Study On The Adsorption Process Of Acetic Acid From DMAC Aqueous Solution

In this paper, we used macroporous weakly basic anion exchange resin to separate acetic acid from N, N-dimethylacetamide (DMAC) aqueous solution. At the mass concentration 0.6-6.0% of acetic acid, we studied adsorption balance, kinetics and fixed bed adsorption process.We chosed D301G as the suitable adsorbent to treat the DMAC aqueous solution through the resin selection experiment. The influence of DMAC concentration on adsorption, adsorption thermodynamics and kinetics were studied by static adsorption experiments. It indicated that the existence of DMAC would decrease the equilibrium adsorption capacity. However, D301G resin had a good adsorption and regeneration performance for acetic acid at lower concentration. The adsorption behavior of acetic acid on resin D301G could be described well by Langmuir equation. Thermodynamic analysis suggested that △Gθ<0, △Hθ<0 and △Sθ<0, which indicated the adsorption process was a spontaneously exothermic reaction with entropy decreasing. The kinetics data fitted the pseudo-second-order model well and the adsorption rate was mainly controlled by the intraparticle diffusion.The dynamic experiments were carried out in a self-made ion exchange column to determine the effect of flow rate, initial concentration and resin dosage on the breakthrough curves at room temperature (298K). According to the adsorption equilibrium and breakthrough curves, we calculated dynamic adsorption process parameters (mass transfer coefficient and mass transfer zone height) and optimized adsorption process conditions. With the increase of flow rate, the mass transfer coefficient and mass transfer zone height increased accompanied by a decrease in mass transfer resistance, but the time of breakthrough point was reduced. Considering all the factors, the dynamic adsorption of acetic acid on resin D301G was acceptable at flow rate 4 mL/min. The initial concentration of acetic acid and the amount of resin filling should be based on the actual size of the experimental setup and operating requirements.In the fixed bed adsorption process, a theoretical model was built to simulate the breakthrough curves. The breakthrough points using the proposed model were found to fit well with the experimental data. With properly identified parameters, this model offers a reliable means for accurate estimation of the breakthrough time.