Preparation Of Chitosan Compound Ultrafiltration Membrane And Efficiency Of Treatment Of Humic Acid In Water

As the disinfection the residual humic acid reacts with chloride to form compound like trihalomethanes which is carcinogenic,teratogenetic and mutagenic,the humic acid is called the precursor of disinfection by-products.Membrane separation is a preponderant water treatment technology,but the problems limited application are nither single membrane process cannot reach ideal treatment effect,and nor the macromolecule of NOM aggravate the membrane fouling.The research shows that optimizing and inventing membrane materials can lighten membrane fouling.Surfaced modified method has been applied to prepare chitosan-polyethersulfone composite ultrafiltration membrane,with the polyethersulfone flat membrane as basement membrane.The chitosan and isophthaloyl chloride was used as additive,and solidification agent seprately.The properties of the membrane materials were investigated such as mechanical strength,hydrophilicity,the pure water flux and anti-pollution ability were investigated.The humic acid removal rate after ultrafiltration membrane was contrasted,and the influence of humate on membrane in different feed solution conditions were comparatively analyzed.Moreover,fouling mechanism and cleaning method of the membranes were discussed,the main research contents are as follows:1.Electronic universal testing machine,contact angle meter and ultrafiltration cell were applied to characterize the mechanical strength,hydrophilicity,the pure water flux and anti-pollution ability of the compound ultrafiltration membrane,The optical microscope,SEM,FTIR and EDS were utilized to observe the membrane surface.Those studies were aimed to analyze the surface elementary composition of the composite membrane,and to confirm the succeed combination of the chitosan and the basement membrane.Meanwhile,the interior structure and the pore size of compound ultrafiltration membrane were observed.2.To treat the humic acid solution,the chitosan-polyethersulfone compound ultrafiltrationmembrane?PESCHIUF-4?andpolyethersulfoneultrafiltration membrane?PESCHIUF-0?were stayed in ultrafiltration for 60 minutes continuously under0.1MPa and 20?²5?,respectively,Then the removal rate of humic acid was measured through ultraviolet spectrophotometer and turbidity meter.The research result showed that the permeate turbidity reduced to 0.1NTU through both the ultrafiltration of PESCHIUF-4 and PESCHIUF-0;the removal rates of humic acid was 97.9%and 88.5%respectively.3.The permeation performance under different pH and feed solution conditions were studied.With the increase of pH,the membrane flux decline rate also increased.It indicated that the low pH condition could relieve membrane fouling,and the pH affect the humic acid removal efficiency differantly.With the increase of Ca²⁺concentration,the membrane flux decline rate increased gradually;maenwhile,the interaction between pH and Ca²⁺concentration would influence the removal efficiency of humic acid.The pollution situation of membrane surface under the different Ca²⁺concentration was observed through SEM to verify that the effect of concentration Ca²⁺addition on the permeation performance.4.The microstructure and pollutant composition of membrane surface was investigate by SEM,AFM and EDS,in order to research the effect of humic acid on the membrane fouling and mechanism of membrane fouling.The optimum method of fouled membrane cleaning was selected,through methods of alkaline?sodium hydroxide?cleaning,surfactant?sodium dodecyl benzene sulfonate?cleaning and surfactant-alkali composite.The result showed that the optimum method of recovery membrane flux was benzene sulfonate with the mass fraction of 0.5%sodium dodecyl and pH 10.