Activation Of Hydrogen Peroxide By CNTs/MIL-88B-Fe For Degradation Of Organic Pollutants

Refractory organic pollutants in water are highly toxic,which can accumulate in the environment or even in the human body,causing environmental pollution and teratogenic,cancer and mutation.Fenton technology has been widely used for the removal of refractory organic pollutants in water due to its strong oxidation ability and non-selectivity.Traditional homogeneous Fenton technology has some problems such as narrow pH range,difficult recovery of catalyst and producing iron sludge.To solve the above problems,heterogeneous Fenton technology is gradually developed.However,heterogeneous Fenton catalysts still face the problem of low catalytic activity due to low content of Fe（Ⅱ）in the catalysts and slow redox cycle of Fe（Ⅲ）and Fe（Ⅱ）.Metal organic frameworks（MOFs）as heterogeneous Fenton catalysts have attracted considerable attention due to their porous structure,high specific surface area and homogeneous distribution of active centers.It is of great significance to develop MOFs with higher Fe（Ⅱ）content and faster Fe（Ⅲ）/Fe（Ⅱ）redox cycle as heterogeneous Fenton catalysts for the removal of refractory organic pollutants in water.In the work,C/M were prepared.The relationship between the catalytic activity and amount or functionalization degree of carbon nanotubes was investigated.The mechanism of activation of hydrogen peroxide by CNTs/MIL-88B-Fe（C/M）to degrade organic pollutants was speculated.The main research contents are as follows:（1）The solvent-thermal method was used to prepare several kinds composites（C/M）.The chemical morphology and structural composition of these composites were characterized.The results showed that CNTs and MIL-88B-Fe were successfully combined.The specific surface area and pore volume of the composites increased,which was beneficial to the adsorption and diffusion of pollutants.（2）Phenol was used as the target pollutant.The activity of the catalyst was investigated from the aspects of influence factor of reaction stability.The results showed that C/M could significantly improve the catalytic degradation performance comparing with MIL-88B-Fe.Under optimal conditions,the pseudo-first-order kinetic constant of C/M for phenol degradation is 7 times that of MIL-88B-Fe,which was even comparable to that of the homogeneous catalysts(Fe²⁺).To some content,the catalytic performance of C/M increases with the increase of carbon nanotube content,functional degree of carbon nanotubes（CNTs）,catalyst dosage and hydrogen peroxide concentration.In addition,C/M can also efficiently degrade other pollutants including sulfamethoxazole,bisphenol A and 2,4-dichlorophenol.Moreover,C/M showed a good catalytic effect in a wide range of pH（4-9）.In addition,the composite catalyst had a good stability and reusability.After repeated use for three times,the degradation of phenol remained almost the same（3）The radicals species in the system were identified by radical quenching experiment and electron spin resonance technology.The valence states of the elements and the contents were analyzed by measuring the X-ray photoelectron energy spectrum.The results showed that hydroxyl group was the main active species.The content of Fe（Ⅱ）increased with the increased content of CNTs.During the reaction,carbon nanotubes further facilitated the redox cycle.