Preparation Of Macromolecule Heavy Metal Flocculant ISXA And Study On It's Performance

In this thesis, macromolecule heavy metal flocculant ISXA with double functions of both removing substance causing turbidity and heavy metal ions was synthesized by grafting some heavy metal ions ligand to graft copolymer flocculant of starch -acrylamide. Heavy metal ions and substance causing turbidity were removed simultaneously with macromolecule heavy metal flocculant ISXA and existing flocculation equipments which made the treatment of heavy metal wastewater much easier.The synthesis experiment was composed of the preparation of graft copolymer flocculant of starch -acrylamide and the preparation of macromolecule heavy metal flocculant ISXA. For the former, the influence of different conditions, including the concentration of reactor (NaOH, initiator and monomer), the molecular ratio of CS₂ to H₂O₂, the temperature and time for the polymerization, etc, on graft yield(G) and intrinsic viscosity([η]) were investigated. The result showed that: 1) The graft copolymerization of acrylamide onto alkaline maize starch was initiated using CS₂/H₂O₂ as initiator, the best concentration of NaOH was 0.15mol/L; 2) While the molecular ratio of CS₂ to H₂O₂ was 1.70, the value of G was the highest and the value of [η] was the lowest; 3) The more dosage of the initiator, the higher value of the G, but the tendency to the [η] was oppositional; 4) As the concentration of monomer became higher, the value of G and [η] became higher also; 5) The best temperature was 30℃for G, and the value of [η] became higher when the temperature was increased; 6) The longer of reaction time, the higher of the value of [η], when the time was around 30min, the value of G was above 90%, after 30min the increase rate of the value of G became slow.For the latter, the influence of different conditions, including the concentration of reactor (cross-linking agent, NaOH and CS₂), the temperature and time for the polymerization, etc, on the performance of removing Ni²⁺, and the production's stability were investigated. It was showed that: 1) The dosage of cross-linking agent affected the performance of ISXA, the degree of cross linking could not be too high and could not be too low; 2) The influence of the concentration of NaOH on reaction was more complex, so it should be controlled carefully when ISXA was synthesized; 3) The more dosage of CS₂, the higher value of sulphur content of ISXA, but the dosage of CS₂ should be calculated contact with that of NaOH; 4) The reaction temperature should be controlled below 30℃, if the temperature was too high, part of CS₂ would have lost because of its volatility; 5) After 2 hours, the reaction completed basically, it has litter effect to extend the reaction time; 6) Under the low temperature, the stability of ISXA was better.Using the graft copolymer flocculant of starch -acrylamide to remove turbidity, it could be seen that the remove rate of turbidity was above 97% using this flocculant together with 0.2mg/L Al₂(SO₄)₃, this effectiveness is clearly better than that using the two flocculants each only, and the dosage can be reduced a lot, only with the concentration of 2mg/L. But too large dosage would made the efficiency worse.Compared the macromolecule heavy metal flocculant ISXA with indissolvable starch xanthate (ISX), using them to remove turbidity and heavy metal ions, The result showed that: 1) Under various of conditions, the performance of removing turbidity of ISXA was superior to that of ISX; 2) Under various of conditions, the performance of removing Ni²⁺ and Cu²⁺ of ISXA was superior to that of ISX; 3) The dosage of ISXA, pH value, original turbidity and reaction time had influence on the result of treatment, so these factors should be controlled carefully when using ISXA to treat with heavy metal wastewater; 4) Treatment of wastewater containing heavy metal ions and substance causing turbidity with macromolecule heavy metal flocculant ISXA, heavy metal ions and substance causing turbidity promoted the removal of each other; 5) According to the mechanism of removing heavy metal ions, we could see ISXA could remove some other heavy metal ions also, the chelation between ISXA and heavy metal ions were different because of different character of each heavy metal ions, so heavy metals could be separated. 6) After the wastewater was treated with ISXA, the stability of the residue was well, so it could not result in secondary pollution.