| With the vigorous development of nuclear power and the large-scale establishment of nuclear power plants worldwide,nuclear power plants and spent fuel reprocessing plants will produce a large number of radioactive non-process low-level liquid waste annually,of which the treatment of radioactive laundry wastewater needs special attention.In the practice of radioactive laundry wastewater treatment,only using a single method to treat radioactive laundry wastewater generally can not achieve the desired results,so it is necessary to combine a variety of processes to achieve the desired results.In this paper,air flotation,membrane separation and adsorption methods were used to treat the simulated radioactive laundry wastewater by a single process and a combination process.Through the use of a single method,the treatment effect of simulated laundry wastewater was analyzed.Intermittent air flotation experiments were carried out on simulated laundry wastewater by air flotation method and continuous air flotation experiments were carried out on self-designed flotation column respectively In the experiment of treating simulated laundry wastewater by membrane separation method,the effects of different membrane pore sizes,different operating pressures and different operating time caused by concentration range and cake precipitation on retention rate and membrane flux were analyzed.In wastewater experiment,the adsorption results were fitted by kinetic equation and adsorption rate mechanism equation.The experimental results show that:(1)The optimum conditions of continuous air flotation are as follows:(1)the liquid level is 33 cm.the inlet velocity is 29.6 m L/min,the inlet velocity is 96mL/min,the pH value is 7.8,the COD removal rate is 30.8%,the turbidity.removal rate is 72.8%,and the Cs+removal rate is 14%.(2)Microfiltration experiment can intercept some macromolecular organic matter and suspended matter,but it has little effect on small molecules and ions.Ultrafiltration has a better interception effect on organic matter and suspended matter,but a worse interception effect on ions Because of the influence of concentration,cake and gel layer,with the extension of the time,the retention first remains unchanged and then increases.The flux decreases first and then remains unchanged.With the increase of operating pressure,the rejection rate decreases and the membrane flux increases.(3)In the process of adsorption experiment,the adsorption rate of activated carbon and carbon felt fibers is greatly influenced by the initial concentration of metal ions,and the adsorption rate is controlled by chemical adsorption rather than mass transfer.The adsorption rate of natural zeolite and artificial zeolite is controlled by both chemical adsorption and mass transfer.The adsorption of Cs+ is mainly controlled by the diffusion process of liquid membrane.The removal efficiencies of COD,turbidity and Cs+ in simulated laundry wastewater were investigated by four combined processes:air flotation-microfiltration-ultrafiltration,air flotation-microfiltration-adsorption,air flotation-ultrafiltration-adsorption,air flotation-ultrafiltration-adsorption,air flotation-microfiltration-ultrafiltration-adsorption.The final results showed that the removal efficiencies of COD and turbidity could reach 99.4%.When only the removal rate is considered,the removal effect of the air flotation-microfiltration-ultrafiltration-adsorption process is the best.When the removal rate of Cs+ is not high,the air flotation-microfiltration-ultrafiltration process can achieve a good treatment effect considering the energy consumption,time,operation cost and subsequent treatment of adsorption materials. |
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