Natural organic matter removal from water by complexation-ultrafiltration

An efficiency of humic acids (HA) removal from aqueous solutions by complexation-ultrafiltration (COUF) process was investigated. The rejection of commercial HA (Aldrich) in the presence of two weakly basic, cationic water-soluble polymers poly(diallyl dimethylammonium chloride) (PDADMAC) and chitosan were studied. The effect of different experimental parameters such as a mass ratio of HA to polymers, operating pressure, pH of solution on the HA removal was evaluated. It was shown that the HA rejection on ultrafiltration UPM-67 membrane (Vladipor) varied from 98.1 to 99.2% or from 90.5 to 92.5% with addition of PDADMAC or chitosan, respectively, when a HA/polymer mass ratio was changed from 1:1 to 1:7. The solute rejection to some extent improved with an increase in the concentration of polymeric complexing agents due to a higher completeness of the HA binding. It was found that a pH value of the feed solution has an important effect on HA removal in COUF with chitosan: the HA rejection increases with an increase in a degree of protonation of chitosan molecules. On the other hand, the HA removal did not essentially change with pH when PDADMAC was used as polymeric complexant owing to the lack of protonation of the quaternary amino groups of this polymer.