| China's water resources are seriously polluted,according to the"China's Environmental Status Bulletin"and related environmental departments reports,China's seven major water systems,lakes,rivers,etc.have different levels of pollution.The main sources of water pollution are inorganic pollutants with complex composition and extremely low concentration produced by the manufacturing,metallurgical,chemical and mining industries.It is difficult to treat harmful ions at low concentrations in wastewater with existing technologies.The electrochemically switched ion permselectivity?ESIP?is a new separation technology,which is specially designed to deal with low concentration ions.It is superior to traditional methods?such as electrodialysis,ion exchange method,or reverse osmosis?,because it is used to trace ion separation recycling consume very little energy and has a very high selectivity,under the complicated system can realize the separation of inorganic salt,recycling and reusing resources,more important is the process does not produce secondary pollution,to prevent water damage,pollution and waste is of great significance.As a clean,efficient and sustainable green cleaning technology,ESIP has broad application prospects in the process of environmental protection and resource recycling.However,ESIP technology still has many difficulties in large-scale applications,such as improved performance of electrochemically switched ion permselectivity membrane?ESIPM?,amplification of ESIPM,optimization of operating parameters of ESIP process,and evaluation of operating energy consumption.The electrochemically switched ion permselectivity process will be understand more deeply from the nature of the transfer by quantitative mathematical analysis of the ESIP process which is the first step in the design and amplification of the ESIP membrane separator.In order to fully understand the transfer process of ions through the ESIP membrane,a two-dimensional steady-state idealized mathematical model which based on the Nernst–Planck equation for ion transfer in the ESIP system was established.The results of a larger operating range will be predicted accurately only by small-scale experimental data.Several factors will do effect to ion separation flux such as inlet concentration,volume flow,cell voltage,pulse potential and reactor size.With the simulating of the model all the above factors can be analyzed more easily.The energy consumption can be calculated under different operating voltages in this model so that the actual running cost can be effectively reduced and the separation effect can be improved.The process of selective separation of lead ions(Pb2+)from three-dimensional porous multi-walled carbon nanotubes/polytetrafluoroethylene?MWCNT/PTFE?membranes was simulated under actual operating conditions.The main results are as follows:?1?The migration law of ions under the electric field drive in the ESIP process can be estimated by credible model which has been proved by comparing the simulation results with the experimental values.?2?The factors including feed concentration,volume flow rate and cell voltage which do effect to ion transport flux can be regard as the influence on channel current density.?3?The"equal potential"can be alternately formed in the source channel and the recovery channel when the membrane electrode potential is equal to the working electrode potential and the counter electrode potential respectively,which can effectively improve the current efficiency of ion separation.?4?The predicted maximum ion flux can reach to 8.5×10-4 g·h-1·cm-2 with the inlet concentration and the volume flow rate of 25 mg/L and 16 mL/min respectively under the operating conditions of the current laboratory.In the process of lead-zinc ore dressing wastewater treatment,Pb2+,Zn2+and Cu2+,would be separated and converted into PbSO4,ZnCO3 and CuSO4 products.The wastewater pretreatment,chemical precipitation separation and ESIP separation and separation process are modeled by the Aspen Plus V8.4 software with built-in Excel custom templates for ESIP selection separation process.The reuse process of ore dressing wastewater is analyzed with the consideration of the concept of system integration and optimization:?1?The wastewater pretreatment,chemical precipitation separation and ESIP separation process are modeled successfully by the Aspen Plus V8.4 software with built-in Excel custom templates.?2?Sensitivity analysis was carried out on the precipitation process to obtain the optimum dosage of the precipitant sodium carbonate.?3?The energy consumption and cost of the whole process flow were preliminarily calculated by modified model.The results show that the operation cost of the ore dressing wastewater reuse project with the core of the ESIP separation device is 3.14?/m3,and the investment cost is 1.12?/m3. |
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