Poly（M-phenylenediamine） Polymerized Chemically By Novel Composite Oxidant And Its SO₄^2- Adsorption Performance

A large amount of sulfate-containing wastewater is produced from melting and chemical production process. High concentration sulfate wastewater without effective disposal will seriously pollute the environment and biological system and harm the human health. Poly(m-phenylenediamine)s in different oxidant state were chemically oxidative polymerized with m-phenylenediamine as monomer and ammonium persulfate-hydrogen peroxide as composite oxidant in this paper. The influence in the polymerization was studied. And the sulfate ions and hexavalent chromium ions removal performance of the polymer was investigated. The removal mechanism was also explored with the characterization of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results as follow:(1) PmPD modificated via amination with triethylenetetramine after epoxidization using epichlorohydrin possess lower solubility in some solvents and improved thermostability in the temperature range of40-250℃. The sulfate adsorption performance of modified PmPD was enhanced obviously with adsorptivity of62.5%which increase with17%and absorbance of187.5mg/g which increase with50mg/g.(2) The process of PmPD polymerized with ammonium persulfate-hydrogen peroxide as composite oxidant was:ammonium persulfate was added into monomer solution to preoxidation and then Fe2+-hydrogen peroxide oxidation system was added for further synthesis. The highest polymerization yield reached86.3%, higher than the yield existing. And composite oxidant instead ammonium persulfate with hydrogen peroxide which is at a low price and can avoid second pollution.(3) With the characterization of FTIR and XPS, the oxidation state can be adjusted and controlled in a large range by changing molar ratio of these two oxidants. This is benefit for the application of PmPD in various fields.(4) PmPD synthesized with composite oxidant was used to adsorp sulfate ions from aqueous solution. It was found that the adsorption ability was improved with decreasing of solution pH. The highest adsorptivity was more than95%and adsorbance was up to257.5mg/g, superior to the most of reported absorbents. Desorption can be easily achieved in10minutes with ammonia water as desorbing agent. In the ten times cycle adsorption experiments, the performance had less attenuate and the accumulative adsorbance reached to1398mg/g.(5) As suggested by the adsorption mechanism, in acidic solution, sulfate ions adsorbed is mainly relied on the protonation (doping) of imino groups. Quinoid imine units were transformed into the protonated benzenoind amine units to adsorb sulfate ions. The desorption is accomplished effectively by adding base solution to neutralize the protonic acid.