Retention Of Heavy Metals By A Novel Thin-film Inorganic Forward Osmosis Membrane And Preparation Of The Membrane

Facing the crisis of heavy metals in the environment, find a way to remove heavy metal ions effectively from environment with energy saving is in the imminent. Forward osmosis is a new membrane technology developed in recent years, which is driven by permeation osmosis, is one of the hot spots in the present world of the film separation field. This technology can operate used in low or no pressure condition, compared with some current technology which is driven by pressure during the separation process, has many advantages: higher retention rate, separate effectively, lower membrane pollution, more simple operation and also more simple equipment. In many field, especially applicated in seawater desalination, drinking water treatment and wastewater treatment, shows a good application prospect.This thesis combined with the previous research and literature, we prepared a kind of a symmetric inorganic membrane witch can be applied in the process of forward osmosis to treat Cd2+ ions. This method can obtain higher retention rate proved by experiments. This thesis aims at making high-performance forward osmosis membrane with dense and non-porous active layer, in order to be able to retain heavy metal ions efficiently; we prepared a kind of inorganic membrane with symmetrical structure, by sol-gel method which has lower concentration polarization, higher water flux. the experimental results show that, the system of inorganic membranes in the preparation of membrane respectively, in the draw solute on concentration of 0.5 mol/L, 1 mol/L, 2 mol/L conditions, the water flux can be as high as 65.64 L/(m2h), the smallest reverse salt flux can be as low as 0.25 g?m-2?h-1, this result is far superior to the traditional methods. The TFI membrane has a good retention effect on the removal of Cd2+, especially for low concentration. For TFI membrane, the average removal rate is about 97%, HTI film is about 95%, slightly better than the HTI membrane in this experiment. and discusses the draw solution concentration and feed concentration on the effect of interception efficiency, found that when the draw solution concentration is 1mol/L, the water flux and retention rate can achieve ideal numerical.The main mechanism determined the TFI membrane interception efficiency is charge repulsion, that is to say the heavy metal ions retention rate of the TFI film is mainly decided by three key parameters: the pore size of the membrane surface, hole wall zeta potential, an-d double Debye length. When the film is too large, Cd2+ ions with high concentration will affect the Cd2+ ions retention rate, can adjust the aperture, membrane potential, ion intensity and solute permeability of heavy metals to optimize charge repulsion reaction and membrane, to ensure that in the membrane of heavy metals have a higher retention rate at the same time, also can maintain higher water flux.