Nano Zero Valent Iron Composites On Removal Performance For Water Pollutants Research

Nano-zero-valent iron materials are widely used in water pollutants treatment due to their high reactivity,low cost,and low toxicity.However,due to high surface energy and inherent magnetism,their particles are easy to oxidize and agglomerate,hindering their interaction with the contact between target pollutants limits the scope of practical applications.Loading modified nano-zero-valent iron is an effective method to improve its reaction in practical industrial applications.The research work uses conductive polymer polyaniline（PANI）containing functional groups and natural mineral diatomaceous earth（DE）with high specific surface area.Nano zero valent iron/polyaniline（n ZVI/PANI）and nano zero valent iron/modified diatomaceous earth（n ZVI/AMDE）composite materials were prepared respectively.Based on the characteristics of nano-zero-valent iron that slowly releases Fe²⁺during the reaction,the reducibility of nano-zero-valent iron is combined with the Fenton-like reaction technology of persulfate to study the adsorption and degradation performance of the two materials for multi-element pollutants.The research results show that the modified nano-zero-valent iron composite material can be used as a kind of high-efficiency,green and environmentally friendly water treatment agent to effectively remove water pollutants such as organic dyes and heavy metal ions.（1）Using Fe³⁺as iron source and oxidant at the same time,aniline as raw material,the polyaniline loaded nano zero valent iron（n ZVI/PANI）composite material was prepared by one-step oxidation method.The method can not only reduce the use of oxidant,but also prevent the prepared n ZVI from being oxidation.It can make iron uniformly dispersed on the surface of polyaniline and reduce the agglomeration of the n ZVI produced.The main factors affecting the removal performance of Cr（Ⅵ）and malachite green（MG）（different materials,p H value,dosage,temperature,coexisting anions,etc.）were investigated,and the removal process was analyzed through kinetic and thermodynamic models.In addition,the designed dynamic circulation adsorption device was used to test the dynamic adsorption performance of the composite material.The results show that:when the composite material dosage is 1g/L and the initial concentration of Cr（Ⅵ）and malachite green（MG）are 50mg/L,respectively,the n ZVI/PANI composite material has an effect on Cr（Ⅵ）and malachite green（MG）.The removal rate can reach 99.3%and 96.2%.The adsorption process of binary pollutants conforms to the quasi-second-order kinetic model,Cr（Ⅵ）conforms to the Freundlich thermodynamic model,and malachite green（MG）conforms to the Langmuir thermodynamic model.The dynamic adsorption experiment showed that the removal rate of Cr（Ⅵ）and malachite green reached 94.3%and 82.6%when running the peristaltic pump at a speed of 100rpm for 120min.（2）Using Fe³⁺as the iron source and oxidant,and aniline as the raw material,the polyaniline-supported nano-zero-valent iron（n ZVI/PANI）composite material was prepared by a one-step oxidation method,and n ZVI/PANI was studied in the presence of persulfate.Removal performance and mechanism of Methyl Orange（MO）and Orange IV（OG4）.The main factors affecting the removal performance of Methyl Orange（MO）and Orange IV（OG4）were investigated（different materials,p H values,different Ps concentrations and different initial concentrations,etc.）.The results show that when the dosage of the composite material is 1 g/L,the initial concentration of Methyl Orange（MO）and Orange IV（OG4）are 50 mg/L,the p H value is 3,and the Ps concentration is 2m M,n ZVI/PANI composite.In the presence of persulfate,the removal efficiency of Methyl Orange（MO）and Orange IV（OG4）reached 96.6%and92.9%.The removal of Methyl Orange（MO）and Orange IV（OG4）is,on the one hand,the adsorption and degradation of the composite material makes the azo dye-N=N-break,and on the other hand,the persulfate reacts with Fe²⁺to generate sulfate radicals.It is oxidized and degraded into small inorgic moleclues H₂O and CO₂.（3）Using acid-modified diatomaceous earth（AMDE）as a carrier,a chemical liquid-phase reduction method was used to synthesize supported nano-zero-valent iron.The effects of different materials,p H value,dosage and coexisting anions on the adsorption and degradation effect of main factors were investigated,and the removal mechanism of Congo red and p-nitrophenol by the composite material in the presence of persulfate was studied.The results show that the removal rate of Congo red and p-nitrophenol by nano-zero-valent iron composite material（n ZVI/AMDE）can be as high as 99.5%and 99.3%.Congo red and p-nitrophenol are reduced to p-aminophenol and other small inorganic molecules under the action of persulfate and Fe²⁺to generate sulfate radicals.