Removal of boron from aqueous solutions by continuous polymer-enhanced ultrafiltration with polyvinyl alcohol

Boron is a highly contaminating metal due to its toxic effects for plants even at very low concentrations. Continuous polymer-enhanced ultrafiltration (PEUF) was applied for removal of boron from aqueous solutions. The effects of operating parameters on the performance of PEUF were investigated. A commercial polymer, polyvinyl alcohol (PVA) was used as the boron-complexing agent. The methodology consists of two steps: complexing boron with PVA following separation of boron and polymer complexes by ultrafiltration process. The pilot scale system utilized for the PEUF process accommodates a spiral-wound cellulose cartridge with 10,000 Da MWCO. The experimental parameters studied are metal/polymer ratio (loading) (0.01-0.5), pH (7-10), and the polymer characteristics such as molecular weight (M-n) of the polymer and degree of hydrolysis (DoH). The results showed that PEUF could be a successful alternative method for removal of boron. The permeate flux remained constant at around 19 L/m(2) hr throughout the runs and the fluxes were not affected by the operating parameters studied and by the polymer characteristics. When the loading values were decreased, the retention of boron was increased. Also, pH had an important influence as increase in pH resulted in increase in retention of boron. The polymeric M-n of the polymer did not have any influence on the retention of boron while an increase in DoH caused a decrease in retention of boron.