Preparation And Properties Of Dithiocarboxyl Amino-methylated Polyacrylamide Used As Macromolecule Chelating–flocculant

Large amounts of heavy metal wastewater emission caused serious harm to the environment and human health,therefore,the management of heavy metal wastewater is imminent.In recent years,the emergence of chelating precipitation of heavy metal wastewater treatment can achieve good effect,and the preparation of high efficiency of heavy metal wastewater treatment is one of focal point of research in the method.In this paper,the existing flocculant(polyacrylamide)as the matrix,through the chemical synthesis method,polyacrylamide is aminomethylated at first,and then sulfur atom coordination group(disulfide carboxyl)is introduced into the polymer chain,a novel polymer chelate-flocculant,dithiocarboxylated amine methyl polyacrylamide(DTAPAM),which has a dual role in chelating precipitation and flocculation and sedimentation of heavy metal ions.Based on polyacrylamide(PAM),formaldehyde(experiment),dimethylamine(HN(CH3)2),sodium hydroxide(NaOH),carbon disulfide(CS2)as raw material,through the single factor experiment to determine DTAPAM,the six influence factors of preparation conditions and respectively by the orthogonal experiment method and response surface analysis to optimize the preparation conditions of DTAPAM.In the response surface analysis method,the main influencing factors of DTAPAM preparation conditions are first screened by Plackett-Burman experiment.Then,the experimental area is close to the optimal region of the response surface or in the optimal region by climbing experiment.And the center point of each influencing factor level is selected.Finally,the preparation of DTAPAM is optimized by the central composite design(CCD)commonly used in response surface analysis to determine the optimal preparation conditions.Structure analysis through the elementary analysis and infra-red analysis has shown that we have successfully inserted the Thio groups into APAM and analyzied the solution properties of DTAPAM such as solubility,stability of storage,Zeta potential and,etc.We have studied DTAPAM's capability to remove Ni(?),Cd(?)by analyzing fractal dimension influence of factors such as the initial concentration of Ni(?)?Cd(?),PH value of the reaction system,EDTA,DTAPAM-Ni(?)and DTAPAM-Cd(?),and also studied the stability of DTAPAM-Ni(?)and DTAPAM-Cd(?)as well as the recycling capability of Ni(?)?Cd(?).The following is our findings:(1)The influencing factors for the synthesis of DTAPAM identified by the single factor experiment is the concentration of APAM,mole ratio of APAM?CS2?NaOH,the pre-reaction temperature,the pre-response time,the main reaction temperature and the main reaction time.(2)The reaction conditions of APAM,mole ratio of APAM ? CS2 ? NaOH,the pre-reaction temperature,the pre-reaction time,the main reaction temperature and the mainreaction time are selected.The results showed that if the contents of Cu(?)and C(?)is different,the removal rate is different for the optimal combination conditions.(3)By Plackett-Burman experiment,the steepest climbing and CCD experiment,the optimal preparation conditions as follows: the APAM concentration is 2.7%,the molar ratio of APAM,CS2,NaOH is 1:2:1.4,the pre-reaction temperature is 23 ?,the pre-reaction time of 15 min,the main reaction temperature is 40 ? and the main reaction time is 90 min.(4)DTAPAM is insoluble in acetone,but soluble in methanol,anhydrous ethanol and distilled water.Infrared and elemental analysis showed that DTAPAM molecular chain is attached to the dithiocarboxylate successfully.The isoelectric point pH of the DTAPAM in distilled water is 7.1,while in tap water is 7.2.DTAPAM has a 30 days' stable preservation duration in ordinary temperature and dark condition.(5)It has been shown in the experiment that DTAPAM had the best capability to remove Cd(?)and Ni(?)when the PH value is 6.0.The removal rate is 98.87% and 91.16%.To sewage samples with different initial concentration of Cd(?)and Ni(?),DTAPAM had a satisfactory capability to remove Cd(?)and Ni(?)in them and there was a ideal dosing point which would increase with the increase of the initial concentration of Cd(?)and Ni(?)in the reaction system.When the dosing amount is beyond the ideal dosing point,the Cd(?)and Ni(?)remove capability of DTAPAM will become weaken.EDTA may inhibit the DTAPAM's capability to remove Cd(?)and Ni(?)and the inhibiting effect would become increasingly strong with the increase of its amount.Besides,turbidity maters in sewage in small concentration can facilitate DTAPAM's capability to remove Cd(?),otherwise inhibit DTAPAM's capability in big concentration.(6)The fractal dimension of DTAPAM-Ni(?),and DTAPAM-Cd(?)has an intimate relationship with their disposal capability.The greater the fractal dimension is,the stronger the capability is.(7)DTAPAM-Ni(?)and DTAPAM-Cd(?)is not easy to precipitate in alkaline conditions,which will not easily cause secondary pollution.DTAPAM-Ni(?)has a high recovery rate in nitric acid while DTAPAM-Cd(?)has a recovery rate in hydrochloric acid and nitric acid.