Micro-interface Regulation Of Iron Based Magnetic Material And Its Removal Mechanism For Typical Pollutants

Nowadays,heavy metal wastewater,textile printing and dyeing wastewater and eutrophic water are some of the typical polluted water bodies that environmental workers are paying close attention to.The effective treatment of pollutants in these water bodies has become a hot topic in environmental field.The heterogeneous micro-interface in water which plays an important role for pollutant removal in water is an important carrier for the transfer and transformation of pollutants.According to the target pollutants,artificial design and construction of the micro-interface materials with corresponding functions,strengthening interface reaction has been an important research.Based on a large number of literature research at home and abroad,this paper summarized the construction and performance improvement methods of microinterfacial adsorption materials,as well as the application methods of iron-based magnetic nano-materials in water treatment adsorbents.Based on this concept,the adsorption treatment of cationic Cu(Ⅱ),anionic Sb(Ⅲ),phosphate,dye and polyvinyl alcohol(PVA)in water using Fe3O4 related nanoparticles was studied.Two magnetic nanocomposites,NH2-Fe3O4-NTA and lanthanum carbonate/Fe304(MLC),were designed according to the contaminant properties.In addition,ferrite materials are synthesized in situ through micro-interface regulation for textile printing and dyeing wastewater.The key influence factors,removal effects,process mechanisms and the magnetic recovery and reuse performance of the adsorbent materials were evaluated.Studies have shown that a regenerable magnetic core-shell nanoparticles NH2-Fe3O4-NTA was developed by an one-pot method through hydrolysis amidation reaction to regulate the micro-interface of Fe3O4.NH2-Fe3O4-NTA exhibited better better surface phycisochemical properties and metal adsorption capacity than the intermediate product of Fe3O4-SiO2-NH2 and the traditional shell-by-shell synthetic product of NH2-Fe3O4-NTAⅡ.The maximum sorption capacities of NH2-Fe3O4-NTA for cationic Cu(Ⅱ)and anionic Sb(Ⅲ)were 55.56 and 5 1.07 ing/L,respectively.After 5 adsorption and desorption cycles,Cu(Ⅱ)and Sb(Ⅲ)sorption capacities of NH2-Fe3O4-NTA were kept above 80%.In real wastewater applications of NH2-Fe3O4-NTA,multiple metals in actual wastewater could be removed to well below the regulation levels.Nonspecific electrostatic interactions,inner-sphere complexation,ligand exchange,chelation and coordination complexation were responsible for Cu(Ⅱ)and Sb(Ⅲ)removal.Due to the inferior phosphate adsorption performance of NH2-Fe3O4-NTA,a magnetic composite MLC was prepared by a modified solvothermal method through co-precipitation reaction to regulate the micro-interface of Fe304.In MLC,lanthanum carbonate was the main phosphorus adsorption site.The phosphate sorption capacity of MLC increased with the increase of the lanthanum ratio in MLC.When the molar ratio of La/Fe was 2:1,MLC-21 has the highest phosphate adsorption capacity and synthetic product yield.MLC-21 exhibits high phosphate adsorption capacity of 77.85 mg P/g,wide applicable scope of pH ranging from 4 to 11,excellent selectivity for phosphate in the presence of competing ions,good reusability with 83%adsorption capacity remained during five recycles.Furthermore,a real effluent wastewater was used to verify the performance of MLC-21 through a magnetic separation integrated system(AMSS).The effluent phosphorus concentration can be efficiently reduced to below 0.1 mg P/L by MLC-21 adsorption at different dosages.Electrostatic attraction and the inner-sphere complexation between La(HCO3)2+/La(CO3)2-and P via ligand exchange forming LaPO4 were responsible for the phosphate adsorption mechanisms of MLC.Due to the inferior dyes and PVA adsorption performance of NH2-Fe3O4-NTA,an in-situ precipitation reaction was used to regulate the micro-interface of the ferrite and improve its reactivity.The in situ copper ferrite oxidation process had the best treatment effect when dealing with the target pollutants of the dye.It could efficiently treat various types of simulated dye wastewater with a moderate reaction temperature and short reaction time.More than 80%dye could be removed in 60 minutes.The Fe/Cu molar ratio and the alkali dosage OH/M were the key influencing factors.The maximum adsorption capacities of the four dyes of methylene blue,tartrazine,crystal violet and Congo red were 349.2,382.2,402.5 and 831.8 mg/g,respectively.The high performance of dye removal by in situ copper ferrite oxidation process was determined by several mechanisms.The removal of dye mainly occured in the in-situ growth of copper ferrites.The highly active Cu2O was one of the most important factors.Electrostatic interactions could be partily reason,and the sweep effect and encapsulation were mainly responsible for dye removal.The precipitate can be used as a high quality magnetic copper ferrite catalytic material after secondary conditioning by high temperature calcination.The in situ Fe(Ⅲ)/Fe(Ⅱ)ferrite neutralization process had both high treatment efficiency and economical performance for PVA removal.More than 80%PVA removal can be achieved in 20 min.Total iron dosage was a key factor.The mechanism study showed that PVA was involved in the in-situ formation of precipitate Fe3O4 in the treatment process,forming a gel-like high surface area magnetic Fe3O4 polymer.The process exhibited great advantages when processing simulated PVA dye mixed wastewater.The precipitates of in situ Fe(Ⅲ)/Fe(Ⅱ)ferrite neutralization process could be directly reused as adsorbent after magnetic recovery.The maximum antimony(Ⅲ)adsorption capacity of the precipitates was 71.94 mg/g owing to its high surface area.