Study On The Proparation Of The Macromolecular Flocculant Mercaptoacety Chitosan Via Trapping Heavy Metal Ions And Its Performancde Of Flocculation

The issue is on the basis of previous studies, with chitosan, mercaptoacetic acid as raw materials, make the strong coordination group-sulfydryl (-SH) of heavy metal ion be grafted onto natural polymer flocculant chitosan (CTS) by amidation reaction, and give its trapping function of heavy metal ions, which developed a new kind of flocculant-mercaptoacetyl chitosan(MAC) having trapping heavy metal ions and removing turbidity dual function. Use of polymer flocculants MAC in existing coagulation equipment can reduce turbidity as well as removing heavy metal ions, thereby The following process unit can be omitted, which make the heavy metal wastewater treatment become easy.In this paper, the performance of new type of polymer flocculant MAC was studied in trapping various heavy metal ions and removing turbidity, the factors influencing the flocculation such as pH, organic complexing agent, and turbidity, etc.are also discussed, the results showed that:1) MAC has good capabilities to trap heavy metal ions, but the degree of deacetylation and molecular weight of CTS influence the flocculation, when molecular weight and the degree of deacetylation are higher, the removal of f ions is better.2) It can achieve good results when using MAC to treat wastewater with Cd2+, Hg2+, Cu2+ floc settling quickly, large and compact, easy to solid-liquid separation, good effluent quality, however, when dealing with wastewater containing Cr6+, in order to make the removal of total chromium achieve better results, MAC needs to associate with inorganic aluminum compound.3) PH has a certain influence on the heavy metal wastewater treatment by MAC, at higher pH, less MAC can have a high removal rate of heavy metal ions, but at lower pH, only increasing MAC can achieve good results.4) When there are alkali metal ions, NO3-, SO42-, organic complexing agents (such as citric acid, fulvic acid, EDTA and humic acid) in waste water, it has different influences on the removal of heavy metal irons by MAC, or to promote or inhibit, using the facilitation to promote the removal rate of heavy metal ions, while increasing the dosage of MAC to reduce or eliminate the inhibition.5) MAC have trapping heavy metal ions and removing turbidity dual function, when using MAC to remove heavy metal ions and turbidity of the same system, the heavy metal ions and turbidity of the wastewater can all be well removed.6) Compared with CTS, the water-solublility and the ability to remove heavy metal ions of MAC have been greatly improved, particularly in the system with heavy metal ions and turbidity at the same time, the removal efficiencies of heavy metal ions and turbidity are all higher than CTS.7) MAC show a certain selectivity when trapping various heavy metal ions, and the order of its chelating ability for heavy metal ions shows that:when the pH value is 7.5, the order of MAC capturing heavy metal ions is Hg2+> Cd2+>Cu2+, so when there are various heavy metal ions in wastewater, separating them by the different strength in chelation with MAC, then they can be removed separately.8) Use of MAC in actual electroplating wastewater, without adjust pH, and adding a reducing agent, the method is simple and has good effect, so there is great social and economic benefits in practice, and also certain worthy of extending to popular use.