| The heavy metal pollution became more and more aggravated with the extensive use of nano-heavy metal materials.The environmental hazards of nZnO a new heavy metal pollution source have been confirmed.The problems of water pollution caused by NOM and water eutrophication are still continuing.In recent years,the problems of outbreak of marine algae and the secondary pollution can't be ignored.The traditional coagulation process still has an indispensable position in the water treatment.Under this background,coagulation was used in simultaneous removal of heavy metal ions and NPs,which was a new exploration and attempt.At the same time,DOC removal in NPs-HA complex system and floc characteristics during coagulation process were studied.The main point of this project is to use of marine waste resource to treat heavymetal pollution,and Ep was extracted from dried Enteromorpha to develop a new effective coagulant-aid,which was used with PAC for pollution treatment.The physical and chemical behavior such as diffusion,agglomeration,precipitation and release of ions of nZnO in water environment were systematically studied.The transportation behavior of nZnO was studied.In addition,the structural characteristics of Ep were studied and identified with the advanced characterization technique,and the molecular model of Ep was constructed.Coagulation efficiency of removal of NPs and heavy metal ions with PAC-Ep,floc characteristics and the coupling mechanism were studied in this paper.Main research contents and the conclusions are summarized as follows:(1)There are three kinds of nZnO state such as compacted sediment,suspended and released,accounting for 36.54%,40.61%and 22.86%respectively.This study is to provide theoretical basis for the subsequent study of the mechanism of simultaneous removal of NPs and ions.And the ion release rate of nZnO in water was 22.86%.The distribution of NPs with different concentrations in water will also be quite different.(2)PAC-Ep was efficient in removing nZnO and Zn2+,which leads to more than 95%particles,50-60%NOM removed and 35%of resolved heavy metal ion adsorbing-chelation.And the treatment efficiency of PAC-Ep is different with different pollutant existence system.(3)Ep is a green and efficient coagulant-aid.The results in coagulation kinetics showed that the coagulation efficiency could greatly enhance with the use of Ep.And the floc characteristics could be improved due to Ep addition.Flocs generated by PAC-Ep had bigger size and faster growth rate.Higher recovery ability was also shown.At the same time,the floc structure formed by PAC-Ep coagulant is looser than floc formed by PAC.(4)The structure of Ep was discussed in this paper.And Ep was formed by rhamnose,xylose,arabinose and glucuronic acid.The molecular structure model was constructed.Long chain was rich in functional groups with high electron density,such as-OH,-COOH,-SO3H.It effectively enhanced the bridging ability and the adsorption effect of unsaturated functional groups on the ions and floes.Therefore,the use of Ep in the coagulation process will greatly improve the efficiency.The development and application of Ep can also solve the environmental problems of marine algae solid waste pollution,and make marine solid waste to resource utilization.(5)The main mechanism of PAC-Ep dual-coagulation was confirmed:Firstly,Al3+charge neutralization to negatively charge which leads colloids to destabilize coagulation;amorphcous hydroxide precipitate and hydroxy aluminium hydroxyl bridging formed polynuclear hydroxy complexes bridge and sweep colloidal particles;Secondly,Ep chain which contains-OH,-SO3H and other groups with high-density of electrons played the role of adsorption and bridging.With strong complexation of-OH,heavy metal ions were easily captured,and formed parts of the floc settling down.It was confirmed that there was a coupling relationship between NPs and NOM,or PAC and Ep.When PAC was used as coagulant,the removal rate of heavy metal ions was almost zero.Compared with PAC,the treating efficiency of PAC-Ep coagulant was higher.PAC-Ep coagulation can be used for simultaneous removal of NPs and heavy metal ions.NOM in the water plays an active role in removal of NPs,and the presence of NPs also has a synergistic effect on the removal of NOM. |
PDF Full Text Request