PEI-grafted Membrane For Adsorbing Cu(?) And Co(?) From Waste Water And Its Electric Field Regeneration

Copper and cobalt are essential metals in human life and has been widely used in different trades.However,with the rapid development of the industrial process,ho to effectively deal with the large amount of copper and cobalt containing waste water has brought great problem to people.The discharge of wastewater with copper and cobalt not only causes serious environmental damage but also wastes a lot of heavy metal resources.Copper and cobalt have the similar chemical properties and they are often born in the mineral deposits.Traditional treatment methods are hard to remove and separate them from waste water.With the depletion of copper and cobalt resources in China,finding out methods to remove and recover heavy metal resources has become a new challenge to people.In this work,PEI-grafted membrane was used to selectively adsorb Cu?II?and Co?II?from waste water based on the different adsorption capacity and the competitive adsorption mechanism.The selective adsorption capacity,membrane regeneration ability with in-suit electro field regeneration and the recovery of heavy metal ion were investigated.These attempts are expected to promote the development of membrane-like adsorbents used in waste water treatment.First,polyethyleneimine?PEI?was immobilized on microfiltration membrane to prepare PEI-modified membranes after the poly?levodopa??PDOPA?pre-coating.The effects of factors such as operating pressure,pH value of solution and the doping of inorganic salt were studied to conform the different adsorption capacity of PEI-grafted membrane to copper and cobalt waste water respectively.the Water purification ability of PEI-grafted membrane on copper and cobalt ions is up to 180 L/m² and 45 L/m² at pH=5,0.02 MPa,respectively.Based on the obvious difference in Single component processing system,the adsorption selectivity of PEI-modified membranes on copper and cobalt ions in the copper-cobalt mixed wastewater was further investigated by dynamic adsorption process.The influence of processing water flux,pH value and the initial concentration ratio of components to the competitive adsorption were studied.Under optimized conditions,when the treated water flux is 3 m³?m^-2h^-1,and the initial concentration of copper and cobalt ions are both 3 mg/L,each modified membrane can deal with simulated wastewater up to 1160 m L with the selective separation ratio of?Cu?II?/Co?II?=147.Finally,the membrane-like adsorbents were regenerated by in-suit electric field regeneration process.The chelated target metal ion can be peeled off from the membrane with a strong enough electric field force,and then deposited onto the cathode.The effects of the electrolyte pH,the plate voltage,the plate spacing and electric field intensity were studied.Under optimized conditions,the regeneration efficiency can still be maintained above 70%even after10 cycles of regeneration.And the concentration of cobalt ions didn't increase with the regeneration times increase,finally staying around 2.8 mg/L,indicating that the desorbed Co?II?was deposited on the cathode.The results showed that the membrane adsorption coupling with in-situ electric field regeneration can treat copper and cobalt ions in wastewater effectively and recover copper and cobalt resources simultaneously.