Column Sorption Research Articles

Uncertainty and variability in laboratory derived sorption parameters of sediments from a uranium in situ recovery site

This research assesses the ability of a GC SCM to simulate uranium transport under variable geochemical conditions typically encountered at uranium in-situ recovery (ISR) sites. Sediment was taken from a monitoring well at the SRH site at depths 192 and 193 m below ground and characterized by XRD, XRF, TOC, and BET. Duplicate column studies on the different sediment depths, were flushed with synthesized restoration waters at two different alkalinities (160 mg/l CaCO3 and 360 mg/l CaCO3) to study the effect of alkalinity on uranium mobility. Uranium breakthrough occurred 25% - 30% earlier in columns with 360 mg/l CaCO3 over columns fed with 160 mg/l CaCO3 influent water. A parameter estimation program (PEST) was coupled to PHREEQC to derive site densities from experimental data. Significant parameter fittings were produced for all models, demonstrating that the GC SCM approach can model the impact of carbonate on uranium in flow systems. Derived site densities for the two sediment depths were between 141 and 178 μmol-sites/kg-soil, demonstrating similar sorption capacities despite heterogeneity in sediment mineralogy. Model sensitivity to alkalinity and pH was shown to be moderate compared to fitted site densities, when calcite saturation was allowed to equilibrate. Calcite kinetics emerged as a potential source of error when fitting parameters in flow conditions. Fitted results were compared to data from previous batch and column studies completed on sediments from the Smith-Ranch Highland (SRH) site, to assess variability in derived parameters. Parameters from batch experiments were lower by a factor of 1.1 to 3.4 compared to column studies completed on the same sediments. The difference was attributed to errors in solid-solution ratios and the impact of calcite dissolution in batch experiments. Column studies conducted at two different laboratories showed almost an order of magnitude difference in fitted site densities suggesting that experimental methodology may play a bigger role in column sorption behavior than actual sediment heterogeneity. Our results demonstrate the necessity for ISR sites to remove residual pCO2 and equilibrate restoration water with background geochemistry to reduce uranium mobility. In addition, the observed variability between fitted parameters on the same sediments highlights the need to provide standardized guidelines and methodology for regulators and industry when the GC SCM approach is used for ISR risk assessments.

Polyethersulfone enwrapped hydrous zirconium oxide nanoparticles for efficient removal of Pb(II) from aqueous solution

Porous matrix immobilization is considered as an effective approach to address the engineering challenges during practical application of nanoadsorbent. In this work, solid and hollow hydrous Zirconium (IV) oxide (ZrO2·nH2O, SHZO and HHZO) nanoparticles were enwrapped into millimeter-level beads by polyethersulfone through a mild liquid-liquid phase inversion technique. The beads possess asymmetric and hierarchical structure with an exterior porous surface dense layer and numerous inner interpenetrating finger-like channels, which promote the transportation of molecule and prevent the leaching of nanoadsorbents. As compared to SHZO beads, HHZO beads exhibited higher efficient adsorption capacity toward Pb (II) (104 mg·g−1), which could remain at 94% of HHZO nanoparticles. The effects of pH, the stability of adsorbents and coexisting ionic are further explored in detail. The Pb (II) removal mechanism is further studied by the EDS mapping, XPS, FTIR measurements, further indicating the surface hydroxyl groups played a key role in the adsorption process. Fixed-bed column sorption experiment and in situ regeneration were conducted so as to examine the practical application of the beads. Therefore, this kind of beads indicated the potential practical application in industrial wastewater treatment.

Complete Column Trials for Water Refinement Using Titanium(IV) Phosphate Sorbents

A titanium phosphate sorbent with linked active units (LTP) is synthesized. XRD, 31P MAS NMR, and TGA techniques are used to disclose the relation between the ion-exchange units of −HPO4 (crystalline α-TiP) and of −H2PO4 (amorphous TiP1) type. The reported kinetics data of TiP1 sorbent in batch mode have been reprocessed according to the nonlinear approach in order to explore further the sorption mechanism. It was found that the data could be well described by the pseudo-second-order model in the case of Ni2+ ions. Consequently, fixed-bed column sorption experiments of Ni2+ ions on LTP were designed, and the effects of both the amount of nickel(II) ions in the feed solution and the flow rates on the sorption equilibrium were studied. The ion-exchange capacity is estimated to be 1.6 meq·g–1 during the first four cycles before decreasing to 1.2 meq·g–1 for cycles five and six. The experimental data were simulated following the Thomas model, and desorption experiments with HCl were performed. Observations sh...

Efficient entrapping of toxic Pb(II) ions from aqueous system on a fixed-bed column of fungal biosorbent

The present research dealt with the successful viability and practicality of Pleurotus eryngii packed bed column for Pb(II) ions biosorption. To achieve the aim of the project, the impact of different parameters including flow rate, initial concentration of Pb(II) ions and bed height were optimized. The column models, i.e.,Thomas and Bed Depth Service Time (BDST) were investigated to assess the column efficiency towards entrapping targeted ion. The adsorption capacity, rate constant and correlation coefficient related to each model for column sorption were also calculated. The adsorption capacity enhanced by increasing the bed height and decreasing initial Pb(II) metal ion concentration along with the flow rate. The maximum Thomas model adsorption (entrapping) capacity was obtained 3.30 mg g−1 for initial concentration of 20 mg L−1 at a constant flow rate of 1 ml min−1, bed height of 3 cm and pH 7. The experimental results implied and affirmed the suitability of the P. eryngii fungal biosorbent for Pb(II) ion biosorption with its nature being favourable, efficient and environment friendly.

Passive Remediation of Acid Mine Drainage Using Ball-Milling Modified Indonesian Natural Bentonite: Laboratory Batch and Column Sorption of Manganese

Manganese (Mn) is an essential element for human body. However, elevated concentration of manganese causes severe problem and disease. Acid mine drainage (AMD), wastewater generated due to open-pit mining, commonly contains Mn with exceeded concentration. This study is to investigate the improvement of ball-milling modified Indonesian natural bentonite (INB) for manganese (Mn) removal from AMD and to increase the pH through batch and column sorption test as a passive treatment system approach. The batch sorption test result showed the maximum Mn adsorbed (Qm) on INB from the Langmuir model increased from 4.69 to 17.12 mg/g after milling. The column sorption test result also showed the amount of Mn adsorbed on INB until breakthrough time (qu) and until saturation time (q) increased after milling. The qu increased from 1.27 to 10.06 mg/g, and the q increased from 4.55 to 12.91 mg/g. The mass transfer zone (MTZ) became significantly shorter after milling from 0.22 to 0.07 cm. The Thomas model exhibited the equilibrium uptake of Mn (q0) increased after milling from 3.91 to 13.72 mg/g. In equilibrium condition, both unmilled and milled INB showed the pH increased from ≈3 to 8.

Oil removing properties of exfoliated graphite in actual produced water treatment

Removal of oil from actual produced water (composed of mainly oil and water emulsion) by exfoliated graphite (EG) was investigated. Laboratory scale sorption columns of EG could reduce the oil concentration in produced water from 278 and 66mg/L to 1.2mg/L, and undetectable, respectively. A separate experiment with TOC (total organic carbon) demonstrated that TOC decreased from 566mg/L in the feed solution to 1.5mg/L in the effluent. Both results (oil densitometer and TOC) showed excellent ability of EG for oil removal from produced water. SEM and FT-IR observations confirmed the deposition of oily material on the surface of EG during the water treatment process. TG-DTA of oil-sorbed EG showed a gradual weight decrease in the temperature range between 100–600°C, being considered to be the decomposition of sorbed oil. Raman spectroscopy and XRD measurements of EG samples, before and after the treatment, indicated no structural change of EG. Molecular dynamics simulations revealed that octadecane molecules are selectively adsorbed on the EG surface. Effect of isomer type of octadecane molecules on the sorption energy was also discussed.

Sorption of heavy metal ions onto crayfish shell biochar: Effect of pyrolysis temperature, pH and ionic strength

Abstract In this study, crayfish shell was pyrolyzed at 300 (CS300), 450 (CS450) and 600 °C (CS600) to identify the optimum temperature for improving the binding capacity of the produced biochar. The removal efficiency of biochars was assessed following mono-element sorption of Pb(II) under batch sorption and fixed-bed column experiments. The effect of pH and ionic strength on Pb(II) sorption was further investigated on the most efficient biochar type to understand environmental factors affecting sorption onto crayfish biochar. Besides, this most efficient biochar was further investigated in multi-element sorption (Pb(II), Cu(II) and As(III)) trial to assess the effect of competitive sorption on Pb(II) bioavailability. Pyrolysis temperature had different effects on elemental composition, surface area and active functional groups of the produced biochar. CS600 showed the highest sorption capacity (190.7 mg/g) of Pb(II). Sorption mechanisms were identified following FTIR, SEM, XRD and ICP analyses suggested the participation of physisorption. Sorption of Pb(II) onto crayfish biochar was strongly pH- and ionic strength-dependent as the sorption capacity showed significant reductions at low pH and high ionic strength values. The competitive sorption of Pb(II) with other metal ions (Cu(II) and As(III)) showed its superiority to bind with active sorption sites of biochar as compared with other heavy metals.

Dissolved organic matter retention in volcanic soils with contrasting mineralogy: a column sorption experiment

There is an increasing recognition that sorption and precipitation reactions between the dissolved phase of organic matter and reactive minerals and metals found in soils are an important carbon stabilization mechanism. We explored the relative importance of this sorption mechanism with pedological shifts in soil properties by conducting a dissolved organic matter leaching/sorption experiment using intact soil cores from a substrate/age gradient in Hawai’i. In the subsurface horizons, sorption of dissolved organic carbon was often positively correlated short-range ordered (SRO) mineral content, with sorption rates approaching 100% when SRO minerals dominated. Dissolved organic matter sorption in the presence of SRO minerals was highly selective towards aromatic compounds, consistent with prior nuclear magnetic resonance spectroscopy conducted on carbon found in SRO rich mineral soil. In subsurface horizons where SRO content was low (youngest and oldest sites in the chronosequence), sorption was also found to be high but much less selective, more reversible and more degradable indicating that different stabilization mechanisms are operative. These experimental results provide further evidence for a direct mechanism by which volcanic soils are able to store disproportionately high amount of soil organic matter via retention of aromatic acids.

Ranking nano-enabled hybrid media for simultaneous removal of contaminants with different chemistries: Pseudo-equilibrium sorption tests versus column tests

The underlying hypothesis of this study was that pseudo-equilibrium and column testing conditions would provide the same sorbent ranking trends although the values of sorbents' performance descriptors (e.g. sorption capacity) may vary because of different kinetics and competition effects induced by the two testing approaches. To address this hypothesis, nano-enabled hybrid media were fabricated and its removal performances were assessed for two model contaminants under multi-point batch pseudo-equilibrium and continuous-flow conditions. Calculation of simultaneous removal capacity indices (SRC) demonstrated that the more resource demanding continuous-flow tests are able to generate the same performance rankings as the ones obtained by conducing the simpler pseudo-equilibrium tests. Furthermore, continuous overlap between the 98% confidence boundaries for each SRC index trend, not only validated the hypothesis that both testing conditions provide the same ranking trends, but also pointed that SRC indices are statistically the same for each media, regardless of employed method. In scenarios where rapid screening of new media is required to obtain the best performing synthesis formulation, use of pseudo-equilibrium tests proved to be reliable. Considering that kinetics induced effects on sorption capacity must not be neglected, more resource demanding column test could be conducted only with the top performing media that exhibit the highest sorption capacity.

Development and treatment procedure of arsenic-contaminated water using a new and green chitosan sorbent: kinetic, isotherm, thermodynamic and dynamic studies

Abstract Arsenic is classified as one of the most toxic elements for humans by the World Health Organization (WHO). With the tightening drinking water regulation to 10 μg L−1 by the WHO, it is necessary to find efficient sorbent materials for arsenic. In this work, the removal of arsenic(V) from water is achieved with an insoluble chitosan sorbent in the protonated form obtained by a simple heating process. Kinetic studies show a very fast sorption (less than 10 min). The Langmuir isotherm model is best describing experimental data with a capacity of 42 mg g−1 at pH 8. The sorption process is based on anion exchange (chemisorption) determined from the Dubinin-Radushkevich model. The sorption efficiency of the chitosan sorbent is 97% at low concentrations (e.g. 100 μg L−1). Thermodynamic analysis reveals that the sorption process is exothermic and is controlled by enthalpic factors. Breakthrough curves (BTC) were acquired in real-time by instrumental chromatography and was better described by the Thomas model. BTC from column sorption and desorption with a salt solution suggest that this sorbent is relevant for large scale applications. With this new renewable product, it will be possible to treat arsenic contaminated water at low cost and with little waste (concentration factor of 1500).

Soil attenuation of the seepage potential of metallic elements (Cu, Zn, As(V), Cd, and Pb) at abandoned mine sites: A batch equilibrium sorption and seepage column study

Soil attenuation of off-site leaching potential of metallic elements at the two abandoned mine sites was investigated using batch sorption and layered column studies. In batch study, the leachate concentration-specific sorption (Kd*) by downgradient clean soils was in the order of Pb>Cu>Cd>Zn>As for DY site and Pb>As>Cu>Cd>Zn for BS site. In the layered (mine+clean) soil column, element elution was significantly reduced (e.g., no initial flush, retarded peak arrival, and lower peak concentration) while sulfate elution can be an indicator of the dissolution of sulfur-bearing minerals in mine soils. The greatest reduction was observed for Pb and Cu while the lowest was for Cd (2–19%) and Zn (6–51%), consistent with the batch data. Both the reduced elution at slow seepage and concentration drop after flow interruption support the time-limited propensity. In column segments, the sorptive elements (Cu, Pb, and As) were dominantly found in the inlet while less sorptive ones (Zn and Cd) in the outlet. Both batch and column data suggest that the element leaching with mine leachate movement can be greatly attenuated by the interactions with the surrounding downgradient soil during the seepage process.

Column adsorption of Cu(II) by polymer-supported nano-iron oxides in the presence of sulfate: Experimental and mathematical modeling

Abstract Polymer-supported hydrous iron oxides (HFOs) are promising for heavy metals removal from aqueous systems. The ubiquitous inorganic ligands, e.g., sulfate, are expected to exert considerable impacts on pollutants removal by these hybrid sorbents. Herein, we obtained a hybrid sorbent HFO-PS by encapsulating nanosized HFO into macroporous polystyrene (PS) resin. Both batch and column sorption experiments of Cu(II) by HFO-PS were carried out in the presence of sulfate. Obviously, the presence of sulfate is favorable for Cu(II) sorption onto HFO-PS. The performances of column Cu(II) removal were fitted and predicted with Adams–Bohart, Clark, Thomas and BDST models. Thomas model is suggested best-fit to predict the breakthrough curves. Besides, a linear correlation is observed between breakthrough time and column length based on BDST model, which might be useful for predicting the breakthrough time for Cu(II) removal by HFO-PS.

Mechanism and sorption parameters of alkali metal ions on strongly acidic cation exchange resins

The kinetic performance of strongly acidic sulfonate cation exchange resins towards ions of alkali metals (Li, K, and Na) under static conditions has been examined. Kinetic parameters of the sorption process, in particular, half-time of exchange and maximum possible flow rate of solution through the sorption column in the dynamic mode have been determined. The sorption kinetics mechanism has been explored. Recovery of the elements from model unicomponent solutions on strongly acidic cation exchange resins is satisfactorily described by pseudo-second-order kinetic model.

Macroporous alginate/ferrihydrite hybrid beads used to remove anionic dye in batch and fixed-bed reactors

Abstract Two-line ferrihydrite was prepared by neutralizing Fe(III) and then characterized by means of various methods, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) theory and zetametry. The alginate/ferrihydrite hybrid beads with various porosities, as synthesized through an entrapment process, were used as an adsorbent for the removal of anionic dye methyl orange (MO). The kinetic and isotherm results were best described by pseudo second-order models and Langmuir models, respectively. An effective diffusion coefficient was calculated for the beads according to the procedure offered by Reichenberg. These results showed that porosity improves the diffusion coefficient of MO as well as the MO sorption capacity. The hybrid beads were further investigated in dynamic system sorption; the effects of operating conditions, such as flow rates and initial MO concentration, have also been studied. The Thomas model displayed a good fit with the experimental results. The results proved that the creation of macroporosity improves the sorption amount in fixed-bed reactor. The better column sorption is characterized by a higher MO concentration but with a lower feed flow rate.

Effects of temperature on graphene oxide deposition and transport in saturated porous media

Laboratory batch sorption and sand column experiments were conducted to examine the effects of temperature (6 and 24°C) on the retention and transport of GO in water-saturated porous media with different combination of solution ionic strength (IS, 1 and 10mM), sand type (natural and acid-cleaned), and grain size (coarse and fine). Although results from batch sorption experiment showed that temperature affected the sorption of GO onto the sand grains at the low IS, the interactions between GO and the sand were relatively weak, which did make the temperature effect prominent. When the IS was 1mM, experimental temperature showed little effect on GO retention and transport regardless of the medium properties. GO was highly mobile in the sand columns with mass recovery rates ranged from 77.3% to 92.4%. When the IS increased to 10mM, temperature showed notable effects on GO retention and transport in saturated porous media. For all the combinations of sand type and grain size, the higher the temperature was, the less mobile GO particles were. The effects of temperature on GO retention and transport in saturated porous media were further verified though simulations from an advection–dispersion-reaction model.

Selective sorption of a Ge(IV) oxoanion by composite sorbent with hydrous oxide of cerium

ABSTRACTIn this work, composite sorbent based on hydrous cerium oxide was used for selective removal of a Ge (IV) oxoanion. Experiments were carried out by batch equilibrium tests and dynamic column sorption. The best sorption capacity of the Ge(IV) anion was reached at a pH of 9, where the sorption capacity was about 1.1 g/L. The negative effect of chlorides and sulfates was not observed in the concentration range of 100–1000 mg/L. The optimal flow rate for Ge(VI) sorption by sorbent CeO2/XAD-7 was determined to be 6–12 BV/h. For regeneration, 10 BV of 1 mol/L HCl solution was used.

Mathematical Modeling of Sorption in a Wearable Artificial Kidney with Dialysate Regeneration

This work is devoted to mathematical modeling of spent dialysate regeneration by sorption. A method for mathematical modeling of sorption of such metabolites as creatinine and uric acid in the sorption columns of a wear able artificial kidney is suggested. The method was tested with different types of activated carbon used in sorption columns. The root-mean-square criterion did not exceed 630 μmol/L.

Flexible core-shell/bead-like alginate@PEI with exceptional adsorption capacity, recycling performance toward batch and column sorption of Cr(VI)

A chemically modified alginate beads for heavy metal removal was prepared using polyethylenimine (PEI) as a modification reagent, which high density active sites were introduced favorably onto the surface by cross-linking reaction, leading to the designing of flexible core-shell/bead-like alginate@PEI sorbent and employed for the adsorption of Cr(VI) from aqueous solutions. This new sorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) etc. The results demonstrated that the optimized pH value was observed at 2.0. The adsorption processes fitted well with the pseudo-second-order kinetic model and the Freundlich isotherm in a batch system. The experimental maximum adsorption capacity for Cr(VI) was 431.6mg/g under an optimal testing condition, which was much higher than that of sodium alginate (SA) (24.2mg/g). Thomas and Bohart–Adams models were successfully fitted with breakthrough curves obtained under different experimental conditions in a continuous column process. More importantly, the adsorption capacity of the alginate@PEI only showed a slight loss after ten cycles of adsorption-desorption studies. Compared to other reported adsorptive materials, this core-shell/bead-like composite promises advantages of ultra-high adsorption capacity, low-cost, environmental friendliness and excellent recycling performance.

The Preparation of Modified Industrial Waste Polyacrylonitrile for the Adsorptive Recovery of Pt(IV) from Acidic Solutions.

Sorption technique is one of the most effective methods for recovering precious metals from wastewater solutions; however, its main drawbacks of the traditional sorbents are the slow kinetics and relatively low sorption capacities. As a solution, thin sorbent fibers have been highlighted because they can lead to fast adsorption kinetics due to their high surface areas and numerous binding sites. In this sense, the applicability of an industrial waste polyacrylonitrile (PAN) textile was examined to recover Pt(IV) from acid solutions. In order to enrich cationic functional groups on the surface of a PAN textile, the textile was chemically modified via polyethylenmine (PEI) coating. Afterwards, using PEI-coated PAN fiber, batch sorption experiments (isotherms and kinetics) and column experiments were conducted to evaluate its sorption performance toward Pt(IV). It was clearly revealed in column experiments that the PEI-coated waste PAN textile (WPAN) has fast kinetics and good performance for Pt(IV) recovery.

Modelling of packed bed adsorption columns for the separation of green tea catechins

ABSTRACTGreen tea is a rich source of catechins, which when purified have a high economic value as they can be used as a supplement in several products, to increase their health benefits. Catechins are regarded as desired components with several applications in a variety of areas such as foods, cosmetics and pharmaceuticals. A multicomponent sorption model has been developed for the separation of catechins from liquid tea streams, with macroporous resins in a packed bed column. Two commercially available food grade resins were considered: Amberlite XADHP and Diaion HP20. For the desorption step, two food grade solvents are used: water and ethanol. The adsorption and desorption behaviour is subsequently mathematically described with one-dimensional axial dispersed plug flow model that can accurately simulate the dynamics of the solvent swing sorption columns. The model parameters were regressed from experimental data. Five components are modelled in the competitive sorption: the main four catechins present in green tea and caffeine. The model was used for the process design and optimization for the recovery of catechins from green tea.