Synthesis And Performance Study Of Several Novel Phosphorus-Free Multifunctional Water Treatment Agents

Water is of vital importance natural resource for human survival and development.In recent years,with the increase of population,the rapidly development of industry and the serious environmental pollution,the water crisis is growing.Circulating cooling water systems are normally used in industrial production in order to ensure the efficient operation of chemical equipment.However,continuous circulation and evaporation of the cooling water will inevitably lead to scale formation on the inner surface of the pipe,which will reduce the cooling efficiency of the circulating cooling water and adversely affect industrial production.In order to reduce inorganic calcium scale deposits,the addition of scale inhibitors is still the most popular and reliable method.As the national environmental protection efforts continue to increase,it can be expected that the development of novel non-phosphorus multifunctional water treatment agents has become a hot research topic.Based on the principle of free radical polymerization,in this paper,three novel water treatment agents of IA-AMPS,IA-AMPS-APEG and IA-AMPS-TA were successfully prepared using the monomers of itaconic acid（IA）,2-acrylamide-2-methylpropanesulfonic acid（AMPS）,polyethylene glycol monoallyl ether（APEG）and tannic acid（TA）.The chemical structure,molecular weight and thermal stability of the copolymer were characterized by fourier transform infrared spectroscopy（FTIR）,gel permeation chromatography（GPC）and thermogravimetric analysis（TGA）,respectively.The effects of synthesis and water conditions on the scale inhibition performance of the copolymer were investigated by static scale inhibition method.Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and X-ray diffraction（XRD）were employed to study the microscopic morphology and crystal structure of the scale deposits.In this paper,the effects of the reaction conditions on the scale inhibition performance and dispersion performance of the copolymer were systematically studied to obtain optimized synthesis conditions.Orthogonal experiments showed that the IA-AMPS copolymer had the excellent dispersion performance(51.10 mg·g^-1)in the following synthesis conditions:the molar ratio of IA to AMPS was 1:2,the amount of initiator was 7%of the total mass of the monomers,the ratio of ammonium persulfate to sodium hydrogen sulfite was 4:1,the reaction temperature was 95°C and the reaction time was 5h.Static scale inhibition experiments demonstrated that IA-AMPS-APEG copolymer had the largest scale inhibition efficiency in the following reaction conditions:the reaction time was 4h,the reaction temperature was 80°C,n（IA）:n（AMPS）:n（APEG）=1:2:0.33 and the amount of initiator was 4%of the total mass of the monomer.The maximum scale inhibition efficiencies of IA-AMPS-APEG copolymer for Ca CO₃ and Ca SO₄ scale deposits were 94.35%(24 mg·L^-1)and 85.69%(22 mg·L^-1),respectively.When the reaction time was 3.5h,the reaction temperature was 75°C,the amount of tannic acid added was 4g,and the amount of initiator was 5%of the total mass of the monomer,the IA-AMPS-TA copolymer had the excellent scale inhibition performance.With the test temperature raised,the basicity of the simulated cooling water increased,and the concentration of CO₃^2-/HCO₃^-enhanced,IA-AMPS-TA had poor scale inhibition performance.TGA analysis proved that the significant thermal degradation of IA-AMPS,IA-AMPS-APEG and IA-AMPS-TA copolymers occurred at 345℃,299℃and 220℃,respectively,which demonstrated that the copolymer had outstanding temperature resistance.Characterization of the inorganic calcium scale deposits indicated that the copolymer significantly destroyed the surface morphology and crystal structure of the scale deposits.Simultaneously,the coal water slurry prepared by using the additive of IA-AMPS-APEG had high concentration,low viscosity and good stability.In addition,the interaction between the IA-AMPS copolymer and the Ca CO₃/Ca SO₄ scale crystal was calculated by molecular dynamics（MD）simulation.The results revealed that the binding energy of IA-AMPS to the calcite crystal（11 0）surface was larger than that of the（104）surface.And the binding energy of IA-AMPS to the surfaces of the anhydrite crystals（001）and（010）was almost equal.Greater binding energy facilitated the interaction of the copolymer with the calcium scale deposits.Therefore,the IA-AMPS copolymer had better scale inhibition performance against Ca CO₃ scale deposits.The three novel water treatment agents prepared in this study will have a bright application prospect in controlling the formation of inorganic calcium scale deposits,which is about to have potential and strategic implications for water conservation and energy efficiency.