Page 79 - ro membanes

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3. DIAGNOSTICS OF MEMBRANE FOULING AND SCALING
32.1 C
25.7
19.3
KCnt
12.9
6.4
N NaASliSCl
0.0
CK NK OK NaK AlK
Sik SK ClK Tik CrK
FeK Matrix
Correction
ZAF
0
0.00 2.00
Ti Cr Fe
4.00 6.00
Energy - kcV
10.00
12.00 14.00
FIGURE 3.21 EDaX equipment-generated graph indicative of membrane fouling of organic origin. 3.4.11 Fourier Transform Infrared (FTIR) Spectroscopy
FTIR spectroscopy applies infrared (IR) radiation through a sample and by analyzing absorption and transmission of the IR it generates a molecular spectrum of the sample. The molecular spectrum (known also as “molecular signature” or “molecular fingerprint”) of every compound is unique and the compound on the RO membrane could be identified by comparing its IR signature to a spectrum library of IR signatures of known compounds.
The FITR spectroscopy can be used for identifying of specific organic foulants such as polymers and antiscalants accumulated on the surface of the RO membranes. For example, in Fig. 3.22 the molecular spectrum of the RO membrane foulant matches with that of Nalco’s polymer Cat-Floc 8103 Plus. As a result, the main source of organic fouling on the membrane surface in this case is polymer accumulation, caused by polymer overdosing.
3.4.12 Weight Loss on Ignition Test
The purpose of this test is to identify organic fouling on the surface of the membranes. For this test, sample of the foulant is collected from the surface of the RO membrane and its weight is measured. After the measurement, the sample is first dried at 110C (230F) and then heated to 550C (1022F). The weight of the residue from the sample ignition is measured and the difference (weight loss) as a result of the ignition process is calculated as percent of the initial weight. If the weight loss on ignition is over 35%, this result is indic- ative of organic foulant. Loss over 50% signifies heavy organic fouling.
8.00
Element
Wt% At%
71.27 79.30 07.42 07.08 12.35 10.32 01.06 00.61 00.34 00.17 01.12 00.53 01.79 00.75 00.75 00.28 00.46 00.13 00.84 00.22 02.60 00.62