Synthesis Of Dual-Functional Anion Exchange Resins For Adsorption Of Naphthalene Sulfonic Acids

Most industrial wastewaters accompanied by the production and use of naphthalene sulfonic acids, contain excessive sodium sulfate or other inorganic salts, which inevitably compete for the active sites, resulting in a significant decrease in adsorption capacity of anion exchangers. Thus, the preparation of selective anion exchange resins with high efficiency and salt resistance has been more and more concerned by researchers.Two novel weakly basic anion exchangers BNH and BN2 bearing two different functional groups was prepared via the reaction of chloromethylated PS-DVB copolymer beads with dibutylamine and dimethylamine. To better understand the benefits of the novel resins for removing 2-naphthalene sulfonic acid (NSA),1,5-naphthalenedisulfonic acid (NDSA) and 1-naphthylamine-3,6,8-trisulfonic acid (NTSA) from aqueous solutions, the adsorption properties of them on BNH and BN2 were compared with two synthesized monofunctional anion exchange resins, BNO and BN6 derived from dimethylamine and dibutylamine respectively. Furthermore, the treatment effect of BN2 and a commercial resin D301 on the actual industrial wastewater was comparatively studied.The static experiment results showed that the optimum pH for the adsorption was about 2, and the equilibrium data could be well matched with the Langmiur isotherm model. The adsorption capacities of all the resins for the tested naphthalene sulfonic acids were in the order of BNO> BNH> BN2> BN6 and NSA> NDSA> NTSA. Thermodynamic parameters indicated that adsorption was a spontaneous, endothermic and entropy increase process. The kinetic data could be well matched with the pseudo-second-order model, and the sorption rate decreased in the order of BN6> BNO> BNH> BN2. NaOH aqueous solution was sellected as an effective desorption agent, and BN2 possessed the best desorption property. In the presence of low levels of Na2SO4 in solutions, the adsorption capacity on BNO was the largest for NDSA as well as NTSA, but for NSA, it was only slightly higher than BN6. In the presence of high levels of NaiSO4 in solutions, BN2 showed the best adsorption ability to all the tested naphthalene sulfonic acids.The dynamic experiment results showed that the treatment effect of BN2 on the actual 2-naphthalene sulfonic acid industrial wastewater was better than that of the commercial resin D301, which suggested the novel dual-functioinal resin had a good application prospect.