Packed Column Tests Research Articles

Divalent cation contributions to the co-transport and deposition of functionalized multi-walled carbon nanotubes in porous media in the presence of bentonite or goethite nanoparticles: Experiment and simulation

This work investigates the influence of cation type (Ca2+ as compared to K+) on the co-transport and deposition of functionalized multi-walled carbon nanotubes (MWCNTs) with negatively (bentonite nanoparticles, BNPs) or positively (goethite nanoparticles, GNPs) charged natural nanoparticles under the same ionic strength (IS = 1 mM) conditions. In packed column tests with quartz sand (QS), the co-transport of MWCNTs was slightly increased by BNPs and inhibited by GNPs in both CaCl2 and KCl solutions, whereas the co-transport of BNPs or GNPs was facilitated by MWCNTs in both solutions. However, the co-transport of MWCNTs in the presence of BNPs or GNPs exhibited a different dependency on the cation type in quartz crystal microbalance with dissipation (QCM-D) tests. No deposition of MWCNTs and BNPs was observed in QCM-D studies in the presence of KCl, while enhanced deposition of MWCNTs and GNPs occurred in this same solution. In contrast, the deposition of both MWCNTs and BNPs or MWCNTs and GNPs increased in QCM-D in the presence of CaCl2. In both column and QCM-D studies, Ca2+ exhibited a more significant impact on co-transport than K+, especially for MWCNTs with GNPs than BNPs. Results from molecular dynamic simulations, aggregation studies, and interaction energy calculations indicate that non-DLVO interactions (e.g., H-bonding and cation-π interaction) between two nanoparticles (MWCNTs with BNPs or GNPs) played a non-negligible role in interpreting the deposition and co-transport in the presence of the divalent cation Ca2+. Mathematical modeling of breakthrough curves and retention profiles and aggregation results suggest that both straining and competitive blocking were enhanced and played dominant roles in the co-transport of MWCNTs in the presence of BNPs or GNPs in QS, especially in the presence of Ca2+. This work sheds novel insights on the contribution of divalent cations to interactions between two colloids and their co-transport in porous media. This information is needed to assess the environmental fate and risks of engineered nanoparticles (ENPs) and natural nanoparticles in aquatic and soil environments with abundant divalent cations.

Efficient Iodine Removal by Porous Biochar-Confined Nano-Cu2O/Cu0: Rapid and Selective Adsorption of Iodide and Iodate Ions.

Iodine is a nuclide of crucial concern in radioactive waste management. Nanomaterials selectively adsorb iodine from water; however, the efficient application of nanomaterials in engineering still needs to be developed for radioactive wastewater deiodination. Artemia egg shells possess large surface groups and connecting pores, providing a new biomaterial to remove contaminants. Based on the Artemia egg shell-derived biochar (AES biochar) and in situ precipitation and reduction of cuprous, we synthesized a novel nanocomposite, namely porous biochar-confined nano-Cu2O/Cu0 (C-Cu). The characterization of C-Cu confirmed that the nano-Cu2O/Cu0 was dispersed in the pores of AES biochar, serving in the efficient and selective adsorption of iodide and iodate ions from water. The iodide ion removal by C-Cu when equilibrated for 40 min exhibited high removal efficiency over the wide pH range of 4 to 10. Remarkable selectivity towards both iodide and iodate ions of C-Cu was permitted against competing anions (Cl-/NO3-/SO42-) at high concentrations. The applicability of C-Cu was demonstrated by a packed column test with treated effluents of 1279 BV. The rapid and selective removal of iodide and iodate ions from water is attributed to nanoparticles confined on the AES biochar and pore-facilitated mass transfer. Combining the advantages of the porous biochar and nano-Cu2O/Cu0, the use of C-Cu offers a promising method of iodine removal from water in engineering applications.

Synthesis and CO2 Capture of Porous Hydrogel Particles Consisting of Hyperbranched Poly(amidoamine)s.

We successfully synthesized new macroporous hydrogel particles consisting of hyperbranched poly(amidoamine)s (HPAMAM) using the Oil-in-Water-in-Oil (O/W/O) suspension polymerization method at both the 50 mL flask scale and the 5 L reactor scale. The pore sizes and particle sizes were easily tuned by controlling the agitation speeds during the polymerization reaction. Since O/W/O suspension polymerization gives porous architecture to the microparticles, synthesized hydrogel particles having abundant amine groups inside polymers exhibited a high CO2 absorption capacity (104 mg/g) and a fast absorption rate in a packed-column test.

Honeycomb-like activated carbon with microporous nanosheets structure prepared from waste biomass cork for highly efficient dye wastewater treatment

Cork, a porous biomass material, is consist of thin-walled hollow prismatic cells arranged into a compact and orderly honeycomb-like structure and could be applied as an adsorption material. Here, cork-activated carbons (CACs) with a fluffy honeycomb-like structure were synthesized by two-step pyrolysis with solid KOH chemical activation to rapidly and efficiently adsorb methylene blue (MB) (maximum wavelength: 664 nm). The structure, morphology and surface functional groups of the CACs were characterized using BET, SEM, and FTIR analysis. The results show that the CACs have a well-developed hierarchical porous structure and an ultra-high specific surface area of 2864.9 m2/g, which would facilitate the efficient diffusion and adsorption of MB molecules onto CACs. MB adsorption performance results show that the CACs have an outstanding maximum MB adsorption capacity (1103.68 mg/g) and fast adsorption kinetics (800 mg/L, 99.8% in 10 min), indicating that CACs possess significant advantages compared with most other adsorbents previously reported. The adsorption mechanism was studied by various kinetic models, isothermal models and thermodynamic models. Langmuir model is the most adapted to describe the adsorption process, indicating that the MB molecules are uniformly adsorbed on CAC’s surface in a single layer. Moreover, MB adsorption by the CACs was an endothermic, spontaneous and randomly increasing adsorption. The regeneration test showed that the uptake of MB onto CACs can still reached 580 mg/g after three adsorption-desorption cycles, demonstrating the excellent reusability of CACs. The continuous adsorption performance of MB onto CACs was evaluated by a packed column test, which further confirmed its potential as an adsorbent for dye wastewater purification.

Modelling and efficiency assessment of the up flow fixed bed process packed with Moringa oleifera for continuous Cd(II) removal from drinking water

The biosorption ability of ‘Moringa oleifera ‘seed powder for the expulsion of cadmium from wastewater was investigated by performing packed column tests. Column tests were conducted as a function of biosorbent dose, influent flow rate and feed sorbate concentration. The findings from column operations revealed that values of maximum cadmium uptake, exhaustion and breakthrough time enhances with rise in bed depth, reduces with rise in feed volumetric flowrate and initial cadmium concentration. At 6 g of Moringa oleifera dose, 2 mL/min of flow rate and 300 µg/L of influent cadmium, the cadmium uptake capacity was found to be 65.44, µg/g. The continuous packed column data for cadmium were well fitted to the Thomas model with the regression coefficient ranges 0.966–0.993. Moreover, the qth values obtained from Thomas model are similar to the experimental breakthrough capacities qexp. The FTIR results reveals that the Moringa oleifera seed contains various active functional groups which are appears to be played a significant role in biosorption of cadmium ions. From practical view, the Moringa oleifera seed could be utilized as safe, inexpensive, sustainable and eco-friendly biosorbent for the elimination of cadmium from drinking water using continuous column mode and also this technology could be considered as an ideal for household usage in rural communities.

The mechanistic aspects of microbial transport in porous media

A mechanistic model is constructed to account for colloidal filtration by incorporating fundamental intersurface forces between individual particle and collector, geometry and elastic properties of bacteria / particles, and flowrate of the electrolytic medium. Particle adhesion on the collector surface is derived from the DLVO theory based on electrostatic double layers and van der Waals attraction, while particle detachment depends on the hydrodynamic shear. Filtration efficiency, α, of a conventional packed column is estimated by numerically solving the governing convection-diffusion equation, and is shown experimentally dependent on both ionic concentration and flowrate of the electrolyte contrasting the classical colloid filtration theory. Model bacterial strains of Aeromonas punctata and Raoultella ornithinolytica were investigated using a conventional packed column test and a homemade microfluidic device. Their behavior were shown to be consistent with the model.

Experimental and modelling analysis of seawater scrubbers for sulphur dioxide removal from flue-gas

Scrubbing with seawater is a reliable technology for flue-gas desulfurization in coal-fired power plants or in marine applications. The introduction of new regulations for emission control in Europe and the due increment of operational efficiency are pushing forward the optimization of scrubber’s design, for which packing columns may be a better solution compared to spray columns. The design of a seawater scrubber mainly relies on a correct assessment of the equilibrium conditions and of the mass transfer coefficients in the absorber. In this work, experiments are performed on a model flue-gas (32 m3·h−1) having a SO2 concentration in the range 500–2000 ppmv, treated in a packed column filled with a structured packing (Mellapak 250X®) at 1 atm and 25 °C, with liquid-to-gas ratio between 1.06 and 3.44 kg·kg−1. Three different absorbing solutions are investigated: (a) a seawater; (b) a basic solution obtained by adding 200 mg·L−1 NaOH solution to the seawater and (c) distilled water, used as benchmark. In order to analyze the packed column tests, SO2 equilibrium absorption tests at low concentrations (100–2000 ppmv) are carried out in a feed-batch reactor, using the same absorbing solutions tested in column tests. The experimental tests in packed column indicate that, for SO2 concentration as low as 500 ppm, an absorption efficiency above 98% can be achieved by using liquid-to-gas mass ratio about to 2.91 kg·kg−1. In this condition, few differences appear among solutions (a) and (b). For the highest SO2 concentration (i.e. 2000 ppmv), a maximum of 85% efficiency is observed for liquid-to-gas mass ratio of 3.44 kg·kg−1. Modeling of both the equilibrium and the dynamic data are implemented in Aspen Plus® V 8.6. However, while modeling assures a very good prediction of the equilibrium data, it is not able to properly describe the dynamic test results, with a systematic underestimation for tests having a removal efficiency higher than 85%.

Nonlinear Flow through a Packed-Column Experiment

AbstractIn order to investigate the behavior of flow through granular materials, a packed column test was employed. The laboratory model consisted of a permeameter having 0.2 m diameter and 1 m length. Two kinds of crushed and rounded gravel particles with six different sizes were used as porous materials. By using flow velocity–hydraulic gradient relationships, it was observed that the relationships between velocity and hydraulic gradient are nonlinear and why it is called non-Darcy flow. Evaluating the results of this research for both kinds of aggregates by means of statistical indicators and comparison of different relationships showed the best empirical equation. The relation between Reynolds number and diameter of materials indicated that the friction factor for higher Reynolds numbers decreased and reached to a constant value for both kinds of materials.

Transport of poly(acrylic acid) coated 2-line ferrihydrite nanoparticles in saturated aquifer sediments for environmental remediation

Groundwater remediation using iron oxide and zero-valent iron nanoparticles (NPs) can be effective, but is limited in many applications due to the NP strong retention in groundwater-saturated porous media after injection, the passivation of the porous surface, and the high cost of nanomaterials versus macro scale iron. In this study, we investigated transport of bare and polymer-coated 2-line ferrihydrite NPs (30–300 nm) in saturated aquifer sediments. The influence of poly(acrylic acid) (PAA) polymer coatings was studied on the colloidal stability and transport in sediments packed column tests simulating groundwater flow in saturated sediments. In addition, the influence of calcium cations was investigated by transport measurements using sediments with calcium concentrations in the aqueous phase ranging from 0.5 (typical for most sediments) to 2 mM. Measurements were also made of zeta potential, hydrodynamic diameter, polymer adsorption and desorption properties, and bio-availability of PAA-coated NPs. We found that NP transport through the saturated aquifer sediments was improved by PAA coating and that the transport properties could be tuned by adjusting the polymer concentration. We further discovered that PAA coatings enhanced NP transport, compared to bare NPs, in all calcium-containing experiments tested, however, the presence of calcium always exhibited a negative effect on NP transport. In tests of bioavailability, the iron reduction rate of the coated and bare NPs by Geobacter sulfurreducens was the same, which shows that the PAA coating does not significantly reduce NP Fe(III) bioavailability. Our results demonstrate that much improved transport of iron oxide NP can be achieved in saturated aquifer sediments by introducing negatively charged polyelectrolytes and optimizing polymer concentrations, and furthermore, these coated NPs retain their bioavailability that is needed for applications in bio-environmental remediation.

Non-Darcy Flow of Water Through a Packed Column Test

As the flow velocity and Reynolds number increase in rockfilled porous media, the flow deviates from Darcy conditions and enters into a new phase known as non-Darcy conditions. Due to a linear relationship between hydraulic gradient and the flow velocity in Darcy formula, the flow can be analyzed with no difficulty. However, as the velocity increases the Darcy law is violated, the flow becomes turbulent, making the analysis more challenging. In this paper a laboratory packed column was built to study high-velocity flow through granular materials and new experimental data have been obtained. The laboratory experiments include application of for six different sizes of rounded aggregates and using different hydraulic gradients to assess the flow behavior. Using new experimental data, the validity of four widely-used head-loss equations were evaluated. The results indicated that the Sidiropoulou et al. (Hydrol Process 21:534–554, 2007) and Ergun’s head-loss equations yield satisfactory results comparing to other available relationships.

Phosphorus Recovery from Urban Wastewater Treatment Plant Sludge Liquor by Ion Exchange

In this study phosphorus recovery from sludge liquor by ion exchange process was investigated. The efficiency of a commercially available anionic iron oxide resin was evaluated in batch and packed column tests using synthetic phosphorus solution and actual sludge liquor, taken from of an urban wastewater treatment plant (UWWTP). When phosphorus recovery from sludge liquor was investigated, experimental data fitted quite well Generalized Langmuir–Freundlich isotherm (R2 = 0.92 for the new resin and R2 = 0.96 for the regenerated resin); the maximum adsorption capacity being 14.2 and 14.4 mg P/g, respectively. The saturation of adsorption sites was not achieved also after 11.5 hours and 120 bed volumes, in column tests. When the reactor was operated with sludge liquor and the new resin, the saturation of packed bed was achieved after approximately 175 min and 31 bed volumes. The recovery efficiency of phosphorus during the regeneration step was as high as 95% (less than 13 bed volumes). According to the results achieved and the increasing cost of phosphorus production from conventional resources (yearly incremental cost 0.012 €/(kg · y)), its recovery from UWWTPs sludge liquor by the ion exchange process is expected to be really useful and beneficial for the following 10–15 years.

Modeling and simulations of the removal of formaldehyde using silver nano-particles attached to granular activated carbon

A combined reaction, consisting of granular activated carbon (GAC) adsorption and catalytic oxidation, has been proposed to improve the removal efficiencies of formaldehyde, one of the major indoor air pollutants. In this study, silver nano-particles attached onto the surface of GAC (Ag-GAC) using the sputtering method were evaluated for the simultaneous catalytic oxidation and adsorption of formaldehyde. The evolution of CO 2 from the silver nano-particles indicated that formaldehyde was catalytically oxidized to its final product, with the oxidation kinetics expressed as pseudo-first order. In addition, a packed column test showed that the mass of formaldehyde removed by the Ag-GAC was 2.4 times higher than that by the virgin GAC at a gas retention time of 0.5 s. However, a BET analysis showed that the available surface area and micro-pore volume of the Ag-GAC were substantially decreased due to the deposition of the silver nano-particles. To simulate the performance of the Ag-GAC, the homogeneous surface diffusion model (HSDM), developed for the prediction of the GAC column adsorption, was modified to incorporate the catalytic oxidation taking place on the Ag-GAC surface. The modified HSDM demonstrated that numerical simulations were consistent with the experimental data collected from the Ag-GAC column tests. The model predictions implied that the silver nano-particles deposited on the GAC reduced the adsorptive capacity due to decreasing the available surface for the diffusion of formaldehyde into the GAC, but the overall mass of formaldehyde removed by the Ag-GAC was increased due to catalytic oxidation as a function of the ratio of the surface coverage by the nano-particles.

Separation of Succinic Acid from Fermentation Broth Using Weak Alkaline Anion Exchange Adsorbents

Succinic acid is one of the platform chemicals that can be bioproduced from renewable resources. Separation of succinic acid by adsorption from model solutions and fermentation broth by weak alkaline anion exchange adsorbents was studied. Adsorption capacities and regenerability of several sorts of adsorbents were tested. In a static test, the adsorbent NERCB 09 has the adsorption capacity of 0.11 g succinic acid g−1 at succinic acid concentrations of 5 g L−1. In packed column test, its capacity was as high as 0.56 g succinic acid g−1 when the feeding concentration was 50 g L−1. NERCB 09 showed the high selectivity toward succinate over both glucose and amino acid at acidic or neutral conditions. Langmuir/Freundlich isotherm models and pseudo-first/second-order equations were presented to simulate the adsorption behavior. Data showed that the temperature had little effect on the adsorption isotherm. Kinetic parameters suggested that about 1.5 h were sufficient for the adsorption equilibrium. The adsorbent was easily regenerated. The adsorption capacity was steady after 30 cycles and showed 96% average recovery.

Study of the physical and chemical mechanisms influencing the long-term environmental stability of natrojarosite waste treated by stabilization/solidification

Natrojarosite is a residue of zinc refining generated in large quantities by zinc producers in many parts of the world. Stabilization/solidification (s/s) is currently used to immobilize heavy metals prior to storage of the solidified material as a heap. Our study aimed at assessing the long-term environmental stability of treated natrojarosite waste in the field situation. Flow-through leaching tests were carried out on monolithic samples in a modified triaxial cell and on crushed samples in packed columns. Tests with monolithic samples simulated natural infiltration through treated material containing few cracks and fractures, whereas, packed column tests were more representative of weathered material. The microstructure of leached and unleached materials was characterized by scanning electron microscopy and X-ray energy dispersive spectrometry (SEM–EDX). The results of flow-through leaching tests combined with microscopic characterization and geochemical equilibrium calculations provided valuable insights on the physical and chemical mechanisms influencing the long-term leaching behavior. This information was used to develop a mathematical model for alkalinity depletion in the treated waste. When infiltration of acid rain through the material was considered, the model predicted that the leachate would remain at high pH for many thousands of years in the field.

Selective removal of copper ions from aqueous solutions using modified silica beads impregnated with LIX 84

Silica beads immobilized with 2-hydroxy-5-nonylacetophenoneoxime (LIX 84) were prepared after silica surface modification by γ-aminopropyltriethoxysilane (SB-L). Batch and packed-column tests were conducted to evaluate the metal ion removal capabilities of the prepared adsorbent. Equilibrium isotherms of the SB-L with aqueous solutions containing copper ions were obtained. In addition, the kinetic performances for copper ion removal from aqueous solutions were investigated. The results showed that the amount of extraction increases with solution pH in the range between 1.5 and 5. The selectivity was also experimentally investigated, these results showed that the SB-L adsorbed copper ions selectively in the presence of other metal ions such as Ni2+, Co2+, Zn2+, Cd2+, Ca2+ and Mg2+. From the regeneration experiments, it was found that the copper ions adsorbed at the SB-L surface were recovered by acidic solutions. The recovery ratios were between 78% and 90%, depending on the types of acidic solutions. The results showed that the SB-L prepared may be used for the selective extraction of copper ions from aqueous solutions. © 1999 Society of Chemical Industry

The Removal of Copper Ions from Aqueous Solutions Using Silica Supports Immobilized with 2-Hydroxy-5-nonylacetophenoneoxime

Silica supports immobilized with 2-hydroxy-5-nonylacetophenoneoxime (LIX 84) were prepared after surface modification by γ-aminopropyltriethoxysilane. Three types of silica beads and a silica powder were used as supports. Batch and packed-column tests were conducted to investigate the capabilities of the prepared adsorbents to remove copper ions. A comparison of the different silica supports was performed with respect to copper adsorption capacity, copper adsorption rate, and nitrogen content. In addition, studies were carried out for the modified silica beads that showed highest copper ion removal capability among the three silica beads (SB2-L). The extraction rate of the SB2-L increases with solution pH in the range between pH 2 and 4. Stability tests show that the SB2-L is stable under acidic conditions. From regeneration experiments it was found that copper ions which are adsorbed at the surface of the SB2-L were recovered by washing with 0.1 M HNO3 and that the regenerated beads are reversible. The recovery ratios were between 80 and 90%. A breakthrough curve was obtained using modified silica powder (SP-L). The copper recovery ratio for SP-L was 74%. The results show that the SP-L prepared is feasible for the extraction of copper ions from aqueous solutions using a fixed-bed reactor.

Effects of organic matter in aquacultural waste on the ammonium exchange capacity of clinoptilolite

Clinoptilolite, an ammonium-selective ion exchanger, is being used to control ammonia accumulation in recirculating culture systems. Studies were conducted to establish a correlation among the ammonium exchange capacity of clinoptilolite, level of organic matter in aquacultural wastewater, and regenerant solution type. A recirculating culture system of 2300-I capacity provided wastewater with a represantative organic matrix. Treatment of the wastewater led to a decrease in the performance of clinoptilolite under non-equilibrium (packed-column) and equilibrium operating conditions. The extent of the effects increased with an increase in organic level of the treatment solution. In packed-column tests, the maximum observed reductions in mean removal efficiency (3.5%), volume of wastewater treated prior to reaching breakthrough (14.9%), and operating exchange capacity (19.7%), occurred in columns regenerated with a brine of pH 7.0. Columns regenerated with a brine of pH 10.5 showed little response. Treatment of aquacultural wastewater produced a brown discoloration of the packing which was removed by treatment with 1 bed volume of a hypochlorite restorant solution (0.5% Cl 2).

In-Situ Leaching of South Texas Uranium Ores—Part 1: Laboratory Studies of Ore Composition and Leaching Performance

Abstract This paper presents data on mineralogy and laboratory chemical-leaching tests for ore samples from several areas of the south Texas tertiary Catahoula formation. Optical microscope, electron microprobe, spectroscopic, X-ray diffraction (XRD), and various chemical analyses were performed. Batch screening tests gave qualitative estimates of leach rate and potential recovery. Packed column tests using hydrogen peroxide or pressurized oxygen gave more quantitative recovery estimates. The frequently friable sandstones contained highly variable amounts of quartz, feldspar, calcite, and clay, and in some cases, zeolite or mica. Clays were mainly mixed layer illite/smectite type. High cation exchange capacities (CEC's) correlated with clay (and zeolite) content, while high reducing capacities were often associated with pyrite level. Coffinite, in various environments, was the main uranium mineral. With batch tests using pseudo-first-order rate constants, ore leach rates were generally characterized as "fast" on a scale of fast, intermediate, and slow. However, there was variability in leach rates, both in samples from different areas and in samples taken at different depths in the same well. Fast rates and recoveries greater than 80% were observed in most column pack tests, but there was variation with leachate composition and sample source. The chemistry and kinetics of leaching are also discussed.