Abstract
Calcium sulfate scale is a typical deposit on the equipment pieces or pipes of an industrial water system. Scale inhibitors could obviously reduce the precipitation of calcium sulfate crystal. The development and research of late-model environmentally friendly polymer inhibitors are often urgent problems to be addressed. A water-soluble poly(ethylenediaminetetraacetic acid-diethanolamine) (PEDTA-DEA) was successfully synthesized by thermal polycondensation of ethylenediaminetetraacetic acid (EDTA) with diethanolamine (DEA). The polymer product was characterized by Fourier infrared spectrum (FTIR) and the molecular weight was measured by gel chromatography, which confirms the polymerization of the two monomers. The inhibition effect of the polymer against calcium sulfate deposition was studied by static scale inhibition tests. When the Ca2+ concentration is 3000 mg/L, and the dosage of the polymer inhibitor is 10 mg/L, the inhibition effect exceeds 90%. The results show that PEDTA-DEA can inhibit the precipitation of calcium sulfate and reduce the deposition of calcium sulfate scale. The precipitate of calcium sulfate collected from the static scale inhibition test solution was analyzed by FTIR, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results revealed that the addition of the polymer significantly changes the calcium sulfate crystal’s growth shape. Therefore, PEDTA-DEA is a potential calcium sulfate precipitation inhibitor for the industrial water system.
Highlights
Water is often used as the heated fluid in the industrial water system because of its large specific heat capacity [1,2,3]
It is necessary to reduce the deposition of calcium sulfate scale in the industrial water system
The typical synthesis process is stated as follows. 2.92 g ethylenediaminetetraacetic acid (EDTA) and 1.0 mL DEA were placed in a three-neck, round-bottom flask with a 1:1 molar ratio, with 10 mL of N,N-dimethylformamide as solvent, and 5 mL phosphoric acid as catalyst dropped into the round-bottom flask
Summary
Water is often used as the heated fluid in the industrial water system because of its large specific heat capacity [1,2,3]. Due to the evaporation of water, scaling ions, such as calcium and magnesium ions, combine with carbonate or sulfate ions [4,5] and form a low-soluble scale precipitating on the surface of equipment pieces and pipes. The equipment pieces and pipes become severely corroded and blocked by calcium scale and may even burst [6,7]. Calcium carbonate scale can be removed by acid treatment, but once calcium sulfate is formed, removal becomes difficult [8,9]. It is necessary to reduce the deposition of calcium sulfate scale in the industrial water system. Using a scale inhibitor is one of the most effective and straightforward methods [10]
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