PEI-grafted Membranes For Separating Co²⁺?Mn²⁺ And Suspended Particles In PTA Waste Water

Pure terephthalic aicd(PTA)is a type of important chemical product and could be used to various production fields,including polyester fiber,beverage bottles etc.In 2015,China PTA production capacity amout to 39 million tons/year,bringing 3-4 ton wastewater per ton PTA that come with it.The wastewater is consist of organic acids,suspended particles and heavy metals such as Co2+,Mn2+.At present,the PTA wastewater is usually discharged directly after biochemical treatment,ignoring the removal of Co2+,Mn2+heavy metal ions and suspended particles.The direct emissions of wastewater which contains organic solids particles and Co2+,Mn2+ heavy metal ions not only result in waste of resources,but also can cause serious damage to the natural environment and human health.This article present and prepare a affinity membrane which chose polyethyleneimine(PEI)as functional group.The membrane either possesses excellent properties including stable chemical structure,high specific surface area and good permeability or can simultaneously remove heavy metals ion and suspended particles from wastewaters.In this work,polycaprolactam(PA-6)membrane was first surface-modfied by a active layer of PDOPA,and then macromolecules PEI was immobilized onto the PDOPA-coated PA-6 membrane,followed by Glutaraldehyde cross-linking.The preparation conditions of the modified membrane were optimized,under optimized DOPA concentration and coating time(4g/L,6h),the coating amount of PDOPA could be up to 50 mg/g,under optimized PEI concentration and coating time(4g/L,8h),the grafting amount of PEI could be up to 220mg/g.In this paper,the adsorption properties of PEI-grafted membrane on Co2+,Mn2+ under dynamic and static adsorption were studied,and it showed that the dynamic saturated adsorption amount of PEI-grafted membranes on Co2+,Mn2+ were respectively 49 mg/g and18.2 mg/g which were more than the static saturated adsorption capacity.In addition,dynamic adsorption can dramatically shorten the period of wastewater treatment compared with the static adsorption.Emphatically studied dynamic adsorption in this paper,represented by the Co2+,studied the water flux,pH value,inorganic salt type and concentration on the influence of the modified membrane dynamic adsorption performance,and also examined the regeneration performance of the modified membrane.Experiment results showed PEI grafted membranes behaved excellently with Co2+dynamic adsorption from wastewater.In details,the modified membranes successfully removed Co2+under high water flux(850 L/m2·h,?P =0.02 MPa),and wide pH range(pH?6).Besides,the modified membranes possess remarkable anti-ion interference and renewability with the renewable degree about 95% even after ten cycles.PTA wastewater usually contained suspended particles except heavy metal ions.With calcium alginate(CA)microspheres(with an average particle size of 550 nm)as a simulation suspended particles,experiment investigated anti-fouling and simultaneously separating heavy metal ions and suspended particles performance of PEI-grafted membranes.Experimental results indicated that the rejection of the modified membrane on suspended particles in wastewater could reach to 99.5% when the adsorption performence of metal ions is essentially constant.Besides,PEI-grafted membranes had good anti-pollution performance.