Modified Nano-zero-valent Iron Supported By Double Carriers And Researched Composites Adsorption And Degradation Performance

Nanometer zero-valent iron?nZVI?material has the advantages of high reactivity,low cost and low toxicity,which is widely used in water pollutant treatment.However,nZVI particle is agglomerated easily and easy to form the passivation layer in the air.Moreover,pH range of nZVI is relatively narrow and the adsorption selectivity is low,which limits its practical application range.The loading and modification nanometer zero valent iron is effective improve its reactivity.This research applied big specific surface area and high adsorption capacity carrier material,such as multi-walled carbon nanotubes?MWCNTs?,natural clay materials concave-convex rod?APT?,natural polymer chitosan?CS?and conductive polymer polyaniline?PANI?to load and modify nZVI.In this paper,the composites multi-wall carbon nanotubes/attapulgite loaded nano zero valent iron?nZVI/MWCNTs/APT?,chitosan/attapulgite loaded nano zero valent iron?nZVI/CS/APT?and polyaniline/chitosan loaded nano zero valent iron?nZVI/PANI/CS?were prepared and applied to control wastewater including the multi-pollutant.The results show that the composites of zero-valent nano-iron supported by double carriers can be used as a kind of efficient and green water treatment agent to remove effectively water pollutants such as organic dyes,antibiotics and heavy metal ions.?1?With multi-wall carbon nanotubes and modified clay mineral attapulgite?MWCNTs/APT?were used as the composite carrier to modify nZVI.MWCNTs/APT composite support can effectively improve the reaction activity and stability of nZVI,which has excellent removal performance for cationic dyes methylene blue?MB?and malachite green?MG?and other types of cationic dyes.The degradation mechanism and degradation products of MG and MB were analyzed by GC-MS and UV-vis.The results showed that the removal rates of MB and MG was 97.9%and 98.9%,respectively,when m_nZVI:m _MWCNTs=1:2,the dosage of adsorbent was 80mg and the initial concentration of mixed dyes was 50mg/L.The degradation processes of MB and MG is accordance with the pseudo-second-order kinetics and the Langmuir thermodynamic model with the maximum adsorption capacities of 149.9mg/g and177.9mg/g.The mechanism of nZVI/MWCNTs/APT remove cationic dyes is based on simultaneous and continuous adsorption and reduction reaction,and degrades dye macromolecules into small molecules with low toxicity.The waste adsorbent was used as the electrode material and its specific capacitance reached 77F/g,which provided a new research idea for the recycling of adsorbent materials.?2?Using natural polymer chitosan and clay mineral attapulgite?CS/APT?as the composite carrier and the one-step method was used to prepare CS/APT loaded nano zero-valent iron composites for removing anion dye naphthol green B?NGB?.The effects of different factors,such as,solution pH,adsorbent dosage and initial dye concentration on the removal performance were investigated.The main removal performance factors of NGB were obtained by Plackett-Burman test.The interaction between different factors and the optimal removal conditions were further studied by response surface method?RMS?.Thermodynamic and kinetic studies provided a basis for the mechanism analysis of NGB removal by nZVI/CS/APT.The results showed that the optimized design could effectively predict the NGB removal performance.Under the optimal experimental conditions,the actual removal rate of NGB was 97.34%when m _Fe/m _CS-APT=4:1,the adsorbent dosage was 75mg,and pH=2 that was shown no significant difference from predicted value of 98.89%.NGB removal conforms to the pseudo-second-order kinetics and Langmuir thermodynamic model with the maximum adsorption capacity is 192.30mg/g.nZVI/CS/APT can effectively adsorb and degrade NGB into non-toxic or weakly toxic small molecules by synergizing interaction.?3?Using polyaniline and chitosan?PANI/CS?as composite carrier,composites nZVI/PANI/CS was prepared by chemical liquid phase reduction method.The removal performance and mechanism of tetracycline?TC?and nickel?Ni?II??binary pollutants were investigated.The main factors affecting the removal of the two pollutants were obtained by using the Plackett-Burman design and the response surface method?RMS?were used to optimize the experimental conditions.The kinetic and thermodynamic model used to analyze the removal process of two pollutants.The experimental results shown that PANI/CS loaded with nano zero valent iron can effectively improve the reactivity of nano zero valent iron and achieve efficient removal.Under the optimal experimental conditions,when m _Fe/m _PANI/CS=2:1,adsorbent dosage 75mg and pH=7,the removal rates of TC and Ni?II?predicted by the model were 95.90%and 98.44%,respectively.The relative deviation between the measured and predicted values is respectively 2.14%and 0.06%,showing that model can effectively predict the TC and Ni?II?removal.The removal of TC and Ni?II?conforms to the pseudo-second-order kinetics and Langmuir thermodynamic models,and the maximum adsorpt ion capacities are 141.84mg/g and 145.35mg/g,respectively.The removal mechanism study shows that the nZVI/PANI/CS composites can degrade TC into small molecule acid and amine compounds,and Ni?II?can be reduced to low toxicity Ni⁰,nZVI/PANI/CS composites can effectively reduce the pollution of pollutants to the water environment.