Piotr Dydo

Scaling analysis of nanofiltration systems fed with saturated calcium sulfate solutions in the presence of carbonate ions

Nanofiltration of saturated calcium sulfate solution of 0.02 mol/L calcium content, with CO32−SO42− molar ratio ranging from 0.0500 to 2.8 × 10−3 was carried out in 6.5 × 10−4 m2 active membrane area laboratory module at 1.2 × 106 Pa transmembrane pressure using the total retentate recycle mode. Permeate mass flow and retentate calcium concentration vs. time and concentration factor (CF) curves allowed identification of calcium sulfate crystallization mechanisms. Though both bulk and surface crystallization mechanisms were identified, they were, however, strongly affected by water quality. A non-fouling CF range up to 2, which is probably due to the existence of metastable supersaturated CaSO4 solution, was also observed in the case of CO32−SO42− molar ratio equal to 2.8 × 10−3. Inorganic scales at the end of each experiment were removed from a NF module, dried at room temperature during 24 h and then examined using the X-ray diffraction method. Gypsum and aragonite were identified as the most common calcium sulfate and calcium carbonate precipitates, respectively. A mixed salt Ca2(CO3)(SO4)·4H2O (so-called rapidcreekite) was also identified as a result of carbonate and sulfate co-precipitation under low carbonate content conditions.

Electrodialysis reversal of calcium sulphate and calcium carbonate supersaturated solution

Electrodialysis reversal (EDR) in single-pass mode was investigated to coal-mine water desalination. Water containing (mg/L): Ca2+ - 284, Mg2+ - 130, SO42− - 1066, Cl− - 359 and HCO3− - 297 was desalinated in EDR laboratory unit with 0.19 mm intermembrane distance. The electrodes polarity was changed each 17 min. 90.1 and 90.6% recoveries were achieved applying diluate velocities 8.35 and 8.14 cm/s respectively, while concentrate velocities were 0.86 and 0.90 cm/s. Mean residence time of concentrate in EDR unit was equal to 352 s. The percent of calcium sulphate saturation in EDR concentrates was equal to 368 and 362% while Langelier Saturation Index (LSI) to 1.92 and 1.60 respectively. Voltage drops vs. EDR time show no increasing tendency, which would be the result of calcium sulphate or calcium carbonate scaling in the EDR unit. It was then demonstrated that EDR in the presented mode could operate at such a high supersaturation level, which has been achieved up to now, only with chemical addition to the concentrate stream.

The nucleation kinetic aspects of gypsum nanofiltration membrane scaling

Abstract Gypsum NF-200 (Filmtec) membrane scaling was examined with respect to the nucleation theory. First the gypsum nucleation kinetic parameters — nucleation rate constant kN and heterogeneous nucleation factor f(θ) — were calculated, with the model based on classical nucleation theory using the nonlinear (quasi-Newtonian) estimation method. Subsequently, the method of the maximum permissible water recovery bound (here expressed as maximum NF retentate supersaturation, Smax) prediction was proposed. When comparing the predicted and experimental data, it was found that predicted Smax values were lower than the measured ones; however, most of the results were within about a 10% confidence interval. The difference in the measured and predicted Smax values was identified to be the result of mass gypsum nucleation and the nuclei growth mechanism. Furthermore, when considering that the presence of the solid phase inside the NF module retentate channel is not recommended, we concluded that the proposed Smax prediction procedure better describes maximum permissible gypsum retentate supersaturation than the experimental one. Powder X-ray diffraction data show that the only solid phase present under our measurements conditions is gypsum.

Hybrid membrane-thermal versus simple membrane systems

Abstract Conventional SWRO systems work under 6.5 MPa with 40% recovery. Developed in Japan, the BCS system can obtain up to 60% recovery under 9.0 MPa in the second stage RO modules. The recovery of desalted water by a high pressure RO (H PRO) can be increased up to 75–80% under 20 MPa in an integrated system for complete usage of components in seawater which is being developed also in Japan. In the process of salt production from seawater, raw seawater is concentrated to TDS of 195 g/l by electrodialysis. Concentration to saturation of NaCI by ED and MD is also investigated. However, the production of such concentrated brine, by means of the previously mentioned membrane methods is questionable. Analysis of performance of the aforementioned systems shows that RO may compete with thermal methods if the inlet salt concentration does not exceed ≈70 g/l and maximum profitable concentration of retentate is ≈90 g/l. While investigating the processing of coal-mine water (TDS 12 g/1) concentration to saturation in an ED-MSF system (as a first step of NaCI recovery), with simultaneous desalination to 1.1 g/l of CI−, an optimum value of TDS of ED concentrate was found. Taking into account co-generation of electricity production and coal-mine waters utilization, cost of electric energy as low as 0.03

BORON REMOVAL FROM WASTEWATER USING ADSORBENTS

/kWh was assumed and TDS 90 g/1 obtained. ED-MSF system seems therefore to be more effective than ED alone in the investigated range of brine concentration. Thermal methods still seem to be more effective than membrane methods in terms of production of highly concentrated brines. The performance of desalination and concentration in hybrid membrane-thermal systems is then higher than the performance of simple membrane methods. Hybrid NF-RO-MSF-crystallization system offer a very promising performance: high water recovery (77.2%) and water cost as low as

Use of the desalination brines in the saturation of membrane electrolysis feed

0.37/m3.

Ion-exchange membranes in chemical synthesis – a review

In the present study, boron adsorption on activated alumina and activated carbon impregnated with calcium chloride, tartaric acid and mannitol was investigated. The adsorbate in question was the wastewater from the chemical landfill in Tarnowskie Gory of 25-70 mg l−1 boron content. The removal of boron from the above-described wastewater was examined in the static (batch) and dynamic (column) experiments. The static experiments were carried out to assess boron adsorption isotherms, based on which the most efficient adsorbent as well as the rough resin load was determined. On the basis of the dynamic experiment results, the boron adsorptive capacities of the examined resins were deduced. It was concluded that the use of the impregnants increased the ability of activated carbon to adsorb boron. Granulated activated carbon WG-12 impregnated with mannitol was found to be the most promising for the boron removal from wastewater of the Chemical Wastewater Plant in Tarnowskie Gory.

Laboratory RO and NF processes fouling investigation by residence time distribution curves examination

Abstract Seawater desalination by reverse osmosis (RO) invokes the necessity of brine disposal. On the other hand, the chlor-alkali industry requires saturated brine with a low content of calcium and magnesium contaminations. This paper describes a preliminary study exploring the possibility of the application of RO, nanofiltration–reverse osmosis, and nanofiltration–reverse osmosis–multieffect distillation seawater desalination brines as a sodium chloride source for membrane electrolysis. A concept has been proposed in which electrodialysis with univalent permselective membranes is used to enrich chlor-alkali lean brine with sodium chloride, and simultaneously desalinate discharge brine. The experiments with an electrodialyzer equipped with Neosepta® ACS and CMS membranes of 42 cm effective length have shown that the desired concentration of membrane electrolysis feed (above 300 g/L as NaCl) can be achieved. At the same time, the concentrations of both calcium and magnesium are decreased, the latter to a...

Study on the electrodialytic nickel concentration from electroplating industry waste

Abstract The applicability of ion-exchange membranes (IEMs) in chemical synthesis was discussed based on the existing literature. At first, a brief description of properties and structures of commercially available ion-exchange membranes was provided. Then, the IEM-based synthesis methods reported in the literature were summarized, and areas of their application were discussed. The methods in question, namely: membrane electrolysis, electro-electrodialysis, electrodialysis metathesis, ion-substitution electrodialysis and electrodialysis with bipolar membrane, were found to be applicable for a number of organic and inorganic syntheses and acid/base production or recovery processes, which can be conducted in aqueous and non-aqueous solvents. The number and the quality of the scientific reports found indicate a great potential for IEMs in chemical synthesis.

Chapter 11 – Boron Removal Using Ion Exchange Membranes

Abstract The fouling phenomena of nanofiltration of calcium sulfate saturated feed solution in the presence of magnesium and carbonates as well as the reverse osmosis of saturated silica feedwater with magnesium chloride content at different pH levels, was investigated by analyzing the membrane residence time distribution curves (RTD) in our laboratory. The fraction of degraded membrane (parameter a), the fraction of active membrane area (parameter b) and the fraction of membrane blocked by impermeable layer (parameter c) as a function of permeate recovery was determined. It was found that not only surface blockage affects permeate efficiency, but also other factors, such as module retentate chamber pressure drop and osmotic pressure increase. The membranes RTD measurements as well as fouling, a, b and c parameters, gathered with ion-selective electrodes (chloride, calcium and cupric ion-selective) and appropriate tracer solutions (sodium chloride, calcium chloride and cupric nitrate) were compared with commonly used conductivity sensor and sodium chloride tracer solution. We found that both the tracer and detector type strongly affects membrane mean residence time and its variance, but at the same time no influence of detector and tracer type on membrane fouling a, b and c parameters was observed.