Fixed‐Bed Removal of Free and Complexed Ni from Synthetic and Industrial Aqueous Solutions

Abstract

This paper evaluates the application of several biosorbents for Ni removal from aqueous solutions in the absence and in the presence of EDTA. Fixed bed experiments were performed (Ni influent concentration, 2 mg dm^?3; EDTA doses, 0, 5, and 10 mg dm^?3; pH=7) to study the process feasibility as refining after conventional physicochemical treatment. In absence of EDTA, uptake capacity followed the order peat > Posidonia oceanica > chitosan > chitin ? Scharlau AC. Maximum uptakes of 8.95 mg g^?1 and 5.10 mg g^?1 were found for peat and Posidonia oceanica, respectively. In the presence of EDTA, removal capacity decreased for all biosorbents; Ni was detected in the effluent from the beginning of the operation, indicating low ability to retain Ni EDTA‐complexes. Activated carbon presented the ability to remove complexed Ni. Peat exhibited the best performance for the treatment of an industrial spill from a metal‐finishing facility, with effluent Ni concentration lower than 0.2 mg dm^?3 for more than two weeks of treatment (3500 pore volumes of treated wastewater).     

Applications of the Biosorption Process for Nickel Removal from Aqueous Solutions – A Review

Wastewaters and contaminants released to the aqueous environment increase due to developing industrialization and technology. These wastewaters should be treated before being discharged to water bodies. Also, reusable materials in wastewaters must be recovered by appropriate techniques. Discharge limits required by the authorities become more stringent with updated legislations. Nickel ions can be reusable by recovering it after the biosorption process. So, this will prevent the loss of raw materials in industries and it also affects the economy in a positive way. Conventional heavy metal removal processes may be costly and inadequate to meet the desired discharge limits and they exhibit low efficiencies. Eco-friendly and economical treatment technologies gain great importance in the removal and recovery of nickel from wastewaters. In this study, biosorption which is the subject of numerous studies and one of the heavy metal removal methods will be investigated, and nickel removal by this technique and the biosorption mechanism will also be elaborated with data from literature studies.     

Fluoride Removal from Aqueous Solutions by Magnesium,Nickel, and Cobalt Calcined Hydrotalcite‐like Compounds

Abstract

Magnesium, nickel and cobalt hydrotalcite‐like compounds (MgHT, NiHT, and CoHT), with similar M²⁺:Al³⁺ ratios were synthesized and characterized by XRD. It was confirmed from XRD that the materials have hydrotalcite‐like structure. MgHT, NiHT, and CoHT were calcined and treated with fluoride solutions in a batch system. F^? ions were determined in the remaining solutions using a fluoride ion selective electrode. The kinetics of the fluoride ions sorption on calcined hydrotalcite‐like compounds (CHT) was best described by the pseudo‐second order model and the equilibrium was reached in less than 300 minutes in all cases (MgCHT, NiCHT, and CoCHT). The sorption isotherms of the fluoride by hydrotalcite like compounds can be explained by the Langmuir‐Freundlich model and, the highest fluoride sorption capacity was obtained for NiCHT (1.202 mgF/gCHT). The fluoride removal from aqueous solutions by calcined hydrotalcite‐like compounds depends on the adsorption properties of the thermal decomposition products and the regeneration reaction mechanism of the hydrotalcite‐like compounds.     

Separation of Arsenic from Aqueous Solutions by Amino-Functionalized γ-Fe2O3-β-Zeolite

In this research, γ-Fe₂O₃-β-zeolite nanocomposite was synthesized and functionalized by 3-amino propyl trimethoxysilane. The magnetic functionalized adsorbent was characterized by FTIR, X-ray diffraction, thermal analysis, vibrating sample magnetometry, scattering electron microscopy, and N₂ adsorption-desorption techniques. The adsorbent was then used for adsorption of arsenic from aqueous solutions. At optimized conditions the adsorption capacity of 30 mg.g^?1 was obtained, which was higher than the previously reported values. The loaded adsorbent was easily separated from the solution by applying an external magnetic field. Regeneration of the adsorbent by NaOH solution indicated that 97% of the initial capacity was remained after four adsorption-regeneration cycles.     

Measurement of the hydroxyl radical formation from H2O2, NO3−, and Fe(III) using a continuous flow injection analysis

Production of hydroxyl radical (OH) is of significant concern in engineered and natural environment. A simple in situ method was developed to measure OH formation in UV/H₂O₂, UV/Fe(III), and UV/NO₃^? systems using trapping of OH by benzoic acid (BA) and measuring fluorescence signals from hydroxylated products of BA. Method development included characterization of OH trapping mechanism and measurement of quantum yields (Φ_OH) for OH. The distribution of OHBA isomers was in the order of o-OHBA > p-OHBA > m-OHBA, although it changed with the H₂O₂ concentration and light intensity. This supports that OH attacks dominantly on the benzene rings. The quantum yields for OH formation in the UV/H₂O₂ process were 1.02 and 0.59 at 254 and 313 nm, which were in good agreement with the literature values, confirming that the method is suitable for the measurement of OH production from UV/H₂O₂ processes. Using the continuous flow method developed, quantum yields for OH in UV/H₂O₂, UV/Fe(III), and UV/NO₃^? systems were measured varying the initial concentration of OH precursors. The Φ_OH values increased with increasing concentrations of H₂O₂, Fe(III), and NO₃^? and approached constant values as the concentration increased. The Φ_OH values were 0.009 for H₂O₂ at 365 nm, showing that OH production is not negligible at such high wavelength. The Φ_OH values during the photolysis of Fe(OH)²⁺ (pH 3.0) and Fe(OH)₂⁺ (pH 6.0) at 254 nm were 0.34 and 0.037, respectively. The Φ_OH values for NO₃^? approached a constant value of 0.045 at 254 nm at the initial concentration of 10 mM.     

Ion Exchange of the Organometallic Aqua‐Ion fac‐[99mTc(CO)3(H2O)3]+ from Aqueous Solutions

Dynamic (column) studies on the ion exchange of triaquatricarbonyltechnetium(I) cation, fac‐[^99mTc(CO)₃(H₂O)₃]⁺ (1), in the system: amphoteric ion exchange resin (Purolite S‐950) ‐ aqueous HNO₃ solutions (0.05–2 M) corroborate the +1 charge of 1. Stability constants of fac‐[^99mTc(CO)₃(H₂O)_3?nCl_n]^1?n complexes, determined from the distribution coefficients in the system anion exchanger (Dowex 1X4) ‐ aqueous HCl solutions (0.1–12 M) differ from the literature values determined at a constant ionic strength. This difference, resulting from the decrease in the activity of water with increasing HCl concentration, may be a measure of the effect of non‐constant ionic strength on ion‐exchange equilibria. Weak acidic properties of 1 in aqueous solution at n.c.a. (no carrier added) level (pK_a ?9) have been demonstrated by paper electrophoresis.     

Modification of Malonamide Ion-Exchange/Chelating Resins Using the Fields–Kabatschnik Reaction and Their Application to Metal Ion Removal from Aqueous Solutions

A resin containing 2-aminoethyl-substituted amides of malonic acid was modified in the Fields–Kabatschnik reaction using diethyl phosphite. The resultant ion-exchange/chelating resins have aminomethylphosphonate groups. Modification proceeds almost quantitatively, giving a resin with P=1.97 mmol/g, N=4.20 mmol/g, and water regain of 0.44 g/g. It can be selectively hydrolyzed by treatment with trimethylchlorosilane/potassium bromide in dry acetonitrile. Both acidic and ester forms of the resin were used in the removal of Cu(II), Cd(II), Ni(II), and Zn(II) from their diluted 1×10^–4 N solutions in 0.2 M acetate buffer at pH 3.7 and 5.6. The affinity of the resin in an acid form toward divalent metal cations is high, and at pH 5.6 the log K _d is 7.54, 3.97, 3.41, and 3.98, respectively. The resins are selective and the presence of an excess of sodium ions does not influence the uptake of metal ions. The type of complexes formed between the resins and Cu(II) ions was studied using EPR spectroscopy. The ester form of the resin was used in the removal of tetrachloroaurate anions from hydrochloric acid solution. It has been found that the log K _d is in the range of 3.14–3.94 for the uptake of AuCl^– ₄ from 5.0–0.5 M HCl solutions.     

Promotional effect of H2O on the activity of In2O3‐doped Ga2O3–Al2O3 for the selective reduction of nitrogen monoxide

Effect of metal oxide additives on the catalytic performance of Ga₂O₃–Al₂O₃ prepared by the sol–gel method for the selective reduction of NO with propene in the presence of oxygen was studied. Of several metal oxide additives, the addition of In₂O₃ enhanced drastically the activity of Ga₂O₃–Al₂O₃ for NO reduction by propene in the presence of H₂O. In addition, the activity of In₂O₃‐doped Ga₂O₃–Al₂O₃ catalyst was extremely intensified by the presence of H₂O below 350°C. The promotional effect of H₂O was interpreted by the suppression of undesirable propene oxidation and the removal of carbonaceous materials deposited on the catalyst surface. We also found that close interaction of In₂O₃ and Ga₂O₃ is necessary for the enhancement of activity by H₂O. A lot of hydrocarbons except methane and oxygenated compounds served as good reducing agents, among which propene and 2‐propanol were the most efficient ones. In₂O₃‐doped Ga₂O₃–Al₂O₃ catalyst was capable of reducing NO into N₂ quite efficiently in the presence of H₂O at a very high space velocity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characteristics of porous mullite developed from clay and AlF3·3H2O

Porous mullite with interlocked needle shape microstructure was developed from China clay and aluminium fluoride trihydrate (AlF₃·3H₂O). The effects of various parameters like sintering temperature, sintering time and the amount of AlF₃·3H₂O on the phase evolution, microstructure and porosity have been studied. Quantitative analysis of mullite was carried out using X-ray diffraction combined with Rietveld-RIR method (Internal standard method). Porous mullite ceramics with 62% open porosity have been prepared at a relatively lower temperature of 1400?°C. The results show that the nucleation of mullite can be achieved from 700?°C onwards using hydrated aluminium fluoride without the formation of intermediate topaz crystals. The high amount of water vapour produced within the system during the in-situ reaction has a crucial role in deciding the reaction mechanism.     

Thermodynamic modeling of the K2O-Al2O3 and K2O-MgO-Al2O3 systems with emphasis on β- and βʹʹ-aluminas

A critical evaluation and thermodynamic modeling study including key phase diagram experiments was performed to investigate the K₂O-Al₂O₃ and K₂O-MgO-Al₂O₃ systems. For the first time, potassium β- and β??-alumina solid solutions were described using the Compound Energy Formalism with accurate cation distributions in their sublattices. From the new experimental results, the stability of potassium β??-alumina was assured up to 1600?°C. A large discrepancy reported in the literature, the eutectic temperature between KAlO₂ and β-alumina in the K₂O-Al₂O₃ system, was resolved. A set of self-consistent Gibbs energy functions for all stable phases in the K₂O-MgO-Al₂O₃ system was obtained. As a result, any phase diagram sections and thermodynamic properties of the K₂O-MgO-Al₂O₃ system can be calculated from the optimized Gibbs energy functions. In particular, the cation distribution in the β- and β??-alumina solid solutions is calculated depending on the non-stoichiometry of solution and temperature.     

Effects of H2O in EtOH–H2O disperse medium on the electrophoretic deposition of CaSiO3 fine powder

The effects of H₂O in the EtOH–H₂O disperse medium on the electrophoretic deposition (EPD) of CaSiO₃ fine powder were investigated. Fine CaSiO₃ powder with average diameter of 1·7 μm was prepared by the coprecipitation method. It was deposited on a stainless steel substrate by EPD in the disperse media with various H₂O concentrations (0–20·2 mass%) under a DC field of 50 V. The amount of the CaSiO₃ deposition increased with increasing H₂O up to 11·2 mass% but decreased rapidly beyond this concentration. The surface potential of the powder showed a similar trend as the amount of deposition against H₂O concentration. The effect of H₂O was summarized as follows: (1) the addition of positive charge on the surface of CaSiO₃ particles (2) the neutralization of the surface charge by OH⁻ caused by the dissolution of CaSiO₃ in the H₂O.     

Effect of Al2O3 and K2O content on structure,properties and devitrification of glasses in the Li2O–SiO2 system

The effect of Al₂O₃ and K₂O content on structure, sintering and devitrification behaviour of glasses in the Li₂O–SiO₂ system along with the properties of the resultant glass–ceramics (GCs) was investigated. Glasses containing Al₂O₃ and K₂O and featuring SiO₂/Li₂O molar ratios (3.13–4.88) far beyond that of lithium disilicate (Li₂Si₂O₅) stoichiometry were produced by conventional melt-quenching technique along with a bicomponent glass with a composition 23Li₂O–77SiO₂ (mol.%) (L₂₃S₇₇). The GCs were produced through two different methods: (a) nucleation and crystallization of monolithic bulk glass, (b) sintering and crystallization of glass powder compacts.Scanning electron microscopy (SEM) examination of as cast non-annealed monolithic glasses revealed precipitation of nanosize droplet phase in glassy matrices suggesting the occurrence of phase separation in all investigated compositions. The extent of segregation, as judged from the mean droplet diameter and the packing density of droplet phase, decreased with increasing Al₂O₃ and K₂O content in the glasses. The crystallization of glasses richer in Al₂O₃ and K₂O was dominated by surface nucleation leading to crystallization of lithium metasilicate (Li₂SiO₃) within the temperature range of 550–900 °C. On the other hand, the glass with lowest amount of Al₂O₃ and K₂O and glass L₂₃S₇₇ were prone to volume nucleation and crystallization, resulting in formation of Li₂Si₂O₅ within the temperature interval of 650–800 °C.Sintering and crystallization behaviour of glass powders was followed by hot stage microscopy (HSM) and differential thermal analysis (DTA), respectively. GCs from composition L₂₃S₇₇ demonstrated high fragility along with low flexural strength and density. The addition of Al₂O₃ and K₂O to Li₂O–SiO₂ system resulted in improved densification and mechanical strength.     

Ceramic Raschig Rings—Improving Removal of Organic Compounds from Landfill Leachate by Perozone (O3/H2O2)

For improving the treatment of landfill leachate by combination O₃/H₂O₂, ceramic Raschig rings (CRR) with different surface areas were added to enhance mass transfer of ozone into liquid phase. To determine optimal conditions of reaction, pH and reaction time was also studied. The optimal pH range of 8–9, optimal reaction time of 80 min was identified in this research. CRR contribute to the significant improvement of efficiency of landfill leachate treatment by O₃/H₂O₂ systems. With added CRR of 728 m²/m³ surface area, color, COD and TOC removal was increased in comparison with experiment without CRR is 8%, 14%, and 9%, respectively. In this condition, the ozone utilization efficiency was also higher than that of experiment without CRR. Content of O₃ was also identified uses 3.441 kg O₃/kg COD.     

Investigation of Selectivity and Kinetic Behavior of Strong‐Base Ion Exchange Resin Purolite A 520E for Nitrate Removal from Aqueous Solution

Abstract

The aim of this work is to present experimental results on the removal of nitrate by nitrate selective ion exchange resin, Purolite A 520E. The resin particle size, nitrate concentration, temperature, and stirring speed were investigated as experimental parameters and the optimum conditions for nitrate removal were determined. Nitrate removal by strong base anion exchange resin Purolite A 520E was carried out with the batch method in the presence of chloride and sulfate ions. The existence of a high concentration of competing ions in a solution resulted in a reduction of nitrate removal. Nitrate removal ratios decreased from 98% to 85% and 88%, respectively, in the presence of chloride and sulfate ions when the chloride and sulfate ratios were increased in solution. The process kinetics were predicted by using Homogenous Diffusion Models. It was seen that about 98% of nitrate in the aqueous solution could be removed using optimum conditions.     

Novel Ti2O3–Al2O3 raw materials with controllable Ti2O3 content from the aluminothermic reduction of ilmenite

Titanium-containing refractories have excellent performance, but the high cost limits their application. A series of Ti₂O₃–Al₂O₃ raw materials with different Ti₂O₃ contents were prepared by aluminothermic reduction of ilmenite, while the generated ferrotitanium alloy can be used as raw materials for special steels. Regulating the amount of aluminum added in the system regulates the degree of titanium reduction, and the formed ferrotitanium alloy can achieve separation from the oxides. With decreasing aluminum content of, the Ti₂O₃ content increased, and the continuous distribution of the corundum area decreased, resulting in a continuously distributed Ti₂O₃ area. Our results indicated that the molar ratio of aluminum to ilmenite should be higher than 1.4 to achieve slag iron separation. The reaction model for the aluminothermic reduction was established, and the formation mechanism of Al₂O₃ and Ti₂O₃ in the system was discussed.     

Fabrication and characterization of La2O3–Fe2O3–Bi2O3 nanopowders: Effects of La2O3 addition on structure,optical, and radiation-absorption properties

In this study, we fabricated and characterized six new nanopowders representing variations of La₂O₃–Fe₂O₃–Bi₂O₃, i.e., 100Bi₂O₃, 30Fe₂O₃–70Bi₂O₃, 3La₂O₃–27Fe₂O₃–70Bi₂O₃, 7La₂O₃–23Fe₂O₃–70Bi₂O₃, 10La₂O₃–20Fe₂O₃–70Bi₂O₃, and 20La₂O₃–10Fe₂O₃–70Bi₂O₃ (represented by 100B, 30F70B, 3L27F70B, 10L20F70B, and 20L10F70B, respectively). These nanopowders were prepared by the microwave-assisted hydrothermal synthesis method. Saponin extract from soapnuts was used as the nanoparticle capping agent. The structural, optical, and gamma radiation characteristics were measured, calculated, and analysed, respectively. The chemical structures of the nanocomposites influenced their optical and radiation shielding characteristics. The optical bandgaps of the 100B, 30F70B, 3L27F70B, 7L23F70B, 10L20F70B, and 20L10F70B nanopowders were 3.16, 3.13, 3.43, 3.45, 3.46, and 3.58 eV, respectively. The ranges of the mass attenuation coefficients of the nanopowders were computed, using XCOM, to be 0.0412–5.1624, 0.0401–4.5406, 0.0401–4.5285, 0.0401–4.5129, 0.0401–0.5015, and 0.0400–4.4156 cm²/g, respectively, and the ranges of mass energy absorption coefficients were found to be 0.0232–1.7525, 0.0228–1.5484, 0.0228–1.5598, 0.0288–1.5746, 0.0228–1.5853, and 0.0227–1.6192 cm²/g, respectively, for photon energies in the range of 0.1–10 MeV. The order of the dose rate trend was as follows: 30F70B < L27F70B < 7L23F70B < 10L20F70B < 20L10F70B. Analysis of the photon interaction parameters showed that the synthesized nanopowders could function well as fillers in radiation-shielding matrices.     

Surface stabilities of 3C–SiC and H2O adsorption on the (110) surface

First-principles calculations and thermodynamics analyses were combined to study the surface stabilities of 3C–SiC and H₂O adsorption on the (110) surface. The stoichiometric (110) surface was predicted to be generally the most stable. Only at the extremely C-poor condition, the nonstoichiometric Si-terminated (100) could become more energetically favored. The adsorption and dissociation of single H₂O molecule on the 3C–SiC (110) were then comparatively investigated. Calculations show that H₂O molecules prefer to partially dissociate into one hydroxyl OH and one H adsorbed at the top-most Si and C sites, respectively, leading to the formation of a hydrogen network on the surface. The calculated equilibrium adsorption diagram further suggested that the 3C–SiC (110) surface can be only either completely clean or fully covered by the partially dissociated species of H₂O, for a wide range of temperature and the partial potential of H₂O.     

Sorption of U(VI) onto Layered Double Hydroxides of Mg and Al with β-Cyclodextrin from Aqueous Solutions

Theoretical Foundations of Chemical Engineering - The possibility of removing U(VI) from aqueous solutions using layered double hydroxides of Mg and Al, which contain β-cyclodextrin...     

Studies on the dispersion states of Fe2O3 on γ-Al2O3 by means of Mössbauer spectroscopy and XRD

XRD and Mössbauer spectroscopy studies show that Fe₂O₃/-Al₂O₃ made by impregnation-calcination method may have monolayer dispersed Fe₂O₃ and -Fe₂O₃ crystallites. There is a threshold monolayer dispersion capacity. If the Fe₂O₃ loading is lower than the threshold, the Fe₂O₃ will disperse on the surface of -Al₂O₃ as a monolayer, then the sample will give an XRD pattern with no crystalline Fe₂O₃ peaks and a Mössbauer spectrum of a doublet with large quadruple splitting (1.11 mm/s). When the Fe₂O₃ loading is higher than the threshold, in addition to the monolayer dispersed Fe₂O₃, crystalline -Fe₂O₃ will appear, then the sample will give an XRD pattern with crystalline -Fe₂O₃ peaks and a Mössbauer spectrum with a quadrupole splitting doublet superimposed on a magnetic splitting sextuplet. Monolayer dispersion capacity obtained by quantitative XRD phase analysis and Mössbauer spectra analysis are consistent with each other, having the same value of 0.052 g Fe₂O₃/100 m² -Al₂O₃ surface.