Water recovery from hydrolysed human urine samples via direct contact membrane distillation using PVDF/PTFE membrane

Abstract

As a potential remedy for addressing water shortage challenges, membrane distillation (MD) presents the possibility of alleviating the water demand in water scarce countries. It offers a promising approach to explore untraditional water resources. In the field of urine treatment, MD enables water recovery for potable use and the recovery of nutrients that can be used in boosting agricultural production. It is in this light that polyvinylidene fluoride/polytetrafluoroethylene (PVDF/PTFE) membranes modified with methyl functionalized silica nanoparticles (MfSNPs) were fabricated to produce microporous hydrophobic composite membranes for water recovery from urine. Contact angles of the membranes indicated an increase in the hydrophobicity brought about by the increase in PTFE loading. The increase in PTFE loading improved the membrane structure (as shown by SEM images) resulting in smaller evenly distributed pores and a porous spongy structure. The composite membrane attained the maximum water recovery of 80% from hydrolysed human urine samples at pH 10.5, against a water vapour gradient of 30 °C. The feed side temperature was kept at 50 °C and the permeate side at 20 °C. The highest permeate flux for the PVDF/PTFE nanocomposite membranes was 8 J/Jo,which is comparable to fluxes reported in the literature obtained in direct contact membrane distillation (DCMD) setups operated at the same temperature gradient. The permeate water quality was assessed and the results showed high rejection of ammonia (>95%), TOC (>98%), Na+ (>98%) and K+ (>89%) by the membranes. This suggests that the (combination/hybrid) convergence of membrane technology and nanotechnology in MD application is a viable alternative for urine treatment to provide sustainable and reliable clean water supply.