Removal Of U(?) In Aqueous Solution By Nano-Fe~0/Ni~0 Bimetallic Materials

In recent years,nano-zero-valent iron?nZ??has been widely used in the field of environmental remediation,but due to its high activity,it is easily deactivated by passivation and reduces the ability to remove contaminants.Therefore,in order to increase its activity,it is common to incorporate another catalytic metal with a high reduction potential to form a more active iron-based bimetallic system.However,Pt and Ag are precious metals,Pb is a toxic heavy metal,and Cu and Ni are less polluting and cheap.In addition,Ni is a moderately strong reducing agent and is not easily eroded by sulfuric acid,hydrochloric acid,organic acids and alkaline solutions.Therefore,the experiment chose Ni as a doping metal.There are many researches on the application of bimetals in environmental water pollution,mainly catalytic degradation of organics,and there are a few reports on the removal of heavy metals.However,there is no report on the use of Fe⁰/Ni⁰ bimetals to remove U???from solutions.In this paper,the Fe⁰/Ni⁰ nano-particles were prepared by synchronous liquid-phase method.The micro-morphologies of the materials before and after the reaction were characterized by SEM,elemental analysis,XPS,nitrogen adsorption-desorption and other means.The effects of pH,U???initial concentration,solid-liquid ratio,contact time and temperature on the U???performance of the solution were investigated by static batch experiments.The mechanism was analyzed by the reduction kinetics model,isothermal adsorption model,and adsorption thermodynamics.The influence of the ionic strength in solution and the different types of anions and cations on the removal of U???from Fe⁰/Ni⁰bimetallic materials were investigated.Finally,a dynamic column experiment was carried out by using PRB column packing method.The effects of different calcium ion concentration,carbonate concentration and flow rate on the experimental results were studied,and the potential of remediation of uranium-contaminated soil was explored.The results of the study are as follows:?1?The characterization results of Fe⁰/Ni⁰ bimetallic materials show that the newly prepared Fe⁰/Ni⁰ bimetallic materials are gathered together by nanoflakes and resemble“petals”,and the surface is loaded with many interconnected spherical nanoparticles,with a better dispersion.The BET results showed that the specific surface areas of nanoscale zero-valent iron and nano-Fe⁰/Ni⁰ bimetallic were 16.23 m²·g^-1 and 26.10 m²·g^-1 respectively,indicating that the addition of nickel effectively increased the specific surface area of the reaction.?2?The results of static batch experiments show that the nano-Fe⁰/Ni⁰ bimetallics have a pH of 3.5,an adsorption equilibrium time of 30 min,and a saturated adsorption capacity of 161.91 mg·g^-1 at 25°C.The removal rate reaches 99%.Compared with nano-zero-valent iron,bimetallic materials can produce better removal effects at a wider pH,accelerate the removal rate,and increase the adsorption capacity.?3?The results of static batch experiments show that the nano-Fe⁰/Ni⁰ bimetallics have a pH of 3.5,an adsorption equilibrium time of 30 min,and a saturated adsorption capacity of 161.91 mg·g^-11 at 25°C.The removal rate reaches 99%.Compared with nano-zero-valent iron,bimetallic materials can produce better removal effects at a wider pH,accelerate the removal rate,and increase the adsorption capacity.?4?The results of effect of ionic strength show that the ionic strength does not affect the ionic strength,indicating that the adsorption reaction is non-specific adsorption and ion exchange does not take place.The greater the effect of cations on Ca²⁺and Mg²⁺ions is,and the smaller that of K⁺and Na⁺ions is.The effect of anions is CO₃^2->NO₃^->ClO₄^-.The presence of humic acid has an inhibitory effect on the removal.?5?The dynamic column experimental results show that the breakthrough volume decreases with the increase of Ca²⁺and CO₃^2-concentrations,which is due to the increase of Ca²⁺and carbonate ion concentration,negatively charged CaUO₂?CO₃?₃^2-and the complexation Ca2UO2?CO3?3?aq?will also gradually increase,which will inhibit the treatment of uranium by materials.With the increase of the flow rate,the volume of the solution required for penetration decreases,and the amount of adsorption decreases.The smaller the flow rate,the longer the contact time between the adsorbent and uranium???,and the more thorough the reaction,the better the penetration of the PRB column.Therefore,a lower flow rate is beneficial to the restoration of soil contaminated by uranium...