Study On Treatment Of DMA Containing Wastewater With Ion Exchange Resin

As a kind of important chemical materials, dimethylamine (DMA) is widely used in pesticides, pharmaceuticals, rubber and some other organic chemical industries which produce large amount of wastewater containing DMA. For instance, wastewater containing DMA as much as several thousands milligrams per liter usually occurs in the top of distillation towers when the polyurethane (PU) synthetic leather corporations send their solvent, N, N-dimethylformamide (DMF) to the distillation process for recovery. If not well treated and exhausted directly, it is not only a waste of resource but also serious pollution to the air and water resources caused by wastewater containing DMA. Since environmental pollution is becoming increasingly serious now, effectively and economically recovering DMA from wastewater has been a crucial research topic. In this work, the ion exchange resin was used to adsorb DMA from aqueous solution with the expectation of providing theoretical direction for further application.The ZGSPC106 resin was selected as suitable adsorbent to treat simulated DMA wastewater of 800～2000 mg/L based on the comparison of static adsorption capacity and adsorption rate with 001×7 and D001. Then static and dynamic experiments were carried out to determine the optimum conditions for adsorption and regeneration such as pH, initial concentration, temperature, contact time, flow rate and so forth. The adsorption process was analyzed from the thermodynamic and kinetic aspects, furthermore, the adsorption mechanism was discussed by infrared spectroscopy analysis.Results of static experiments indicated that the ZGSPC106 resin had high adsorption capacity with a maximal static saturated adsorption capacity of 138.89 mg/g (dry resin) at 293 K. The process was pH dependent and the optimum adsorption for DMA was found to occur at natural pH of DMA solution. Moreover, the adsorption equilibrium could be attained within 12 min. Cations such as Na+, Ca+, Mg2+ and Fe3+ could cause great interference owing to competitive adsorption.Dynamic experiments showed the dynamic adsorption of DMA on rein was acceptable at flow rate 20 ml/min. With 2 mol/L hydrochloric as regenerant for saturated resin, the desorption efficiency reached as high as 90% at 10 ml/min. Under selected conditions, the ZGSPC106 resin had stable performance with regeneration rate close to 95% and could be well reused due to its good stability.Under the studied conditions, thermodynamic calculations showed the feasibility, endothermic and spontaneous nature of the adsorption. The equilibrium data can be preferably modeled with the Langmuir isotherm, while kinetics data well followed the pseudo-second-order model and the adsorption rate was mainly controlled by the intraparticle diffusion. The fourier transform infrared spectroscopy (FT-IR) of ZGSPC106 resin before and after adsorption implicated that ion exchange occurred between H+ and (CH3)2NH2+.