Evaluating Binary Sorption of Phenol/Aniline fromAqueous Solutions onto Granular Activated Carbon and Hypercrosslinked Polymeric Resin (MN200)

Sorption equilibrium of phenol and aniline onto the granular activated carbon and hyperreticulated un-functionalized polymeric resin (MN200) was investigated in single and binary component aqueous systems. Higher loading was obtained for aniline than phenol onto both sorbents, which is probably due to hydrophobic difference between both solutes and the greater electronic density of the aromatic ring of the aniline. Granular activated carbon reported larger uptake than resin MN200 for both solutes, which may be attributed to the better physical properties of the granular activated carbon, for instance, larger surface area. The experimental sorption could be properly described by the Langmuir and Freundlich isotherms. Five models for predicting the binary equilibrium sorption isotherm were compared in order to determine the best fit model to correlate binary experimental data: the extended Langmuir isotherm with and without a constant interaction factor, a simplified model based on the single equilibrium factors, the empirical extended Freundlich isotherm and the modified extended Langmuir equation, which considers the synergistic interactions between sorbate–sorbate and not only the competition between them defined by the extended Langmuir model. The modified extended Langmuir model provides the best agreement between predicted and experimental data indicating that the synergistic interactions between solutes play an important role in the binary phenol/aniline sorption system.     

Competitive Adsorption of Some Hazardous Organic Pollutants from their Binary and Ternary Solutions onto Granular Activated Carbon Columns

Competitive adsorption of some priority pollutants, namely phenol, o-cresol, p-nitrophenol, m-methoxyphenol, benzoic acid and salicylic acid from their aqueous solutions onto granular activated carbon (GAC) column was studied. Experiments were carried out to determine the breakthrough curves for adsorbates when present in aqueous solutions as single-, bi- and tri-solute system to evaluate the competitive adsorption phenomenon. Results indicate that in single-solute-GAC systems, p-nitrophenol is most strongly adsorbed as compared to other phenol derivatives studied. The substituted phenols were found to adsorb to a greater extent than phenol itself. The GAC-bisolute and GAC-trisolute systems clearly show the competitive or preferential adsorption of one solute over the other, as the solutes are competing for the available GAC surface for adsorption. Initially, all the adsorbates are taken up by the GAC surface, but near the breakthrough point the more adsorbable solute is able to desorb the less adsorbable one.     

Behavior of phenol and aniline on selected sorbents and energy-related solid wastes

The sorption and desorption of phenol and aniline on selected soils and soil components and on some energy-related solid wastes were investigated. Isotherms were generally nonlinear and were described usually by the Freundlich equation. Most partition coefficients were low, and no significant correlation was shown with organic C content, pH, cation exchange capacity, or particle-size of the sorbent. It appears that sorption of small polar aromatic compounds, such as phenol and aniline, cannot be defined by a single sorbent characteristic, but is affected by both the organic and mineral components of the sorbents. Hysteresis was observed in most sorption-desorption experiments; a fraction of the sorbate was irreversibly held by the sorbent.     

Sorption and leaching of atrazine and MCPA in natural and peat-amended calcareous soils from Spain.

The sorption and leaching of atrazine and MCPA (0.02 M CaCl(2) aqueous solution at 25 degrees C) by a calcareous soil from Southeastern Spain, after organic carbon (OC) amendment with a commercial peat (from 0.18% to 4.61% OC), were studied in batch and soil column experiments. Adsorption capacity (K(f)) values, obtained by fitting the experimental data to the Freundlich equation, ranged from 0.24 mg kg(-)(1) for MCPA sorption on the original soil to 5.47 mg kg(-)(1) for atrazine sorption on the peat-amended soil containing 4.61% OC. The breakthrough curves obtained from the step-function soil column experiments indicated that the amount of herbicide adsorbed ranged from 17.5 mg kg(-)(1) for MCPA in the original soil to 331 mg kg(-)(1) for atrazine in the peat-amended soil containing 1.67% OC. The results obtained from the pulse experiments indicate that the mobility of MCPA is much greater than that corresponding to atrazine.     

Removal of Copper and Cadmium Ions from Diluted Aqueous Solutions by Low Cost and Waste Material Adsorbents

The sorption of copper and cadmium ions using activated carbon,kaolin, bentonite, diatomite and waste materials such as compost,cellulose pulp waste and anaerobic sludge as sorbents is reported. Equilibrium isotherms were obtained for the adsorption of these metals in single and binary solutions. Bentonite presented the highest adsorption capacities for both copper and cadmium. A competitive uptake was observed when both metals are present; copper being preferentially adsorbed by all materials with theexception of anaerobic sludge. Equilibrium data were fitted toLangmuir and Freundlich models, with satisfactory results for most of the adsorbent-metal systems studied.Of all the adsorbents studied, bentonite and compost presentedthe highest removal efficiencies, reaching 99% for copper whencadmium is also present, for initial solution concentrations ofup to 100 mg L^-1. Anaerobic sludge has a greater preferencefor cadmium, even in the presence of copper, with removal efficiencies of 98% for similar concentrations to those mentioned above.     

Groundwater Purification in a Polymetallic Mining Area (SW Sinai,Egypt) Using Functionalized Magnetic Chitosan Particles

A magnetic glycine-grafted chitosan sorbent (Gly) was functionalized to produce a hydrazide derivative (HGly). The two sorbents were tested in batch mode for the sorption of a series of 10 metal ions present in the groundwater collected in three wells in the Wadi (valley) Nasib mining area (SW Sinai, Egypt). HGly is much more efficient for metal recovery than Gly. Under selected experimental conditions (sorbent dosage 1.5 g L^?1), the sorption efficiency is not sufficient for achieving the standard levels for drinking water: the most problematic metal ions in terms of drinkability remain aluminum (too high metal concentration in the groundwater), cadmium, and chromium for the three wells (and nickel in the case of only one well). Increasing the sorbent dosage improves the treatment efficiency. The sorbent (HGly) was tested in fixed-bed columns. The breakthrough curves were compared for the different metals for the groundwater collected in the most contaminated of the three wells. The levels of metal concentration in the treated groundwater are too high for direct use in irrigation. However, they are consistent with the standards for livestock drinking water (based on FAO recommendations, Food and Agriculture Organization of the United Nations). The metals can be readily desorbed using 0.5 M HCl solutions with a relatively high concentrating effect (i.e., 50 times). The re-use of the sorbent for three successive cycles of sorption/desorption cycles shows a progressive but weak decrease in sorption and desorption performances.     

Removal of Arsenic from Aqueous Solutions by Sorption onto Sewage Sludge-Based Sorbent

This study aimed at evaluating and comparing the removal of arsenic from solutions by a low-cost waste-based sorbent, produced by pyrolysing sewage sludge under appropriate conditions, and by a commercially activated carbon. Batch sorption experiments were performed under isothermal conditions (20°C), in order to evaluate the effect of pH on the arsenic sorption kinetics and on the equilibrium sorption capacity of the materials under study. Kinetic data revealed that the arsenic sorption was faster onto the activated carbon than onto the pyrolysed sludge. The sorption process was well described by both the pseudo-first and pseudo-second-order kinetics equations for both materials. Changes in the initial solution pH have distinct effects on the removal of arsenic onto pyrolysed sludge and activated carbon. While for pyrolysed sludge, pH affects essentially the equilibrium time, for activated carbon it affects the sorption capacity. Equilibrium results were well described by both Freundlich and Langmuir isotherm models, although fittings corresponding to the Langmuir isotherm were slightly better. The Langmuir maximum sorption capacity determined for the pyrolysed sludge was 71???g?g^?1, while for activated carbon was 229???g?g^?1. Despite the relative lower capacity of the pyrolysed sludge, the considerable lower cost and the valorisation of the sludge may justify further research on its use for water decontamination.     

Feasibility Assessment of Chromium Removal from Groundwater for Drinking Purposes by Sorption on Granular Activated Carbon and Strong Base Anion Exchange

The goal of this study was to compare the performances of strong base anion (SBA) exchange and activated carbon adsorption in the removal of hexavalent chromium, Cr(VI), from a real groundwater matrix exploited for drinking purposes. Two SBA resins and three granular activated carbons (GAC) were tested by batch experiments for kinetics and equilibrium isotherm determination. SBA resins showed higher affinity toward Cr(VI) (present in raw water at about 20 μg L^?1) with respect to the GACs, with faster kinetics and higher equilibrium adsorption capacities. Among GACs, vegetal-based carbons showed higher Cr(VI) removal efficiencies than the mineral-based carbon, which can be related to the more developed textural properties. SBA resins also displayed relevant removal capacities towards nitrate and sulfate (present at mg L^?1 concentration levels), while boron (present at about 60 μg L^?1) was effectively removed by GACs. Batch experiment results were elaborated to estimate the chromium throughputs for the studied materials, to preliminary compare their performances in a real-scale application. The monitoring of a real-scale GAC adsorption stage permitted to validate throughputs estimation and confirmed that, despite being effective toward synthetic organics, GAC adsorption is a not feasible solution for Cr(VI) removal, with extremely early breakthrough. SBA exchange process resulted to be the most suitable solution, providing the best sorbent usage rates. However, SBA resin usage rates can strongly increase when considering the removal of nitrate and sulfate ions, requiring much shorter cycle times.     

Sorption of Selected Aromatic Substances��Application of Kinetic Concepts and Quantum Mechanical Modeling

Prediction of the sorption behavior of environmental pollutants is of utmost importance within the framework of risk assessments. In this work two approaches are presented with the aim to describe sorption of aromatic substances to geosorbents. First, analytical solutions of kinetic models were fitted to experimental data of batch sorption experiments with aniline and 1-naphthylamine onto animal manure-treated soil and the soil mineral montmorillonite. The models, accounting for equilibrium and nonequilibrium sorption coupled to transformation and/or irreversible sorption processes, could well reproduce the concentration course of the sorbates. Results suggest that the amounts transformed/degraded and irreversibly bound were higher for the soil than for the clay mineral. In the second part, quantum chemical calculations were performed on aniline and 1-naphthylamine interacting with acetic acid, acetamide, imidazole, and phenol as models of functional groups present in humic substances. Molecular modeling showed that formation of hydrogen bonds is the dominating binding mechanism in all modeled complexes, which are energetically very similar between aniline and 1-naphthylamine.     

Exchange resin cores for the estimation of nutrient fluxes in highly permeable tropical soil

There is an urgent need to improve the methods to estimate solute fluxes in soil, e.g. cumulative capture of leaching ions by exchange resin cores. We compared the suitability of different resin materials, core sizes, and installation procedures to assess nutrient leaching in a highly permeable, tropical Xanthic Ferralsol. Three different cation and anion resins, respectively, and two combined anion-cation resins were tested in laboratory experiments with respect to their removal and recovery of nutrients (Mg, NH₄⁺, NO₃^—) and total dissolved organic carbon (TOC) from solution. In a field experiment, cores with three different diameters (25, 100, and 200 mm) were installed either vertically from the soil surface or laterally from a soil pit. Cumulative leaching of NO₃^— and NH₄⁺ and of applied Sr was determined after 45 days. The combined anion and cation exchange resin (MB 20) showed satisfactory recovery of NO₃^— and NH₄⁺ from solution. None of the investigated resins could be used for TOC removal from solution due to high contents of soluble carbon compounds in the resins. Wetting and drying cycles did not affect the removal of solutes from solution or subsequent recovery from the MB 20 resin. Additionally, the combined resin MB 20 was easier to handle than separate anion or cation resins and was therefore used for further field experimentation. The smallest core size (25 mm) was not suitable for nutrient leaching determination due to high preferential flow along the inner core walls. The medium diameter cores (100 mm) showed the lowest variability and the best correlation between NO₃^— and Sr capture. They were easier to install and retrieve than the large diameter cores (200 mm), which posed serious handling problems and soil disturbance. The lateral installation caused significantly lower artificial flow in comparison to a vertical installation, which was shown by the lower Sr loss and slightly lower N capture. Therefore, a lateral installation of medium sized resin cores (100 mm diameter) from a soil pit was superior to the other alternatives tested in this study.     

Transport of Strontium Through a Ca-bentonite (Almer??a, Spain) and Comparison with MX-80 Na-bentonite: Experimental and Modelling

In this work, the sorption of strontium on a Ca-bentonite (CGA) from Almer??a (Spain) in column experiments was studied, and the results obtained were compared with the sorption onto the Na-bentonite (MX-80). The code CTXFIT (two site non-equilibrium sorption model) was used in order to fit the experimental data and to determine sorption and transport parameters. The effect of inlet Sr(II) initial concentration and the ionic strength were evaluated. The results obtained showed that the sorption capacities as well as the transport and sorption parameters of both bentonites were affected by the initial metal concentration. In experiments with higher inlet concentrations, columns were saturated faster, leading to shorter breakthrough and exhaustion times. On the other hand, a decrease of sorption and transport parameters was observed at higher ionic strengths, which would confirm ion exchange as the main mechanism of Sr(II) sorption onto both bentonites. The sorption parameters (sorption capacity and retardation factor) obtained indicated that the Ca-bentonite from Almer??a (Spain) presented better sorption performance than the Na-bentonite, which was related to the physical properties of the Ca-bentonite.     

Phosphorus sorption in soils of the Mekong Delta (Vietnam) as described by the binary Langmuir equation

Phosphate adsorption isotherms were determined for 20, mostly very acidic, soils from the Mekong Delta. The experimental data were well described by a binary Langmuir equation which considers two groups of sorption sites that differ in their P bonding energies. The maximum P-sorption capacities of these sites were related to the soil properties by simple linear correlation and by stepwise multiple regression. Results suggest that high energy sites are on Al-oxihydroxides or small Al-substituted Fe-oxides and, to a lesser extent, on poorly ordered Fe-oxihydroxides. On the other hand, the P-sorption capacity of low energy sites is mainly related to clay content, and it increases as pH decreases. These sites are also positively correlated with organic carbon and poorly crystalline Fe-oxihydroxides. However, as these two variables are closely correlated with each other, organic matter is likely to be considered as an indirect factor of P fixation through its association with Fe-oxihydroxides and not as an important source of P-sorption sites. The maximum sorption capacity, i.e. the sum of sorption capacities of the two groups of sites, is well described (r²= 0.88) by an equation that takes into account the four variables identified above: Al-bearing oxihydroxides, poorly ordered Fe-oxihydroxides, clay content and pH. Grouping the soils according to the orders of Soil Taxonomy, the P-sorption capacity increases in the following sequence: ultisols < entisols < inceptisols. A P concentration often considered adequate for plant nutrition is 0.2 mg P 1^?1 solution, and only the high energy sites are involved in sorption at that concentration. Thus an equation including only Al- and Fe-oxihydroxides could be used to fix P norms in these soils.     

Batch Chromium(VI), Cadmium(II) and Lead(II) Removal from Aqueous Solutions by Horticultural Peat

The selectivity and uptake capacity of horticultural peat available in Romania was evaluated with respect to the removal of Cd(II), Cr(VI) and Pb(II) ions from aqueous solution. The kinetics, sorption capacities, selectivity and pH dependence of sorption were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir and Freundlich isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solutions containing 300 mg/l of metal, the observed uptake capacities were 20 mg Cd(II)/g peat, 15 mg Cr(VI)/g peat and 30 mg Pb(II)/g peat. The study proved that horticultural peat is a suitable material for the removal of the studied heavy metal ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II), Cr(VI) and Pb(II) ions.     

Investigation of Arsenic Removal from Water by Iron-Mixed Mesoporous Pellet in a Continuous Fixed-Bed Column

Natural clay combing with iron oxide and iron particle was developed to be iron-mixed mesoporous pellet that was packed in a fixed-bed column for removing arsenic from water. The performance of the column in terms of breakthrough curve analysis was investigated with the variations of influent flow rate, adsorbent bed height, initial solution pH, and initial adsorbate concentration. The results indicated that increasing in the flow rate decreased the removal capacities of the adsorbent. A relatively low bed height provided a better and beneficial performance. Higher adsorption capacity was observed with an increase of initial adsorbate concentration. At higher initial solution pH, the repulsive process occurred between adsorbate species and the surface charge of the adsorbent, resulting in a poor performance of the column. The Thomas model fitted very well to the experimental data for all cases. Estimated from the model, the highest adsorption capacity for arsenite and arsenate was found to be about 509 and 430 μg/g, respectively. The Adam-Bohart model provided only a relatively satisfactory fit to the initial part of the experimental data. From a practical view, the new developed pellet could be used as the effective and efficient adsorbent to treat elevated arsenic contaminated groundwater.     

Comparison of field and laboratory H2S adsorption capacity of activated carbon

A comparison study on fixed-bed H₂S adsorption capacity of a commercial activated carbon both in the laboratory and in the field was conducted. Pure H₂S gas at an inlet concentration of 10 000 ppm was used for the laboratory test, while the field activated carbon was subjected to adsorption of sewage gas with H₂S concentrations ranging from 0.1 to 28 ppm with an average concentration of 5.3 ppm. The carbons were tested under gas/carbon contact times of 1, 2, 3, and 4 s. Based on the results obtained at a carbon/gas contact time of 3 s and a H₂S breakthrough concentration of 1 ppm, the H₂S adsorption capacity of the field activated carbon was found to be only 30% of that in the laboratory. It is possible that the adsorption of other sewage volatiles has resulted in a significant decrease in the activated carbon's H₂S removal efficiency.     

Co-adsorption of Cd(II) and Sb(III) by ferrihydrite: a combined XPS and ITC study

Purpose

Heavy metal and metalloid commonly coexist in soils and sediments, and interact frequently with various minerals. The coexistence of Sb and Cd is commonly observed in Sb mine area, but their co-adsorption behaviors to soil minerals still remain poorly understood. This study aimed to elucidate the co-adsorption characteristics of Cd(II) and Sb(III) by ferrihydrite (Fh) under anoxic condition.

Materials and methods

Batch experiments were performed to determine the sorption capacity of Cd(II) and Sb(III) in both single and binary systems. The major functional groups that were responsible for Cd(II) and Sb(III) sorption were determined by X-ray photoelectron spectroscopy (XPS), while the thermodynamic sorption mechanisms were elucidated using isothermal titration calorimetry.

Results and discussion

Cd(II) sorption on Fh increases with increasing pH levels (4–8) whereas Sb(III) sorption shows less variation with pH level variations. The Langmuir adsorption capacity is 55.54 mg/g for Cd(II) and 188.19 mg/g for Sb(III). In Cd–Sb binary systems, Cd(II) sorption is significantly diminished whereas Sb(III) uptake is close to single Sb(III) sorption. XPS indicates the Fe–OH groups are mainly responsible for the binding of Cd and Sb, possibly through the formation of inner-sphere complexes. This hypothesis is further confirmed by the positive entropy (ΔS) after Cd and/or Sb binding. A larger ΔS in the binary Cd–Sb titration than in their single titrations implies the formation of a ternary Fh–Sb–Cd complex, which results in a higher disorder of the sorption system.

Conclusions

The presence of Sb(III) reduces Cd(II) sorption whereas Cd(II) has a negligible effect on Sb(III) sorption to ferrihydrite; moreover, Sb(III) and Cd(II) might form surface ternary complexes in binary systems. These new findings have important implications for predicting the sequestration, migration, and fate of Cd and Sb in soils.

     

Waste Activated Sludge as an Additive for Increment of Lime Sorption Capacity

Lime was physically blended with Waste Activated Sludge (W.A.S) in various proportions. These blends were hydrated, dried, ground, and sieved to size of utmost 200 μm. The sorbents were then used in fixed-bed reactor for dry desulfurization tests. It was found that the blends had higher sorption capacities than lime alone which means that W.A.S augmented lime's sorption capacity. Higher surface area and porosity of the blended sorbents compared to lime was the main cause of the improved sorption capacity, a conclusion supported by Brunauer–Emmett–Teller surface area analysis (surface area increment with sorption capacity) and scanning electron microscopy imaging (rough morphology being formed). This higher surface area and porosity was caused by pozzolanic reaction between lime and the alumina silicate constituents of W.A.S. The products of this reaction are high surface area, complex calcium alumina silicates.     

Performance Evaluation of Fixed Bed of Nano Calcium Oxide Synthesized from a Gastropod Shell (Achatina achatina) in Hexavalent Chromium Abstraction from Aqua System

The shell of a gastropod (Achatina Achatina) was used as a precursor for the synthesis of nano calcium oxide (NC) via the sol–gel technique. The NC was characterized and the performance evaluation in chromium (Cr) (VI) abstraction was assessed in a fixed bed. The operating characteristics of the NC-Cr (VI) system were analysed with the mass transfer model and the mass transfer zone parameters were found to fluctuate with changes in the initial Cr (VI) concentration. The evaluation of the equilibrium data, generated from the fixed bed studies, showed that the sorption of Cr (VI) occurred via monolayer adsorption mechanism, and the monolayer sorption capacity was 833.33 mg/g. Different kinetic models (i.e., Adams–Bohart, Thomas, Wolborska, and Yoon–Nelson models) were applied to experimental data to predict the breakthrough curves and to determine the parameters of the column useful for process design. The kinetic analysis showed that the Yoon and Nelson model had the best fitting of the experimental data. The data obtained for Cr (VI) removal, when the NC bed height was optimized, were well described by bed depth service time model.     

激活的绢云母：一种使水生环境中铯衰减的高效天然粘土物质)

Sericite is mica-based natural clay that is annealed at 800 ℃ for 4 h, followed by acid activation using 3.0 mol L-1HCl at 100℃. The interaction of cesium(I), Cs(I), with sericite could provide useful data for the study of soil erosion or mass water movement utilizing the natural radioactive Cs. In this study sericite and activated sericite were used to assess their suitability in the attenuation of Cs from the aquatic environment under both batch and column experiments. The surface morphological studies indicated that a disordered and heterogeneous surface structure was exhibited by the activated sericite, whereas the native sericite exhibited a compact and layered structure. The Brunauer-Emmett-Teller(BET) specific surface area results indicated a significant increase in the surface area due to the activation of sericite. The batch reactor data collected for various parametric studies revealed that an increase in p H(from 2.0 to 8.0) and sorbate concentration(from 10.0 to 100.0 mg L-1) apparently favored the attenuation of Cs(I). The timedependent sorption data revealed that Cs(I) uptake was very rapid, and it achieved its saturation value within just 50 min of contact.The kinetic modeling studies indicated that the uptake of Cs(I) followed a pseudo-second-order rate equation; hence, the attenuation capacity of these solids for Cs(I) was estimated to be 0.858 and 4.353 mg g-1for sericite and activated sericite solids, respectively.The adsorption isotherm modeling data showed a reasonably good applicability of the Freundlich model than the Langmuir model.The effect of background electrolyte concentrations(0.001 to 0.1 mol L-1) of Mg(NO3)2indicated that the presence of this electrolyte could not significantly affect the percent removal of Cs(I) by activated sericite. Furthermore, the fixed-bed column reactor operations were performed to obtain the breakthrough data, which were fitted well to the Thomas non-linear equation. Therefore, the loading capacity of Cs(I) was estimated to be 1.585 mg g-1at the initial influent Cs(I) concentration of 30.0 mg L-1at p H 5.0.     

A new method to quantify how water repellency compromises soils' filtering function

Soil water repellency (SWR) is known to lead to preferential flow and to degrade the soil's filtering efficiency. However, no method is available to quantify directly how SWR affects the transport of reactive solutes. We propose a new method for conducting solute transport experiments in water‐repellent soils. It involves sequentially applying two liquids, one water, the other a reference fully wetting liquid, namely aqueous ethanol, to the same intact soil core with air‐drying between liquids. We applied this approach to quantify the impact of SWR on the filtering of the herbicide 2,4‐Dichlorophenoxyacetic acid (2,4‐D) in two Andosols. In batch experiments conducted prior to the transport experiments, 2,4‐D sorption was not influenced by aqueous ethanol for one soil. However, sorption in the second soil followed the co‐solvency theory, which predicts decreasing sorption with increasing solvent fractions. Thus, sorption experiments are necessary to complement our new method. Breakthrough curves were characterized by preferential flow with large initial concentrations, tailing and a long prevalence of solutes remaining in the soil. In the soil in which 2,4‐D sorption was unaffected by aqueous ethanol, SWR increased 2,4‐D losses by four and 50 times in the first 5‐mm outflow compared with the 2,4‐D losses with water. After 50‐mm outflow, the 2,4‐D losses were similar for one core, but in the other core they were still about four times greater with water than with aqueous ethanol. This method to quantify the reduction of the soil's filtering efficiency by SWR is needed for assessing the increased risk of groundwater contamination by solutes exogenously applied to water‐repellent soils.