Initial HCl Concentration Research Articles

Thermodynamic analysis and application for extracting valuable components from iron-phosphorus residue of spent catalysts

The method of extracting valuable metals from spent catalysts has been developed in recent years. In this paper, the solid waste produced in the treatment of spent catalyst was studied and named iron-phosphorus residue (IPR). IPR was composed of FePO4·2H2O, Fe3(PO4)2·3H2O, Fe5(PO4)4(OH)3·2H2O, and SiO2. Appreciable quantities of Ni, Co, V, Mo, and W were detected in IPR. Based on E-pH diagrams, different atmospheric leaching strategies were used to extract valuable components from IPR. Both the HCl and NaOH leaching are appropriate for treating IPR. An in-depth investigation on HCl atmospheric leaching showed that >95% of Fe, Ni, Co, V, and Mo, 76.9% of W, and 89.3% of P were extracted efficiently and SiO2 was enriched into the leach residue, at leaching temperature of 90 ℃, leaching time of 180 min, initial HCl concentration of 5 mol/L and liquid to solid ratio of 8:1 mL/g. The leaching mechanism was discussed via XRD, XPS, and FTIR. An efficient and green process for the recovery of valuable components in IPR has been developed. This research achieves the sufficient extraction of valuable components in IPR and provides significant guidance for the management of similar solid waste.

CaO hydrated with ethanol solution for flue gas HCl immobilization. Part II: Influences of gas components

The injection of alkaline adsorbent into flue gas for HCl removal technology is greatly impacted by the complex flue gas components. The newly developed ethanol-modified Ca-based adsorbent was demonstrated a superior dechlorination performance. In this work, the effect of flue gas components on the dechlorination was comprehensively studied by experiments, micro-insight characterization and mechanism analyses. The results showed that the high initial HCl concentration boosts the reaction rate but lowers the Ca/Cl mole ratio. O2 promotes the HCl adsorption efficiency by impelling the reaction between HCl and adsorbent to generate Ca(ClO)2 that enhances the chlorination and converting CaClOH to CaO. The presence of SO2 and CO2 hinders the removal of HCl in both physical and chemical aspects. The product layers of CaSO3 and CaCO3 may cover the adsorbent active sites that deteriorates the pore structure and seriously inhibits the adsorption of HCl on the adsorbent surface and prevents mass diffusion into the inner pores. It was discovered that HCl, SO2 and CO2 have an affinity to the Ca site, so there exists nonnegligible competitive adsorption between them that reduces the number of basic sites to which HCl can adhere. The HCl removal efficiency falls from 72.33% to 41.34% as SO2 concentration rises from 0 ppm to 1600 ppm. While it decreases from 72.33% to 51.17% as CO2 concentration changes from 0% to 20%.

Elimination of Terbinafine Hydrochloride Antifungal Drug Traces from Water, Pharmaceutical Formulations and Blood Plasma using Low-Cost Bio and Synthetic Sorbents

<p>:<strong> </strong>Chitosan (CS) biosorbent and polyurethane foam (PUF) synthetic sorbent have been utilized to eliminate terbinafine hydrochloride (TRB HCl) antifungal drug in its pure and pharmaceutical forms from both contaminated aqueous and biological media using a batch process. The experimental conditions for efficient removal of TRB HCl for both CS and PUF were optimized depending on various experimental parameters such as the pH of the solution, contact periods, initial TRB HCl concentration, and sorbents dosage in the solution.</p><p>SEM, FT-IR, and XRD characterizations were carried out to study the adsorption of a drug by both sorbents. The optimum conditions for removing TRB HCl by CS and PUF were achieved at a pH of 8.5 and a contact time of 60 min at 250 rpm, using 0.4 g for both sorbents. The measured spectrophotometric absorbance at λ<sub>max</sub> of TRB HCl was 242 nm. In addition, the zero-point charge (pHpzc) was determined for the studied sorbents. The pHpzc of the surface of sorbents has shown that electrostatic attraction is one of the mechanisms in TRB HCl sorption. The adsorption process was modeled using the pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion kinetic models. The results indicated that the adsorption of TRB HCl on CS and PUF does follow a pseudo-first-order type of reaction kinetics. The adsorption process was modeled using Langmuir and Freundlich isotherms. The adsorption data found that the Freundlich isotherm model was more suitable for the PUF sorbent, while the Langmuir isotherm model better fit the CS biosorbent.</p><p>Evaluation of the experimental data using the Langmuir equation revealed that the maximum adsorption capacities of PUF and CS were 2.807 and 1.2297 mg. g<sup>-1</sup>, respectively. The solution was also used to estimate TRB HCl in its pharmaceutical form, and the assessed recoveries were 97.25 and 98.437% for CS and PUF, respectively. The proposed procedure was validated for other complex mediums by removing TRB HCl from spiked human blood plasma.<em> In-silico</em> aquatic toxicity forecast of TRB HCl was also carried out.</p>

Removal of hydrogen chloride from simulated coal gasification fuel gases using honeycomb-supported natural soda ash

In this study, we examined the HCl absorption performance of cheap natural soda ash loaded on a honeycomb support as a hot-gas cleanup method. Air-blown and oxygen-blown coal gasification fuel gases were used to simulate the gas composition. The effect of fuel gas composition on the HCl removal performance of the prepared absorbent was studied. It was found that the removal performance in an inert atmosphere was maintained in the presence of H2. On the other hand, the performance deteriorated in the presence of CO due to carbon deposition from the disproportionation reaction of CO. When CO2 was added to the CO, carbon deposition was suppressed in the air-blown gas and the HCl removal performance recovered. The performance recovery for an oxygen-blown gas was smaller than that for an air-blown gas. However, when the amount of CO2 added to the oxygen-blown gas was increased, the removal performance improved. The HCl removal performance of the absorbent was dependent on the initial HCl concentration and treatment temperature in the following order: 2000 ppm < 1000 ppm < 500 ppm, and 400 °C < 600 °C ≈ 500 °C. Recycled absorbents were prepared by loading natural soda ash once again on the recovered honeycomb supports that had been washed with water. Their HCl removal performance was similar to the fresh absorbent regardless of air-blown or oxygen-blown gasification. Thus, honeycomb supports were recyclable.

Experimental study on HCl uptake by MgCl2 and sea salt under humid conditions.

We studied HCl uptake by MgCl2 and sea salt over a relative humidity (RH) range from 0% to 34% at 278-313 K using a differential bead-filled flow tube coupled to a high-pressure chemical ionization mass spectrometer. The results showed that dry MgCl2 and sea salt are essentially inert to gaseous HCl with a probability of less than 10-6 . However, under humid conditions, HCl was found to be efficiently taken up by wet inorganic surfaces. The HCl uptake coefficient for MgCl2 and sea salt increased squarely with RH, reaching a value of 0.00123 and 0.00171, respectively, at 29% RH and 298 K. Such wetting behavior is even enhanced at elevated temperatures, with the coefficient reaching 0.00208 and 0.00239, respectively, at 313 K. Based on the study of the dependence of γHCl on the initial HCl concentration, we estimate γHCl as 0.012 at 24% RH at a typical HCl concentration in the troposphere. In addition, the observation of the remarkable enhancement in the OH uptake by the HCl-treated salts agrees with the results of our previous investigation, which suggested that water absorption on salts enhances γOH by lowering the surface pH. The proposed mechanism of HCl uptake by sea salt aerosol has implications for ozone production in the marine boundary layer.

Investigation of alumina preparation from aluminum chloride aqueous solution by electrical transformation

High-alumina fly ash is an alumina-rich mineral resource that can potentially replace low-grade bauxite. While a wide range of different traditional processes are available for extracting alumina from high-alumina fly ash, these processes have many disadvantages. Northeastern University has recently proposed a new electrotransformation processing technique for transforming AlCl3 into Al2O3 in the process of extracting Al2O3 from high-alumina fly ash by the hydrochloric acid method. The feasibility of this new electrotransformation method was studied in this paper. The effects of the current intensity, electrotransformation time, initial electrotransformation temperature and initial HCl concentration on the electrotransformation process and roasting products were investigated. The results show that the pH of the electrolyte increases with increasing current strength, electrolytic time, initial electrotransformation temperature and HCl initial concentration, and its value tends to be 3.2. Under these conditions, XRD and SEM examinations confirm that the roasting products are Al2O3 sheets with a cubic crystal system. An examination of the grain size shows that the grain sizes are uniform. Elemental content examinations show that the Cl contents of the obtained products are <0.08%. These results confirm that the new electrotransformation method is feasible for industrial use.

Oxidation leaching of copper smelting dust by controlling potential

Abstract A study was conducted for metal extraction from copper smelting dust using the oxidation leaching and control of potential technology. The effects of H2O2 dosage, H2O2 feeding speed, initial HCl concentration, leaching temperature, liquid-to-solid ratio and leaching time on metals leaching efficiencies were investigated. The following optimized leaching conditions were obtained: H2O2 dosage of 0.8 mL/g (redox potential of 429 mV), H2O2 feeding speed of 1.0 mL/min, initial H2SO4 concentration of 1.0 mol/L, initial HCl concentration of 1.0 mol/L, leaching temperature of 80 °C, initial liquid-to-solid ratio of 5:1 mL/g and leaching time of 1.5 h. Under the optimized conditions, copper and arsenic can be effectively leached from copper smelting dust, leaving residue as a suitable lead resource. The average leaching efficiencies of copper, arsenic and iron are 95.27%, 96.82% and 46.65%, respectively.

Nickel and platinum in high-temperature H2O + HCl fluids: Implications for hydrothermal mobilization

The dissolution of NiS and NiAs (nickeline) in 0.1 and 1 molal HCl at 400 °C, 80 MPa, and of PtAs2 (sperrylite) and Pt metal in 1 and 6.86 molal HCl at 500 °C, 80 MPa was studied in-situ using synchrotron radiation X-ray fluorescence and absorption spectroscopy. The Pt concentration in the fluid averaged 8 · 10−5 molal (12.8 ppm) during dissolution of Pt metal in 6.86 molal HCl, and was below the minimum detection limit (mdl; 2.6 · 10−5 molal) in all other experiments. Dissolution of NiS was congruent or nearly congruent. Equilibrium was attained rapidly in about 250 min at an initial HCl concentration of 1 molal HCl, and in about 500 min at 0.1 molal HCl. Addition of HCl resulted in a large increase in the Ni solubility from 7.2 · 10−3 molal Ni (423 ppm) at 0.1 molal HCl to 8.72 · 10−2 molal Ni (4959 ppm) at 1 molal HCl. Dissolution of NiAs in 0.1 and 1 molal HCl was incongruent. A steady state was not reached even at a run duration of more than 16 h, and the maximum recorded Ni concentrations in the fluid were much lower than the Ni solubility in the corresponding experiments with NiS at the same HCl molality. Measured K-edge XANES spectra in comparison with literature data indicated that arsenic in the fluid was present as As(V) and that nickel complexed with Cl and H2O as tetrahedral [NiCl2(H2O)2]0 and [NiCl3(H2O)]− and octahedral [NiCl2(H2O)4]0 species. In addition, Raman spectra of H2O + NiCl2 and H2O + NiCl2 + HCl solutions and of H2O + HCl fluids reacted with NiS crystals were acquired at temperatures (T) up to 600 °C and pressures (P) up to 1.15 GPa. All spectra at T ≥ 300 °C and P < 600 MPa showed a previously not reported Raman peak at ∼280 cm−1 together with a weaker peak at ∼230 cm−1. These peaks can be assigned to Ni–Cl vibrations. The band at 280 cm−1 was not detected at the other P-T conditions. Based on calculated vibrational frequencies available in the literature, it may stem from the species [NiCl4]2– or [NiCl2(H2O)4]0, although particularly the first assignment is in conflict with the information from published XAS data.The results of this study demonstrate that nickel is readily mobilized by acidic chloridic hydrothermal fluids, but platinum remains practically immobile in such fluids at any HCl concentration that is conceivable to occur in nature. Therefore, the enrichment of Pt relative to Ni in footwall-type deposits in the Sudbury District and the growth of large sperrylite crystals are likely related to magmatic processes. Furthermore, the experiments point to the importance of redox reactions for the mobilization and precipitation of arsenides and suggest that arsenate species are more stable in hydrothermal fluids than previously thought.

The adsorption of HCl on volcanic ash

Understanding the interaction between volcanic gases and ash is important to derive gas compositions from ash leachates and to constrain the environmental impact of eruptions. Volcanic HCl could potentially damage the ozone layer, but it is unclear what fraction of HCl actually reaches the stratosphere. The adsorption of HCl on volcanic ash was therefore studied from −76 to +150 °C to simulate the behavior of HCl in the dilute parts of a volcanic plume. Finely ground synthetic glasses of andesitic, dacitic, and rhyolitic composition as well as a natural obsidian from Vulcano (Italy) served as proxies for fresh natural ash. HCl adsorption is an irreversible process and appears to increase with the total alkali content of the glass. Adsorption kinetics follow a first order law with rate constants of 2.13⋅10−6 s−1 to 1.80⋅10−4 s−1 in the temperature range investigated. For dacitic composition, the temperature and pressure dependence of adsorption can be described by the equation ln⁡c=1.26+0.27ln⁡p−715.3/T, where c is the surface concentration of adsorbed HCl in mg/m2, T is temperature in Kelvin, and p is the partial pressure of HCl in mbar. A comparison of this model with a large data set for the composition of volcanic ash suggests that adsorption of HCl from the gas phase at relatively low temperatures can quantitatively account for the majority of the observed Cl concentrations. The model implies that adsorption of HCl on ash increases with temperature, probably because of the increasing number of accessible adsorption sites. This temperature dependence is opposite to that observed for SO2, so that HCl and SO2 are fractionated by the adsorption process and the fractionation factor changes by four orders of magnitude over a temperature range of 250 K. The assumption of equal adsorption of different species is therefore not appropriate for deriving volcanic gas compositions from analyses of adsorbates on ash. However, with the experimental data provided here, the gas compositions in equilibrium with the ash surfaces can be calculated. In particular, for dacitic composition, the molar ratio of S/Cl adsorbed to the ash surface is related to the molar S/Cl ratio in the gas phase according to the equation ln⁡(S/Cl)adsorbed=2855T−1+0.28ln⁡(S/Cl)gas−11.14. Our data also show that adsorption on ash will significantly reduce the fraction of HCl reaching the stratosphere, only if the initial HCl content in the volcanic gas is low (<1 mol%). For higher initial HCl concentrations, adsorption on ash has only a minor effect. While HCl scavenging by hydrometeors may remove a considerable fraction of HCl from the eruption column, recent models suggest that this process is much less efficient than previously thought. Our experimental data therefore support the idea that the HCl loading from major explosive eruptions may indeed cause severe depletions of stratospheric ozone.

Extraction of iron (III) from chloride leaching liquor with high acidity using tri-n-butyl phosphate and synergistic extraction combined with methyl isobutyl ketone

Separation of iron (III) from simulated chloride leaching liquor with high acidity by tri-n-butyl phosphate (TBP) and methyl isobutyl ketone (MIBK) extraction was investigated. Synergistic effect in iron extraction was found using TBP and MIBK extractant and evaluated by synergistic enhancement coefficient. Based on the physical properties and extraction ability of organic phase, the suitable composition was 70vol.% TBP and 30vol.% MIBK. Iron extraction increased with an increase in HCl concentration from 4.22mol/L to 7.74mol/L. Under optimal extraction conditions, that is, TBP volume fraction 70%, contact time 2min, temperature of 25°C, and phase ratio (O/A) 1:1, the iron extraction in one stage was above 91.0% with initial HCl concentration 5.1–5.5mol/L and iron concentration 36–39g/L, consistent with the practical chloride leaching liquor. Results showed that negligible metal ions Cr, V, Ca, Mg, Al, Mn, Ti and Si were co-extracted. The loaded organic phase can be effectively stripped by 0.1mol/L ammonia compared with other stripping reagents. Under the optimal stripping conditions: contact time 2min, reaction temperature 25°C, and phase ratio (A/O) 2:1, more than 89.0% of iron was stripped in one stage so the organic phase could be regenerated. The Fe2O3 product with high purity was prepared from the stripping solution by precipitation and calcination processes. The mechanism of iron (III) extraction using synergistic system was discussed according to FT-IR spectra results.

THE INFLUENCE OF HYDROCHLORIC ACID ON THE ZINC EXTRACTION FROM FLUX SKIMMING

This paper presents experimental results obtained by agitation leaching of hazardous waste sample – flux skimming. Such flux is formed by Zn(OH)Cl and NH4Cl phases. Distilled water and water solutions of hydrochloric acid were selected as a leaching media.The aim of this study was to determine optimal conditions of zinc extraction into the solution. The apparent order of reaction with regard to the initial HCl concentration in the leaching solution is n=0.18 in the concentration range from 0.01 mol.dm-3 to 0.25 mol.dm-3. The obtained results also indicate that the temperature does not significantly affect zinc extraction. The value of apparent activation energy was estimated to Ea=3.985 kJ.mol-1. Optimal liquid to solid ratio L:S=80 for both used leaching media was also determined experimentally as well as the stirring rate at 200 rpm.

Treatment of Hydrochloric Acid in Flue Gas from Municipal Solid Waste Incineration with Ca–Mg–Al Mixed Oxides at Medium–High Temperatures

A calcium–magnesium–aluminum (Ca–Mg–Al) mixed oxide sorbent was synthesized for the removal of HCl at medium–high temperatures. The operating conditions were specified in terms of the temperature of the gas (300–700 °C), the initial HCl concentration (500–1000 ppm), and the mass flow rate (0.5–1.3 L/min). X-ray powder diffraction (XRD) was applied to investigate the characteristics of Ca–Mg–Al mixed oxides. The results show that, because of the better properties of Ca–Mg–Al mixed oxides than traditional sorbents, which is related to the special structure in as-prepared, the reaction between HCl and Ca–Mg–Al mixed oxides is accelerated. The adsorption capacity of Ca–Mg–Al mixed oxides is the highest when compared to MgO, NaHCO3, and CaO. The removal efficiency of Ca–Mg–Al mixed oxides is more than 95% and even up to 99% under all of the operating conditions.

PP-008 Implementing appropriate compounded paediatric Midazolam 3mg/ml syrup in the Clinical hospital Bitola

BackgroundIn our country there are no authorised drugs for pre-procedural/preoperative sedation and anxiolysis in paediatric patients. As demand for such medicines has risen from the anaesthesiologists in our hospital we...

On the use of imidazolium and ammonium-based ionic liquids as green solvents for the selective recovery of Zn(II), Cd(II), Cu(II) and Fe(III) from hydrochloride aqueous solutions

This work analysed the extraction of Zn(II), Cd(II), Cu(II) and Fe(III) from hydrochloride aqueous solutions using imidazolium and ammonium-based ionic liquids as sole extraction agents. The selective separation of the different species is desired for potential valorization of aqueous effluents in which these ions are involved, for example, in zinc refineries. The influence of parameters affecting the extraction of the target metal ions, such as the ionic liquid composition, metal ion concentrations and hydrochloric acid concentration in the aqueous phase was analysed. It was found that the ionic liquid methyltrioctylammonium chloride [MTOA+][Cl−] allowed almost the complete removal of Zn(II), Cd(II) and Fe(III) from the aqueous solutions while the use of 1-methyl-3-octylimidazolium tetrafluoroborate [omim+][BF4-] allowed the selective separation of Zn(II) and Cd(II) over Fe(III) and Cu(II). An increase in metal ion concentration decreases the extraction percentage of the assayed metal ions. The initial HCl concentration has also an important effect on the efficiency of the extraction process, founding that an increase in HCl concentration involves a significant increase in the extraction percentages for Zn(II), Cd(II) and Fe(III). This work demonstrates the exciting potential of ionic liquids for use as green extraction agents in liquid/liquid extraction of heavy metal ions.

Preparation of Poly(vinylidene fluoride-co-tetrafluoroethylene)-Based Polymer Inclusion Membrane Using Bifunctional Ionic Liquid Extractant for Cr(VI) Transport

A series of novel polymer inclusion membranes (PIMs) were prepared and applied in Cr(VI) transport. The PIMs were composed of bifunctional ionic liquid extractant (Bif-ILE) [trialkylmethylammonium][bis(2,4,4-trimethylpentyl)phosphinate] ([A336][C272]), [trialkylmethylammonium][di-2-ethylhexylphosphinate] ([A336][P204]), or [trialkylmethylammonium][di-(2-ethylhexyl)orthophosphinate] ([A336][P507]) as the carrier, 1-octyl-3-methylimidazolium hexafluorophosphate or tetrafluoroborate ([C8mim][PF6] or [BF4]) as the ionic liquid plasticizer (ILP), and poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF) as the polymer. ILP played a key role for the permeability coefficient (P). The maximum P values of [A336][C272], [A336][P204], and [A336][P507] PIMs were 1.39, 1.41, and 0.66 times higher than that without the plasticizer, respectively. The HCl concentration in the feed phase and NaOH concentration in the stripping phase had effects on the flux of Cr(VI). The maximum initial flux (Ji) was 40.08 μmol m–2 s–1 using the [A336][P204] PIM when the initial HCl concentration in the feed phase was 0.20 mol L–1 and the NaOH concentration in the stripping phase was 0.05 mol L–1. The selectivity of three PIMs followed as [A336][P204] ≈ [A336][P507] > [A336][C272]. Compared with Cyphos IL 104, the P value of Cr(VI) using [A336][C272], [A336][P204], or [A336][P507] was all higher than using Cyphos IL 104.

Modeling of batch electrodialysis for hydrochloric acid recovery

Electrodialysis (ED) is a feasible method for acid recovery because it has the capability of separating ionic chemicals from non-ionic chemicals in process or waste streams to achieve product purity or eliminate wastes. At the same time, it can also enrich the separated chemicals. In this work, a model based on first principle was developed in order to understand the behavior of electrodialysis process. The Nernst–Planck derived relationship was used to build the ED process model which contains a set of ordinary differential equations (ODE). A degree of freedom analysis was carried out and a unique solution with 38 unknown parameters were identified. The parameters were determined from the literature and various equations. The developed model was then simulated and the results were compared to that from previous experimental work. The accuracy of the developed model was high with 99% degree of confidence. The sensitivity analysis of various ED parameters towards its performances was also analyzed. It was found that process time and energy consumption increased when higher initial HCl concentration in the dilute and concentrate tanks, higher current density and lower V conc / V dil ratio were applied. However, the effect of flowrate on process time and energy consumption was found to be insignificant.

Kinetics of processes and energy distribution in an electric discharge upon pumping a XeCl laser

Radiation energies and efficiencies of the XeCl laser are calculated for different pump regimes in a broad range of variations in the initial parameters [pump energy of 50 — 350 J L-1, pulse duration of 30 — 150 ns, initial concentration of HCl molecules of (0.7 — 2.5) × 1017 cm-3]. The sequence of kinetic processes during which the pump energy is converted into induced radiation and heat is determined. It is shown that when 80% — 90% of the initial HCl concentration is used per pulse, the optimal ratio between the radiation energy and the laser efficiency is provided. In these regimes, about 50% of the pump energy is spent on production of excimer molecules in the entire range of the experimental parameters and for one HCl molecule 10 ± 1.5 eV is spent.

Hierarchically Nanostructured Rutile Arrays: Acid Vapor Oxidation Growth and Tunable Morphologies

A general acid vapor oxidation (AVO) strategy has been developed to grow highly oriented hierarchically structured rutile TiO(2) nanoarrays with tunable morphologies from titanium thin films. This is a simple one-pot synthesis approach involving the reaction of a titanium surface with the vapor generated from a hydrochloric acid solution in a Teflon lined autoclave. To the best of our knowledge, this is the first successful attempt to grow ordered tree-like titania nanoarrays. A possible formation mechanism for the interesting architectures has been proposed based on series of time-dependent experiments. By adjusting the initial HCl concentration, films of different rutile structures including nanotrees, dendritic nanobundles, and nanorods can be selectively obtained. Subsequently, the surface morphologies and wettability can be readily tuned.

Electrodialytic utilization of boron IE column post-regeneration lyes

Presently boron-rich chemical landfill leachate originating from Tarnowskie Góry is being treated by boron-selective ion-exchange resin. Since the boron concentration in this feed water type is relatively high (approx. 70 mg of B/L), the IE column post-regeneration lyes, that are strongly acidic and contain up to 2.5 g of B/L, utilization cost increases the boron removal cost to a large extent. Thus, based on the authors’ previous research, an attempt was made to propose a low-cost method for utilization of the lye of this type. Primarily, by observing the species, namely HCl and boron, distribution into the post-regeneration lye (eluate) it was concluded that three distinct fractions may be identified. The first, approx. 25% of the total eluate volume, is rich in both acid and boron (approx. 2.33 g B/L and 17.57 g HCl/L), the second is rich in acid and contained some boron (approx. 1.8 g B/L and 30 g HCl/L) and the third that contained both acid and boron at low level (0.163 g B/L and 1.05 g HCl/L). The first fraction of the highest boron content is suspected to be treated electrodialytically to regenerate spent acid. The resulting dilutate contain only small part of the initial HCl concentration and all or at least most of the boron. This may be easily neutralized and co-precipitated with Al(OH) 3 as we proposed elsewhere. Simultaneously obtained the ED concentrate (concentrated HCl soln. of 40.7 g/L HCl content at boron level of 0.307 g/L) may be further used for column regeneration. The second part of the eluate of high HCl content is suspected to be directly used for IE column regeneration (together with the ED concentrate). This, by proper mixing, the boron level may be kept low to ensure enough driving force for regeneration. The third eluate fraction together with the supernatant solution, originating from Al(OH) 3 precipitation, may be recirculated to the main stream (mixed with the treated leachate) since the boron content does not differ much. Thus a technology with no boron-containing wastewater is obtained. The only boron form here is the B co-precipitated with Al(OH) 3.

Facilitated supported liquid membrane transport of gold (I) and gold (III) using Cyanex ® 921

The commercially available extractant Cyanex ® 921 (phosphine oxide) was studied to be applied in the carrier-facilitated transport of gold (I) (cyanide media) and gold (III) (chloride media), across a flat-sheet supported liquid membrane (FSSLM). Gold (I) is transported from alkaline pH values. The presence of lithium salts in the aqueous media improves the transport. In chloride media, the carrier is able to transport gold (III), decreasing the permeability as the initial HCl concentration is increased. From both aqueous media, a model is presented that describes the transport mechanism, consisting of diffusion through a feed side aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier and metal complexes through the organic membrane. The organic membrane diffusional resistance ( Δ o), aqueous diffusional resistance ( Δ a) were calculated from the proposed model, and their values were 1.1 × 10 4 and 9.1 × 10 8 s/cm ( Δ o, cyanide and chloride media) and 5.3 × 10 2 and 2.6 × 10 2 s/cm ( Δ a, cyanide and chloride media). The values of the bulk diffusion coefficient ( D o,b) and diffusion coefficient ( D o) calculated from the model were D o,b (cyanide) = 4.1 × 10 −6 cm 2/s, D o,b (chloride) = 5.2 × 10 −11 cm 2/s; D o (cyanide) = 1.1 × 10 −6 cm 2/s, D o (chloride) = 1.4 × 10 −11 cm 2/s.