Adsorption of selected herbicides from aqueous solutions on activated carbon

The adsorption of MCPA and 2,4-D on the activated carbon Filtrasorb 300 was studied. The adsorption isotherms of herbicides from aqueous solutions were measured over a wide range of solute concentrations and at different temperatures. The experimental equilibrium data were analyzed by the Langmuir–Freundlich isotherm taking into account the energetic heterogeneity of adsorption system. The effect of temperature and herbicide properties on its uptake was discussed. The thermal analysis was applied in order to find the differences in herbicide interactions with carbon surface. The kinetic dependences were measured and the relations between solute properties and adsorption rate were discussed.     

Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste

Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.     

Adsorption of aqueous metal ions on oxygen and nitrogen functionalized nanoporous activated carbons

In this study, the adsorption characteristics of two series of oxygen and nitrogen functionalized activated carbons were investigated. These series were a low nitrogen content (approximately 1 wt % daf) carbon series derived from coconut shell and a high nitrogen content (approximately 8 wt % daf) carbon series derived from polyacrylonitrile. In both series, the oxygen contents were varied over the range approximately 2-22 wt % daf. The porous structures of the functionalized activated carbons were characterized using N(2) (77 K) and CO(2) (273 K) adsorption. Only minor changes in the porous structure were observed in both series. This allowed the effect of changes in functional group concentrations on metal ion adsorption to be studied without major influences due to differences in porous structure characteristics. The surface group characteristics were examined by Fourier transform infrared (FTIR) spectroscopy, acid/base titrations, and measurement of the point of zero charge (pH(PZC)). The adsorption of aqueous metal ion species, M(2+)(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M(2+)(aq) metal species adsorbed have a linear relationship for the carbons with pH(PZC) < or = 4.15. Hydrolysis of metal species in solution may affect the adsorption of metal ion species and displacement of protons. In the case of basic carbons, both protons and metal ions are adsorbed on the carbons. The complex nature of competitive adsorption between the proton and metal ion species and the amphoteric character of carbon surfaces are discussed in relation to the mechanism of adsorption.     

Competitive adsorption of aqueous metal ions on an oxidized nanoporous activated carbon

Competitive adsorption is the usual situation in real applications, and it is of critical importance in determining the overall performance of an adsorbent. In this study, the competitive adsorption characteristics of all the combinations of binary mixtures of aqueous metal ion species Ca2+(aq), Cd2+(aq), Pb2+(aq), and Hg2+(aq) on a functionalized activated carbon were investigated. The porous structure of the functionalized active carbon was characterized using N2 (77 K) and CO2 (273 K) adsorption. The surface group characteristics were examined by temperature-programmed desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, acid/base titrations, and measurement of the point of zero charge (pHpzc). The adsorption of aqueous metal ion species, M2+(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M2+(aq) metal species adsorbed have a linear relationship for both single-ion and binary mixtures of these species. Hydrolysis of metal species in solution may affect the adsorption, and this is the case for adsorption of Hg2+(aq) and Pb2+(aq). Competitive adsorption decreases the amounts of individual metal ions adsorbed, but the maximum amounts adsorbed still follow the order Hg2+(aq) > Pb2+(aq) > Cd2+(aq) > Ca2+(aq) obtained for single metal ion adsorption. The adsorption isotherms for single metal ion species were used to develop a model for competitive adsorption in binary mixtures, involving exchange of ions in solution with surface proton sites and adsorbed metal ions, with the species having different accessibilities to the porous structure. The model was validated against the experimental data.     

Adsorption of neodymium ions on activated charcoal from aqeous solutions

Summary A commercial activated charcoal has been tested as an adsorbent for the removal of neodymium ions from aqueous solutions. The adsorption behavior of neodymium ions on activated charcoal from aqueous solutions has been studied as a function of shaking time, neodymium ions concentration and concentration of different acids. Results reveal that the adsorption equilibrium is attained within 30 minutes, and diffusion of neodymium ions into the pores of activated charcoal controls the adsorption process. The adsorption process follows the first order kinetics. The Langmuir isotherm equation was obeyed well in the whole range of concentration studied. The influence of different cations and anions on the adsorption of neodymium ion from aqueous solutions have also been investigated. Approximately 98% of neodymium ions adsorbed onto activated charcoal could be recovered with 40 ml of 3M HNO₃ solutions.     

Ligand adsorption on an activated carbon for the removal of chromate ions from aqueous solutions

The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods. The nature of oxygen-carrying functions and the acid-base behavior of the AC surface were characterized by TPD and potentiometric titration methods, respectively. The adsorption and desorption equilibria of the aromatic compounds on activated carbon were measured in aqueous solutions, and the hysteresis between adsorption and desorption, which reveals irreversible adsorption, was discussed on the basis of the frontier orbital theory. HOMO and LUMO orbitals of the adsorbent and adsorbates were calculated, and irreversible adsorption was attributed to the small energy difference between HOMO and LUMO of the aromatic adsorbates and the adsorbent. Adsorption equilibria of K2CrO4 in aqueous solution on the AC alone and on the AC-aromatic ligand adsorbents, respectively, prove the efficient development of specific chemical functions at the carbon surface provided by the adsorbed aromatic compounds.     

Multi-element preconcentration of heavy metal ions from aqueous solution by APDC impregnated activated carbon

Ammonium pyrrolidinedithiocarbamate impregnated activated carbon (APDC-AC) has been used for the preconcentration of Cd(II), Cu(II), Ni(II), and Zn(II) from aqueous solution by column solid phase extraction (SPE) technique. Trace metal ions in aqueous solution were quantitatively sorbed onto APDC-AC packed in a SPE column at pH 5.0 with a flow rate of 1.0 mL min⁻¹. The sorbed metals were eluted with 1 M nitric acid in acetone solution at a flow rate of 0.6 mL min⁻¹ and analyzed by flame atomic absorption spectrometry. The effects of sample volume, amount of APDC-AC, volume of eluent and ionic strength of working solution on metal ion recovery have been investigated. The present methodology gave recoveries from 90 to 106% and R.S.D. from 0.6 to 5.5%.     

Adsorption of some bivalent heavy metal ions from aqueous solutions by manganese nodule leached residues

The leached residue, generated after selective extraction of Cu, Ni, and Co in sulfur dioxide-ammonia leaching of manganese nodules, was characterized and batch isothermal adsorption experiments were conducted at ambient temperature to evaluate the effectiveness of the water-washed leached residue for removal of different bivalent metal ions from aqueous synthetic solutions. The effects of pH, initial metal ion concentrations, amount of adsorbent, interfering ions, and heat treatment were also investigated. The uptake of metal ions increased with increasing pH. Under identical conditions the adsorption capacity increased in the order Cd(2+)相似文献   

Removal of heavy metal ions from aqueous solutions by alkaline-earth metal phosphates

The possibility of utilization of calcium or magnesium phosphates of various composition for heavy and non-ferrous metal extraction from aqueous solutions has been studied. The efficiency of the phosphates in removal of Pb(II), Cr(III) and Fe(III) ions has been shown to decrease in the following sequence: Mg₃(PO₄)₂>MgNH₄PO₄>Ca₃(PO₄)₂>CaHPO₄>Ca₁₀(PO₄)₆(OH)₂ which is inverse to their hydrolytic stability series. It has been established that phosphates of non-apatite structure are capable of binding up to 12 mmol g⁻¹ of the named heavy metals by a chemical interaction. Hydroxyapatite interacts with the polyvalent metal ions via either the above mentioned or ion-exchange mechanism, depending on preparation method used for the apatite and the nature of metal.     

Thermodynamic study of triclosan adsorption from aqueous solutions on activated carbon

The change in the thermodynamic properties of triclosan adsorption on three activated carbons with the different surface chemistry was studied through immersion calorimetry and equilibrium data; the amount adsorbed of triclosan (Q) during calorimetry was determined and correlated with the energy associated with adsorbate–adsorbent interactions in the adsorption process. It was noted that triclosan adsorption capacity decreases with an increase in oxygenated surface groups. For an activated carbon oxidized with HNO₃ (OxAC), the amount adsorbed was 8.50?×?10^?3 mmol g^?1, for a activated carbon without modification (GAC) Q?=?10.3?×?10^?3 mmol g^?1 and for a activated carbon heated at 1073 K (RAC1073) Q?=?11.4?×?10^?3 mmol g^?1. The adsorbed amounts were determined by adjusting the isotherms to the Sips model. For the activated carbon RAC1073, the immersion enthalpy (ΔH_imm) was greater than those of the other two activated carbons due to the formation of interactions with the solvent (ΔH_immOxAC?=?? 27.3 J g^?1?<?ΔH_immGAC?=?? 40.0 J g^?1?<?ΔH_imm RAC1073?=???60.7 J g^?1). The changes in the interaction enthalpy and Gibbs energy are associated with adsorbate–adsorbent interactions and side interactions such as the adsorbate–adsorbate and adsorbate–solvent interactions.

     

Electrosorption of ions from aqueous solutions by nanostructured carbon aerogel

Electrosorption is generally defined as potential-induced adsorption on the surface of charged electrodes. After polarization of the electrodes, ions are removed from the electrolyte solution by the imposed electric field and adsorbed onto the surface of the electrodes. Experimental and modeling studies were conducted using two types of carbon aerogel composites of different surface areas to provide a better understanding on the mechanisms of electrosorption. The experimental results revealed that no significant specific adsorption of F- ions occurred, while strong specific adsorption was observed for NO3- and Cu2+ ions. In addition, although the two types of carbon aerogel electrodes had different surface areas, their capacities were found to be very similar because of the electrical double-layer overlapping effect in micropores. An electrical double-layer model developed in our previous work (16), in which the electrical double-layer overlapping correction is included, is expanded in the present work by considering the effect of the specific adsorption on the electrosorption process. Modeling results were compared with experimental data obtained under various conditions. When the overlapping effect and specific adsorption were considered, the model provided results that were in good agreement with experimental data.     

Recovery of heavy metal ions from aqueous solutions using modified organosilicas

Sorption of Cu(II), Pb(II), Cd(II), and Zn(II) from aqueous solutions on two-component organosilicas was studied as influenced by sorbent composition, contact time, ratio of solid and liquid phases, solution pH, nature and concentration of heavy metal ions, and content of modifying agent. The degrees of sorption of these metal ions from aqueous solutions using organosilicas modified with aluminum(III) added into the siloxane matrix or with copper(II) grafted to the sorbent surface layer were compared.     

Adsorption of heavy metal ions from aqueous solution by polyrhodanine-encapsulated magnetic nanoparticles

The influence of salt concentration on the terminal velocities of gravity-driven single bubbles sliding along an inclined glass wall has been investigated, in an effort to establish whether surface forces acting between the wall and the bubble influence the latter's mobility. A simple sliding bubble apparatus was employed to measure the terminal velocities of air bubbles with radii ranging from 0.3 to 1.5 mm sliding along the interior wall of an inclined Pyrex glass cylinder with inclination angles between 0.6 and 40.1°. Experiments were performed in pure water, 10 mM and 100 mM KCl solutions. We compared our experimental results with a theory by Hodges et al. which considers hydrodynamic forces only, and with a theory developed by two of us which considers surface forces to play a significant role. Our experimental results demonstrate that the terminal velocity of the bubble not only varies with the angle of inclination and the bubble size but also with the salt concentration, particularly at low inclination angles of ～1-5°, indicating that double-layer forces between the bubble and the wall influence the sliding behavior. This is the first demonstration that terminal velocities of sliding bubbles are affected by disjoining pressure.     

Adsorption of copper(II) ions from aqueous solutions on alumina industrial wastes

Equilibrium adsorption of copper(II) ions on red mud (alumina industrial wastes) modified by various methods was studied. The effect exerted by the nature the modifier (NaHSO₄, NaCl + HCl, and H₂SO₄) on the sorption activity of red mud was determined.     

Adsorption of Cu(II) ions from aqueous solution by hazelnut husk activated carbon prepared with potassium acetate

Hazelnut husk (HH), an agricultural waste, was converted to carbonaceous material by chemical activation using potassium acetate. The produced activated carbon (KAHHAC) was characterized by FTIR, SEM, N₂ adsorption–desorption experiments, CHN elemental analysis, and determination of moisture, ash, and point of zero charge. KAHHAC was used for the batch adsorption of Cu(II) ions from aqueous solutions. Optimum pH and contact time were found to be 5.0 and 240 minutes, respectively. The adsorption equilibrium data were described well by the Langmuir equation providing 105.3?mg?g^?1 Cu(II) adsorption capacity. The pseudo-second-order model successfully described the kinetic of Cu(II) adsorption by KAHHAC. The adsorbed Cu(II) onto KAHHAC was completely desorbed by 0.5?M nitric acid. In conclusion, HH activated carbon (AC) produced by the potassium acetate activation method is a very useful and efficient sorbent material for the removal of Cu(II) from aqueous solution.     

Adsorption of nitromethane on carbon black and polarized graphite from aqueous salt solutions

Conclusions By comparing the amounts of nitromethane that are absorbed by a graphite electrode and by carbon black, suspended in aqueous NaCl and phosphate buffer solutions, it was shown that the behavior of the nitromethane in the adsorption layer is practically independent of whether the surface of the carbon adsorbent is polarized or is not polarized from the outside.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khitnicheskaya, No. 10, pp. 2327–2329, October, 1973.     

Granulated sulfur-containing sorbents for recovery of heavy metal ions from aqueous solutions

Granulated sorbents that can recover zinc salts from aqueous solutions were produced by poly-condensation of organochlorine wastes from manufacture of epichlorohydrin with sodium polysulfide on the surface of ash-and-slag particles formed at thermal power plants in the system constituted by aqueous hydrazine and an alkali.     

Adsorption of chromium ions from aqueous solution by using activated carbo-aluminosilicate material from oil shale

A novel activated carbo-aluminosilicate material was prepared from oil shale by chemical activation. The chemicals used in the activation process were 95 wt% sulfuric and 5 wt% nitric acids. The produced material combines the sorption properties and the mechanical strength of both activated carbon and zeolite. An X-ray diffraction analysis shows the formation of zeolite Y, Na-X, and A-types, sodalite, sodium silicate, mullite, and cancrinite. FT-IR spectrum shows the presence of carboxylic, phenolic, and lactonic groups on the surface of this material. The zero point of charge estimated at different mass to solution ratio ranged from 7.9 to 8.3. Chromium removal by this material showed sorption capacity of 92 mg/g.