| Heavy metals are typical persistent pollutants, which have toxic effect long-term andsustainability, bioaccumulation, non-degradable characteristics and so on．In recent years, with the rapid development of metallurgy, papermaking and electroplating technology, theemission of wastewater which have heavy metals was increased．Soil, air, water, and eventhe drinking water was contaminated．In addition, the requirements toward heavy metalwastewater discharge standards are also increasingly strict, the topic on the heavy metalpollution are rapid warming, and how to remove heavy metals effectively and recycle thembecome a hot subject nowadays．After years of research, chemical, physical and biologicalmethod are considered as the primary approaches treated wastewater which have heavymetals．These techniques and methods can remove the heavy metals, while they are alsoshortcomings of high cost, flocculent scraps instability, easy to cause secondary pollution, difficult to recover heavy metals etc．However, coagulation is an important operation unit inthe water treatment．Its process of removing is simple, operation is easy, etc．So it is a viabletechnology for treating this kind of wastewater．With chitosan(CTS), L-cysteine(L-CySH) as the raw materials, catalyzed in the activatorcarbodiimide hydrochloride(EDC·HCl), the strong coordination group sulfydryl of trappingheavy metal are grafted in the molecular chain of chitosan by way of amidation reaction, anovel macromolecular heavy metal flocculant-2-Amino-3-mercapto-propionyl chitosan(MCC)which traps heavy metals was prepared．It can improve the solubility of chitosan, reduce the solubility of these complexes, increase the coordination and chelation ability of theflocculant, besides the polymer chains of chitosan provides powerful absorption and bridgeconditions, the aggregation and sedimentation function of flocs are enhanced, with the resultthat, the containing sulfur macromolecule flocculant MCC can play the dual role of chelatingprecipitation and flocculating sedimentation, so that it make the wastewater which have heavymetal are treated easily．Using the copper and cadmium ions-containing wastewater samples as the processingtarget, the optimum preparation condition of MCC through orthogonal experiment wasobtained, the flocculation performance which remove the heavy metals copper ions andcadmium ions were also investigated totally, and the morphology of flocs were also observedand analyzed, the fractal dimension of the flocs were also calculated．In view of the type andnature of the general heavy metals wastewater containing metal ions, coordination ions, organic complexing agents, the sodium ion；potassium ion；calcium ion；magnesian ion；aluminium ion and iron ion and other metal ions, inorganic ligands such as chloridion；nitrate ion；fluorinion and sulfate ions as well as the citric acid；EDTA；glycine；humic acid；sodiumpyrophosphate and other organic complexing agents were choosed as the object, the influenceof them on the flocculation performance of the noval MCC were studied, in the coexistsystem of turbidity and heavy metals wastewater, the removal of heavy metals and turbiditywere also discussed, the results showed that：the optimum MCC had double function ofremoving turbidity and trapping metal ions, flocs was less；sedimentation velocity was morerapid；treated water quality was better；heavy metal recovery rate was higher, and residue wasstable, not easy to cause secondary pollution．From the other side, the fractal dimensionreflects the aggregation characteristics of the flocs particles which were formed in differentconditions, the outcome showed the regularity that the more interstices were, the less thefractal dimension of flocs were, the better removal efficiency of heavy metalswere．Wastewater containing metal ions, inorganic ligands, organic complexing agent wouldaffect the removal of heavy metals in the wastewater, or to promote or inhibit；themorphology and fractal dimension of flocs have diversity in the different conditions．... |
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