A radiotracer study of adsorption on activated carbon cloth from aqueous solution

A study has been made on the effect of pH upon the equilibrium adsorption capacity of triethyl phosphate, dimethyl phosphate and orthophosphate on to activated carbon cloth. It is shown that for molecular phosphates no dependence upon pH exists, whilst the adsorption of ionic phosphates exhibit a strong pH dependence. These adsorption trends may be explained in terms of pKa values, ionic strength and the surface charge of the activated carbon cloth is aqueous solution.     

Oxyhumolite influence on adsorption and desorption of phosphate on blast furnace slag in the process of two-stage selective adsorption of Cu(II) and phosphate

Two-stage adsorption was used for selective removal of Cu(II) and phosphate from aqueous solutions. In the first stage, adsorption of Cu(II) and phosphate on oxyhumolite (OX) was examined. The pseudo second-order equation was found to be the best fit for the kinetic adsorption data. The adsorption capacity of OX for Cu(II) and phosphate depends on the adsorption time, the equilibrium pH influences only the adsorption of Cu(II). The high adsorption efficiency (E = 95 %, pH 3.5, 0.5 g of the solid sorbent and 50 cm³ of the solution, c = 4 mmol dm^?3) of OX for Cu(II) is caused by the presence of humic acids (HA). In the second stage, blast furnace slag (BFS) and activated blast furnace slag (BFS-A) were used to remove phosphates. The presence of OX in the first stage positively influences the adsorption efficiency of sorbents in the second stage due to the soluble humic compounds and residues of humic acids (HA) which support the precipitation of Ca-phosphates on BFS and the ions exchange reactions on BFS-A. Adsorption equilibrium of phosphate on both slags at 298 K can be well described by the Langmuir isotherm equation. Desorption of Cu(II) from OX was around 70 %. The presence of OX in the first stage also influences the desorption of phosphate bound in the second stage. Desorption efficiency of both slags for phosphate was about 60 %.     

Adsorption of Dyes from Aqueous Textile By-Products on Activated Carbon from Scenedesmus obliquus

The adsorption of activated carbon prepared from Scenedesmus obliquus (algae) was evaluated through adsorption of Astrazon red. The adsorption efficiency of activated carbon was determined based on the specific surface area and pore size distribution. These results were compared with the results obtained with untreated algae. Approximately a 3-fold increase in the percentage of dye removal was observed for activated carbon compared to the untreated material. The primary reason for this observation may be the increase in specific surface area and total pore volume by chemical activation from 0.0136 to 423.7001?m²?g^?1 and from 0.0012 to 0.1643?cm³?g^?1, respectively. A pseudo-second-order model was fit with the kinetic data and the results indicate chemical adsorption. The maximum adsorption capacity of activated carbon was 181.82?mg?g^?1 at 25°C according to Langmuir isotherm model.     

Enhanced removal of phosphonates from aqueous solution using PMS/UV/hydrated zirconium oxide process

Traditional treatment processes cannot completely remove phosphonates in circulating cooling water by one-step method. Herein, we designed peroxymonosulfate/UV irradiation/hydrated zirconium oxide (PMS/UV/HZO) coupling process to enhance the phosphonates removal. In particular, nitrilotris-methylenephosphonic acid (NTMP) removal efficiency by PMS/UV/HZO process was much higher than that of PMS/UV process, UV/HZO process and other processes in comparison experiments. Specifically, almost 97.2% NTMP in water was degraded, and the total phosphorous (TP) reduced from 9.3 mg/L to 0.26 mg/L at pH 7 within 180 min. TP removal efficiency still reached above 90% after 5 cycles adsorption-desorption of HZO. Moreover, Clˉ, NO₃ˉ and SO₄²ˉ ions all had negligible effect on NTMP removal. During the process, NTMP was first destroyed to form phosphates and other intermediates by the reactive oxygen species (ROS), then phosphates were in situ immobilized via HZO adsorption. Sulfate radical (SO₄^??) has been confirmed to be the major ROS in the reaction system by quenching experiment and electron paramagnetic resonance (EPR) characterization. And the excellent selective adsorption capacity of HZO for phosphate produced was attributed to the strong inner-sphere coordination between H₂PO₄ˉ/HPO₄²ˉ and Zr-OH on the surface of HZO. These results suggest that PMS/UV/HZO process is a promising technique for enhanced phosphonates decontamination.     

On uranium(VI) adsorption on activated carbon

The uranium adsorption on activated carbon from dilute solutions was studied as a function of pH, uranium concentration and ageing time. Optimum conditions for quantitative adsorption of uranium from water solutions were determined: uranium concentration 2.5.10⁻⁴ g/l or less; adsorption must be carried out in fresh prepared solutions with ageing time not more than one hour; pH 7.5–8.5; time for achieving the adsorption equilibrium not less than 20 min. The instrumental neutron activation method was used for the uranium analysis.     

Fast Removal and Recovery of Methylene Blue by Activated Carbon Modified with Magnetic Iron Oxide Nanoparticles

A magnetic adsorbent was synthesized by modification of activated carbons with magnetic iron oxide nanoparticles (AC‐MIONs). The preparation method is fast and could be carried out in an ordinary condition. The AC‐MIONs were used as quite efficient adsorbents for separation of methylene blue (MB) from aqueous solution in a batch process. The effect of different parameters such as pH, temperature, electrolyte concentration, contact time and interfering ions on the removal of MB were studied. The adsorption data were analyzed by Langmuir and Freundlich isotherm models and a maximum adsorption amount of 47.62 mg g^‐1 and a langmuir adsorption equilibrium constant of 3.0 L mg^‐1 were obtained. The obtained results revealed that AC‐MIONs were effective adsorbents for fast removal of MB from different aqueous solutions. This adsorbent was successfully used for removal of MB from Karoon River water.     

The determination of chromium in water samples by neutron activation analysis after preconcentration on activated carbon

A method is presented for the determination of chromium in sea-and fresh water. Chromium is concentrated on activated carbon from neutral solution after a previous reduction of chromate with sodium sulfite at pH 1.5. The final determination of the total chromium content is performed by instrumental neutron activation analysis. By preconcentration on activated carbon a differentiation between tervalent and hexavalent chromium is possible. A separate determination of both species is not yet feasible due to the high carbon blank and to the necessity of measuring the adsorption percentage on carbon. The lower limit of determination, which depends on the value of the carbon blank, is 0.05 μg Cr·1⁻¹ with a precision of 20%.     

β-Carotene removal from soybean oil with smectite clay using central composite design

In this study removal of β-carotene from soybean oil by adsorption on acid activated smectite clay from Serbia was investigated and a factorial 2³ experimental design was applied. The effects of relevant factors, such as temperature, solid-to-liquid ratio and time, on removal of β-carotene were investigated. In order to check these factors and their effect on the removal of β-carotene, we have established a model of this technique following a methodological strategy using experiments design. The mathematical model is established using a central composite design. The model describes the changes of the measured responses of β-carotene removal efficiency according to the temperature, solid-to-liquid ratio and time. The graphical representation of this model in the space of the variables enabled us to define the optimum conditions of these parameters. The optimum conditions to obtain the maximum removal of β-carotene from soybean oil were a temperature of 80°C, a solid-to-liquid ratio of 1: 25 and a time of 1255 s. Under these optimal conditions, the experimental values agreed with the predicted values, using analysis of variance, indicating a high goodness of fit of the model used and the success of response surface methodology for optimizing adsorption β-carotene of acid activated smectite clay from soybean oil. The article is published in the original.     

Equilibrium studies and modeling on the removal of <Superscript>56</Superscript>Mn(II) by alumina and kaolinite

The removal of manganese from aqueous solutions on synthetic alumina and natural kaolinite was investigated in batch experiments as a function of pH. Experiments were carried out by using the radiotracer ⁵⁶Mn, produced by neutron activation. Theoretical analysis of manganese removal was performed considering the existence of a single type of surface sites, denoted as?≡?SOH°. The uptake of manganese on kaolinite is similar to that on alumina, indicating that adsorption occurred on the variable-charged aluminol sites. Adsorption experiments suggest that?≡?AlOH° group is the most probable edge site for complexing manganese cations through mononuclear surface complexes (≡?AlOMn⁺) and (≡?AlOMnOH).     

Inorganic ion exchangers in radioactive waste management

The removal behavior of stannic and zirconium phosphates was assessed for Sr(II) ions as a function of sorptive concentration, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solutions. First order uptake of Sr(II) followed the Freundlich adsorption isotherm for the entire range of sorptive concentration (10^-2 to 10^-8 mol^.dm^-3). The study of temperature dependence showed that the endothermic and irreversible type of uptake proceeds by an ion-exchange type mechanism.     

Adsorption Characteristics of Chromium(VI) on Granular Activated Carbon

The adsorption of Chromium(VI) from aqueous solutions was studied on different commercial grades of granular activated carbon namely Filtrasorb F‐400, F‐300, F‐200 and F‐100. The adsorption of Chromium (VI) on F‐400 carbon was found to be maximum in comparison to the other grades of carbon. The Chromium (VI) adsorption process in dilute aqueous solutions agreed with the Langmuir and Freundlich models and also obeyed first order kinetics. Metal sorption characteristics of as received activated carbons were measured in batch experiments. The maximum removal (60–65%) for different grades of raw carbon was observed at 25 °C with an initial concentration of 15.16 mg dm^?3. It is evident from the study that granular activated carbon holds a particular promise in the removal of metal ions from aqueous solutions.     

The use of solid-state nuclear track detection for the study of boron and fissile nuclide distributions in steel samples

The technique of boron autoradiography using cellulose acetobutyrate (CAB) film for measuring the distribution of boron in stainless steels, is described. The method involves the irradiation of the specimen and detector with thermal neutrons, and the development of the α-particle tracks arising from the nuclear reaction¹⁰B(n, α)⁷Li. A related technique for the measurement of fissile nuclides in steel hulls, is also described. In this case, a polycarbonate detector, Lexan, is used to detect the fission-particles from the thermal neutron fission of²³⁵U or²³⁹Pu, present in the surfaces of the specimens. The principles of the methods are described, and an outline of the techniques presented. The quantitative aspect of the method is considered and the results on various specimens discussed.     

Mesoporous activated carbon from <Emphasis Type="Italic">Pentace</Emphasis> species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer–Emmett–Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418 W, radiation time of 6.4 min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15 m²/g, 0.52 cm³/g, and 3.19 nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich–Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Sips equations. However, the exponential value of Redlich–Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14 mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.     

Boron Removal from Aqueous Solutions by Adsorption on Waste Sepiolite and Activated Waste Sepiolite Using Full Factorial Design

In the present paper, boron removal from aqueous solution by adsorption was investigated and 2³ full factorial design was applied. Non activated waste sepiolite (NAWS) and HCl activated waste sepiolite (AWS) were used as adsorbents. Regression equation formulated for boron adsorption was represented as a function of response variables. The results obtained from the study on parameters showed that as pH increased and temperature decreased boron removal by adsorption increased. Adsorbed boron amount on AWS was higher than that of NAWS. Maximum boron removal was obtained at pH 10 and 20°C for both adsorbents. Adsorption data obtained from batch adsorption experiments carried out with NAWS and AWS fitted to the Langmuir equation. The batch adsorption capacities were found in mg/g: 96.15 and 178.57 for NAWS and AWS, respectively. The capacity value for column study was obtained by graphical integration as 219.01 mg/g for AWS. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design.     

Radiochemical neutron activation analysis of traces of vanadium in biological samples: A comparison of prior dry ashing with post-irradiation wet ashing

Summary A radiochemical neutron activation technique for nanogram and subnanogram levels of vanadium in biological samples was developed, based on dry ashing of the sample prior to irradiation, but without any chemical treatment. It was compared to and validated by parallel analyses of low-level reference materials and human blood using a previously developed totally post-irradiation technique based on rapid wet ashing of the irradiated sample. The irradiated ash was also wet ashed after neutron bombardment to ensure complete dissolution, equilibration with carrier and removal of ³⁸Cl. Results for reference materials, including Versieck's Second Generation Human Serum Reference Material and IAEA Animal Blood, were in excellent agreement by the two techniques, and with reference to literature values. Both methods give exceptionally good radiochemical decontamination of ⁵²V from other nuclides and have nearly quantitative yields. The dry ash mode is slightly quicker and easier to manipulate.     

Evaluation of PANI-Averraoha bilimbi leaves activated carbon nanocomposite for Cd2+ and Pb2+ removal from wastewater

In current investigation, we synthesized new Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposites and utilized as cost effectual for the elimination of Cd²⁺ and Pb²⁺ ions from the wastewater. The synthesized nanocomposite was confirmed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX), Fourier Transform-Infrared (FT-IR) spectroscopy and X-Ray Diffraction (X-RD) techniques. A batch adsorption study carried in wastewater containing different concentrations of Cd²⁺ and Pb²⁺ ions in the temperature range of 303–343 K. The results show that, around 80% of Cd²⁺ and Pb²⁺ ions from the wastewater was successfully isolated by using PANI-ABLC nanocomposite. Attempts were made to fit adsorption to different isotherm models. The PANI-ABLC nanocomposite complied Langmuir adsorption model (R² = 0.999) and pseudo-second order kinetics. Further, maximum adsorption efficiency observed at 0.5 g of Polyaniline-Averraoha bilimbi leaves activated carbon nanocomposites. AC- Impedance Spectroscopy (IS) technique shows that, Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposite is suitable for removal of Cd²⁺ and Pb²⁺ ions from the wastewater. AC impedance spectroscopy technique study shows that, the process of adsorption was controlled by charge transfer process.     

Biosorptive behavior of mango (<Emphasis Type="Italic">Mangifera indica</Emphasis>) and neem (<Emphasis Type="Italic">Azadirachta indica</Emphasis>) barks for <Superscript>134</Superscript>Cs from aqueous solutions: A radiotracer study

The role of dead biomasses viz., mango (Mangifera indica) and neem (Azadirachta indica) bark samples are assessed in the removal behavior of, one of important fission fragments, Cs(I) from aqueous solutions employing a radiotracer technique. The batch type studies were carried out to obtain various physico-chemical data. It is to be noted that the increase in sorptive concentration (from 1.0·10⁻⁸ to 1.0·10⁻² mol·dm⁻³), temperature (from 298 to 328 K) and pH (2.6 to 10.3) apparently favor the uptake of Cs(I) by these two bark samples. The concentration dependence data obeyed Freundlich adsorption isotherm and the uptake follows first order rate law. Thermodynamic data evaluation and desorption experiments reveal the adsorption to be irreversible and endothermic in nature proceeding through ion-exchange and surface complexation for both dead biomasses. Both bark samples showed a fairly good radiation stability in respect of adsorption uptake of Cs(I) when irradiated with a 300 mCi (Ra-Be) neutron source having an integral neutron flux of ∼3.85·10⁶ n·cm⁻²·s⁻¹ and associated with a nominal γ-dose of ∼1.72 Gy·h⁻¹.     

Factors affecting the sorption behavior of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> using biosorbent material

In this study, saw dust has been used as precursor for production of low cost activated carbon using potassium hydroxide (KOH) and steam activation technique. The activated carbon was used to remove Cs⁺ and Sr²⁺ ions from aqueous solutions by batch operation, and the extent of adsorption was investigated as a function of solution pH, temperature, shaking time, and initial concentration. The influence of interfering ions was also investigated. The removal of metal ions was pH dependent and the adsorption capacity reaches its maximum 43% and 61.5% at pH 5.0 and 6.0 for Cs⁺ and Sr²⁺ ions, respectively. Thermodynamic studies showed different behaviours where an endothermic, non-spontaneous process was shown for Cs⁺ while an exothermic, spontaneous process was obtained for Sr²⁺. The kinetic data of both ions was described well by pseudo-second order rate equation. The two equilibrium models (Langmuir and Freundlich) have been also applied. Desorption studies indicated that HCl was the most effective desorbing eluent. The investigated adsorbent showed good results towards cesium and strontium removal from aqueous media that could be a promising method due to its low-cost and good efficiency.     

Highly Efficient Adsorption of Bilirubin by Ti3C2Tx MXene

We discovered that the 2D Ti₃C₂T_x MXene sheet displays an ultra-high removal capability for bilirubin (BR). In particular, MXene shows 47.6 times higher removal efficiency over traditional activated carbon absorbents. The effect of MXene on the removal rate of BR in BR solution containing different concentrations of bovine serum albumin (BSA) was studied. The adsorption capacity of BSA for BR at high concentration of 5 g L⁻¹ was about 85% of the best adsorption capacity. The MXene before and after adsorption was characterized by SEM, FT-IR and XPS. Furthermore, MXene beads were prepared, and the hemoperfusion simulation experiment was carried out. The results show that the adsorption capacity of MXene for bilirubin can reach 1192.9 mg g⁻¹. This study suggests that MXene may be promising in the treatment of hyperbilirubinemia.     

Adsorption of some toxic elements from water samples on modified activated carbon,activated carbon and red soil using neutron activation analysis

A simple and sensitive method for the determination of some metalloids and heavy metals in water samples is presented. The method is based on the preconcentration of the attachment of chelating functionalities with metalloids and toxic metals irreversibly and targeted towards toxic metals adsorbed on modified activated carbon, activated carbon and red soil particles at pH 3.0–9.0±0.2, followed by quantitative determination using instrumental neutron activation analysis (INAA), on the absorbers. Attachment results from attraction that may be physical, chemical, electrical, or a combination of all three. The efficient removal of metalloids and toxic metals, especially arsenic, chromium and mercury is anticipated. The adsorption capacity of the chemically modified activated carbon materials was evaluated for the above mentioned metalloid and toxic metal ions in the presence of iron ions and simulated water samples. Red soil particles containing iron was utilized in the control of oxidation-reduction reaction with metalloids and toxic metals. The preconcentration of the elements of interest on red soil particles, activated carbon and modified activated carbon at different depths, pH and oxidation states was investigated. The results obtained showed good agreement with certified values giving relative errors of less than 10%.