Study On The Removal Of Copper Oxide Nanoparticles In Water By Enteromorpha Polysaccharides-polyaluminum Chloride

Copper oxide nanoparticles(CuO NPs)have been widely applied,but at the same time,they have caused serious heavy metal pollution to the environment.In addition,the complex of natural organic matter(NOM)and CuO NPs has led to the dual pollution of CuO NPs and copper ions in water.In recent years,the environmental pollution caused by the outbreak of Enteromorpha prolifera along the coast has made more and more experts focus on the resource treatment of Enteromorpha prolifera.Therefore,on the basis of the research status at home and abroad and the related literature,the resource utilization of Enteromorpha was carried out.The Enteromorpha polysaccharides(Ep)extracted from Enteromorpha prolifera was developed into a green and secure efficient coagulant aid,which was used with polyaluminium chloride(PACl)coagulant to coagulate copper oxide nanoparticles-humic acid(CuO NPs-HA)simulated water samples.The coagulation behavior and performance of PACl-Ep coagulation system were systematically studied.Meanwhile,the characteristics of flocs formed by PACl-Ep were studied in depth,and the coagulation mechanism of PACl-Ep was also explored based on the structure characterization of flocs formed by coagulation.Furthermore,due to the physical and chemical characteristics of CuO NPs,the migration and transformation of CuO NPs in water environment were also preliminarily explored.The main research contents and conclusions are as follows:1.There were three main forms of copper oxide nanoparticles in water:free ion state,suspended solid state and precipitation state.Its aggregation in water also included three parts:rapid growth,slow decline and stable equilibrium.Under different water conditions,the release of copper ions and the aggregation size of CuO NPs were different.In the presence of humic acid(HA)and at pH=4.78,the dissolved Cu2+concentration in water was higher,but the agglomerated particles were smaller.The distribution of CuO NPs in water and the dissolution of Cu2+ in different concentrations were also significantly different.2.Results showed that the simultaneous removal efficiencies of CuO NPs and Cu2+by PACl-Ep were higher,and the presence of HA was conducive to improving the stability of CuO NPs and bringing about better coagulation effect.The effect of different A1 species in PACl combined with Ep on the removal of CuO NPs was obviously different,and the pH value of water had a great influence on the coagulation effect.Among them,PAClb-Ep obtained the best removal effect for Cu2+ and CuO NPs,and PAClc-Ep had the highest removal efficiency for HA;PAClc-Ep was less affected by pH,and the coagulation effect was the most stable;when pH<6.0,the coagulation effect was the worst,and the removal effect of Cu was more obvious at the condition of pH?7.0.3.In terms of the floc properties,flocs formed in the presence of HA were smaller,but the strength and regeneration ability of floes became stronger;floes generated by PAClb and PAClc combined with Ep have higher strength and better recoverability,although smaller in size.When pH=9.0,floes were not only larger and stronger in shear resistance,but also more compact in structure than those produced at pH=5.0.However,the recovery ability of flocs after crushing is weaker than that under acidic conditions.4.Coagulation mechanisms of PACl-Ep in the treatment of CuO NPs-HA were investigated by infrared spectroscopy,scanning electron microscopy and solid-state 27Al NMR.Firstly,HA complexed with CuO NPs to form negatively charged colloidal particles.Secondly,PACl with positive charge was added into water and hydrolyzed to some extent;Ala and Alb combined with colloidal particles and destabilized them mainly by neutralization,Alc primarily trapped colloidal particles by solid precipitated A1 network to form smaller flocs.Finally,long-chain Ep was added as the coagulant aid,its hydroxyl,carboxyl and sulfonic groups adsorbed Al3+ and microflocs by bridging effect,to form the chelate network structure,and then forming larger and denser flocs to settle down.At the same time,the dissociate Cu2+ and other impurities in water would further be absorbed by the hydroxyl and carboxyl groups of Ep,which will be removed with flocs precipitation.