Synthesis Of Nano Zero-valent Iron Composite For The Reduction Of Paranitrochlorobenzene In Aquesous Solution

Chlorinated organics are a priority for controlling pollutants in seriously polluted water bodies.Nano zero-valent iron technology provides a new direction for the removal of chlorinated organics,but zero valent iron was easy to agglomerate and passivation layers was formed on the surface of iron by oxidation.In order to overcome these defects and give full play to the advantages of strong reduction of zero valent iron,this paper selected attapulgite as the carrier,sodium carboxymethyl cellulose as the modifier,and nickel as the composite metal to construct the nano zero valent iron composite material（CMCNa-ATP-Fe/Ni）.The performance,removal mechanism and influencing factors of CMCNa-ATP-Fe/Ni for the removal of p-nitrochlorobenzene were studied by using p-nitrochlorobenzene as the target pollutant.The main results are as follows:（1）After loading and modification,it can be seen from the morphology analysis of SEM and TEM that the agglomeration status of nano-Fe（/Ni）was improved.Some agglomerates were dispersed into single nano-Fe（/Ni）particles,and the BET specific surface area increased from 14.15m²/g to 94.67m²/g.In addition,the test of Zeta potential also showed that the epulsion of the composite increased.（2）Compared with the unloaded and modified nano-Fe/Ni,the efficiency and rate of CMCNa-ATP-Fe/Ni removal of p-chloronitrobenzene were enhanced.When the removal rate reaches 98%,the time required by the composite material was 9 times shorter than that of nano-Fe/Ni,and the mass of iron in the composite material only accounted for 1/3 of the dosage.Therefore,the use cost could be greatly reduced.（3）The removal of p-chloronitrobenzene by CMCNa-ATP-Fe/Ni conforms to the Langmuir-Hinshelwood model,and the removal process was the result of synergistic effect of adsorption and reduction.The reaction rate constant k₁ was 20.02mg·(L·min^-1)and the adsorption constant k₂ was 0.0041L/mg.Thus adsorption is a rate control step in the removal process.（4）The reduction route of p-chloronitrobenzene by CMCNa-ATP-Fe/Ni composite material was as follows:first,the nitrogroup on p-chloronitrobenzene was reduced to amine group by CMCNa-ATP-Fe/Ni composite material,then the p-chloraniline was dechlorinated,and the final product was aniline.（5）The mechanism of reduction of the nitrogroup onto the p-chloronitrobenzene to the amine group was as follows:（1）zero valent iron reduces nitro groups by direct electron transfer.（2）the corrosion product H₂ of zero valence iron was converted into active hydrogen through the action of Ni,and the active hydrogen reduced the nitro group.The mechanism of dechlorination reduction of p-chloronitrobenzene by composite materials was as follows:the C-Cl bond on the benzene ring of p-chloranilinewas was broken by the active hydrogen atom and aniline was formed.（6）Increasingthetemperatureisconducivetotheremovalof p-chloronitrobenzene;The reduction efficiency of p-chloronitrobenzene was higher in the pH range of 5-9.Common ions in water,such as Cl^-and SO₄^2-inhibit the reduction of p-chloronitrobenzene by composites to some extent.