The Treatments Of Copper(?) Wastewaters With The Adsorption Of The Grafted Polypropylene Nonwoven Fabrics And Electrodeionization

Electroplating effluents are currently one of the major industrial pollutants in the world.Adsorption by functional polymer materials is the simple but effective method for removing heavy metal ions from wastewaters,while the electrochemical desorption of those metal-adsorbed polymer materials can effectively recover metal ions.Electrodeionization(EDI)consists of electrodialysis and ion exchange process and can be used to remove the heavy metal ions from the low metal ion-containing wastewaters.It does not cause secondary pollution and shows wide application prospects.In this thesis,the grafted polypropylene fabrics were used to treat the heavily contaminated copper(?)wastewaters,and then the secondary copper(?)wastewaters were treated by EDI.The combination application of adsorption and electrodeionization for the heavily contaminated wastewaters showed practical and feasible.Firstly,styrene and acrylic acid were grafted onto the polypropylene nonwoven fabrics and further sulfonated by sulfuric acid,resulting in(PP-g-(SPS-co-PAA));Secondly,the adsorption of simulated copper(?)electroplating wastewaters and the reusability via a route of electrochemical desorption of the grafted and sulfonated polypropylene nonwoven fabrics were investigated.Finally,the treatment effectiveness of highly concentrated copper(?)wastewaters with the adsorption-electrodeionization(AS-EDI)and electrodialysis-electrodeionization(ED-EDI)techniques were compared in the aspects of the conductivity,p H,content of copper ion and current of the device with time.Among them,the electrochemical adsorption and desorption processes were mainly studied.The microstructure and properties of the raw and modified polypropylene nonwovens,ion exchange membranes and resins were characterized with scanning electron microscopy,infrared resonance and thermal analysis.The following conclusions are shown:(1)A little of pure PS was grafted on the surface of the PP fiber.The cografts of PSand PAA uniformly covered on the PP surface and tended to penetrate into the interior of the fabric.The grafting copolymerization of acrylic acid effectively increased the grafting rate and improved the sulfonation of polystyrene chain segments.The addition of an oily crosslinker made the fabric soft,but the resultant grafted material easily peeled off and the grafting rate was significantly reduced.(2)The 10 repetition adsorption rate of PP-g-(SPS-co-PAA)fabrics was all over 88%,and the adsorption capacity maintained above 140 mg/g.Ten-time repetition electrochemical desorption confirmed the reusability of the ion exchange fabrics.(3)While the copper(?)ions were electrochemically adsorbed,monovalent cations such as sodium or hydrogen ions were released at the same time and thus the electric current would increase.Formation and escape of hydrogen and oxygen from the electrode surface resulted in a short-term current drop.Contrarily,while the copper(?)ions were electrochemically desorbed,monovalent sodium or hydrogen ions were also adsorbed and thus the current tended to be decreased.(4)As the distance between the anode and cathode plates increased,the electrolytic current decreased significantly.The closer distance between the two plates,the more fluctuation and suppression of the electrolytic current took place due to intensive bubbling of hydrogen and oxygen.(5)The adsorption and desorption rates,and current efficiency increased significantly with the increase of poly(acrylic acid)component in the grafted polypropylene nonwoven fabrics,PP-g-(SPS-co-PAA)at the ratio St to AA of one produced much more black precipitates than the other two.Cu SO4 as a desorption solution and 20 V as desorption voltage are good choice in practice.(6)The copper(?)concentration and the removal rate were 84.8mg/L and 91.52%respectively after the adsorption treatment of 1000mg/L copper sulfate solution with 99 pieces of PP-g-(SPS-co-PAA)fabrics(ca.1m2),while the average copper(?)concentration and the average removal rate were 102 mg/L and 89.8% after the electrodialysis lasting for 50 h.From the removal rate of high concentration copper ion wastewaters,adsorption method is superior to electrodialysis.(7)The AS-EDI combination mode promoted the work area of resins,and the peeled grafts indirectly increased the adsorption capacity,and thus enhanced the copper(?)removal rate.The ED-EDI combination mode presented plenty of black precipitates andthe resin aging in anion exchange compartment.Therefore,treatment effectiveness of heavy metal wastewaters with AS-EDI mode is slightly better.This following features and innovation of the thesis are drawn:(1)The features of the thesis lie in the simultaneous and detailed studies of electrochemical adsorption and desorption,which will provide theoretical and technical supports for rapid treatment of heavy metal ion wastewaters;AS-EDI and ED-EDI were applied to separate and purify the heavy metal ion wastewaters respectively.The copper ion removal effectiveness is better with AS-EDI mode.(2)The innovations of the thesis are the dual monomer grafting and successive sulfonation of polypropylene nonwovens,which has solved low degree of sulfonation of single styrene grafting at all.A system for the separation and purification of highly concentrated heavy metal ion wastewaters is established through first adsorption treatment of highly contaminated copper(?)wastewaters with the modified nonwoven fabrics and then the separation and purification of the secondary copper(?)wastewaters with EDI technique.