Development Of Environmental Functional Resin-based Materials And Their Removal Of Mo(?)and Cr(?)Anions From Aqueous Solution

The protection of water and the control of water pollution has become one of the focuses of global attention in the 21st century.Therefore,how to purify and reuse polluted water is the primary task to solve this problem.Resin are a new class of porous materials that have emerged in recent years.In recent years,resin materials have shown excellent application prospects in the treatment of water environmental pollutants due to their advantages such as good thermochemical stability,reusability,and ease of functionalization.On this basis,two modified resin composites were synthesized in this paper,and their adsorption properties and possible adsorption mechanisms for molybdate and Cr???in water were studied.The specific research contents and results are as follows:In this study,a polymer-functionalized nanocomposite?HFO-Ps AX?was fabricated for selective adsorption of molybdate from aqueous solution.HFO-Ps AX was prepared by grafting hydrous ferric oxide nanoparticles?HFOs?into the porous structure of a polystyrene anion exchanger?Ps AX?by in situ synthesis method.The resultant HFO-Ps AX exhibited greatly enhanced selectivity toward molybdate as compared with the matrix,Ps AX,which is also a fair adsorbent for scavenging molybdate.The competitive abilities of the ubiquitous anions,i.e.,chloride,carbonate,sulfate,and phosphate,on the adsorption of molybdate by HFO-Ps AX followed the order:chloride<phosphate<carbonate<sulfate.The optimal p H for the adsorption of molybdate was determined as p H?4,which is associated with the dissociation constants of molybdic acid;certain adsorption capacities were also observed even under extremely alkaline condition?p H=14?for single-component molybdate solution.Fixed-bed column adsorption experiments validated the potential of HFO-Ps AX in treating Mo?VI?contaminated water for practical application,and the exhausted HFO-Ps AX can be regenerated by a binary Na OH-Na Cl solution?both 5%in mass?without loss in adsorption capacities.The adsorption of Mo?VI?by HFO-Ps AX was due to the ion exchange of quaternary amino groups and the coordination complex of Fe-O.The reduction-adsorption bifunctional material CMPs@NH₂ was successfully synthesized by grafting ethylenediamine onto chloromethylated polystyrene resins?CMPs?through a one-step hydrothermal reaction.Furthermore,the morphology,pore structure,elemental analysis and functional group composition of CMPs@NH₂ were characterized by XRD,FT-IR,XPS and N₂ adsorption-desorption isotherm tests.The adsorption properties and possible adsorption mechanisms were studied by using CMPs@NH₂ as adsorbent.The results of FT-IR show that the amino group was successfully grafted onto CMPs,and it contained both amino/amino groups?-NH₂/-NHR'?on the CMPs.The adsorption kinetics of Cr on CMPs@NH₂ accords with the pseudo-second-order kinetics model,indicating that the adsorption was mainly chemical adsorption.The adsorption isotherm satisfies the Langmuir model,indicating that the adsorption process was single-layer adsorption.The maximum adsorption capacities of CMPs@NH₂ for 283 K,298 K,313 K calculated by Langmuir model were 234.19,272.09and 323.84 mg/g.The adsorbent can be desorbed and regenerated through 5%Na OH alkaline solution and 5%nitric acid solution.After 5 adsorption-desorption experiments,the adsorbent still had high removal efficiency for Cr???.The XPS analysis showed that Cr???and Cr???coexisted on CMPs@NH₂.At the same time,compared with the weak acid and neutral conditions,the amino group has stronger reducing ability under acidic conditions?p H=2?,and the amino group and a small amount of methylene are involved in the reduction reaction.In the CMPs@NH₂ system,Cr???was removal due to the electrostatic adsorption by-NH₃⁺,and the removal of Cr???was due to the complexation of imino group.