Evaluation of AMP–PAN composite for adsorption of Cs+ ions from aqueous solution using batch and fixed bed operations

Ammonium molybdophosphate–polyacrylonitrile (AMP–PAN) as an organic–inorganic composite ion exchanger was synthesized and investigated for adsorption of cesium from aqueous solutions. The synthesized composite was characterized by various techniques including X-ray powder diffraction, Fourier Transform Infrared Spectroscopy, thermogravimetry-differential scanning calorimetry, specific surface analysis, scanning election microscopy, X-ray fluorescence spectroscopy and CHN elemental analysis. The cesium adsorption on composite adsorbent was studied as a function of contact time, pH, temperature, and presence of various cations. In addition, adsorption thermodynamic parameters were determined and it was observed that the adsorption of cesium on the adsorbent is an endothermic and spontaneous process. The Langmuir and Freundlich adsorption isotherms were fitted to the adsorption data and the results showed that the Langmuir model best predicates the cesium adsorption on the adsorbent. The dynamic behavior of cesium adsorption on AMP–PAN ion exchanger was also investigated for a fixed bed column and desorption was carried out.     

Bengal gram seed husk as an adsorbent for the removal of dyes from aqueous solutions – Column studies

A continuous fixed bed (column) study was carried out by using seed husk of Bengal gram (Cicer arietinum) (SHBG) as a biosorbent for the removal of direct dye, Congo red (CR) from aqueous solutions. The effects of important factors, such as the value of initial pH, the flow rate, the influent concentration of CR, bed depth, particle size of SHBG, foreign ions and regeneration of CR were studied. The effect of similar type of direct dyes like direct turquoise blue 86 (DTB) and direct black 38 (DB) on the adsorption of CR in column containing SHBG is also studied by keeping other parameters constant. The studies confirmed that the breakthrough curves were dependent on flow rate, initial dye concentration, size of SHBG, initial pH of solution of CR and bed depth. The bed depth service time analysis (BDST) model was applied at different bed depths to predict the breakthrough curves. The model is found suitable for describing the biosorption process of the dynamic behaviour of the SHBG column and the data were in good agreement with BDST model. When the flow rate was 0.67 mL/min and the influent concentration of CR was mg L⁻¹, the column capacity was 6.572 mg g⁻¹. The removal capacity of SHBG was more in case of CR (6.572 mg g⁻¹) compared to other similar direct dyes of DTB (1.984 mg g⁻¹) and DB (1.612 mg g⁻¹). The removal of CR was enhanced in the presence of foreign ion potassium (8.308 mg g⁻¹) and decreased in the presence of calcium (5.58 mg g⁻¹). 120 ml of acetone is required for the completion of regeneration of the column and the total amount of CR recovered in this case. All the results suggested SHBG as a potential adsorbent for removal of CR from aqueous solution so that the rate of bio-sorption process is rapid.     

Radiation synthesis of starch-acrylic acid–vinyl sulfonic acid/multiwalled carbon nanotubes composite for the removal of 134Cs and 152+154Eu from aqueous solutions

Starch-acrylic acid-co-vinyl sulfonic acid/multiwalled carbon nanotubes (starch-AA-VSA/f-MWCNTs) bionanocomposite was successfully synthesized using gamma radiation for initiate the grafting of AA/VSA on starch in the presence of f-MWCNTs by template polymerization technique. The structural characteristics were confirmed by FTIR, SEM, and TGA. The adsorption behaviors of bionanocomposite toward Eu(III) and Cs(I) were examined using the batch adsorption experiments. Langmuir and Freundlich’s models were used to fit the experimental data of the adsorption isotherms. Kinetic studies showed that the adsorption data followed the pseudo-second-order model. Thermodynamic studies indicated that the reaction was favorable at high temperature and endothermic process.

     

Activated carbon cloth as adsorbent and oxidation catalyst for the removal of amitrole from aqueous solution

Removal of amitrole from water was studied by adsorption on an activated carbon cloth and by oxidation with hydrogen peroxide using the same activated carbon cloth as catalyst. Study variables included the solution pH, ionic strength, and temperature in the adsorption process and the solution pH and the surface chemistry of the activated carbon cloth in the oxidation process. Results showed that amitrole adsorption on activated carbon cloth was not adequate to remove amitrole from water due to the high solubility and low aromaticity of the herbicide, which reduced its adsorption on the carbon. A higher amitrole removal rate was obtained with the activated carbon/H₂O₂ system. The best results were obtained on basic activated carbon surfaces at pH 7–10, when hydroxyl radical formation is favored, achieving the removal of 35–45% of the AMT, compared with 20–25% under the best adsorption conditions. Importantly, oxygen fixed on the carbon surface during AMT oxidation must be removed by heat treatment in order to regenerate the surface basicity of the carbon before its reutilization in another oxidation cycle.     

Preparation of thorium oxalate–silica sorbent and its application for the sorption of americium from aqueous solutions

A new sorbent, thorium oxalate incorporated in silica gel matrix was prepared. This material was characterized by X-ray, Thermo-gravimetric Analysis, surface area and porosity analysis. The material was obtained in the form of granular particles in the mesh size range of 80–150 American Standard of Testing Materials, yielding good liquid flow, when packed in ion exchange column. This sorbent was investigated for the sorption of americium from various aqueous media such as nitric acid, oxalic acid and sulphuric acid by distribution coefficient studies. Column experiments were carried out to study the practical application of this sorbent for removal of americium from oxalic acid-nitric acid solutions. Elution studies were also carried out for the recovery of americium.     

Sol–gel synthesis of a humic acid-silica gel composite material as low-cost adsorbent for thorium and uranium removal

In the present work, three neutral ^99mTc(CO)₃ complexes of nitroimidazole were synthesized and their potential to detect tumor hypoxia is evaluated in vivo. Triazole derivatives of 2-, 4- and 5-nitroimidazole were synthesized via ‘click chemistry’ route. The ligands synthesized were characterized and subsequently radiolabeled using [^99mTc(CO)₃(H₂O)₃]⁺ precursor complex to obtain corresponding neutral ^99mTc(CO)₃ complexes in >90 % radio chemical purity. The complexes were subsequently evaluated in Swiss mice bearing fibrosarcoma tumor and in vivo distribution observed was thoroughly analyzed. All complexes showed uptake in tumor, however, contrary to general expectations, the 5-nitroimidazole complex showed significantly higher tumor uptake (p < 0.05) at 30 min and 60 min p.i., compared to the 2-nitroimidazole counterpart. Though a conclusive explanation for this observation could not be obtained, present study underlined the significance of evaluating nitroimidazole radiotracers other than 2-nitroimidazole for detecting tissue hypoxia.     

Synthesis of novel ZnAl2O4/Al2O3 nanocomposite by sol–gel method and its application as adsorbent

Journal of Sol-Gel Science and Technology - In this research, ZnAl2O4/Al2O3 nanocomposites with different ZnAl2O4 (30, 50, and 70?wt.%) were successfully prepared in one step by sol–gel...     

Adsorption of Cd2+ and Cu2+ ions from aqueous solutions by a cross-linked polysulfonate–carboxylate resin

A new cross-linked polyzwitterion (CPZ) was synthesized through cyclocopolymerization of 3-[diallyl(carboxymethyl)ammonio]propane-1-sulfonate (92.5 mol%), and a cross-linker 1,1,4,4-tetraallylpiperazine-1,4-diium chloride (7.5 mol%) in the presence of tert-butylhydroperoxide. The cross-linked polyzwitterion/anion (CPZA) was obtained by the basification of CPZ with NaOH. The adsorption data fit both Temkin and Freundlich isotherm models. The adsorption trend on CPZA is as Cu²⁺ > Cd²⁺ and both followed pseudo-second-order kinetic model. The negative ΔG and positive ΔH values ascertained the spontaneous and endothermic nature of the adsorption process. The effectiveness of a zwitterionic–anionic motif consisting of quaternary nitrogen, sulfonate and carboxylate groups has been tested for the first time for capturing Cd²⁺ and Cu²⁺ ions at low concentrations.     

Synthesis and Application of a New Acrylic Ester Resin for Recycling SIPA from its Water Solution

A new acrylic ester polymer YWB-7 resin was prepared and characterized. The properties of YWB-7 resin were compared with those of the commercial Amberlite XAD-7, Diaion HP2MG and hypercrosslinked macroporous polymer NDA-150 resins. Both surface area and micropore area of YWB-7 resin were bigger than those of XAD-7 resin and HP2MG resin. The YWB-7 resin was successfully employed to recycle 5-sodiosulfoisophthalic acids （SIPA） from its solutions with and without methanol.     

Synthesis of a hydrophilic α-sulfur/PDA composite as a metal-free photocatalyst with enhanced photocatalytic performance under visible light

The polydopamine (PDA) coating α-S hydrophilic composites (S_D) were fabricated by a self-assembly process for enhanced α-S photocatalytic performance under visible light. The XRD patterns analysis indicated that we had successfully prepared the orthorhombic α-S. The SEM, FT-IR and TGA showed that PDA had been successfully coated on α-S. The photocatalytic ability was illustrated by the DRS and FL. Moreover, the measurement of the water contact angle of S_D and the corresponding original α-S (S_A) showed the hydrophilicity of α-S had been improved. The photocatalytic ability of S_D and S_A was evaluated by photocatalytic decomposition of Methylene blue (MB) solution. The MB elimination rate with S_D in the photocatalytic process was 2.46 times as great as that with S_A under visible light. The enhanced photocatalytic ability could be attributed to the improved hydrophilicty of α-S.     

Synthesis of cobalt–nitrogen-doped mesoporous carbon from chitosan and its performance for pollutant degradation as Fenton-like catalysts

Research on Chemical Intermediates - Supported cobalt oxides on mesoporous nitrogen-doped carbon (CoxOy/NC) were prepared by a simple pyrolysis method using cobalt acetate as the cobalt source and...     

Synthesis and characterization of nano−zinc wire using a self designed unit galvanic cell in aqueous medium and its reactivity in propargylation of aldehydes

Electrochemistry is used for propargylation of carbonyls in aqueous ZnCl₂ medium. For electrochemical process we designed a unit galvanic cell. ZnCl₂ is used as stoichiometric reagent and causes electrochemical deposition of zinc in cathode. Wire shaped nano zinc architecture has been formed in cathode during electrochemical process which is the active reagent. Homopropergylic alcohols are synthesized in good yields. After the organic reaction is over aqueous solution containing zinc salts can be reused up to 5th cycle without significant loss of reactivity.     

Removal of Th(IV), Ni(II)and Fe(II) from aqueous solutions by a novel PAN–TiO<Subscript>2</Subscript> nanofiber adsorbent modified with aminopropyltriethoxysilane

A novel polyacrylonitrile (PAN)–titanium oxide (TiO₂) nanofiber adsorbent functionalized with aminopropyltriethoxysilane (APTES) was fabricated by electrospinning. The adsorbent was characterized by SEM, FTIR, TEG and BET analyses. The pore diameter and surface area of the adsorbent were 3.1 nm and 10.8 m² g^?1, respectively. The effects of several variables, such as TiO₂ and amine contents, pH, interaction time, initial concentration of metal ions, ionic strength and temperature, were studied in batch experiments. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and double-exponential models. Two isotherm models, namely Freundlich and Langmuir, were used for analysis of equilibrium data. The maximum adsorption capacities of Th(IV), Ni(II) and Fe(II) by Langmuir isotherm were found to be 250, 147 and 80 mg g^?1 at 45 °C with pH of 5, 6 and 5, respectively, and greater adsorption of Th(IV) could be justified with the concept of covalent index and free energy of hydration. Calculation of ΔG°, ΔH° and ΔS° demonstrated that the nature of the Th(IV), Ni(II) and Fe(II) metal ions adsorption onto the PAN–TiO₂–APTES nanofiber was endothermic and favorable at a higher temperature. The negative values of ΔG° for Th(IV) showed that the adsorption process was spontaneous, but these values for Ni(II)and Fe(II) were positive and so the adsorption process was unspontaneous. Increasing of ionic strength improved the adsorption of Ni(II) and Fe(II) on nanofiber adsorbent but decreased the adsorption capacity of Th(IV). The adsorption capacity was reduced slightly after six cycles of adsorption–desorption, so the nanofiber adsorbent could be used on an industrial scale. The inhibitory effect of Ni(II) and Fe(II) on the adsorption of Th(IV) was increased with an increase in the concentration of inhibitor metal ions.     

Synthesis of LiFe(1−x)V x PO4/C composite cathode materials with high performance via an aqueous solution–evaporation method

The modification techniques of applying carbon coating on particle surface and doping vanadium at Fe site were applied to make the LiFePO₄ cathode materials achieve high rate performance in lithium ion batteries. To design and synthesize these LiFe_(1?x)V _x PO₄/C (x?=?0, 0.02, 0.05, or 0.08) composites, an aqueous solution–evaporation method was taken, in which every kind of raw material was distributed at a high degree of uniformity. The LiFe_0.95V_0.05PO₄/2.57 wt% C composite displayed the best electrochemical performances. At rates of 0.1, 0.5, 2, 5, and 10 C (1 C?=?170 mAg^?1), it delivered a discharge capacity of 157.8, 156.9, 149, 139.6, and 130.1 mAh g^?1, respectively. The composite exhibited perfect cycle stabilities as well, maintaining 100 % (0.5 C), 99.7 % (2 C), 98.9 % (5 C), and 96.6 % (10 C) of the first discharge capacity after 100 cycles at different rates, respectively.     

Thermodynamic quantities for the interaction of Cl− with Mg2+, Ca2+ and H+ in aqueous solution from 250 to 325°C

The aqueous reactions, Mg²⁺+Cl^–=MgCl⁺, Ca²⁺+Cl^–=CaCl⁺, and H⁺ +Cl^–=HCl(aq), were studied as a function of ionic strength at 250, 275, 300, and 325°C using a flow calorimetric technique. The logK, H, S and C_p values were determined from the fits of the calculated and experimental heast. The data were reduced assuming a known functionality of the activity coefficient. Hence, the logK, H, S and C_p values determined in this study are dependent on the activity coefficient model used. These thermodynamic values were compared with literature results. The logK values for the formation of MgCl⁺ agree reasonably well with those reported in the literature. The logK values for CaCl⁺ formation agree reasonably well with those reported in the literature at 300 and 325°C. At lower temperatures, the agreement is poorer. The logK values for the formation of HCl(aq) are generally lower than those reported in the literature. The logK, H, S and C_p values for all three ion association reactions are positive and increase with temperature over the temperature range studied. These values are the first determined calorimetrically for the formation of MgCl⁺ and CaCl⁺ in the temperature range 275–325°C.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

A novel magnetic biosorbent prepared using an oak shell waste material as an efficient adsorbent for consecutive removal of Pb2+, Ag+, Ba2+, Sr2+, and CrO42− from aqueous solutions

In this research, the performance of a new biosorbent prepared using low-cost oak shell waste materials for consecutive removal of particular cations and chromate anions from aqueous solutions was studied. The adsorbent impregnated with Pb²⁺, Ag⁺, Ba²⁺, and Sr²⁺ was used to remove chromate anions by the formation of an appropriate insoluble precipitate. The biosorbent was characterized by FTIR, XRD, SEM, TG-DTG, and VSM techniques. The adsorption capacities of 133.84, 53.12, 50.12, and 40.39 mg g^?1 were obtained for chromate for the samples containing Pb²⁺, Ag⁺, Ba²⁺, and Sr²⁺ cations, respectively. The chromate uptake was inversely proportional to the k_sp of the chromate precipitate and increased with the cation content of the adsorbent. The adsorption process was kinetically fast and the equilibrium was established within 10 min. The experimental data were analyzed by the Langmuir, Freundlich, Sips, and Redlich-Peterson isotherm models. The data were fitted to the Langmuir isotherm, indicating that chromate was adsorbed homogeneously on the adsorbent surface.     

Synthesis of a conjugate of 3´-sialyllactoside with recombinant flagellin as a carrier protein and assessment of its immunological activity in comparison with that of a similar hemocyanin-based conjugate

In the framework of a project directed to the design of synthetic cancer vaccines based on carbohydrate chains of tumor-associated gangliosides, a new prototype cancer vaccine, a polyvalent carbohydrate-protein conjugate 1 with ～11 3´-sialyllactoside ligands conjugated to one molecule of recombinant flagellin was synthesized. Dendritic cell vaccines were designed using the conjugate 1 and a neoglycoconjugate 2 consisting of ～400 3´-sialyllactose residues linked to hemocyanin from a snail Megathura crenulata (KLH). Comparative ELISA study was conducted to assess the induction of carbohydrate-specific immunoglobulins IgM and IgG after immunization of mice with conjugates 1 and 2 and dendritic cells loaded with 1 and 2. Synthetic polyacrylamide carrier conjugated to 3´-sialyllactose ligands and B16F0 melanoma cells were used as coating antigens.     

Coordination model,stability constant,and kinetics study of cystamine and l-cystine with [PdCl4]2− in hydrochloric aqueous solutions

Stoichiometry, equilibria, and kinetics of [PdCl₄]^2?interactions with l-cystine (H₄CysS²⁺) and cystamine (H₂Cyst²⁺) have been investigated spectrophotometrically in strong hydrochloric acidic media. Interactions lead to the formation of highly stable S/(S,N)-coordinated binuclear, and then with excess [PdCl₄]^2? trinuclear (S,S,N) or tetranuclear (S,S,N,N) species without disulfide bond cleavage. The reaction of [PdCl₄]^2? with H₄CysS²⁺ or H₂Cyst²⁺ at [PdCl₄]^2? excess has irreversible first-order kinetics, and with H₄CysS²⁺ or H₂Cyst²⁺ excess, by irreversible parallel reaction of [PdCl₄]^2? addition to the ligand. The influence of leaving groups on the kinetics has been explained in terms of formation of stable ionic pairs with complex species and of efficient overlap of d and π orbitals in a transition state. The reactions proceed through an associative mechanism with the first step being formation of the S-coordinated complex. Coordination models and mechanisms have been proposed. Applicability of spectrophotometry for establishment of disulfide bond state in organic disulfides in complexation processes has been demonstrated.     

Thiophene and diethylaminophenol-based “turn-on” fluorescence chemosensor for detection of Al3+ and F− in a near-perfect aqueous solution

A new fluorescent sensor 1, based on thiophene and diethylaminophenol moieties, has been synthesized and its binding capabilities for metal-ion and anion recognition were investigated. The sensor 1 showed ‘turn-on’ fluorescence in the presence of Al³⁺ and F^?. The sensing behaviors of 1 with Al³⁺ and F^? were studied by using photophysical experiments, ¹H NMR titration, and ESI-mass spectrometry analysis. The detection limits for the analysis of Al³⁺ and F^? were found to be 0.41 μM and 14.36 μM, respectively, which are below the WHO guidelines for drinking water (7.41 μM for Al³⁺ and 79 μM for F^?). Moreover, turn-on fluorescence of 1 toward Al³⁺ and F^? caused by intramolecular charge transfer (ICT) was well explained by density functional theory (DFT) calculations. Importantly, 1 could be used to detect Al³⁺ in the living cells.