화학공학소재연구정보센터
Desalination, Vol.179, No.1-3, 237-244, 2005
Ground water treatment by enhanced ultrafiltration
The efficiency of heavy metal removal from simulated ground water containing humic substances has been investigated by means of enhanced ultrafiltration (UF) with chitosan. The rejection coefficient of Cu (II), Pb (11), Ni (11) and Co (11) in the presence of humic, fulvic acids and polysaccharide biopolymer chitosan was studied for single-metal and multi-component systems. The different experimental parameters such as time contact, initial concentration of metal ions, background electrolyte concentration, pH solutions, and diverse cellulose acetate UF membranes of different molecular weight cut-off on the extraction kinetic were investigated. Humic substances rejection increased with pH due to conformational transformation of ionizable molecules. The interactions of humic substances with multi-charged metals do not practically affect the retention of organic matter. Involvement of heavy metal ions into complexation with chitosan and humic substances provides effective removal of trace metals from solutions as a result of complex retention. In conformity with this principle, the degree of heavy metal rejection improved with an increase in the ratio between chitosan or humic substances and metal due to an increase in completeness of metal binding. This ratio is also responsible for the phase-dispersion state of the solution initiating a transition of intra-molecular complexes to inter-molecular ones at higher concentrations of metal ions with respect to a higher molecular weight of complex formation substances. This leads to an aggregation of humic acids-metal complexes and a decrease in the transmembrane flux. Fulvic acids do not tend to form intermolecular aggregates, and chitosan-metal complexes allow metal ions to be rejected without any substantial reduction of membrane productivity.