Reverse Osmosis Separation of Nickel from Dilute Solutions

Abstract

Cellulose acetate membranes were characterized in terms of the pure water permeability constant, the solute transport parameter, the mass transfer coefficient, and percent solute separation using a reference system of aqueous sodium chloride solution. The membranes were used in the determination of reverse osmosis characteristics such as product rates and solute separation of dilute nickel salt solutions. The effect of the chemical species present in aqueous nickel salt solution on the degree of separation of nickel has been determined. The results of this study can be used in predicting the general reverse osmosis separation behavior of metals such as Zn, Cu, Pb, Mg, and Mn encountered in acid mine-water samples     

Reverse Osmosis Separation of Thiosalts from Mining Effluents

Abstract

Cellulose acetate membranes were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with a reference system of aqueous sodium chloride solution. Reverse osmosis separation behavior of sulfate, thiosulfate, dithionate, trithionate, and tetra-thionate was studied. Plant effluents containing various thiosalts and metal ions were subjected to reverse osmosis at 300 psig, and product water of suitable quality for use in recycle operations was obtained.     

The application of polyethyleneimine draw solution in a combined forward osmosis/nanofiltration system

The objective of this study is to investigate the effect of solution chemistry of branched polyethyleneimine (PEI) draw solute and to evaluate the PEI draw solute in a combined forward osmosis (FO)/nanofiltration (NF) system. Pure water was extracted from feed solution using the FO process, and the separation of pure water was achieved by the NF process. Lower molecular weight PEI showed higher water flux than higher molecular weight PEI, due to the lower internal concentration polarization caused by a higher diffusion rate and the easy permeation of pure water by lower viscosity of the draw solution (DS). The FO water flux was determined by the osmotic pressure induced by protonation/deprotonation of PEI, and the reverse draw solute flux was determined by the combination of PEI size due to the speciation and electrostatic interaction between the membrane and PEI. This study shows that the J_s/J_w value of PEI at pH 7 was smaller than those of sodium chloride and magnesium sulfate. The recovery of PEI DS using NF has a higher value (99.4%) than of sodium chloride (20.6%) and magnesium sulfate (97.0%); this means that PEI would be a promising draw solute in an FO–NF combined system for the saline water desalination. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42198.     

Aromatic Polyamide Hydrazide Membranes for Reverse Osmosis Separations

Abstract

Wholly aromatic polyamide hydrazide (PAH) polymers were synthesized by low temperature polycondensation from freshly prepared m-amino benzhydrazide, p-amino benzhydrazide, isophthaloyl chloride, and terephthaloyl chlorides in dimethyl acetamide solvent. A series of film-forming polymers prepared by altering the molar ratios of the reacting monomers was characterized in terms of % moisture regain, η_inh, and x-rays. Asymmetric membranes prepared from selected polymer samples were tested in reverse osmosis test cells, and the pure water permeability and the membrane constant were determined. An optimum meta: para molar ratio of the reacting monomers has been identified for the best performance under reverse osmosis which gave solute separation close to 98% for a feed concentration in the range of seawater. The PAH membranes appear to be potential barrier candidates for treatment of effluents containing ammonium, nitrates, etc. and radioisotopes. Separation data for a few other solute systems were also evaluated and compared with those obtained from cellulose acetate membranes.     

Reverse Osmosis Transport of Alkali Halides and Nickel Salts through Cellulose Triacetate Membranes. Performance Prediction from NaCl Experiments

Abstract

The separation of alkali metal halides, nickel chloride, and nickel sulfate was determined for cellulose triacetate reverse osmosis (CTA RO) membranes. From transport analysis, the relative free energy parameters for transport of these salts through CTA membranes were determined. From these relative free energy parameters of salts, the solute separation by CTA membranes could be predicted from RO experiment with NaCl solution. The transport analysis and an illustration of how the concept is useful are presented in this paper.     

Reverse Osmosis Separation of Some Organic Acids from Their Aqueous Solutions

Abstract

Cellulose acetate membranes were characterized as previously described and were found to reject 91.7% of sodium chloride. The reverse osmosis separation behavior of benzoic, 2-chlorobenzoic, 2-nitrobenzoic, 2-hydroxybenzoic, and 2-aminobenzoic acids as a function of pH was studied. Experimentally obtained pK_a values are compared with literature values. The calculated polar substituent constant σ* values for the o-substituents were also found to agree with literature values.     

Reverse osmosis separations of polyethylene glycols in dilute aqueous solutions using porous cellulose acetate membranes

Reverse osmosis separations of eight polyethylene glycol (PEG) solutes in the average molecular weight range of 200 to 6750 in single-solute dilute aqueous solutions have been studied using porous cellulose acetate membranes at the operating pressures of 50, 75, and 100 psig. Diffusivity data for the above PEG solutes have also been obtained from experimental data on intrinsic viscosities. From an analysis of all experimental data, numerical values for the parameters representing the polar (?ΔΔG/RT), steric (δ^*ΣE_s), and nonpolar (ω^*Σs^*) forces governing reverse osmosis separations of PEG solutes have been generated. These numerical values are useful for precise characterization of cellulose acetate membranes for whose specifications sodium chloride is not the appropriate reference solute because of its low or practically negligible separation under reverse osmosis operating conditions. This work also illustrates that solute separation in reverse osmosis can predictably increase or decrease with increase in operating pressure depending on experimental conditions.     

Effects of organic acids on the performance of cellulose triacetate forward osmosis membrane

Forward osmosis (FO) membrane performance was improved using different organic acids (formic acid, acetic acid, lactic acid) for the addition of the casting solution. Scanning electron microscope (SEM) images of all the FO CTA membranes exhibited essentially the membranes have a structure of looking like two dense skin layers and a sponge‐like supporting layer. Additionally, based on the surface roughness values analysis of Atomic Force Microscope (AFM), the membranes with lactic acid, with similar roughness to the membranes without any acid, have bigger roughness than the membranes with formic acid or acetic acid. Furthermore, the water flux of membranes with acids has been improved and the reverse salt flux decreased. The membranes with lactic acid, with an outstanding penetration performance, were utilized to test the performance when 1 mol/L sodium chloride (NaCl), magnesium chloride (MgCl₂)_, magnesium sulfate (MgSO₄), and sodium sulfate (Na₂SO₄) were, respectively, as the draw solutions. The results revealed that the membranes have a higher rejection ratio for MgSO₄. Besides, in the process of separating oil–water mixture, the membranes with the organic acids have a better separation efficiency than the membrane without any acid during FO process and the water flux recovery rate could achieve above 90% insuring the membrane anti‐fouling. POLYM. ENG. SCI., 59:E138–E145, 2019. © 2018 Society of Plastics Engineers     

A physicochemical approach for the choice of polymeric membrane materials for water desalination by reverse osmosis

Interfacial properties such as the thickness of interfacial water layer, the distribution coefficient of solute between interfacial and bulk water phases, and the volume of interfacial water per unit mass of polymer material have been identified as relevant physicochemical quantities governing reverse osmosis transport and determined by gas and liquid chromatography methods with respect to different polymeric membrane materials. They are further split into the contribution from the structural component of polymer repeating unit. Force constants A and D for sodium chloride, representing the repulsive force working between membrane surface and solute, have been calculated on the basis of inter-facial properties obtained above. Using these force constants, the pore sizes required to achieve 99.9% of sodium chloride separation are obtained for different polymeric membrane materials. Furthermore, the prediction procedure for the effect of preferentially adsorbed organic molecules on the separation of sodium chloride and product rate is illustrated as a model for “fouling” in the desalination process by reverse osmosis.     

New thin-film composite reverse osmosis membranes and spiral wound modules

Two new series of thin-film composite reverse osmosis membranes have been developed and fabricated into spiral wound modules. The NTR-7100 series membrane is able to desalt sea and brackish water. The NTR-7250 membrane is designed for use at pressures below 20 kg/cm². The membrane has a very high water permeability and is resistant to chemical and microbiological attack. In particular, the membrane is stable to chlorine, as shown by long-term reverse osmosis tests with tap water containing about 1 ppm of residual chlorine. The membrane has an unusual pattern of solute rejection. Salts containing divalent anions, such as sodium sulphate or magnesium sulfate, are rejected more than 98%; while salts with monovalent anions and bivalent cations, such as magnesium chloride, are rejected about 90% and salts with monovalent anions and cations, such as sodium chloride, are rejected 30–50%. Neutral solutes have relatively high rejection; for example, glucose, 90% and sucrose, <99%.     

Reverse osmosis separations of aldehydes,ketones, and ethers in aqueous solutions using porous cellulose acetate membranes

Reverse osmosis data for a number of aldehyde, ketone, and ether solutes whose polar parameters Σσ* lie in the ranges of ?0.2 to 0.6, ?0.4 to 0.6, and ?0.49 to 0.6, respectively, have been analyzed. The results show that solute transport parameters can be expressed as a function of steric parameters ΣE_s only for ethers, polar parameter Σσ* only for aldehydes, and both ΣE_s and Σσ* for ketones. The numerical values of the functional proportionality constants ρ* and δ* associated with Σσ* and ΣE_s respectively, for the above class of solutes have been determined for operating pressures up to 500 psig, and a method of predicting solute separation from data on any reference solute only in each class has been established. The data on solute transport parameters for ethers, aldehydes, and ketones have been correlated with the corresponding data for sodium chloride through appropriate link constants. Analysis of data on mixed solute systems involving aldehydes and ketones show that the solutes behave independently in reverse osmosis.     

Reverse Osmotic Separation of Sodium Chloride and Cobalt (II) Chloride through Membranes Prepared from Schiff Bases of Polyallylamine

Abstract

Crosslinked membranes from Schiff base derivatives of polyallylamine were prepared with 2-pyridinecarboxaldehyde (P) and with P followed by salicyl-aldehyde, and used for the reverse osmotic separation between sodium chloride (NaC1) and cobalt (II) chloride (CoCl₂). The membranes whose rejection (R) was high against CoCl₂ and low against NaCl at each single feed supply showed a reduced difference in R in the case of a mixed solute feed due to Donnan exclusion by fixed charges in the CoCl₂-complexed membrane. An approximate calculation of the complexed CoCl₂ revealed that a very small portion of Schiff base groups took part in the complexation. Composite membranes on a cellulosic sheet solved the problem of an extreme reduction of the membrane strength after complexation, enabling continuous and repeated use. Some transport parameters were determined. Since they indicated a semipermeable character for CoCl₂, multistage runs of a single membrane or low pressure runs of a more porous composite membrane were suggested for the effective separation of NaCl and CoCl₂.     

ION-EXCHANGE PROPERTIES OF HYDROUS TITANIUM DIOXIDE WITH A FIBROUS FORM OBTAINED FROM POTASSIUM DITITANATE

ABSTRACT

Ion-exchange properties of a new type of hydrous titanium dioxide with a fibrous form, which was obtained from potassium dititanate (K₂O(TiO₂)2), have been studied. The pH titration curve snowed that this material behaved as a bifunctional ion-exchanger. Distribution coefficients of some divalent metal ions on this material were measured as a function of pH and the selectivity series were found to be Ba > Sr > Ca > Mg for alkaline earth metal ions and Cu > Zn > Mn > Co > Ni for divalent transition metal ions. Large separation factors were obtained between some metal ion pairs and the mutual separations such as Cu from Sr, Ca, Mg, Co and Ni, and Mg from Ba and Zn have been achieved on columns of this material.     

Reverse osmosis separation of inorganic solutes in aqueous solutions using porous cellulose acetate membranes

Using a modified form of the Born expression for the free energy of ion-solvent interaction, to both the bulk solution phase and the membrane–solution interface, a parameter is obtained to express the repulsion of the ion at the interface. This parameter, called the free energy parameter for ions, is then related to solute transport parameter obtained from reverse osmosis experiments. Numerical values of this free energy parameter have been obtained for six monovalent and four divalent cations and for 12 monovalent anions. Using the experimental data for the reverse osmosis separation of sodium chloride as reference, the utility of the above parameter for predicting solute separation in reverse osmosis is illustrated for 32 other inorganic salts.     

膜集成技术处理氯化法钛白后处理废水的研究

氯化法钛白无机包膜处理工序会产生大量中性废水,其中包含少量钛白粉和水溶性盐,现阶段企业多以外排为主。采用膜集成（陶瓷膜+反渗透膜+纳滤膜）技术对氯化法钛白后处理废水的处理进行研究。将氯化法钛白后处理废水用陶瓷膜过滤,分离回收二氧化钛;将陶瓷膜清液用反渗透膜浓缩,清水回收利用;将反渗透浓液用纳滤膜分离硫酸钠和氯化钠。结果表明：利用陶瓷膜处理氯化法钛白后处理废水,平均通量为650 L/（m ²·h）,浓液中钛白粉质量浓度达到90 g/L以上,清液中钛白粉质量浓度低于0.001 g/L;使用反渗透膜截留清液中的硫酸钠和氯化钠,硫酸钠和氯化钠的截留率为99.5%,浓水中的盐质量分数达到4%以上;浓水中的硫酸钠和氯化钠通过纳滤膜分离,纳滤膜对硫酸钠的截留率为97%,硫酸钠质量分数达到14%以上。     

Polar and steric effects in reverse osmosis

The effects of polar parameter Σσ^* and steric parameter ΣE_s on reverse osmosis separations of alcohols, aldehydes, ketones, and ethers (noncyclic) in aqueous solutions involving single solute systems and porous cellulose acetate membranes are discussed. The least-squares and multiple-regression analyses of solute transport parameter data show that the separation of aldehydes, just as that of alcohols, is predominantly a function of Σσ^*, and that of ethers is predominantly a function of ΣE_s, whereas that of ketones is best represented as a function of both Σσ^* and ΣE_s. The results also indicate that even where water is preferentially sorbed at the membrane solution interface, solute separation in reverse osmosis is affected by the nonpolar character of the solute molecule. A general expression for solute transport parameter in reverse osmosis is presented for further study.     

Chemical Modification of Poly(Vinyl Chloride) with Ethylene Glycol and its Application in Ion-Chromatography

ABSTRACT

Poly(vinyl chloride) (PVC) has been chemically modified through crosslinking with different molar ratios of sodium ethylene glycoxide in ethylene glycol. The crosslinked PVC was used for coating of silica gel 60 particles and the obtained products were impregnated with tetramethylammonium hydroxide (TMAH). The crosslinking reaction as well as the insertion of TMAH were followed up and quantitatively determined with the aid of FT-IR spectroscopic and elemental analyses. The obtained materials were roughly tested for ion chromatographic separation of different ions. Retention time ( t _R) was determined for lithium, magnesium, strontium, and calcium cations whereas chloride, nitrate, and sulfate were selected as representatives for anions.     

Water and solute transport across cellulose acetate membranes in the treatment of soybean whey by reverse osmosis

In processing full-fat soy flour to produce an acid-precipitated lipid protein concentrate, there results a by-product whey fraction which, because of its high biological oxygen demand, represents a serious disposal problem. Processing of food waste streams by reverse osmosis has received considerable attention because of its low theoretical energy requirement, since no phase change is involved. A series of statistically designed and analyzed experiments were conducted on a pilot-plant reverse osmosis unit to study the effect of the operating parameters on solute and solvent transport in cellulose acetate membranes. Sucrose and sodium chloride solutions were tested in addition to soybean whey to relate the mixed solute system in whey to that of single-solute organic and inorganic feed solutions. Water flux was shown to have an Arrhenius dependency on temperature, and some membrane compaction was observed with the more porous membrane. Concentration polarization for sucrose and sodium chloride solutions increased linearly with water flux. Solute flux for soybean whey solutions decreased with molarity and was independent of pressure, whereas solute rejection increased with temperature and pressure and was independent of molarity. Good agreement was obtained using the derived parameters A, B, and τ for soy whey in the diffusion transport model when compared to the observed experimental values.     

Hydration of inorganic solid powder in the presence and absence of polar and nonpolar oil

The hydration of powdered barium sulfate in the presence and absence of oils has been thoroughly investigated by the isopiestic vapor pressure technique. The water vapor adsorption isotherms studied at three different temperatures are in good agreement with the type II BET isotherm. Values of n₁ and Δn₁° at a given value of p/p_o in the presence of polar and nonpolar oils are always higher than the corresponding values in the absence of oil. The adsorption of water vapor depends on the nature and amount of oil present. Temperature has a significant effect on the adsorption process in the presence of oil. The magnitude of the integral enthalpy change (ΔH _int ^o ) is much larger than that observed for barium sulfate in the absence of oil. The absolute binding of water (Δn₁) and solute (Δn₂) in the presence of sodium chloride are much higher than those for barium sulfate in the absence of oil.     

Regeneration of Mixed Solvent by Ion Exchange Resin: Selective Removal of Chloride and Sulfate

Abstract

The selective extraction of sulfate and chloride ions from mixed solvent solutions was investigated. The mixed solvents consisted of water and 50 to 100%‐w (salt‐free solvent) ethylene glycol. The extraction was measured for mixed solvent solutions containing only sulfate and chloride, and mixed solvent solutions saturated with trona (sodium sesquicarbonate, Na₂CO₃ · NaHCO₃ · 2H₂O(s). Three anion exchange resins, Dowex 1X8‐50, Dowex 21K‐Cl, and Dowex MSA‐1, were investigated for their chemical and physical resistance to the mixed solvent carbonate/bicarbonate solutions, for their swelling behavior in the different mixed solvents, and for their extraction efficiency for chloride and sulfate.

The loading of the ion exchangers was fitted to a Langmuir‐type sorption model. While the extraction from trona‐free mixed solvents was well reproduced, the loading of the ion exchangers with chloride and sulfate from trona‐saturated mixed solvent solutions did not fit the sorption model. It appears, rather, that under these conditions chloride and sulfate are “salted out” of the bulk solution and driven into the ion exchangers.