Humic substances: A sequential device for fractionation by ultrafiltration with molecular size basis.

Abstract

A sequential system for fractionation by ultrafiltration (SSFU) equipped with advanced membranes filters (molecular size cut-off: 5, 10, 30, 50 and 100 kDalton) of the polyethersulfone type mas developed for analytical fractionation of humic substances (RS) extracted from aquatic systems or soils. The device consists of five membrane filters (Sartocon(R) Micro) operated by a multi-channel peristaltic pump, enabling an easy handling, working in a closed system and with simple collection of the six obtained fractions (F-1>100; F-2: 100-50; F-3: 50-30; F-4:30-10; F-5: 10-5 and F-6 <5 kDalton), Then, the RS sample (250 mt solution 1.0 mg/mL, pH 5.0 to 6.0) to he fractionated is pumped hy Dump through the series of membrane filters with a tangential flow of 85 mL/min, initial pressure 0.2 to 0.3 bar and permeation flux through the membranes of 0.8 to 1.4 mL/min. The overall time for fractionation and cleaning of the device is about 10 h and 25 mi of each fraction is obtained.