Study On Application Of Carboxylic Acid Scale Inhibitor In Reverse Osmosis Membrane Water Treatment

The reverse osmosis membrane method plays an important role in the industrial circulating cooling water treatment process.The supplemental water obtained by treating the circulating cooling water by reverse osmosis technology meets the water quality and water saving requirements.However,the problem of scale adhesion during operation is still a bottleneck restricting its development.Such phenomena lead to a rapid decline in reverse osmosis performance,affecting the efficiency and sustainability of membrane operation.In the process of circulating water treatment,a scale inhibitor suitable for the water quality condition of the reverse osmosis membrane water treatment system is added to achieve the purpose of controlling scale formation.Therefore,the development of high-efficiency,non-polluting reverse osmosis membrane scale inhibitor has important practical application value in the experimental research of reverse osmosis technology to treat circulating water.According to the principle of green chemistry,selecting a dicarboxylic acid-itaconic acid?IA?with five carbons,and hydroxyethyl methacrylate?HEMA?,2-acrylamide-2-methylpropanesulfonic acid?AMPS?as a comonomer.Using aqueous solution as the reaction mechanism,tert-butanol as molecular weight regulator and potassium persulfate as initiator,a novel terpolymer IA-HEMA-AMPS was synthesized by free radical polymerization.Through single factor experiments and orthogonal experiments,the conditions of the polymerization reaction are optimized to achieve high performance,low energy consumption and no waste of the reaction process.The optimized synthesis conditions are:n?HEMA/IA?=1:1,n?HEMA/AMPS?=1:1,the amount of initiator is 6%of the total amount of monomers,the initiation temperature is 80?,The reaction time?dropping time and holding time?are 2h and 2.5h respectively,and the copolymer IA-HEMA-AMPS synthesized under the above optimized conditions had good scale inhibition performance.The gel chromatogram shows that the molecular weight of the copolymer exhibits a normal distribution tendency and belongs to a polymer having a narrow molecular weight distribution.The infrared spectrum confirmed that the structure of the copolymer contained a large amount of functional groups such as a sulfonic acid group,an ester group,a hydroxyl group,and an amide group in addition to the carboxylic acid group,and the ratio of the sulfonic acid group to the carboxylic acid group was equivalent.Static and dynamic scale inhibition experiments show that the copolymer effectively inhibits the formation of calcium scale.adding 5 mg/L copolymer respectively to the calcium ion concentration of 120³800mg/L,bicarbonate mass concentration of 146¹500mg/L,and the sulfate concentration is 3600⁹000 mg/L of experimental water.The results show that the scale inhibition efficiency of the copolymer can reach more than 90%,and the performance is good.Moreover,the copolymer can be applied to circulating water quality of high temperature,medium and high hardness,medium and high alkalinity,and high SO₄^2-concentration.When the 5 mg/L copolymer was added,the iron oxide transmittance was 43.1%.,indicating that the copolymer has a certain ability to disperse iron oxide.According to the international standard OECD301B,The copolymer was determined to have reached a standard of biodegradability within 28 days.which was biodegradable.Comparing it with the commercially available scale inhibitors,all of them show certain advantages and have good prospects for popularization and application.The copolymer IA-HEMA-AMPS and high-purity polyaluminum chloride were simultaneously placed in the low-temperature water to determine the compatibility of the copolymer with the flocculant in the reverse osmosis process pretreatment.The results show that the copolymer exhibits good compatibility in the water quality in which it coexists with the polyaluminum chloride.After adjusting the S-4800 electronic scanning microscope,and the generated calcium scale samples were scanned by electron microscopy.The scale inhibition mechanism was analyzed:various functional groups in the copolymer act on the crystal surface,disturbing the normal arrangement and orientation of crystals,and deform the calcium scale.Distorted the crystal lattice of calcium scale,inhibiting the normal growth of calcium scale.Simultaneously accelerate the reduction of the surface energy of the crystal,The crystal structure is broken,which reduces the tendency of flocculation to form scale,making it difficult to scale.This paper has a total of 35pictures,15 charts and 88 references.