Adsorption and desorption of DMF on macroporous resin NKA-II in the fixed bed

To reduce the high energy consumption during the traditional ordinary distillation process for recycling N,N-dimethyl formamide (DMF), this paper utilized the NKA-II macroporous adsorptive resin in combination with a distillation process to recycle DMF in wastewater. First, the adsorption equilibrium data were measured in the intermittent agitation tank, which showed that the DMF adsorption equilibrium on the NKA-II resin complies with the Henry equation. The dynamic experimental studies indicated that the adsorption temperature has little effect on the adsorption process; the flow rate and the bed height affect the breakthrough time but have little effect on the mass transfer zone. With the combination of the fixed-bed adsorption model and the breakthrough curve, the surface diffusion coefficient of the DMF on the resin in the fixed bed was approximately 3.50 x 10(-10) to 1.06 x 10(-9) m(2) s(-1). The simulated values were in good agreement with the breakthrough curves determined by experiments. Furthermore, ethanol was selected as a better desorption agent. The appropriate desorption conditions were determined to be a flow rate of 8.00 x 10(-5) m s(-1) to 1.58 x 10(-4) m s(-1) and a temperature of 308-318K. Under these conditions, the desorption rates were all greater than 99%. Finally, wastewater that contained 5% DMF was used as an example to analyze the energy consumption. The results indicated that the adsorption-distillation process can reduce the energy consumption by 79%. The adsorption-distillation process has a good applicable value for the recovery of DMF in wastewater, especially for wastewater with a low concentration of DMF. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.