双胺“可逆”溶剂强化正渗透脱盐及过程优化

Enhancement and optimization of forward osmosis desalination process using diamine switchable solvent

正渗透作为非压力驱动膜脱盐技术,具有能耗低、膜污染轻、水回收率高等优点,其中汲取液的分离回收是整个正渗透技术的关键。本文提出采用双胺(TEPDA,N,N,N’,N’-四乙基-1,3-丙二胺)“可逆”溶剂经质子化-脱碳可逆循环作为正渗透汲取液进行脱盐的策略。首先,使用TEST软件预测发现,相比传统有机溶剂及单胺溶剂(如DMCHA,N,N-二甲基环己胺),TEPDA具有较低的挥发性、较高的安全性和低生育毒性。正渗透实验发现在两种模式下TEPDA的反向通量选择性均高于DMCHA,证明TEPDA具有更好的正渗透效果。同时发现TEPDA汲取液在PRO模式下效果要优于FO模式。通过对操作条件的优化得到TEPDA汲取液的最优操作温度为30℃,最佳流速为500mL/min。在最优条件下对1%(质量分数)的氯化钠溶液进行5h的连续运行发现,TEPDA汲取液在5h后仍能保持6.09L/(m^(2)·h)的正向渗透通量,具有连续运行的稳定性。循环实验也证明了TEPDA具有较好的循环稳定性。上述结果为双胺(TEPDA)“可逆”溶剂应用于正渗透脱盐领域提供了基础的理论指导。

As a non pressure driven membrane desalination technology,forward osmosis has the advantages of low energy consumption,light membrane pollution and high water recovery.In this paper,the strategy of desalting using diamine(TEPDA,N,N,N′,N′-tetraethyl-1,3-propanediamine)switchable solvent through protonation decarbonization reversible cycle as forward osmosis extraction solution was proposed.Firstly,TEST software was used to predict that compared with traditional organic solvents and monoamine solvents(such as DMCHA,N,N-dimethyl cyclohexyl amine),TEPDA had lower volatility,higher safety and lower reproductive toxicity.The results of forward osmosis experiment showed that the reverse flux selectivity of TEPDA was higher than that of DMCHA in both modes,which proved that TEPDA had better forward osmosis effect.At the same time,the effect of TEPDA in PRO mode was better than that in FO mode.The optimal operating temperature of TEPDA was 30℃and the optimal flow rate was 500mL/min.Under the optimal conditions,the 1%(mass ratio)sodium chloride solution was operated for 5h.It was found that the TEPDA could still maintain the forward permeation flux of 6.09L/(m^(2)·h)after 5h,which had the stability of continuous operation.The cycle experiment also proved that TEPDA had good cycle stability.The above results provided a basic theoretical guidance for the application of diamine(TEPDA)switchable solvent in the field of forward osmosis desalination.