Synthesis Of Amino Acid Copolymer And Its Complexing Ability With Metal Ions

In recent years,due to the increasingly serious water crisis,the water source of make-up water is gradually replaced by reclaimed water in the industrial circulating cooling water system.To a certain extent,the measures ease the water shortage situation.The fouling of recirculating cooling system causes by reclaimed water,as well as sewage effluent pollution has become increasingly serious environmental problems.Therefore,it is necessary to synthesize an efficient and environmentally friendly water treatment agent.In this paper,a novel water treatment agent has been synthesized by the modification of polyaspartic acid to solve the problems in the system.Firstly,aspartic acid-malic acid copolymer?PAMA?was synthesized from aspartic acid and malic acid by microwave heating.The yield of intermediate products and the scale inhibition performance of the products were investigated under different conditions?raw material ratio,catalyst type,catalyst amount,organic solvent type,organic solvent amount,microwave power and time?.The optimum synthesis conditions were obtained: KH2PO4 was used as catalyst,N-N-dimethylformamide was used as organic solvents,the molar ratio of Asp/?Asp+CA?is 0.5,Cat/?Asp+MA?is 0.10,V?DMF?is 6 ml,microwave power is 1000 w and time is 3.5min.The yield of the synthesized copolymer reached 98.91%,and the complexed amount reached 500mg/g.The product was analyzed by FTIR and NMR.The results showed that the product was aspartic acid-malic acid copolymer.Secondly,the biodegradability of aspartic acid-malic acid copolymer was studied.The results showed that the higher the molecular weight,the lower the biodegradability of the copolymer.On the contrary,with the increase of malic acid content,the degradation rate of PAMA increased gradually.The addition of Al³⁺ and Mn²⁺ had no negative effect on the biodegradability of PAMA,and the biodegradability of PAMA was enhanced in the presence of Mn²⁺.Addition of Zn²⁺ and Cu²⁺ had a negative effect on the biodegradability of PAMA,and the negative effect of Cu²⁺ was the most serious.The degradation effect of PAMA was worse than that of the two monomers.The biodegradability of PAMA was better than ATMP and HEDP performance,but it was worse than the performance of PASP and PBTCA.Then,the scale inhibition of aspartic acid-malic acid copolymer was studied.The influences of the scale dosage,pH value,metal ion concentration,constant temperature and constant temperature time on Ca CO₃ and CaSO4 scale were studied.The results showed that PAMA was suitable for the cooling water system with high temperature and long residence time of water.The complexation performance of PAMA decreased with the addition of metal ions in the solution.After the metal ions were above a certain concentration,the complexation performance was almost completely lost.Therefore,we should strictly controll the content of metal ions in the circulating cooling system.Finally,the inhibition mechanism of aspartic acid-malic acid copolymer was studied by XRD and SEM.The results showed that the crystal structure changed from calcite to vaterite after adding PAMA,and the crystalline form changed from regular hexahedron to irregular loose structure.