Development of a simple and versatile ultrafiltration system for the fractionation of aquatic humic substances

A new fractionation system using membrane ultrafiltration was developed and applied to aqueous extracts of humic substances (HSs). Four polyethersulfone membranes of molecular weight cut offs of 10, 30, 50 and 100 kDa were used. The system was quite efficient in fractionating HSs with different molecular sizes. HS fractions were characterized by Fourier transform infrared spectroscopy and ultraviolet/visible spectrophotometry to obtain E2/E3 ratios, which describe the aromaticity of the fractions. The E2/E3 ratios were in agreement with those obtained using current commercial systems, and FTIR spectra of all fractions presented characteristic bands of the HSs. Therefore, it can be concluded that this system is a simple, versatile and low cost alternative to the current systems on the market.