Modification Of (Poly) Acrylamide With Mercaptoacetyl And Their Performance For Removing Copper

Amide has a high react Ive activity in the molecular structure of(poly)acrylamide, and can be introduced new groups(such as the xanthogenate, thiosemicarbazide, etc.) into the molecular structure to prepare new types of water treatment agents. In this paper, a strong ligand of heavy metal ions—sulfhydryl(—SH) is introduced to the molecular chains of(poly) acrylamide to prepare two kinds of model flocculant by chemical reaction. The two novel flocculants, called thiol-acetylated polyacrylamide(MAPAM) and poly-thiol-acetylated acrylamide(PMAAM), can be directly applied to the treatment of heavy metal waste water becausethey have dual function of chelating and flocculation.In this paper,(poly) acrylamide and thioglycolic acid are used to synthesize the MAPAM and PMAAM flocculants. The single factor experiments are employed for determinating the level of factors which influences the MAPAM and PMAAM. And the preparation conditions are optimized by orthogonal experiments and response surface experiments, and then the two kinds of the optimum conditions for the preparation are obtained. Finally, the structures of MAPAM and PMAAM are characterized by elemental analysis and infrared analysis, and the solution properties and storage stability of MAPAM and PMAAM are also studied. Furthermore, considering Cu(II) water samples as the object to study, the MAPAM and PMAAM performances for removal of turbidity and heavy metal ions(Cu(II)) are mainly investigated by flocculation experiments. The influencing factors, such as Cu(II) initial concentration, pH of water sample, coexisting cations, coexisting anions, organic complexing agents, coexisting turbidity, etc., was discussed in this paper. The morphological property and thestability about flocs, and the recycle ability of heavy metal are also discussed.The main research results are summarized as follows:(1) On the basis of single factor experiments, using theorthogonal experiments and response surface experiments are optimizedthe preparation conditionsof MAPAM in the level of factors. Theoptimum conditions for the preparation of MAPAM are as the molecular weight of PAM is 250,000,the concentration of PAM is 1%, the moore ratio of reagents TGA and PAM is 3.2:1, pH value is 3.6, and the reaction temperature is 25? and the reaction time is 2.1h.(2) On the basis of single factor experiments, using theorthogonal experiments and response surface experiments are to optimizedthe preparation conditions of PMAAM in the level of factors. The optimum conditions for the preparation are as follows :(1) Thiol conditions: the concentration of AM is 1%, the moore ratio of reagents TGA and AM is 4:1, pH value is 3.0, the reaction temperature is 30? and the reaction time is 1.5h;(2)Conditions of polymerization: the amount of ammonium sulfate is 38 mg, sodium formate dosage is 75 mg, the polymerization temperature is 70? and the polymerization time is 2.0h.(3) MAPAM and PMAAM are anionic flocculants, whose Zeta potential is negative in distilled water and tap water, and its absolute value of Zeta potential of MAPAM and PMAAM in distilled water is lower than the absolute value of Zeta potential in tap water.MAPAM's stability is so well that can be stored about 40 d under the condition of low temperature 4?; while PMAAM's stability is relatively poor, which only can be stored about 30 d.(4) MAPAM and PMAAM have a better removal performance on Cu(II), and are less dependent on the pH in system. The performance of MAPAM and PMAAM removing Cu(II) are affected certainly by the coexistence of inorganic cations, inorganic anions, organic coordination agent. The EDTA's effect(inhibition) is extremely significant, other interference factors influence degree(inhibition or promotion effect) is insignificant.(5) The existence of the substances causing turbidity rarely affected the performance of MAPAM and PMAAM removal of Cu(II). Hower, the flocs, which is the formation of MAPAM or PMAAM Cu(II) by chelate reaction, can effectively removal of the water turbidity during the settlement by bridging netting mechanism. PMAAM and MAPAM have good removal effect on different initial concentrations of the water containing Cu(II), and the optimal dosage increases with the increase of the initial concentration of Cu(II) increased,which showed a stoichiometric relationship.(6) Infrared spectroscopy and elemental analysis demonstrated that the MAPAM and PMAAM molecular structures are successfully connected to the thiol groups, which can be reacted with Cu(II) in water samples to generate the flocs of MAPAM-Cu(II) and PMAAM-Cu(II). The fractal dimensions of MAPAM-Cu(II) and PMAAM-Cu(II) are showed that the compact structure is increased with the fractal dimension, the fractal dimensions of chelating flocs are higher, the more compact of the structure and the better effect of the precipitation.(7) The stability of MAPAM-Cu(II) and PMAAM-Cu(II) are poor, and the flocculation should be recovered and treated, otherwise they will produce pollution. The recovery rate of MAPAM-Cu(II) in HNO3, HCl, H2SO4 is higher, which can be recovered by HNO3, HCl or H2SO4. The recovery rate of PMAAM-Cu(II) in H2SO4 and HNO3 is high that can be recovered by H2SO4 or HNO3.In summary, the chelating flocculants of MAPAM and PMAAM, which are prepared by the dual optimization of orthogonal experiments and response surface experiments, have a good performance on trapping Cu(II), and can also as a water treatment agent with excellent properties. It will play an important role in the treatment of heavy metal pollution.