| Scale inhibitors are the water treatment chemicals commonly used in circulating water system. Due to the excellent scale inhibition performance and a series of unique property, such as less dosage, low (no) pollution as well as good good collaboration and threshold effects, water-soluble polymer inhibitors has been widely applied in circulating water system. The concentration of polymer inhibitors in circulating water is of critical importance for the normal operation of system. Subsequently it is in high need to monitor the concentration of polymer inhibitors timely and accurately in order to obtain both economy and scale inhibiting benefits.Turbidimetric method is estabished to determine the concentration of polymer inhibiotrs in circulating water, which based on the formation of turbility between polymer inhibiotrs and dodecyl dimethyl benzyl ammonium chloride (1227) with the turbility being measured via spectrophotometer in visible light region. Factors thar effect the extent of reaction, such as the dosage of 1227, pH value and stabilization time were studied to obtain the optimal experimental conditions. At the same time influences coming from the existence of other substances were also discussed as well as the elimination of their effects. The major conclusion are as follows:(1) Within certain concentration range, better linear relationships between absorbance and the concentration of polymer inhibitors were observed.(2) The optimum determination conditions of various polymer scale inhibitor are as follows:The optimal experimental conditions of polyacrylic acid (PAA):1227 concentration of 250 mg/L, pH range of 8-9 and measurement of the absorbance at 410 nm after placing 30 min. The optimal experimental conditions of polyepoxysuccinic acid (PESA):1227 concentration of 250 mg/L, pH range of 9-10 and measurement of the absorbance at 420 nm after placing 30 min. The optimal experimental conditions of carboxylate-sulfonate-noniobic terpolymer TH-3100:1227 concentration of 211 mg/L, pH value approximately equal to 5 and measurement of the absorbance at 520 nm after placing 35 min. The optimal experimental conditions of modified sodium polyacrylate TH-2000:1227 concentration of 280 mg/L, pH value approximately equal to 5 and measurement of the absorbance at 570 nm after placing 35 min. Also the optimal experimental conditions of hydrolyzed polymaleic anhydride (HPMA):1227 concentration of 105mg/L, pH value approximately equal to 4 and measurement of the absorbance at 410 nm after placing 35 min.(3) When the concentration of 1,2,3-benzotrialole (BTA),2-mercaptobenzothiazole (MBT), Zn2+ is less than 4 mg/L; the concentration of SO42-, Cl" is less than 1000 mg/L; the concentration of amino trimethylene phosphonic acid (ATMP) is less than 20 mg/L; the concentration of 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), PO43- is less than 50 mg/L; their existence exerted no influences to the determination of PESA, TH-3100, TH-2000 and HPMA. Besides, when the concentration of SO42-, Cl- is less than 1000 mg/L; the concentration of ATMP is less than 20 mg/L; the concentration of HEDP, PO43- is less than 50 mg/L; the concentration of BTA, Zn2+ is less than 4 mg/L, their existence also exerted no influences to the determination of PAA. The existence of Ca2+and Mg2+served no influences to the determination of PAAand HPMA, whlie their existence could serve influences to the the determination of PESA, TH-3100 and TH-2000, which can be eliminated by adding desired amount of EDTA-2Na with with the least mole ratio of 1:1 (EDTA-2Na:Ca2+ or Mg2+). In order to eliminate the interferences of sodium hexametaphosphate (SHMP) to those 5 polymer inhibitors, a proper amount of HC1 was added into the solutions and then it was boiled after mixing.(4) It was demonstrated that the turbidity method is of practical feasibility through the recovery experiments of actual power plant circulating water. This method, which has strong practical application value, was simple and low cost with a lower detection limit. |
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