Preparation Of Modified Polyaniline And Its Adsorption Of Lead Ions, Dyes And Photocatalytic Activity

In this paper,phytic acid-doped polyaniline was synthesized by chemical oxidation polymerization using aniline and m-phenylenediamine as monomers,phytic acid as dopant and ammonium persulfate as oxidant.Effects of aggregation parameters and absorption conditions on Pb²⁺ions and dyes absorption capacity of phytic acid-doped polyaniline were investigated.Pb²⁺ions and dyes adsorption kinetics and adsorption thermodynamics as well as regeneration performance of phytic acid-doped polyaniline were studied.The structures and morphologies of phytic acid-doped polyaniline were characterized by FTIR,SEM,XRD and TGA.Possible adsorption mechanism of Pb²⁺ions onto phytic acid-doped polyaniline was investigated.PANI/AgCl photocatalysts were synthesized by chemical oxidation polymerization of AgCl and aniline monomer selecting phytic acid as dopant.The structures and morphologies of PANI/AgCl photocatalysts were characterized by XRD,FTIR,SEM and UV-vis diffuse reflection.The visible light photocatalytic degradation of dyes and possible photocatalytic degradation dyes mechanism for PANI/AgCl were investigated.The main conclusions are as follows:?1?FTIR indicated that the prepared phytic acid-doped polyaniline have target structures.XRD showed that the wide and diffuse diffraction peaks of phytic acid-doped polyaniline and no crystalline peaks,indicating that phytic acid-doped polyaniline is a typical amorphous structure.SEM showed that phytic acid-doped polyaniline is formed by the accumulation of irregularly arranged flocs,with rough and uneven surface,and three-dimensional foam structures with different sizes.TGA indicated that the initial decomposition temperature of phytic acid-doped polyaniline was 367°C,and the thermal stability of phytic acid-doped polyaniline was higher than that of polyaniline with emeraldine base structure.?2?Phytic acid-doped polyaniline had maximum adsorption capacites for Pb²⁺ions,methyl orange and methylene blue dyes in the condition of monomer concentration of 6%,phytic acid/monomer molar ratio of 1:4,oxidant/monomer mole ratio of 1.5:1,and m-phenylenediamine/aniline mass ratio of 10:90.?3?With the increase of pH value,Pb²⁺ions adsorption capacity of phytic acid-doped polyaniline was firstly increased,then decreased secondly,the adsorption capacity of methyl orange decreased continuously,while the adsorption capacity of methylene blue increased gradually.With the increase of the initial concentrations of Pb²⁺ions and dyes,Pb²⁺ions and dyes adsorption capacities by absorbents gradually increased and then the increase rate slowed down.When the temperature was raised,the adsorption capacity of the adsorbents to Pb²⁺ions and methyl orange were decreased,while the adsorption capacity for methylene blue was gradually increased.?4?In the early stage of adsorption,the adsorption rate of phytic acid-doped polyaniline to Pb²⁺ions,methyl orange and methylene blue were large,and then reduced gradually until reaching adsorption equilibrium.adsorption equilibrium time for Pb²⁺ions,methyl orange and methylene blue were 45 min,60 min and 120 min,respectively.?5?Pb²⁺ions adsorption process for phytic acid doped polyaniline conformed to the pseudo-second kinetic equations and the Langmuir isotherm adsorption model.Methyl orange adsorption process accored with pseudo-second kinetic equations and Freundlich model.Methylene blue adsorption process accored with pseudo-second kinetic equations and the Langmuir model.?6?FTTR could be determined that PANI/AgCl composites had high molecular weight polyaniline.XRD could be used determine the characteristic diffraction peak of AgCl in the PANI/AgCl composite photocatalysts.The crystallinity of AgCl was good,and its crystal structure was not destroyed in the chemical oxidation polymerization of polyaniline.The SEM showed that AgCl nanoparticles exhibited a relatively uniform cubic phase morphology with a smooth surface and a particle size of 400-800 nm.With the increase of aniline monomer content,enwrapped AgCl by polyaniline was obviously enhanced.UV-vis diffuse reflectance showed with the increase of aniline monomer content,the absorption of PANI/AgCl composite photocatalysts were enhanced in the visible region and near infrared region with redshift absorption edge.?7?AgCl nanoparticles could degrade methyl orange and methylene blue under visible light irradiation.PANI/AgCl composite photocatalysts had dark adsorption of methyl orange and methylene blue.PANI/AgCl composite photocatalysts had better photocatalytic degradation of methylene blue and methyl orange with higher amount of aniline monomer.Photocatalytic degradation ratio of methyl orange and methylene blue reached 90.5%and 74.8%,respectively under 60min visible light irradiation for4%-PANI/AgCl composite photocatalyst.?8?After five times recycling utilization,the adsorption capacity of phytic acid-doped polyaniline to Pb²⁺ions was 72%of the adsorption capacity with the first use,and photocatalytic degradation rate of 4%-PANI/AgCl composite photocatalyst to methyl orange was 82.9%of the photocatalytic degradation rate with the first use.