Modification Of Ceramic Membrane And Its Use In MD

Membrane distillation (MD), a new type of membrane separation process, which has the characteristics of good separation ability, low energy consumption and low capital investment, was widely used in desalination, sewage treatment and other fields. Although membrane distillation technology has been greatly developed, the scale of industrial production has not yet formed for higher mass transfer resistances, lower heat transfer efficiency and imperfect mechanism of heat and mass transfer process.Compared to the other three common forms of membrane distillation, vacuum membrane distillation (VMD) has a higher flux and lower heat conduction losses. In order to solve the lack of membrane materials, the hydrophobic properties of ceramic membranes have been obtained by grafting (CH3)SiCl2 on the surface of the membrane. Hydrophobicity was characterized by contact angle measurement. The effect of grafting time, modifying number, heat treatment time, heat treatment temperature and grafting solution concentration for the grafting process were studied. The optimum conditions were as follows:grafting time is 24h, modifying number is 3, heat treatment time is 24h, heat treatment temperature is 100℃, grafting solution concentration is 0.1mol/L.After completed the ceramic membrane modification, VMD experiments for NaCl solution desalination is carried out. Experiments showed that desalination used modified ceramic membrane works well and the rejection rate reached almost 99.99%.Under the suitable operation condition the pure water flux has achieved 15.80 kg/m2·h.Additionally, a model of heat and mass transfer for VMD process was established to simulate the effect of operation conditions and membrane properties on membrane flux. By comparing the simulation results and experimental results, the results in the low concentration range is consistency well.Through simulation analysis, the operation conditions effect on the flux as follows:with the temperature, flow rate and vacuum increasing, the membrane flux increased. With the feed concentration increasing, the membrane flux decreased. With the pore size, porosity increasing, the membrane flux increased, and with the membrane thickness, tortuosity decreasing, the membrane flux increased.