Study On Preparation Of Porous Membrane And Removal Of Iron And Manganese In Groundwater

Geopolymer is a kind of inorganic polymer material similar to zeolite.Under the alkaline environment,the aluminosilicate was dissolved and released Si and Al monomer,and then the monomer was reconstituted and polycondensed.Geopolymer can be cured at room temperature,and more energy-saving compared to conventional materials such as zeolite.The internal structure of geopolymer can capture metal ions,thereby providing an alternative solution for the damage to environment caused by metal ion contamination.In this paper,the optimum ratio of geopolymer porous self-supporting membrane was investigated by adjusting the water content of the slurry,the amount of hydrogen peroxide and the amount of peanut oil.And the porous membrane was applied to the treatment of turbidity,chrominance,and iron and manganese ions in water.A composite membrane was prepared by coating the geopolymer separation membrane which obtained from the previous research with porous self-supporting membrane.The prepared composite membrane was used for removing the turbidity,iron and manganese ions in groundwater.The structure and properties of the porous self-supporting membrane and composite membrane were characterized by permeation flux system,scanning electron microscope,specific surface area and porosity tester and so on.The concentration of residual substances in filtrate was measured by means of inductively coupled plasma emission spectrometer,ultraviolet visible spectrophotometer and other instruments.The conclusions are as follows:(1)The experimental formula for preparation of geopolymer porous membrane:the mass ratio of metakaolin,slag,and 1.3 modulus of water glass was 1:1:1.7,and the water content of the slurry,the amount of hydrogen peroxide and the amount of peanut oil accounted for 29.5%,1.0%and 0.4%of the mass of geopolymer slurry.The performance parameters of geopolymer porous membrane are as follows:The water flux was 67000 kg·m-2·h-1,specific surface area was 25.39 m2·g-1,porosity was 63.4%and compressive strength was 5.47 MPa.After heat treatment and washing alkalinity,the porous membrane was used to remove turbidity,chromaticity,Fe2+ and Mn2+ in water,but the treatment effect was poor.And the experimental results showed that,the removal rate of porous membrane to Fe2+ was 70.8%,and Mn2+ was 14.94%.(2)Geopolymer composite membrane prepared by coating method.The composite membrane has high efficiency in removal of turbidity,but the permeability of the membrane was attenuated during the filtration process,and it can be restored to 74.49%after backwashing.Excessive alkali in the composite membrane increases the pH value of filtrate.At lower experimental temperature,the higher the initial concentration of the solution was,the higher the removal rate of the composite membrane to Fe2+was.When Fe2+ and Mn2+ coexist in the solution,the removal rate of the composite membrane to Fe2+ was higher.The removal mechanism included:neutralization precipitation,contact oxidation,ion exchange and physical adsorption.