This research investigated a proof of concept, two-step process of forward osmosis (FO) and membrane distillation (MD) to uniquely separate and concentrate urea from urine. Urea is a critical compound used for many products such as diesel exhaust fluid, fertilizer, and resins. Urine can provide a natural, abundant source of urea. However, the current fabrication process for urea is energy intensive and costly. Both FO and MD are low pressure, low energy processes that have the ability to run off of waste heat or solar power which has implications for even remote communities. In a novel application, FO was used to separate urea from the other components in urine by capitalizing on the membrane’s poor rejection of urea (10–20%). MD was applied to the product solution from FO to further concentrate the urea solution. Four fresh urine conditions were tested by the two-step process: real fresh urine, real fresh urine with acetic acid addition, real fresh urine with calcium hydroxide addition, and synthetic fresh urine. Acid and base addition were applied for urea stabilization. FO separated ~30% of the urea from urine, and MD concentrated the urea by a factor of 2. The final concentration of urea was 60% of the original urea concentration in urine. The flux for real fresh urine was the greatest but declined to the same flux as the acetic acid condition by the end of the 24 h. The flux for the calcium hydroxide condition was the lowest and decreased the greatest extent over the 24 h. The flux and urea transport is expected to be the greatest for the synthetic fresh urine condition.<br/>

Urea recovery from fresh urine by forward osmosis and membrane distillation

256th National Meeting (2018)

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