Membrane fouling characterization at filtration of different pollutants

Namen magistrke naloge je bil očistiti pitno vodo, obogateno s huminskimi kislinami (HA), železovimi(II) ioni, kadmijevimi ioni in fosfati ter določiti stopnjo mašenja membrane. Hoteli smo ugotoviti, kako interakcije med onesnažili, pH vzorca in masne koncentracije onesnažil vplivajo na stopnjo mašenja membrane. Vzorce smo pripravili v laboratoriju in jih filtrirali skozi polietersulfonsko (PES) membrano na ultrafiltracijski (UF) aparaturi. Začetnim vzorcem in permeatu, ki smo ga zbirali med UF, smo izmerili fizikalno kemijske parametre: motnost, električno prevodnost, absorbanco, s katero smo določili masne koncentracije onesnažil in koncentracijo Cd2+ ionov na aparaturi za atomsko absorpcijsko spektrometrijo (AAS). Stopnjo mašenja smo izračunali preko pretokov, posneli smo tudi FTIR spektre čiste PES membrane in membrane po UF vzorcev ter izmerili kontaktni kot, s katerim smo določili naravo membrane. Rezultati so pokazali, da se membrana precej maši pri vseh onesnažilih. Najvišje stopnje mašenja zaznamo pri vzorcih, obogatenih s HA in vzorcih, obogatenih s HA in Fe2+. Visoko stopnjo mašenja zaznamo tudi pri vzorcih, obogatenih s HA in PO43-, medtem ko pri vzorcih, obogatenih s HA in Cd2+, izstopajo vzorci pri pH 5, ki imajo visoko stopnjo mašenja, potem pa stopnja s pH vrednostjo pade. Ugotovili smo tudi, da se membrana bolj maši pri nižjih masnih koncentracijah HA, ni pa nujno, da se bolj maši pri nižjih masnih koncentracijah drugih onesnažil, saj smo ugotovili, da je stopnja mašenja membrane odvisna od sposobnosti vezave HA in onesnažila v kompleks in od tekmovanja med HA in PO43-, ki sta v vodi negativno nabita. Rezultati masnih koncentracij so pokazali, da nam je uspelo vodo očistiti onesnažil. Masne koncentracije HA so se pri vseh vzorcih znižale pod 1 mg/L, ob prisotnosti drugih onesnažil pa celo pod 0,5 mg/L. Prav tako so se znižale masne koncentracije PO43- in Fe2+, in sicer pod 0,06 mg/L. Masne koncentracije Cd2+ so se najbolj znižale pri pH 9, in sicer pod 1 mg/L, pri ostalih vzorcih pa so bile masne koncentracije višje. Pod dovoljeno mejo, tj. 0,2 mg/L, nam je uspelo znižati masne koncentracije Fe2+. Prav tako nam je uspelo pod dovoljeno mejo, tj. 0,3 mg/L, znižati masne koncentracije PO43-.The purpose of the master\u27s thesis was to clean the drinking water enriched with humic acids (HA), iron (II) ions, cadmium ions and phosphate and determine the membrane fouling rate. We wanted to find out how interactions between pollutants, the pH of the sample and the mass concentration of pollutants influence the membrane fouling rate. Samples were prepared in the laboratory and filtered through the polyethersulfone (PES) membrane on the ultrafiltration (UF) apparatur. The physicochemical parameters were measured in the initial samples and the permeate collected during UF: turbidity, electrical conductivity, absorbance through which the mass concentration of pollutants was calculated and we determined Cd2+ ion concentration on the atomic absorption spectrometry apparaturs (AAS). Membrane fouling rate was calculated through flows, we also recorded the FTIR spectra of pure PES membrane and membrane according to UF samples and measured the contact angle by which we determined the nature of the membrane. The results showed that the membrane fouls with all pollutants. We have the highest membrane fouling rates in samples enriched with HA and samples enriched with HA and Fe2+. We also have a high membrane fouling rate in samples enriched with HA and PO43-, while for samples rich in HA and Cd2+, samples with pH 5 have a high membrane fouling rate and with higher pH membrane fouling rate drops. We also found that the membrane fouling rate is higher at lower mass HA concentrations, but it is not necessary for lower mass of other pollutants, since it was found that the membrane fouling rate depends on the ability to bind HA and the pollutant to the complex and from the competition between HA and PO43-, both of which are negatively charged in water. The results of mass concentrations showed that we managed to clean the water of pollutants. The HA mass concentrations decreased in all samples below 1 mg/L, in the presence of other contaminants even below 0.5 mg/L. The mass concentrations of PO43- and Fe2+ also decreased below 0.06 mg/L. Cadmium ion mass concentrations decreased the most at pH 9, below 1 mg/L, while in other samples the mass concentrations were higher. Under the permitted limit of 0.2 mg/L, we were able to reduce the mass concentrations of Fe2+ ions. We also succeeded in reducing the mass concentration of PO43- under the permitted limit 0.3 mg/L