Increase In Sorption Capacity Research Articles

Sorption of metals onto natural organic matter as a function of complexation and adsorbent–adsorbate contact mode

The effect of complexing anion and adsorbate–adsorbent contact mode (static equilibrium or dynamic non-equilibrium) on binding and partition of Cu 2+, Cd 2+ and Zn 2+ onto organic matter (exemplified in a low-moor peat) was studied. The study comprised comparative batch and column flow-through sorption experiments on monometallic solutions of Me–Cl and Me–SO 4 salts, at pH 4.0, and sequential fractionation of sorbed metals with respect to binding strength. Both the presence of an anion having complexing properties (Cl −) as well as a contact mode was found to quantitatively and qualitatively affect the sorption capacity and binding strength of organic matter (peat) for metal ions. Complexing effect of Cl − on metal ions resulted mostly in reduction of metal ability to form strongly bound metal–organic compounds, in accordance with the order of stability constant of complex ions log K: Cd>Zn>Cu. Flow-through (dynamic) contact mode, which is the most appropriate to simulate environmental conditions, appeared to strongly attenuate the complexing effect of chloride ions on Cd and Zn sorption, and significantly enhance sorption capacity also in the absence of complexing ions. For Cd, it was mainly due to the enrichment in the strongly bound “insoluble organic” fraction, while for Zn the quantitative increase of sorption capacity did not alter significantly its partitioning. Neither a quantitative nor qualitative effect of contact mode on Cu binding was observed. Complex and diverse effects of different environmental parameters on metal sorption capacity and binding strength onto organic matter, which strongly influence metal mobility, leads to the conclusion that the correct simulation of these parameters for ecotoxicological testing is crucial for the reliable predicting of metal bioavailability under actual terrestrial environmental conditions.

Removing viruses using zeolites

Natural mordenite (NM), natural clinoptilolite (NC), HDTMA-modified natural mordenite (SMNM) and HDTMA-modified natural clinoptilolite (SMNC) have been proposed for the removal of As(V) from aqueous solution (HDTMA = hexadecyltrimethylammonium bromide). Influence of time on arsenic sorption efficiency of different sorbents reveals that NM, NC, SMNM and SMNC require about 20, 10, 110 and 20 h, respectively to reach at state of equilibrium. Pseudo-first-order model was applied to evaluate the As(V) sorption kinetics on SMNM and SMNC within the reaction time of 0.5 h. The pseudo-first-order rate constants, k are 1.06 and 0.52 h−1 for 1 and 0.5 g of SMNM, respectively. The observed k values 1.28 and 0.70 h−1 for 1 and 0.5 g of SMNC, respectively are slightly high compared to SMNM. Surfactant surface coverage plays an important role and a significant increase in arsenate sorption capacity could be achieved as the HDTMA loading level on zeolite exceeds monolayer coverage. At a surfactant partial bilayer coverage, As(V) sorption capacity of 97.33 and 45.33 mmol kg−1 derived from Langmuir isotherm for SMNM and SMNC, respectively are significantly high compared to 17.33 and 9.33 mmol kg−1 corresponding to NM and NC. The As(V) uptake was also quantitatively evaluated using the Freundlich and Dubinin–Kaganer–Radushkevich (DKR) isotherm models. Both SMNM and SMNC removed arsenic effectively over the initial pH range 6–10. Desorption performance of SMNM and SMNC were 66.41% and 70.04%, respectively on 0.1 M NaOH regeneration solution.

Pd and Pt recovery using chitosan gel beads. II. Influence of chemical modifications on sorption properties

Chitosan is very efficient at removing precious metals from dilute acid solutions. Its sorption properties can be improved by the chemical modification of the polymer. Several methods have been tested for chitosan modification including poly(ethylene imine) (PEI)-grafting, hydrogenation of imine function on glutaraldehyde-cross-linked chitosan, and thiourea-grafting. Depending on the modification technique, the improvement in sorption performance may consist, in an increase in sorption capacity (PEI-grafted chitosan), a change in the stability of the sorbent (hydrogenation of imine linkage) or an increase in the selectivity of sorption in the presence of co-ions (thiourea derivatives of chitosan). Chitosan gel beads were chosen rather than the flaked material, since the gel beads have enhanced diffusion properties. The influence of drying and re-hydration of the beads are studied for some of these chitosan derivatives with regard to their diffusion properties.

Wheat Germ Lectin Sorption by Chitosan Polyelectrolyte Complexes

The possible application of polyelectrolyte complexes (PEC) of chitosan and copolymers of maleic acid with N-vinylpyrrolidone, styrene, and ethylene and/or cross-linked chitin sorbents (CLCS) synthesized on the basis of PEC for sorption of wheat germ lectin (WGL) was studied. The synthesis of spherically granulated sorbents was shown. Compared to unmodified chitosan, there was a significant increase in sorption capacity of WGL by the sorbents: PEC, 2.5-fold, and CLCS, from 3.5-fold to 7-fold.

Uranium sorption on amorphous titanium and zirconium phosphates modified by Al3+ or Fe3+ ions

The sorption of uranium from aqueous solutions on titanium and zirconium phosphates in H+ and K+ forms modified by iron or aluminum ions has been investigated. The modified pattern of porosity is much better, than for none modified analogous, owing to their increased sorption capacity and kinetics of uranium absorption. The modified sorbents display selectivity towards uranium, that allows to purify solutions up to the content of uranium below the limit of its analytical definition.

Chromium Adsorption by Chitosan Impregnated with Microemulsion

Removal of chromium(III) from aqueous solutions by chitosan impregnated with a microemulsion was investigated. The modified chitosan showed a remarkable increase in chromium sorption capacity as compared to an untreated sample. Dynamic column experiments were performed to study the influence of pH, concentration, and the presence of others metal ions (copper and nickel) in the chromium solutions. The adsorption process is pH-dependent, and the amount of Cr(III) retained increases with increasing heavy metal initial concentration. It can be observed that the best bed efficiency was for copper, followed by chromium and then nickel. The nature of chromium(III) adsorption equilibrium at different temperatures (30, 40, and 50 °C) was investigated, and the Freundlich and Langmuir isotherm models were applied to fit the experimental data. The uptake process obeys the Langmuir isotherm. Following the adsorption step, the desorption process was carried out using several eluant solutions. The best results were obta...

Removal of chromium from aqueous solutions by diatomite treated with microemulsion

In order to evaluate the sorption of heavy metals, a crude diatomite was impregnated with a microemulsion which showed remarkable increase in chromium sorption capacity as compared to untreated diatomite. Samples with two different granulometries were investigated, both yielding practically complete adsorption. The adsorption process is pH dependent and the best results for the initial Cr (III) concentration of 1.5 g/L were obtained at pH 2.95. The effect of the concentration of the chromium synthetic solution was also investigated. The adsorption isotherms were obtained (30, 40 and 50°C) and the Freundlich and Langmuir models were used to determine the adsorption capacity of the adsorbent. Following the adsorption step, a desorption process was carried out using several eluant solutions. The best results were obtained using hydrochloric acid (100%) as eluant.

Preparation, characterization, and sorption properties for Ni(II) of iron oxyhydroxide–montmorillonite

The preparation, characterization, and sorption properties for Ni(II) of combined phases of iron oxyhydroxide and montmorillonite were investigated. Two different preparation procedures were explored. In the first method, Fe(III) was contacted with montmorillonite at pH 2.5, and ferrihydrite was formed on the montmorillonite surface by slowly raising pH to 8.0 (Fe–mont). In the second method, O 2 was bubbled through a solution (pH 7.0) containing Fe(II) and montmorillonite. This caused Fe(III) to precipitate as lepidocrocite (lep–mont). Batch adsorption experiments and the physical chemical properties of the solids, e.g. specific surface area, the point of zero charge, and the particle size distribution reflected a varying degree of interaction among the phases. In the Fe–mont system, a ferrihydrite coated montmorillonite surface was created. The result was an increase in specific surface area and sorption capacity for Ni(II) compared to the pure solids. The isoelectric point observed was typical for pure ferrihydrite. In the lep–mont system, predominantly separate phases of lepidocrocite and montmorillonite were created. The specific surface area, the isoelectric point, and the sorption capacity were significantly better predicted given the properties and weight fractions of the individual phases.

Removal of Selected Metal Ions from Aqueous Solutions Using Chitosan Flakes

Commercially available chitosans potential in the adsorption of heavy metals like zinc, copper, cadmium, and lead from aqueous solutions under variable physicochemical conditions was investigated. The results obtained from equilibrium and kinetic studies showed that there was significant uptake of these metal ions by chitosan and that chitosan flakes had a maximum sorption capacity for copper ions. The order of metal ion adsorption by chitosan decreased from Cu2+ to Zn2+ as follows: copper lead cadmium zinc. There was a considerable increase in sorption capacity with an increase in chitosan amount; however, this parallelism diminished when the chitosan mass exceeded 0.24 g in 25 mL of metal solution. The sorption of metal ions from various salt solutions by chitosan flakes was not improved by agitation. The heavy metal uptake by chitosan was found to be pH-dependent, with a maximum at pH 6.0 and 7.0. Sorption equilibrium studies were conducted with a constant sorbent weight and varying initial concentration of metal ions. The experimental data of adsorption from solutions containing metal ions were found to correlate well with the Langmuir isotherm equation.

Sorption of Atrazine and Simazine by Model Associations of Soil Colloids

AbstractThe effect of association processes between single model soil components (i.e., Ca‐saturated montmorillonite [CaSWy], ferrihydrite [Ferrih], and soil and commercial humic acid [HA]) upon their association in binary and ternary CaSWy‐Ferrih‐HA systems on physicochemical properties (specific surface area, pH, and basal spacing) and on triazine herbicide sorptive behavior was determined. Ferrihydrite coatings on CaSWy increased the specific surface area of the clay and slightly decreased pH, whereas HA coatings on CaSWy and Ferrih decreased both specific surface area and pH. Further association of HA with the CaSWy‐Ferrih binary system decreased the specific surface area, but did not change the pH. Atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) and simazine (2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine) sorption‐desorption data showed that the sorptive behavior of the associations is not the simple sum of the sorption on single components. The HA association with CaSWy increased sorption of both herbicides by the clay, as suggested by an increase in sorption capacity (Koc) for the CaSWy‐HA binary system. Although Ferrih did not sorb either triazine, Ferrih coatings on CaSWy increased sorption of both herbicides on the clay. The association of HA with Ferrih sorbed both triazines, but Koc decreased compared with HA alone. Further association of the CaSWy‐Ferrih binary system with soil HA decreased the sorption, whereas association with commercial HA increased it. Desorption isotherms of atrazine and simazine showed that sorption by the model associations was reversible.

Nonideal transport of reactive solutes in heterogeneous porous media 2. Quantitative analysis of the Borden natural-gradient field experiment

Field experiments constitute an integral component of research on transport and fate of contaminants in the subsurface. One of the most well known of the few field experiments performed with reactive solutes is the natural-gradient experiment conducted at the Borden site during 1982 to 1984. A major finding of the experiment was that the transport of the reactive, organic compounds was nonideal. First, the velocities of the centers of mass of the plumes decreased with time, which was reflected in a temporal increase in effective retardation. Second, the longitudinal spreading observed for the organic solutes was about three times larger than that of the nonreactive tracers for an equivalent travel distance. Third, the breakthrough curves measured at selected monitoring points exhibited greater asymmetry compared to the nonreactive tracers. The cause(s) of the nonideal transport observed for the organic solutes has remained unexplained, despite a number of attempts. We have used a multi-scale, multi-factor mathematical model to successfully predict the displacement and spreading behavior of the tetrachloroethene and tetrachloromethane plumes. Based on our analyses, we conclude that a near-field trend of increasing sorption capacity was a primary cause of the deceleration of the centers of mass of the organic-solute plumes. The coupled effects of nonlinear sorption and enhanced spreading caused by spatially variable hydraulic conductivity and spatially variable sorption also influenced plume displacement. In addition, it is possible that the combination of spatially variable hydraulic conductivity and sorption contributed directly to plume deceleration. However, a magnitude of sorption variability larger than has been measured to date is required for this contribution to be significant. The combined spatial variability of hydraulic conductivity and sorption, and a potential negative cross correlation between them, appears to have been the major cause of the enhanced longitudinal spreading observed for the organic-solute plumes in comparison to the nonreactive-solute plumes. However, nonlinear sorption, the spatial trend of increasing sorption capacity, and rate-limited sorption/mass transfer also influenced spreading behavior. In total, it is evident that the transport of the organic compounds during the Borden natural-gradient field experiment was influenced by several interacting factors and coupled processes, and that accurate prediction of the observed behavior requires the use of a mathematical model that accounts for this complexity.

Dissolved Organic Matter‐Enhanced Retention of Polycyclic Aromatic Hydrocarbons in Soil Miscible Displacement Experiments

Natural dissolved organic matter (DOM) may alter the mobility of polycyclic aromatic hydrocarbons (PAHs) in soils. The influence of DOM on the mobility of PAHs was studied in medium-scale soil column experiments under unsaturated flow conditions. Miscible displacement experiments were carried out with PAHs alone (anthracene, pyrene, benzo(e)pyrene), with DOM alone, and with a mixture of the PAHs and DOM. Two different sandy materials were used, a spodic B horizon and a commercially available seasand. The DOM transport could be explained by assuming total DOM consisting of two physicochemically different fractions: A mobile fraction, composed of the hydrophilic moieties of DOM, and an immobile fraction, composed of hydrophobic DOM moieties. The PAH mobility in the column experiments was controlled by both solid and liquid phase organic matter. The PAH breakthrough in the absence of DOM was significantly retarded in both the seasand and the spodic B material. The observed breakthrough times were considerably lower than those estimated from calculations using published Kd values, that resulted in an overestimation of PAH mobility. The addition of DOM resulted in reduced mobility of PAHs and reduced PAH effluent concentration, but more so in the spodic B soil material than in the seasand. The reduced mobility of PAHs in the presence of DOM can be explained by sorption of DOM-associated PAHs to the bulk soil, that is, co-sorption. Alternatively, the continuous sorption of DOM by the bulk phase results in an increase of sorption capacity for free PAHs, which will also lead to PAH retardation (cumulative sorption).

97/01888 Biocide for treating sandboxes

Fixed bed slow pyrolysis experiments on rice husks were carried out in order to determine the effect of pyrolysis temperature upon: porous structure; surface morphology; phase composition; total amount, nature and distribution of the volatile compounds finely dispersed on the solid pyrolysis residues. The pyrolysis experiments were performed within the temperature range 250–700 °C. The sorption capacity of pyrolyzed rice husks for crude oil was determined. The results indicate that the increase in oil sorption capacity of rice husks after pyrolysis is the result of mutual influence of the above mentioned parameters. It was established that the oil sorption capacity was more strongly influenced by the porous structure of the adsorbents than by their phase composition and by the nature and amount of finely dispersed fluids. For achieving the purpose that was set in advance, the capabilities of: scanning electron microscopy, mercury porosimetry, Brunauer–Emmett–Teller method, Fourier transform infrared spectroscopy, gas-chromatography/mass spectrometric analysis, extraction and gravimetric analysis were used.

Removal of copper using marine brown alga, Undaria Pinnatifida modified with oxime

As oxime is selective for Cu2+, oxime groups were introduced to the cell wall of alga by glutaraldehyde. Such modified biomass showed high affinity for Cu2+, which resulted in the increase of copper sorption capacity about 4.5 times higher than that of natural alga. For pH range from 2.5 to 3.0, only Cu2+ were removed by alga biomass modified with oxime, while other heavy metal ions such as Ca2+,Cd2+,Pb2+ were not adsorbed. By changing pH, selective recovery of Cu2+ was achieved.

Studies on removal and recovery of Cr(VI) from electroplating wastes

Phosphate treated sawdust shows remarkable increase in sorption capacity of Cr(VI) as compared to untreated sawdust. The adsorption process is pH dependent. 100% adsorption of Cr(VI) was observed in the pH range <2 for the initial Cr(VI) concentration of 8–50 mg 1 −1. The effect of various adsorbent doses at pH 2 confirms Langmuir adsorption isotherms. 100% removal of Cr(VI) from synthetic waste as well as from electroplating waste containing 50 mg 1 −1 Cr(VI) was achieved by batch as well as by column processes. The adsorbed Cr(VI) on phosphate treated sawdust was recovered (87%) using 0.01 M sodium hydroxide.

NKS-0.8 fast cryosorption pump with increased sorption capacity

NKS-0.8 fast cryosorption pump with increased sorption capacity

Sorption sites in biofilms

The distribution of pollutants in water is strongly dependent on the processes at the solid-liquid interface, such as soprtion. The solid phase is represented by many different materials, mostly minerals but also metals and organics. In technical and natural water systems, biofilms occur to a greater or lesser extent. They will cover the underlying material (substratum) at least partially and represent a gel-type layer, mainly consisting of extracellular polymeric substances (EPS), formed by biofilm organisms, in which the latter are embedded. Thus, the sorption properties of biofilms will significantly determine the overall process. This effect may have been almost completely overseen, e.g., in the assessment of the fate of pollutants in waters, in the process of sediment diagenesis, and in chemical sorption studies. Sorption data can differ considerably between sterile and non-sterile assays; this aspect puts in question many results gained in biologically uncharacterized systems. Sorption in biofilms can be undesired, if pollutants accumulate in biomass such as activated sludge. The same effect, however, can be biotechnologically exploited, e.g. in biosorption reactors. Biofilms can sorb water, inorganic and organic solutes and particles. As sorption sites can serve: EPS, cell walls, cell membranes and cell cytoplasm. These sites display different sorption preferences, capacities and properties. The situation becomes even more complex as biofilms may respond physiologically to sorbed substances. For example: the uptake of toluene can lead to the formation of uronic acids in the EPS and, thus, to an increased sorption capacity for cations. When decomposing, biofilms will release sorbed substances. This can be of significance if trickling deposition of sewage water on soil is finished. The biomass will decompose, sorbed pollutants are remobilized and can contaminate the ground water if not retained abiotically by other soil components. A substantial research demand is identified regarding the following questions: (i) what do biofilms sorb; (ii) what are the binding sites; (iii) what are the sorption mechanisms and capacity, and (iv) what is the remobilization potential?

Sorption sites in biofilms

The distribution of pollutants in water is strongly dependent on the processes at the solid-liquid interface, such as sorption. The solid phase is represented by many different materials, mostly minerals but also metals and organics. In technical and natural water systems, biofilms occur to a greater or lesser extent. They will cover the underlying material (substratum) at least partially and represent a gel-type layer, mainly consisting of extracellular polymeric substances (EPS), formed by biofilm organisms, in which the latter are embedded. Thus, the sorption properties of biofilms will significantly determine the overall process. This effect may have been almost completely overseen, e.g., in the assessment of the fate of pollutants in waters, in the process of sediment diagenesis, and in chemical sorption studies. Sorption data can differ considerably between sterile and non-sterile assays; this aspect puts in question many results gained in biologically uncharacterized systems. Sorption in bioflinis can be undesired, if pollutants accumulate in biomass such as activated sludge. The same effect, however, can be biotechnologically exploited, e.g. in biosorption reactors.Biofilms can sorb water, inorganic and organic solutes and particles. As sorption sites can serve: EPS, cell walls, cell membranes and cell cytoplasm. These sites display different sorption preferences, capacities and properties. The situation becomes even more complex as biofilms may respond physiologically to sorbed substances. For example: the uptake of toluene can lead to the formation of uronic acids in the EPS and, thus, to an increased sorption capacity for cations.When decomposing, biofilms will release sorbed substances. This can be of significance if trickling deposition of sewage water on soil is finished. The biomass will decompose, sorbed pollutants are remobilized and can contaminate the ground water if not retained abiotically by other soil components.A substantial research demand is identified regarding the following questions: (i) what do biofihns sorb; (ii) what are the binding sites; (iii) what are the sorption mechanisms and capacity, and (iv) what is the remobilization potential?

Effects of slash burning on soil phosphorus fractions and sorption and desorption of phosphorus

Soil P fractions and P sorption-desorption characteristics were studied 7 months after clearfelling and slash burning at a mixed Eucalyptus forest site in eastern Australia. Depending on the fire intensity, three different microsites were generated: unburnt, burnt and intensely burnt (ashbed). Phosphorus fractions were extracted from the soil with NH 4F (0.03 N) + HCl (0.025 N) (Bray I), NaHCO 3 (0.5 N), NaOH (0.5 N), and H 2SO 4 (1 N). Adsorption isotherms were obtained by equilibrating soils with solutions having concentrations of P, and desorption of the adsorbed P was studied by extracting the soils with Bray I extract. The effects of fire on soil P were greatest in the surface soil horizons and depended upon fire intensity. Ashbed soils differed from unburnt soils for P fractions and P sorption and desorption characteristics. Labile inorganic P (Bray I) increased from less than 1 mg kg −1 in the unburnt soil to 5–13 mg kg −1 in the ashbed. Inorganic P (NaOH and H 2SO 4 extractions) increased markedly after fire, especially in the surface layers. The increase in labile organic P (NaHCO 3-extractable) contrasted with a decrease in total organic P (H 2SO 4) and less labile organic P (NaOH) in ashbed soils, suggesting marked transformation of organic P pools after intense fire. After incubation for 2 months, labile organic P in the unburnt soil increased, whereas large decreases were observed in ashbeds and surface (0–5 cm) burnt soils. The ashbed soil showed an increase in sorption capacity in the 0–5 cm soil layer, but the sorbed P was generally less tightly bound to the solid phase. Seedling growth and foliage P concentrations were greatest in ashbed soils. Harvesting and burning increased the spatial distribution of soil P in the field. The ashbed and burnt microsites represented 19% and 18% respectively, of the surface area of the slash burnt coupe, and about 8 kg P ha −1 was deposited in ash.

Conformer isomerization kinetics in glassy amorphous poly (ethylene terephthalate) and their effect on penetrant sorption

Amorphous poly(ethylene terephthalate) is a binary mixture of repeat units with the ethylene segments exhibiting either a trans or a gauche rotational conformation. The ratio of these conformational species varies as reversible isomerization reactions induced by CO 2 sorption or thermal annealing occur. Incorporation of a critical amount of CO 2 into the polymer catalyzes isomerization from the trans to the gauche conformation. Exposure of the polymer to temperatures slightly below the glass transition temperature initiates the reverse isomerization reaction. Analysis of the rate data for both of these reactions suggests that the isomerization mechanism involves simultaneous rotation of three adjacent chain segments. A corresponding increase in Langmuirian sorption capacity of the polymer is observed with increasing gauche fraction. A stochastic model is developed relating the number of Langmuirian sorption sites to the number of volume elements containing a fixed quantity of gauche segments.