Application of modified polysulfone membranes to the treatment of water solutions containing humic substances and metal ions

The results of ultrafiltration removal of humic substances and metal ion admixtures from aqueous solutions have been presented. The membranes applied were made of sulfonated polysulfone. Transport and separation properties of the membranes in relation to model solutions have been investigated. In the experiments two types of modified polysulfone membranes (of a different amount of sulfonated groups) were applied. Removal of iron and manganese ions as well as co-removal of these ions in the case of solutions containing both metal ions and humic substances were tested. It was found that ultrafiltration membranes made of sulfonated polysulfone can be useful in a highly effective (up to 98%) removal of humic substances from water. It was noticed that the increase of sulfone group content in polymeric matrix limited the occurrence of membrane fouling, which contributed to the increase of effectiveness of the process. Applied membranes allowed an effective removal of iron ions (up to 95%) from solutions also containing humic substances by retention of their metal-organic complexes or co-precipitating metal hydroxides. Manganese ions, which form complexes with humic substances in a very limited amount, were removed in a limited extent (up to 45%).

Porous ion-exchange membranes made o f sulfonated polysulfone provided efficient separation o f iron ions from aqueous solutions which contained humic substances, by retaining metalorganic complexes or co-precipitated metal hydroxides and humic colloids. The retention o f manganese ions (which are not very prone to form complexes with humic substances) totalled 45% or less. The presence o f metal ions had little influence on the efficiency o f humic acid removal. Only under conditions favorizing precipitation o f lowsolubility metal compounds was the retention o f humic substances slightly better, but this effect was concomitant with a decrease in membrane permeability.