| Transition metal carbide(MXenes)is a new type of two-dimensional crystal with high specific surface area and unique nano-layer structure.It has been investigated in the fields of physics,chemistry and material science.More importantly,the precursor of MXenes(MAX phase)have a very highly irradiation stability,thus the MXenes are becoming a popular adsorbent for radioactive metalts.However,the lack of surface functional groups,samll layer spacing and poor water solubility is still a major drawback that limited the investigation of MXenes.In recent years,a series of reports has emerged in the fields of surface modification and functionalization of MXenes,which mainly focus on the catalysis and energy.Two-dimensional nano titanium carbide(Ti3C2)is one type of the MXenes materials,which has a relatively stable chemical properties and high-safety performance in preparation,and considered as an ideal supported materials for nanoparticles loading.New type of nanoparticle/Ti3C2 composite can be prepared by complexing with different nanoparticles.Nano-zero-valent iron(nZVI)is a widely used environmental remediation material,due to earth abundant and low cost.However,aggregation and inactivation are two major disadvantages for nZVI.The Ti3C2 could solve this problem well can by providing stable sites for pristine nZVI nanoparticles loading to prevent their oxidation and aggregation.Cr(?)is a heavy metal pollutant with great toxicity and strong oxidizing and carcinogenicity.Traditional treatment processes such as ion exchange and chemical precipitation have some disadvantages such as economy and secondary pollution.The remediation of Cr(?)Wastewater is important for environmental protection and human health.In addition,the redox behavior of Cr(?)is relatively simple and can be used as a model pollutant for the mechanism study of multivalent metal ions,especially some radioactive anionic pollutants,such as 103-,SeO32-,SeO42-,TcO4-,etc,and studying the migration and transformation mechanism on the surface of the adsorbent material.This thesis focused on the above aspects,has explored the etching process of Ti3C2,established the best hydroxyl modification method,and prepared the nano-zero-valent iron intercalated Ti3C2 composite(nZVI-Alk-Ti3C2)and optimized the best synthesis conditions.In additiong,the removal ability and the mechanism of heavy metal anions adsorption in the aqueous phase were studied by using Cr(?)as a model pollutant.The SEM,TEM,BET and other characterization methods has been used to prove that nZVI was effectively inserted into the interlayer of Alk-Ti3C2,and the dispersion and particle size was effectively controlled,the BET shows that the specific surface area of nZVI-Alk-Ti3C2(31.191 m2/g)was expanded by 4.5 times compared with pristine Ti3C2(7.004 m2/g).In addition,the effects of iron/Ti3C2 mass ratio,adsorption time,pH and initial concentration on the adsorption process of Cr(?)was investigated.The results show that the iron/Ti3C2 mass ratio is 1:2;the adsorption process of Cr(?)by nZVI-Alk-Ti3C2 conforms to the pseudo-second-order kinetic equation(R2=0.9981),and the adsorption rate is mainly controlled by chemical process;The adsorption of Cr(?)on nZVI-Alk-Ti3C2 was also affected by the pH value,and the adsorption capacity decreases with the increase of pH,and the removal efficiency was highest at pH=2;the initial concentration-adsorption capacity curve shows that the adsorption of Cr(?)by nZVI-Alk-Ti3C2 is consistent with Langmuir adsorption model(R2=0.9779),the highest adsorption capacity can reach 194.87 mg/g,which has obvious advantages compared with activated carbon,molecular sieve,graphene,etc.In addition,the research also studies the interaction mechanism between Cr(?)and nZVI-Alk-Ti3C2 composites in solution system through the combination of first-principles calculation and material chemistry experiments. |
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