Solute rejection experiments

In a permeation experiment, an HERO module with a membrane area of 200 m is used to remove a nickel salt from an electroplating wastewater. TTie feed to the module has a flowrate of 5 x IQ— m /s, a nickel-salt composition of 4,(X)0 ppm and an osmotic pressure of 2.5 atm. The average pressure difference across the membrane is 28 atm. The permeate is collected at atmospheric pressure. The results of the experiment indicate that the water recovery is 80% while the solute rejection is 95%. Evaluate the transport parameters Ay and (D2u/KS). 

The influence of metal oxide derived membrane material with regard to permeability and solute rejection was first reported by Vernon Ballou et al. [42,43] in the early 70s concerning mesoporous glass membranes. Filtration of sodium chloride and urea was studied with porous glass membranes in close-end capillary form, to determine the effect of pressure, temperature and concentration variations on lifetime rejection and flux characteristics. In this work experiments were considered as hyperfiltration (reverse osmosis) due to the high pressure applied to the membranes, 40 to 120 atm. In fact, results reproduced in Table 12.3 show that these membranes do not behave as h)qjerfiltra-tion membranes but as membranes with intermediate performances between ultra- and nanofiltration in which surface charge effect of metal oxide material plays an important role in solute rejection. 

Both calculations by Perry and Schirg have been performed to describe and to predict the rejection characteristics of organic nanofiltration membranes when ionic and charged molecular solute mixtures are used in the feed solution. Recently experiments were carried out with ceramic nanofilters [67] which showed that similar properties can be obtained. As an example, results concerning the rejection of a dye/electrolyte mixture at pH = 9 through a zirconia nanofilter are reported in Table 12.5. 

J/p) and solute rejections (r) over a broad range of pH. Experiments were carried out at temperatures between 30 and 70 C, pressures up to 6.9 MPa (1,000 psig), and cross flow velocities of 1 to 2 m/s. Electrolyte rejections were determined by measuring the conductivity of the feed and permeate solutions. The concentrations of the sugar solutions were measured with a refractometer. 

Graphs for Equations 15, 16, and 20 are shown in Figure 2, and for Equation 17 in Figure 3. Horizontal lines in Figure 2 represent the asymptotic limit for C /C for an experiment with a given P6cl6t number. For example, for a rejection experiment of myoglobin from saline solution D = 0,172 x 10 cm/sec, r =... 

The rejection experiments have shown that flux depends on the salt solution composition. Figure 7.17 shows results for the different components of the chosen background solution with FA for the TFC-S membrane which, due to its high salt rejection, should be most sensitive to the salt used. 

The other set studied the influence of solute concentration and applied pressure on the permeate flux and solute rejection. A wide range of experiments was performed using toluene solutions of docosane (MW=310 Da) and TOABr (MW=546 Da) using a range of pressures 0-50 bar, and concentrations 0-20 wt% (0-0.35 M, 0-0.04 mole fraction) for TOABr in toluene and 0-20 wt% (0-0.67 M, 0-0.09 mole fraction) for docosane in toluene. The construction of the crossflow rig made it difficult for exactly the same flow rate to be maintained through the cells at different pressures, however, it was always kept in the range of 40-80 L h in one of the cells, 120-150 L h in the other. 

Nurlaila prepared SPPO TFC membranes by coating Desal E-500 substrate membranes with 0.5 or 1.0 wt % of SPPO (intrinsic viscosity of the base PPO polymer, 1.58 dL/g in chloroform lEC value, 1.87 meq/g). e membranes were then heat treated in a hot water bath, before being subjected to reverse osmosis experiments with NaCl or MgS04 solution. The results of RO experiments are given in Table 11. Comparison of the results from several series of experiments such as 1-4, 6-9, and 10-14, leads to a conclusion that the flux increases with heat treatment with little sacrifice in solute rejection. 

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 5-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the hght of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hke substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 215-216°, which is fluorescent in dayhght, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from p /r-iV -alkyl-l-methyl-3,4-dihydro-j8-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption (A jax 280 mp) which was not encountered in the spectra of the anhydro-bases under discussion. This is in accord with general experience. Pseudo-bases are generally found only when dehydration to anhydro-bases is structurally impossible Indole-type absorption was indeed found in the case of the product obtained by treatment of 3,4-dihydro-)3-carboline methiodide (452 R = H) with alkali.In acid solution this compound gave the expected absorption (A jax 355 mp). In alkaline solution, however, an indole-type absorption (A jax 285 mp) was observed. On this basis formulation of the product as a derivative of 2-formylindole (454) ( max 315 mp) was rejected. Although the indole-type absorption is in accord with the pseudo-base structure 453 (R = H), the elemental analysis and molecular weight were not compatible with this formulation and the product was regarded as a dimeric anhydro-base (455). 

With the plant interview information, verification of the data, and the completion of the simple calculations, an experienced troubleshooter will develop a set of hypotheses for the root cause of the defect. After the hypotheses are established, a series of experiments need to be developed that accept or reject the hypotheses. Once a hypothesis is accepted via experimentation, then the next step is to develop a technical solution to remove the defect. Often more than one technical solution Is possible. The best technical solution will depend on the cost and time to implement the solution, machine owner acceptance, and the risk associated with the modified process. An accepted hypothesis must drive the technical solution. If a hypothesis is not accepted prior to developing a technical solution, then the troubleshooter may be working on the wrong problem and the defect may not be eliminated from the process. 

Limited testing on chlorine sensitivity of poly(ether/amidel and poly(ether/urea) thin film composite membranes have been reported by Fluid Systems Division of UOP [4]. Poly(ether/amide] membrane (PA-300] exposed to 1 ppm chlorine in feedwater for 24 hours showed a significant decline in salt rejection. Additional experiments at Fluid Systems were directed toward improvement of membrane resistance to chlorine. Different amide polymers and fabrication techniques were attempted but these variations had little effect on chlorine resistance [5]. Chlorine sensitivity of polyamide membranes was also demonstrated by Spatz and Fried-lander [3]. It is generally concluded that polyamide type membranes deteriorate rapidly when exposed to low chlorine concentrations in water solution. 

Feed solution used in all experiments contained sodium chloride at a concentration level of 5,000 ppm. Membrane salt rejection is evaluated from conductance measurements of product water and expressed as percent rejection, %R, or desalination ratio, D. . These units are defined by the following equations in which Cp and Cf are sodium chloride concentrations in feed and product respectively. Note that D. is very sensitive to concentration changes and expands rapidly as 100% rejection is approached. 

The composite membrane was subjected to the permeation experiments in which the volume flux of water and the rejection of polymer solutes, defined by... 

Figure 24 shows the rejections of polymer solutes, polyethylene glycols) (PEG) with monodispersed molecular weights. From Fig. 24, it is apparent that the composite membrane can find application for ultrafiltration. The molecular weight cut-off drastically decreased by more than 10 fold from the swollen state at 25 °C to the shrunken state at 45 °C. Thus the switching ability of the gel was demonstrated in the permeation experiments. 

In Hydrocyclones A Solution to Produced Water Treatment, Meldrum presents the basic design principle of a dc-oilmg hydrocy leone. System design, early operational experiences, and test results on a full-scale application in the North Sea are discussed. Oil-removal efficiency was seen to rise with increasing reject ratio up to around 1%, producing acceptable outlet concentrations Early field test results on a tension leg platform in the North Sea are discussed. Preliminary data on a pumped system are also given. 

Figure 6.12 Rejection of 1 % dextran solutions as a function of pressure using Dextran 20 (MW 20000), Dextran 40 (MW 40000), and Dextran 80 (MW 80000). Batch cell experiments performed at a constant stirring speed [17]...

---