Study And Pilot Design On Ion Selective Electrosorption Desalination For Circulating Cooling Water

Circulating cooling water accounts for 70%?80%of industrial water.After several application cycles,the salt concentration,especially the hardness of the solution becomes high,which may lead to scaling and corrosion of the pipeline.Meanwhile,the water with high hardness is not suitable for usage resulting in water resource waste.Electrosorption desalination technology has been widely used in desalination regeneration of salty industrial wastewater.As composition of industrial wastewater is complicated,it is difficult to simultaneously achieve ion selective removal and high-efficiency desalination at present.In this paper,the adsorption-regeneration process and the adsorption-descaling process have been designed aiming to the circulating cooling wastewater with high hardness ions.The electrosorption process was studied by means of electrode modification and scale removal to achieve hardness ions selective electrosorption desalination.In the adsorption-regeneration process,the fibers of multiple modified graphite carbon felt(GCF)formed a large space structure and the specific surface area was large;Typical hydrophilic oxygen-containing functional groups appeared.The specific capacitance was higher than that of the unmodified electrode.The surface morphology and electrochemical performance of the modified electrode were better than those of the unmodified electrode.The modified electrode was beneficial to provide adsorption sites,reduced the common ion benefit,and improved the adsorption capacity of hydrophilic ions and hardness ions.For the circulating cooling water with conductivity of 3400±100?/cm,rate of desalination in adsorption-regeneration process could reach 42.6%and the conductivity reduced to 1934 ?S/cm.The Cl-concentration was 275.4 mg/L,the removal rate was 50.6%.The Ca2+concentration was 280.0 mg/L,the removal rate was 54.9%.And the Mg2+ concentration was 275.4 mg/L,the removal rate was 44.23%.In the electrosorption-descaling process,CO2 gas was introduced which was beneficial to the formation of insoluble or poorly soluble scales of hardness ions and CO32-ions on the electrodes,accelerating the adsorption and removal of hardness ions.The electrosorption-descaling process had a rate of desalination of 66.2%,a conductivity of at least 1130 ?S/cm.When the Cl-concentration was 232.5 mg/L,the removal rate was 58.3%.The Ca2+concentration was 159.0 mg/L,the removal rate was 74.4%.And the Mg2+concentration was 119.0 mg/L,the removal rate was 67.4%.It was superior to most of the electrosorption processes currently on the market.In the pilot scale research,two sets of electrosorption desalination equipment for circulating cooling water recycling were designed for the electrosorption-regeneration process and the electrosorption-descaling process.Electrosorption-regeneration process pilot designed 2 sets of modules operated in turn,the processing scale was 4 t/d,the reactor internal electrode assembly mode was slot type.The electrosorption-descaling process pilot designed 4 sets of modules operated at the same time,the processing scale was 200 L/h,and the assembly of the electrodes in the reactor was the threaded rod assembly.It was expected that the effluent can meet the water quality requirements of the recirculating cooling water.