Adsorption of thorium from aqueous solutions by perlite

The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 ± 1 °C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as ΔG^o, ΔH^o and ΔS^o were calculated as a function of temperature.     

Removal of uranium (VI) from aqueous solution by adsorption of hematite

Hematite, a type of inorganic-sorptive medium, was used for the removal of U (VI) from aqueous solutions. Variables of the batch experiments including solution pH, contact time, initial concentration, temperature, calcium and magnesium ions were studied. The results indicated that the adsorption capacities are strongly affected by the solution pH, contact time and initial concentration. A higher pH favors higher U (VI) removal. The adsorption was also affected by temperature and calcium and magnesium ions, but the effect is very weak. The maximum adsorption capacity (q_m) only increased from 3.36 mg g⁻¹ to 3.54 mg g⁻¹ when the temperature was increased from 293 K to 318 K. A two-stage kinetic behavior was observed in the adsorption of uranium (VI): very rapid initial adsorption in a few minutes, followed by a long period of slower uptake. It was found that an increase in temperature resulted in a higher uranium (VI) loading per unit weight of the sorbent. The adsorption of uranium by hematite had good efficiency, and the equilibrium time of adsorbing uranium (VI) was about 6 h. The isothermal data were fitted with both Langmuir and Freundlich equations, but the data fitted the former better than the latter. The pseudo-first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model were used to describe the kinetic data, but the pseudo-second-order kinetic model was the best. The thermodynamic parameter ΔG⁰ were calculated, the negative ΔG⁰ values of uranium (VI) at different temperatures confirmed the adsorption processes were spontaneous.     

Equilibrium,kinetics and thermodynamics studies on adsorptive removal of cobalt ions from wastewater using MIL-100(Fe)

This study describes experiments in which MIL-100(Fe) was used to remove Co²⁺ ions from the waste water. The synthesised adsorbent was characterised by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, Brunauer–Emmett–Teller (BET) and scanning electron microscope. Statistical analysis was used to investigate the effects of different parameters. From the obtained results, the removal efficiency was enhanced with increasing contact time and pH but decreased with increasing cobalt initial concentration. The maximum removal efficiency of Co⁺² was 93.4% under optimum conditions. The equilibrium adsorption data were best fitted to linearly transformed Freundlich isotherm. Adsorption kinetic data followed the pseudo second-order kinetic model. The maximum adsorption capacity of Co⁺² on to the MIL-100(Fe) was found to be 119 mg g^?1. The results showed that ?G of adsorption was negative, while ?H was positive which showed that the adsorption process was spontaneous and endothermic. The positive value of ?S showed that disordering and randomness increased at the solid–solution interface of cobalt ions with MIL-100(Fe) particles.     

Assessment of hydrothermally modified fly ash for the treatment of methylene blue dye in the textile industry wastewater

Dyes and pigments are one of the major water pollutants and if not discharged properly cause ecological disturbance. Considering this, the current study investigates the application of thermal power plant by-product, i.e., fly ash for the elimination of a hazardous methylene blue dye from its synthetic aqueous solution. Experiments were conducted in batch mode to study the effect of pH, temperature, adsorbent dose and contact time. Highest dye removal (94.3%) was achieved at pH 10 using adsorbent dose of 10 g/L in 90 min of contact time at 40 °C. However, for cost-effective operation at neutral pH and room temperature (30 °C), it yields 89.3% dye removal having similar dose and contact time. Equilibrium isotherms for adsorption were analyzed by Langmuir and Freundlich, Temkin and Dubinin–Radushkevich isotherm equations. The results revealed that the best fit model of adsorption closely followed Langmuir adsorption. Based on adsorption isotherm models, thermodynamics parameters ΔG, ΔH and ΔS were calculated. The negative value of ΔG and ΔH revealed that adsorption process was exothermic, spontaneous and physical. The present work suggests that through simple process hydrothermally modified fly ash has the potential to be used as cost-effective and efficient adsorbent for the treatment of wastewater from textile industries.     

Removal of uranium(VI) from aqueous solutions and nuclear industry effluents using humic acid-immobilized zirconium-pillared clay

Removal of uranium [U(VI)] from aqueous solutions with humic acid-immobilized zirconium-pillared clay (HA-Zr-PILC) was investigated using a batch adsorption technique. The adsorbent was characterized using XRD, FTIR, SEM, TG/DTG, surface area analyzer and potentiometric titration. The effects of pH, contact time, initial concentration, adsorbent dose, and adsorption isotherm on the removal process were evaluated. A maximum removal of 97.6 ± 2.1 and 94.7 ± 3.3% was observed for an initial concentration of 50 and 100 mg L⁻¹, respectively at pH 6.0 and an adsorbent dose of 2.0 g L⁻¹. Equilibrium was achieved in approximately 180 min. The mechanism for the removal of U(VI) ions by HA-Zr-PILC was based on an ion exchange reaction. The experimental kinetic and isotherm data were analyzed using a second-order kinetic equation and Langmuir isotherm model, respectively. The monolayer adsorption capacity for U(VI) removal was found to be 132.68 ± 5.04 mg g⁻¹. An increase of temperature of the medium caused an increase in metal adsorption. Complete removal (≅100%) of U(VI) from 1.0 L of a simulated nuclear industry effluent sample containing 10.0 mg U(VI) ions was possible with 1.5 g of HA-Zr-PILC. The adsorbent was suitable for repeated use (over 4 cycles) without any noticeable loss of capacity.     

Behavior and analysis of Cesium adsorption on montmorillonite mineral

The adsorption of Cs by montmorillonite and the effects of experimental conditions on adsorption were investigated by using ¹³⁴Cs as a radioactive tracer. Additionally, the Cs-adsorbed and the modified montmorillonite were analyzed by X-ray Diffractometer System (XRD) and Scanning Electron Microscopy (SEM). The results showed that the adsorption of Cs by montmorillonite was efficient in the initial concentration (C₀) of 30 μg/L Cs nitrate solution with 20 g/L montmorillonite at room temperature. In this condition, more than 98% Cs⁺ ions could be adsorbed at pH 8. The adsorption equilibrium was achieved within 5 min and the relationship between the concentration of Cs⁺ in aqueous solutions and adsorption capacities of Cs⁺ can be described by the Langmuir adsorption isotherm. The adsorption rate would decrease when temperature increase from 0 °C to 50 °C or in presence of coexistent K⁺, Na⁺ and Ca²⁺, while modification by (NH₄)₂SO₄, [Ag(NH₃)₂]⁺, [Cu(NH₃)₄]²⁺ or 450 °C could improve the adsorption abilities of montmorillonite for Cs⁺. However, more than 89% of adsorbed Cs⁺ on montmorillonite could be desorbed by 2 mol/L HNO₃ solutions. The XRD and SEM analysis further showed that the structure of the Cs-adsorbed or modified montmorillonite were different from that of the original one.     

Study of Ni adsorption on NKF-6 zeolite

The adsorption of ⁶³Ni from aqueous solutions using NKF-6 zeolite was investigated by a batch technique under ambient conditions. The adsorption was investigated as a function of contact time, pH, ionic strength, foreign ions, humic substances (FA/HA) and temperature. The kinetic adsorption was well described by the pseudo-second-order rate equation. The adsorption of ⁶³Ni on NKF-6 zeolite was strongly dependent on pH and ionic strength, and the adsorption of ⁶³Ni increased with increasing NKF-6 zeolite content. At low pH values, the presence of FA enhanced the adsorption of ⁶³Ni on NKF-6 zeolite, but the presence of HA had no drastic effect. At high pH values, the presence of FA or HA decreased the adsorption of ⁶³Ni on NKF-6 zeolite. The adsorption isotherms were well represented by the Langmuir model. The thermodynamic parameters (i.e., ΔH⁰, ΔS⁰and ΔG⁰) for the adsorption of ⁶³Ni were determined from the temperature dependent isotherms at 293.15, 313.15 and 333.15 °K, respectively, and the results indicate that the adsorption reaction was favored at high temperature. The results suggest that the adsorption process of ⁶³Ni on NKF-6 zeolite is spontaneous and endothermic.     

Chemisorption and Physical Adsorption Roles in Cadmium Biosorption by Chlamydomonas Reinhardtii

Abstract

The aim of this study was to investigate the mechanism of cadmium (Cd) adsorbed by microalgae Chlamydomonas reinhardtii (C.reinhardtii). The kinetic and adsorption isotherm of the process could be well described by mathematical models. Chemical modification experiments and Fourier transform infrared spectra indicated that carboxyl and amine groups were the important functional groups for adsorption of Cd. The maximum contribution of physical adsorption in the overall adsorption process was evaluated as 5.5%. These results indicated that chemisorption was the dominating mechanism of Cd biosorption by C.reinhardtii.     

Removal of uranium(VI) from aqueous solutions by manganese oxide coated zeolite: discussion of adsorption isotherms and pH effect

This paper discusses the adsorption properties for uranium(VI) by manganese oxide coated zeolite (MOCZ). The removal of uranium(VI) from aqueous solution by adsorption onto MOCZ in a single-component system with various contact times, pH, competitive ions, temperatures and initial concentrations of uranium(VI) was investigated. The experimental results were fitted to the Langmuir, Freundlich and the three-parameter Redlich-Peterson model isotherms to obtain the characteristic parameters of each model. Both the Langmuir and Redlich-Peterson isotherms were found to best represent the measured adsorption data. According to the evaluation using the Langmuir equation, the maximum adsorption capacity of uranium(VI) ions onto MOCZ was 15.1 mg g(-1) at 293K and pH 4.0. Using the thermodynamic equilibrium constants obtained at different temperatures, various thermodynamic parameters, such as DeltaG(0), DeltaH(0) and DeltaS(0), have been calculated. The thermodynamics of uranium(VI) ion/MOCZ system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent.     

Phosphate removal by activated carbon–silica nanoparticles composite,kaolin, and olive cake

This work aimed to utilize four low-cost materials, namely activated carbon (AC), activated carbon–nanoparticle composite, kaolin, and olive cake, for phosphate removal. Batch mode tests were used to evaluate the performance of the adsorbents. The parameters affecting the adsorption process such as pH, initial concentration, mixing time, dosage, and temperature were studied. The obtained results showed that the removal efficiency of the adsorbents followed the order of: activated carbon–nanosilica > activated carbon > kaolin > olive cake. The addition of silica nanoparticles significantly enhanced the removal efficiency of activated carbon by 18.1% reaching a removal efficiency of 98% at 15wt% nanosilica loading. The adsorption isotherm data fitted well with Langmuir and Redlich–Peterson models with a correlation coefficient of >0.98, which indicates a monolayer homogenous adsorption. The fitness of the kinetic models was ranked as: pseudo-second-order > pseudo-first-order > intraparticle model. The calculated values of ΔH° = 23.4 kJ/mole, ΔS° = 0.11 kJ/mole, and ΔG = ?7.4 to ?11.8 kJ/mole indicated the endothermic and spontaneous nature of adsorption. The positive value of activation energy (17.66 kJ/mole) and the very low value of the sticking probability (2.4 × 10^?4) suggest high indefinite sticking of the phosphate ions to the adsorbent surface. The removal efficiency increased with time, dosage, and temperature, while it decreased with the increase in the initial concentration at an optimum pH of 7. The obtained results buttressed the benefit of using silica nanoparticles to enhance activated carbon capacity for phosphate removal, while kaolin and olive cake provided lower removal.     

Evaluation of decoloration potential of <Emphasis Type="Italic">Xanthium Strumarium</Emphasis> seed hull for adsorption of Direct red 81 in aqueous solution

An unmodified natural adsorbent, Xanthium Strumarium, was explored for its decoloration potential for treatment of textile effluents. Batch mode experimentation was carried out to optimize several process parameters with the well characterized adsorbent. For proper assessment of optimized pathway of adsorption, adsorption isotherms were implemented to the experimental data using nonlinear method. Apart from coefficients of determination, three error analysis methods standard error (S.E.), Chi-square (χ²) statistic and residual mean square error were additionally used to determine the best fitted isothermal model for the system. Freundlich model was creditably fitted to the adsorption data with minimum errors and high R ² values. The adsorption capacity obtained was 14.7, 15.2 and 18.7 mg g^?1 at 30, 40 and 50 °C, respectively. Overall adsorption process was endothermic with positive enthalpy and entropy values. Kinetic study revealed adsorption to be a two stage process initially controlled by film diffusion followed by pseudosecond order as the rate administering step during adsorption. About 95 % decoloration was achieved in 60 min. High decoloration tendency of the opted adsorbent proved that it is an effective and cheap adsorbent for treatment of coloured effluents providing a good alternative to activated carbon.     

三峡库区悬移质泥沙对磷污染物的吸附解吸特性

就三峡库区悬移质泥沙对磷污染物的吸附解吸特性从野外同步监测和室内试验研究两个方面展开研究。选取长江干流、嘉陵江和乌江共7个监测断面于2002年和2003进行野外同步监测,测试结果表明：水中的悬移质泥沙对水中各种覆存形态的磷污染物浓度具有显著影响,单位重量泥沙对磷的吸附量与水体总泥沙含量、泥沙粒径有密切关系。采集寸滩断面泥沙对磷酸盐吸附解吸特性进行室内试验研究,并根据Langmuir吸附动力学方程对吸附解吸过程进行了拟合,发现吸附速率常数k随着泥沙粒径的增加而呈递增变化,而磷酸盐初始浓度对k值的影响并不明显,同时,磷酸盐解吸量随着泥沙浓度的增加和粒径的增加呈递减变化,k值随着泥沙粒径的增加而呈递增变化,泥沙浓度对k值的影响不明显。     

Improved performance of a biomaterial-based cation exchanger for the adsorption of uranium(VI) from water and nuclear industry wastewater

The amine-modified polyhydroxyethylmethacrylate (poly(HEMA))-grafted biomaterial (tamarind fruit shell, TFS) carrying carboxyl functional groups at the chain end (PGTFS-COOH) was prepared and used as an adsorbent for the removal of uranium(VI) from water and nuclear industry wastewater. FTIR spectral analysis revealed that U(VI) ions and PGTFS-COOH formed a chelate complex. The adsorption process was relatively fast, requiring only 120 min to attain equilibrium. The adsorption kinetic data were best described by the pseudo-second-order equation. The equilibrium adsorption data were correlated with the Sips isotherm model. The maximum U(VI) ions uptake with PGTFS-COOH was estimated to be 100.79 mg/g. The complete removal of 10 mg/L U(VI) from simulated nuclear industry wastewater was achieved by 3.5 g/L PGTFS-COOH. The reusability of the adsorbent was demonstrated over 4 cycles using NaCl (1.0 M) + HCl (0.5 M) solution mixture to de-extract the U(VI). The results show that the PGTFS-COOH tested is very promising for the recovery of U(VI) from water and wastewater.     

Impact of water quality parameters on the sorption of U(VI) onto hematite

In this study, the sorption of U(VI) from aqueous solution on hematite was studied as a function of various water quality parameters such as contact time, pH, ionic strength, soil humic acid (HA) or fulvic acid (FA), solid content and temperature by using a batch technique. The results demonstrated that the sorption of U(VI) was strongly dependent on ionic strength at pH < 6.0, and outer-sphere surface complexation may be the main sorption mechanism. The sorption was independent of ionic strength at pH > 6.0 and the sorption was mainly dominated by inner-sphere surface complexation. The presence of HA/FA increases U(VI) sorption at low pH, whereas decreases U(VI) sorption at high pH. The thermodynamic parameters (ΔH⁰, ΔS⁰, and ΔG⁰) were calculated from the temperature dependent sorption isotherms, and the results suggested that U(VI) sorption was a spontaneous and endothermic process. The results might be important for the application of hematite in U(VI) pollution management.     

The effect of complex formation on the adsorption characteristics of heavy metals

In most aqueous environmental systems, inorganic and organic metal complexes represent a significant contribution to the total soluble metal. Metal adsorption is often a highly pH-dependent phenomena. Such behavior can generally be attributed to changes in metal speciation with solution acidity as well as variation in the extent of surface protonation. Thus, because adsorbability may vary drastically between different metal species, (e.g. Cu²⁺ (aq) compared to CuOH⁺) a knowledge of metal species distribution is essential to understanding and interpreting metal adsorption behavior.Organic complexation has been reported to enhance, suppress and have no perceptible effect on trace metal adsorption. Such differences arise because adsorption depends on factors such as the ligand/metal ratio, adsorbability of the free ligand, and various solution parameters (e.g. pH). Most important in determining the effect of complexation on adsorption is the adsorbability of the resulting complexes. Thus, it is difficult to make generalizations about the influence of organic complexation on metal adsorption.Adsorption of metal complexes is frequently reported to be predominantly coulombic in nature; that is, binding of an anionic or cationic complex to an oppositely charged colloidal particle. However, electrostatic forces can often represent an insignificant contribution to the total free energy of adsorption and can be overshadowed by chemical reactions with the surface, hydrogen bonding, and hydrophobic effects.     

The interaction of heavy metals with urban soils: sorption behaviour of Cd, Cu, Cr, Pb and Zn with a typical mixed brownfield deposit

This study investigated the sorption characteristics and release of selected heavy metals (Cd, Cu, Cr, Pb and Zn) from a typical urban soil material from a derelict brownfield site in Western Scotland, UK. The study aimed to evaluate contaminant interactions with an urban substrate, comprising a mix of mineral soil and residue materials (e.g. brick, concrete, wood). This type of material has received little consideration in the literature to date. Soil samples were subject to a sequence of test involving batch equilibration and dynamic leaching, in single (non-competitive) and multi-element (competitive) solutions. The batch experiments were carried out in unadjusted and close to soil field pH conditions (pH 2 and 7, respectively). The equilibrium adsorption capacity for heavy metals was measured and extrapolated using the Langmuir isotherm. The parameters of the isotherms x(m) (the maximum amount adsorbed per unit mass of adsorbent (mg/g)) and b (adsorption constant (m(3)/g)) were calculated for Cd, Cu, Cr, Pb as single-element and multi-element solutions. The adsorption from the single-element solution was more effective than adsorption under multi-element conditions, due to competitive effects. For example, the adsorption of copper from a single-element solution was over four times greater than for a multi-element solution. In the case of Cr and Zn, migration of metal from soil to solution was observed. Adsorption capacity at pH 2 followed the order Cr>Cu>Pb>Cd and at pH 7 Cd>Zn, with precipitation affecting Cu and Pb behaviour. During the column leaching experiment, most of the heavy metals were irreversibly bound to the soil, but in the case of Cr some movement from soil into solution was observed. The results also showed that Cd, Cu, Pb and Zn were removed from the solution and adsorbed on the soil. No significant difference in the metal removal from single- and multi-element solutions was observed. Overall, the urban residue behaved in a similar manner to mineral soils despite a significant component of anthropogenic solid materials.     

Chemisorption and Physical Adsorption Roles in Cadmium Biosorption by Chlamydomonas Reinhardtii

The aim of this study was to investigate the mechanism of cadmium (Cd) adsorbed by microalgae Chlamydomonas reinhardtii (C.reinhardtii). The kinetic and adsorption isotherm of the process could be well described by mathematical models. Chemical modification experiments and Fourier transform infrared spectra indicated that carboxyl and amine groups were the important functional groups for adsorption of Cd. The maximum contribution of physical adsorption in the overall adsorption process was evaluated as 5.5%...     

Biosorption of uranium (VI) by immobilized Aspergillus fumigatus beads

Biosorption of uranium (VI) ions by immobilized Aspergillus fumigatus beads was investigated in a batch system. The influences of solution pH, biosorbent dose, U (VI) concentration, and contact time on U (VI) biosorption were studied. The results indicated that the adsorption capacity was strongly affected by the solution pH, the biosorbent dose and initial U (VI) concentration. Optimum biosorption was observed at pH 5.0, biosrobent dose (w/v) 2.5%, initial U (VI) concentration 60 mg L⁻¹. Biosorption equilibrium was established in 120 min. The adsorption process conformed to the Freunlich and Temkin isothermal adsorption models. The dynamic adsorption model conformed to pseudo-second order model.     

Adsorption studies on coir pith for heavy metal removal

Biosorption efficiency of coir pith, a waste product from coir industry, was investigated in this study for the removal of metallic pollutants such as Ni, Cu and Zn from aqueous solutions. The disposal of coir pith is a major problem associated with the coir industries, especially working in the small-scale sector. The present study explores the effectiveness of utilization of coir pith, an accumulating waste, as a biosorbent for heavy metal removal. Batch mode studies were done to evaluate the efficiency of removal of metals under varying adsorption conditions of pH, metal concentration and contact time. Characterization studies of the biosorbent and SEM analysis were done. Kinetic modelling studies were tried using Lagergren pseudo-first-order and second-order models. Equilibrium studies were done using well-known Freundlich, Langmuir and D–R isotherm models. It was found that all isotherms are fitting well indicating the efficiency of coir pith as an adsorbent of heavy metals. The applicability of all the three isotherms to the sorption processes shows that both monolayer adsorption and heterogeneous energetic distribution of active sites on the surface of the adsorbent are possible. Due to the abundance and low cost of these materials, adsorption technologies developed can act as good sustainable options for the future in heavy metal removal from industrial effluents.     

A toxicity assessment of soils sampled from the Balapan site of the Semipalatinsk nuclear test site

Toxicity of soils sampled from the area of the “Chagan” explosion (the Balapan site of the Semipalatinsk nuclear test site, Kazakhstan) were assayed with the use of biological tests and physicochemical analysis. Soils from the most part (2.56 km² out of 4 km²) of the area studied were found to be toxic. Soil aqueous extracts toxicity substantially resulted from ¹³⁷Cs and ⁹⁰Sr effects. The soil toxicity assessment with the use of biological test—an increase Chlorella vulgaris Beijer. biomass production after 24 exposure of soil aqueous extracts in 63% cases are in agree with conclusions on the degree of radioactive contamination based on Basic Sanitary Rules of Radiation Safety (BSRRS-99). The IAEA safety norms were found to be quite stricter than the results of the biological test.