics of variable valence,low reduction potential and environmental friendliness,and is widely used in different kinds of sewage treatment.However,with the increase of demand,the current large-scale preparation of zero-valent iron still has the disadvantages of high cost,easy secondary pollution and poor stability.Therefore,it is critical to develop efficient processes for the preparation of zero valent iron-based materials.Red mud is a strong alkaline solid waste rich in iron produced in the production of alumina.At present,the storage reserves of red mud in our country have reached 790 million tons.The damming process will cause inestimable pollution to atmosphere and soil environment and is a large solid waste requiring urgent treatment.However,red mud is rich in iron ore and its own alkaline environment helps to promote biomass heat interpretation and release of reducing gases.From this,we thought of organically combining red mud with waste biomass,using forestry waste poplar powder to reduce iron ore in red mud to prepare zero valent iron-based environmental functional materials,and using it for heterogeneous Fenton and heavy metal ion removal.At the same time,this provides a new idea for the comprehensive utilization of red mud and poplar wood powder and the preparation of zero-valent iron,which is in line with the environmental governance strategy of "Waste Cleaning Waste".The specific research content is as follows:1.Preparation and characterization of red mud-derived zero valent iron-based materialsIn this study,the structure,composition and morphology of the red mud used were characterized by X-ray diffraction(XRD),inductively coupled plasma mass spectrometry(ICPMS),field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),which mainly includes typical mineral components such as iron oxide,quartz and diaspo,among which the highest metal element is iron,and red mud is composed of irregular Fe,Al,Si oxide particles.The specific surface area is about 23.15 m2/g,and its main pore structure is mesoporous.XRD analysis was carried out by the composite materials prepared by the co-pyrolysis reaction of red mud and poplar wood powder at different temperatures,and the iron elements in red mud were mainly magnetic iron oxide after the copyrolysis reaction of 700℃ and 800℃,and mainly existed as zero-valent iron after the copyrolysis reaction of 900℃ and 1000℃.We found that zero valent iron-based materials were successfully prepared by simple co-pyrolysis reaction,and the products of 900℃ co-pyrolysis of red mud and poplar powder were mainly composed of carbon materials loaded with zero valent iron crystals with a size of several hundred nanometers.2.Red mud-derived zero valent iron-based materials for heterogeneous Fenton degradation of 4-CPA zero valent iron-based material prepared by simple co-pyrolysis using red mud and poplar wood powder as raw materials,and H2O2 was activated by this,and p-chlorophenol(4CP)was used as the target pollutant.The Fenton-like activities of red mud and poplar powder in 800 and 900℃ co-pyrolysis products and 900℃ pyrolysis poplar powder produced by carbon,red mud and commercial iron powder were compared,and the experimental results showed that the co-pyrolysis products of red mud and poplar powder at 900℃ had the best performance.Quenching experiments and electron spin resonance(ESR)proved that hydroxyl radicals(·OH)were the main active species in the Fenton-like system catalyzed by red mud-derived zerovalent iron-based materials,and the conversion mechanism of 4-CP was revealed by X-ray photoelectron spectroscopy(XPS).At the same time,cycling experiments show that the ZVI iron-based materials derived from red mud have good reusability and stability.3.Red mud-derived zero valent iron-based materials for the removal of Cr(VI)We prepared zero valent iron-based materials by co-pyrolysis of red mud and poplar powder,and selected hexavalent chromium Cr(VI),which is listed as a priority pollutant by the US Environmental Protection Agency,as the target pollutant.The Cr(VI)removal performance of red mud and poplar powder 800 and 900℃ co-pyrolysis products and commercial iron powder were compared,and it was found that the zero valent iron-based materials derived from red mud had better removal performance.Combined with XPS,the mechanism of Cr(VI)removal was clarified.The effects of material dosage,Cr(VI)concentration and pH on removal efficiency,as well as the reusability and stability of materials were explored,and the results showed that this red mud-derived zero valent iron-based material had a good application prospect in the treatment of real heavy metal ion contaminated wastewater.