Strontium Separation with Ultrafiltration Membranes from Dilute Aqueous Solutions

Abstract

The separation of Sr²⁺ from dilute and trace solutions of low activity by means of hollow fiber Amicon ultrafiltration membranes is studied. The cation is absorbed on colloidal particles of titanium oxide formed directly in solution, and the colloidal dispersion is filtrated. The method has been studied under several different operative conditions (pH, Ti/Sr ratio, the presence of interfering ions, colloid formation time) with the aim of determining the optimum conditions to develop a separation process.     

Separation and Recovery of Valuable Metals from Nickel Slags Disposed in Landfills

With the increased requests for more sustainable extraction processes feedstocks with low metal content are becoming more attractive. In this research, an additional refining step is investigated in order to recover valuable metals from slag generated during nickel extraction process, particularly copper, nickel, and cobalt. Slag was settled at the different temperatures for various times in conditions that simulated the industrial environment. The chemical composition and morphology of newly formed matte and slag were determined. Kinetic parameters of matte formation, valuable metal recovery rates and partition coefficients were deduced. Metals separation and settling rate was found to be strongly dependent on temperature. The highest recovery rates were found to occur at 1598 K (1325°C) for two hour settling while the most economical combination of parameters was found when settling at 1573 K (1300°C) for one hour. Silica additions generated higher partition coefficients for copper and nickel than the addition of lime. It is concluded that an additional refining step involving SiO₂ and CaO fluxes is an economical way to recover more than 60% of valuable metals from slag that is disposed in landfills.     

Recovery of Hydrazine and Glycerol from Aqueous Solutions by Membrane Separation Techniques

Hydrazine and glycerol are two widely utilized solvents in the chemical industry, which form aqueous solutions during various stages of their production or application. Distillation of these aqueous solutions is either hazardous due to the explosive nature of hydrazine or energy intensive in case of the high boiling glycerol. The focus of this study was to develop and compare alternative safe and economical methods such as Pervaporation (PV) and Membrane Distillation (MD) for separation of water from these solvents. PV experiments using the indigenously developed thin film composite (TFC) Pebax membrane revealed a high selectivity of 107 at a reasonable flux of 0.05 kg/m² h for a typical hydrazine hydrate feed composition of 64 wt.% N₂H₄. For glycerol-water mixtures, MD through a microporous, hydrophobic polytetrafluoroethylene (PTFE) membrane gave better flux (0.1 kg/m² h) than PV through the Pebax membrane. Interestingly, both membrane types exhibited a selectivity of infinity throughout the range of feed composition (10–90% glycerol) studied due to poor volatility of glycerol. The effect of operating parameters such as permeate pressure (0.5–10 mmHg) and feed temperature (37–100°C) on MD performance for glycerol-water separation was evaluated. The membranes were characterized by scanning electron microscopy (SEM) and sorption experiments to explain the observed results.     

Silver Recovery from Dilute Aqueous Solutions Using Semi‐Batch RF‐Pertraction

Silver recovery from dilute nitrate solution was studied by using a rotating film‐pertraction technique in a semi‐continuous mode. Tri‐isobutylphosphine sulphide (TIBPS) dissolved in kerosene was used as a carrier and an aqueous ammonia solution as a stripping phase. A high transfer flux of silver ions during the pertraction process was observed. It was shown that the selectivity of silver transport through the TIBPS‐containing liquid membrane provides an excellent separation of silver from other metals such as copper, nickel, and iron presented in the treated solutions.     

还原-磁选不锈钢酸洗污泥中的金属

以石墨粉为还原剂,与不锈钢酸洗污泥混合煅烧,再进行磁选,回收酸洗污泥中的金属. 结果表明,在还原温度1350℃、保温时间300 min、配碳比为1.2(碳与污泥质量比为11.8:100)时,酸洗污泥中Fe, Cr和Ni的回收率分别为92.7%, 86.7%和93.6%;酸洗污泥经还原-磁选后Cr和Ni含量分别降到0.07%和0.04%,达到了国家排放标准.     

Electrolytic Recovery of Nickel from Dilute Solutions

Abstract

Electrolytic recovery of metals from dilute solutions using vertical electrodes is limited due to low current density and mass transfer rate. Therefore, a rotating tubular bed reactor with extended cathode surface areas was developed to improve mass transfer. In this study, nickel solutions from industrial Watts baths were used for the electrolytic recovery of nickel. The results showed that this process reduces the nickel concentrations to low levels with an optimum deposition rate. Electrolytic treatment followed by an ion-exchange process can further reduce the nickel content, even below the ppm level.     

Solvent Extraction,Membranes, and Ion Exchange in Hydrometallurgical Dilute Metals Separation

Abstract

The separation methods which are used in the hydro-metallurgical field are reviewed and compared. Some processes in solvent extraction in use for recovery of crucial metals which are important to the U.S. defense and economy are presented. Various commercial extractants are reviewed and categorized. Other methods such as liquid membranes and ion exchange resins used for dilute metal ions separation are summarized. These methods are compared with solvent extraction. Problems to overcome in the further development of these separation methods are also identified and discussed in this paper.     

Recovery of n-Butanol from Dilute Solution by Extraction

Abstract

A simple but effective strategy is suggested to seek extraction agents for recovery of oxychemicals from dilute aqueous solution. Application of this strategy, which is based on specialization of UNIFAC and UNIFAP, to n-butanol identified highly effective solvents as well as a promising polymer. The best solvent identified, 4-n-butylphenol, has an n-butanol mass distribution coefficient relative to water of up to 25 and selectivities of about 200. The polymer, poly(p-vinylphenol), is somewhat less effective, but there is a good probability of finding related compounds of practical interest.     

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     

Recovery and Separation of Metal Ions from Aqueous Solutions by Solvent‐Impregnated Resins

The recovery and separation of metals from aqueous solutions is one of the research hotspots in hydrometallurgy, environment protection, analytical chemistry, etc. Much attention has been paid to solvent‐impregnated resins (SIRs) since these were firstly proposed for the extraction of metals. SIRs are characterized by high efficiency and selectivity, convenient preparation, and easy operation because they combine the unique advantages of solvent extraction and ion exchange. The preparation and features of SIRs are summarized and their applications in the extraction of various metals from solutions are reviewed. In addition, the equilibrium, thermodynamics, and sorption kinetics of the metals onto SIRs are elucidated in detail.     

Removal of Suspended Solids and Petroleum Products from Aqueous Media

Theoretical Foundations of Chemical Engineering - Helical filter elements and a fibrous material based on basalt wool have been studied as potential filtering materials for removing solid...     

Adsorption of Uranium from Dilute Aqueous Solution on Inorganic Adsorbents

Abstract

The adsorption of uranium from a dilute aqueous solution by a large number of inorganic adsorbents has been investigated. A mixture of aluminum hydroxide, ferric hydroxide, and activated carbon in the weight ratio 1:3:4 has shown a high adsorbability for uranium. The separation of uranium from a dilute aqueous solution by this mixed adsorbent under various temperatures and pH values has been studied. The adsorbability was found to exhibit a maximum at pH 4.0 to 5.5 and to decrease with increasing temperature. A number of eluting solutions for the desorption of uranium from the mixed adsorbent were also tested; 1 N (NH₄)₂ CO ₃ was found to be the most suitable eluting solution (93% recovery of uranium).     

Study on Metals Recovery from –0.074 mm Printed Circuit Boards by Enhanced Gravity Separation

Nowadays study on discarded printed circuit boards (PCBs) reutilization has great significance for achieving secondary resources recycling and preventing environmental pollution. Physical methods show great potential and advantages on discarded PCBs reutilization, comparing with chemical and biological methods. However for the particles of -0.074 mm PCBs, little work has been done in the past because of lower separation efficiency and recovery. In this paper, the conundrum of -0.074 mm PCBs reutilization was resolved successfully with the help of Falcon concentrator. Separation mechanism for fine particles with different mass densities in a Falcon centrifugal concentrator was analyzed. The main factors such as magnitude of rotation frequency (centrifugal acceleration), anti-charge water pressure and feeding concentration were studied, and interaction of different factors was analyzed using Design-Expert software. The experimental results show that metals grade of -0.074 mm PCBs and integration efficiency were obtained as 76.89% and 80.77% respectively when feeding concentration was 40 g/L with water pressure of 0.01 MPa and rotation frequency of 50 Hz.     

Palladium Recovery from Dilute Effluents using Biopolymer‐Immobilized Extractant

Abstract

Cyanex 301‐immobilized material (prepared by immobilization into an alginate matrix) was tested for Pd sorption in 1 M HCl solutions with a special attention to sorption isotherms and uptake kinetics. This immobilized extractant had great affinity for Pd, as shown by the initial slope of the sorption isotherms. Sorption capacities as high as 150 mg Pd g^?1 were obtained in 1 M HCl solutions. However, kinetics was slow, compared to conventional resins. The main limiting step in the process is the diffusion of metal ions into the matrix. The influence of parameters such as HCl concentration, NaCl addition, presence of Pt (as a competitor metal) has been checked. It appeared that sorption performance of Cyanex 301‐immobilized material was hardly influenced by the addition of NaCl and by HCl concentration (below 2.5 M). The resin was remarkably selective for Pd, versus Pt, especially at 1 M HCl concentration. Loaded resins can be desorbed using thiourea solutions.     

Extraction Equilibria of Acetic and Propionic Acids from Dilute Aqueous Solution by Several Solvents

Abstract

Extraction equilibria of acetic acid and propionic acid with hexane solutions of trioctyl amine, trioctyl phosphine oxide, and tributyl phosphate were studied. The species formed in the systems were estimated, and the distribution coefficients and the equilibrium constants for these species were evaluated.     

Separation of Solids at Liquid-Liquid Interface

Abstract

The possibility of separation of solids at the interface of two liquid phases by utilizing surface tension to overcome gravity was studied. The proposed theoretical model was verified in several experimental examples.     

Separation of Tetrahydrofuran from Aqueous Mixtures by Pervaporation

Abstract

Studies on the separation of tetrahydrofuran (THF) and water by pervaporation were conducted. A silicalite-filled silicone composite membrane was used for organic permeation and a polyvinyl alcohol composite membrane for dehydration. Effects of feed concentration, feed temperature, permeate-side pressure, and type of membrane were studied. The silicone composite membrane yielded a selectivity of 205 and a THF flux of 1.1 kg/m²·h at benchmark conditions of 50°C feed temperature, 2 torr permeate-side pressure, and a feed concentration of 4.4% w/w THF. An increase in temperature increased the flux exponentially in an Arrhenius-type manner, but had little effect on selectivity. These data show that the trend agrees with an Arrhenius-type relationship. An increase in feed concentration increased the flux, but the selectivity for THF decreased. As the permeate-side pressure increased, the flux decreased in a sigmoidal fashion, but the selectivity for THF increased. Some initial studies on dehydration were also performed. Use of pervaporation in a solvent recovery/reuse system in industry has also been examined.     

Electrophoretic Separation of Dilute TiO2 Suspension

ABSTRACT

A simple apparatus to separate TiO₂ from dilute aqueous suspensions by using electrophoretic principles has been described. Experiments were carried out at different voltages and flow rates. It was observed that voltages lower than 10 V and higher than 50 V were largely ineffectual in separation; 15 V and a 200 mL/h flow rate were established to be the optimum parameters. It was further observed that 96% separation was the maximum obtainable in one stage for this geometry.