Potassium and ammonium recovery in treated urine by zeolite based mixed matrix membranes

Nitrogen, phosphorus and potassium are essential for crop growth, which are abundant in urine. Although numerous studies have developed techniques to recover ammonium and phosphorus from urine, limited research made efforts on the recovery of potassium, which is a non-renewable resource with uneven global distribution. In this study, we explored the possibility of zeolite based mixed matrix membranes (MMMs) to selectively recover ammonium and potassium from urine, with minimal detention of sodium. The findings demonstrated that upon the pre-treatment of zeolites with sodium chloride solution, a 70 wt% zeolite loaded MMM could achieve 69.3 % recovery of potassium and almost full recovery of ammonium. By varying the desorption temperatures and MMMs production process, it was discovered that stepwise backwash at low temperature (276 K) greatly lowered sodium recovery whilst simultaneously enhancing the recovery of potassium and ammonium. This study demonstrates the potential of recovering potassium and ammonium from urine using zeolite-loaded MMMs, coupled with achieving low-sodium recovery.