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This paper develops the sulfate scale inhibitor WUR-201 for RO using uniform design method, and the results show that the scale inhibition performance of WUR-201 can reach or even exceed that of scale inhibitor Foreign 1#; the scale inhibition ability increases with pH increasing but decreases with temperature increasing; Fe and Al can lead to WUR-201 poisoning; WUR-201 has also good scale inhibition for CaCO3. Introduction According to the investigation, 85% of the operational failure of reverse osmosis (RO) system in China is caused by the pretreatment. And the main form of the operational failure is the membrane parts pollution and plugging, and the property includes biological slime and scaling substance. The primary preventive measure of biological slime is sterilization management. Different kinds of scaling substance need different preventive measures, for example, measures such as the acid addition, scale inhibitors addition and water softening can be taken for carbonate scale. In China the primary scaling substance threatening the operation of RO system are CaCO3 and sulfate (including BaSO4, SrSO4 and CaSO4). To prevent the scaling of RO system, some foreign special scale inhibitors for RO have been developed, such as PTP-2000, PTP-0100, Flocon 260, SJ-881, TPT-0510, LA302, TianASD 200/SC and so on, which have been used in China. However, these inhibitors are expensive, and scale inhibitors for sulfate are few. Thus, the sulfate scale inhibitor WUR-201 is developed in this paper compared with the control, that is the foreign inhibitor. Materials and Methods Table 1 gives the preparation of the experimental water. After the scale inhibitors are mixed with a certain volume of experimental water, keep the water at the constant temperature for a certain time, and then determine the scale inhibition rate (η). Table 1 Test Conditions Experimental Water Water Temperature/ °C Scaling Substance Composition/mg.L BaSO4 ρ(Ba)=400, ρ(SO4)=1200 60±1 SrSO4 ρ(Sr)=438, ρ(SO4)=480 60±1 CaSO4 ρ(Ca)=2000, ρ(SO4)=4800 80±1 CaCO3 ρ(Ca)=400, ρ(HCO3)=1200 80±1 Experimental Results In this paper the scale inhibition rates for BaSO4, SrSO4 and CaSO4 are respectively denoted by ηBa, ηSr and ηCa. 4th International Conference on Mechatronics, Materials, Chemistry and Computer Engineering (ICMMCCE 2015) © 2015. The authors Published by Atlantis Press 2424 Scale Inhibition Performance of Monomer In order to compound the inhibitor, the sulfate scale inhibition performance of four kinds of monomers (respectively numbered A, B, C and D) are determined. These monomers include ATMP, EDTMP, HEDP, DETPMP, PBTCA and HPMA. And two kinds of RO running conditions have been taken into account, that is acidification operation (pH of concentrate is about 6.5) and operation without acid (pH of concentrate is about 8.5). Table 2 gives the results and the usage amount of the inhibitors (Dn) is 9mg/L. The order of the inhibition difficulty of three kinds of sulfate is as follows: BaSO4>SrSO4>CaSO4. And for BaSO4, the scaling substance most difficult to control, the order of the scale inhibition performance is D>C>A>B, which should be payed attention to when selecting inhibitors. Table 2 Scale Inhibition Rates of Monomer (%) Scaling Substance BaSO4 SrSO4 CaSO4 pH 6.5 8.5 6.5 8.5 6.5 8.5 A 2.06 17.82 22.33 56.33 68.23 66.9 B 1.03 5.94 43.67 56.12 49.02 50.78 C 20.11 36.28 52.09 70.58 74.66 75.23 D 30.51 52.32 44.12 60.45 62.8 63.09 Scale Inhibition Performance of Compound Medicine In order to make the most of synergistic effect of the inhibitors, taking the dispersing ability and inhibiting ability of biological sludge into account, three series (respectively numbered X, Y and Z), that is eighteen kinds of complex formulations of those monomers are made, and the initial tests show that the X series has good scale inhibition performance. To improve the inhibition performance further, the X series is optimized. The technical route is as follows: 1 Determine the formulation composition according to the uniform design table. 2 Measure the scale inhibition rates of these formulations. 3 Use the resulting data to build a mathematical model of the relationship between scale inhibition rates and the complex formulations, then utilize the regression analysis to determine the coefficients in above model. 4 Utilize the F-Test to select the most important factors and remove the secondary factors, getting the experiential formula. 5 Solve the conditional maximum value of the experiential formula (multivariate function) and get the best formulation, which is called WUR-201. 6 Measure the scale inhibition rate of WUR-201. Table 3 gives the computational and verified values, and the test results are in concordance with the results of calculation. Table 3 The Computational and Verified Scale Inhibition Rates of WUR-201 (%) Scaling Substance BaSO4 SrSO4 CaSO4 pH 6.5 8.5 6.5 8.5 6.5 8.5 Computational Value 64.20 77.63 100.00 100.00 98.45 99.14 Verified Value 67.16 80.78 100.00 100.00 95.55 96.98 The Comparison Between WUR-201 and The Foreign Inhibitor The contrast test is conducted for WUR-201 and a foreign sulfate scale inhibitor (called Foreign 1#). The results are as follows: (1) Scale Inhibition Performance Fig. 1 shows the changing curves of scale inhibition rates of WUR-201 and Foreign 1# for BaSO4, SrSO4 and CaSO4 at different dosages and pH of 8.5. According to Fig. 1, the scale inhibition rates of WUR-201 for BaSO4, SrSO4 and CaSO4 exceed Foreign 1#. For example, at the dosage of 12mg/L, ηBa, ηSr and ηCa of WUR-201 are respectively 15.8%, 29.7% and 8% higher than Foreign 1#. (2) The Influence of pH Fig. 2 shows the influence of pH on WUR-201 and Foreign 1# at the dosage of 9mg/L. Overall

The Development of Sulfate Scale Inhibitor for RO System