Resoucres Recovery By The Hybrid Technology Of Complexation-ceramic Membrane From Copper Wastewater

It is of difficulty in treating wastewater containing heavy metals due to its greathazard and fluidity, which leads to resources lost and harm to living environment of humans and other lives in the world. So the recycling technology of heavy metal wastewater has become a hot issue with a desperately lack of fresh water source and a more strict discharge criteria. The general treatment currently is coagulation and precipitate by simply transferring heavy metals out from the water, which cannot solve the problem essentially and achieve recycling and reuse. Meanwhile the discharging amount of wastewater containing low density heavy metals in many industries is comparativelylarge and the conventional treatment cannot meet the standard. The complexation-ceramic film coupling method, conforming to the concept of circular economy, can dispose the heavy metal wastewater and recycle the heavy metals effectively and economically. It has a positive significance to slow the lack of resource and reduce environmental pollution.The complexation-ceramic film coupling technology has been studied using ceramic film with200nm in pore diameter to treat low concentration copper wastewater. Theeffect of influencing factors are systematically discussed in the view of interception and dissociation characteristics of complexation, film contamination and cleaning and chelating agents reuse based on the mechanism of heavy metals removal using polyacrylic acid(PAA) and chitosan(CTS). Acidolysis is used to recycle the chelating agents andthe removal efficiency by recycled agents is investigated in the research.During the experiment, ultrafiltration is applied to determine the equilibrium constant in the reaction between PAA and chitosan-Cu2+complex and to illustrate the complexation-ceramic film coupling mechanism. Accordingly,10mg/L copper wastewater isused to investigate the effect of pH, mass concentration ratio of chelating agent andCu2+, agent density, ionic strength, operating pressure and volume concentration factor on coupling and the optimal processing condition is determined. The results of experiments indicate that pH is a key factor to a successful coupling process. The Cu2+interception rate reach100%when mass concentration ratio (PAA/Cu2+) and pH are5and5.8, respectively. When the mass concentration ratio（CTS/Cu2+）and pH rise to10and6individually, the Cu2+interception rate can also remain99.8%. In addition, monovalent salt (NaCl and Na2SO4) or bivalent salt (CaCl2) has a great effect on chelating efficiency of PAA, however, a little on chelating reaction of chitosan and Cu2+. Theincrease of volume concentration factor has no influence on treating process with a stable and high copper interception rate and no chelating agent waste.Additionally, chelation agent recycling through acidolysis and heavy metals enriching recovery technology are experimentally investigated. The results indicate that pH control can achieve the dissociation of metal complex and the recovery of chelating agents and targeted heavy metals by ceramic film. When pH is2and a full-flow filtering multiple is2.53, the recovery of PAA can reach78%. The recycled PAA can be reused for5times to treat the copper wastewater realizing a stable100%interception rate of Cu2+. When pH is1.25and the full-flow filtering multiple is2.7, the chitosanrecovery rate is64%. The recycled chitosan can be used for5times to treat the copper wastewater with a whole98.3%interception rate of Cu2+. There is no obvious lossof those two chelating agents and it is suggested that the times of reuse can be increased accordingly to improve the economic feasibility of the complexation-ceramic film coupling technology.The presence position, form and components of pollutants are analyzed and defined through film resistance calculation, SEM and EDX. The results indicate that the pollution of film ascribes to the deposition of PAA or chitosan and the cleaning agent like nitrogen acid and sodium hydroxide can easily restore the film.The whole experiment demonstrate that complexation-ceramic film coupling technology is a promising resource recycling way towards heavy metal wastewater which can achieve wastewater recycling and heavy metals recovery simultaneously.