Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Adsorption: Journal of the International Adsorption Society (v.12, #4)
Chromium uptake from tricomponent solution in zeolite fixed bed by M. A. S. D. Barros; A. S. Zola; P. A. Arroyo; C. R. G. Tavares; E. F. Sousa-Aguiar (pp. 239-248).
Removal of Cr3+,Ca2+,Mg2+ and K+ in equilibrium isotherms and in tricomponent solutions (Cr/Ca/K, Cr/Ca/Mg and Cr/Mg/K) were investigated in NaX and NaY packed beds at 30∘C. The equilibrium selectivity was obtained as Cr+3 > Mg2+ > Ca2+≈K+ for zeolite NaY and Ca2 +≫Cr3 + > Mg2 +≈K+ for zeolite NaX. The breakthrough curves showed sequential ion exchange where chromium ions are able to replace the competing cations. Some mass transfer parameters, such as length of unused bed and overall mass transfer coefficient, were investigated. Chromium retention was also investigated through a mass balance. Based on the breakthrough results, it was concluded that chromium-uptake mechanism was hardly influenced by the competition and interaction between the entering ions. NaY showed a higher affinity towards Cr3+ for both equilibrium and dynamic systems and its sites were more efficiently used in the ion exchange process. Chromium was less retained in NaX due to the high selectivity towards calcium ions.
Keywords: Zeolite; Chromium; Breakthrough; Multicomponent; Ion exchange
Adsorption of chromium from aqueous solution using chitosan beads by W. S. Wan Ngah; A. Kamari; S. Fatinathan; P. W. Ng (pp. 249-257).
A basic investigation on the removal of Cr(III) and Cr(VI) ions from aqueous solution by chitosan beads was conducted in a batch adsorption system. The chitosan beads were prepared by casting an acidic chitosan solution into an alkaline solution. The influence of different experimental parameters; pH, agitation period and different concentration of Cr(III) and Cr(VI) ions was evaluated. A pH 5.0 was found to be an optimum pH for Cr(III) adsorption, and meanwhile pH 3.0 was the optimum pH for the adsorption of Cr(VI) onto chitosan beads. The Langmuir and Freundlich adsorption isotherm models were applied to describe the isotherms and isotherm constants for the adsorption of Cr(III) and Cr(VI) onto chitosan beads. Results indicated that Cr(III) and Cr(VI) uptake could be described by the Langmuir adsorption model. The maximum adsorption capacities of Cr(III) and Cr(VI) ions onto chitosan beads were 30.03 and 76.92 mg g−1, respectively. Results showed that chitosan beads are favourable adsorbents. The Cr(III) and Cr(VI) ions can be removed from the chitosan beads by treatment with an aqueous EDTA solution.
Keywords: Chitosan beads; Adsorption capacities; Adsorption isotherm; Favourable adsorbers; Desorption
Gas sorption kinetics by differential closed-loop recycle method: Effect of heat of adsorption by Shivaji Sircar (pp. 259-266).
An analytical mathematical model is used to investigate the influence of minute adsorbent temperature changes on the kinetics of sorption of a gaseous adsorbate from mixture with a carrier gas using a differential closed loop recycle method. Isothermal operation may not be achieved even when a very high gas circulation rate is used. Very small changes in the adsorbent temperature during the process can cause substantial departure from isothermal uptake behavior. It is shown that the kinetic process can be assumed to be isothermal only for trace adsorbate concentrations. A criterion for validity of isothermal data analysis is proposed.
Keywords: Ad(de)sorption; Kinetics; Equilibrium; Non-isothermal; Closed-loop recycle
Biosorption of copper (II) and lead (II) from aqueous solutions by nonliving green algae Cladophora fascicularis: Equilibrium, kinetics and environmental effects by Liping Deng; Yingying Su; Hua Su; Xinting Wang; Xiaobin Zhu (pp. 267-277).
Biosorption of Cu2+ and Pb2+ by Cladop- hora fascicularis was investigated as a function of initial pH, initial heavy metal concentrations, temperature and other co-existing ions. Adsorption equilibriums were well described by Langmuir and Freundlich isotherm models. The maximum adsorption capacities were 1.61 mmol/g for Cu2+ and 0.96 mmol/g for Pb2+ at 298 K and pH 5.0. The adsorption processes were endothermic and biosorption heats calculated by the Langmuir constant b were 39.0 and 29.6 kJ/mol for Cu2+ and Pb2+, respectively. The biosorption kinetics followed the pseudo-second order model. No significant effect on the uptake of Cu2+ and Pb2+ by co-existing cations and anions was observed, except EDTA. Desorption experiments indicated that Na2EDTA was an efficient desorbent for the recovery of Cu2+ and Pb2+ from biomass. The results showed that Cladophora fascicularis was an effective and economical biosorbent material for the removal and recovery of heavy metal ions from wastewater.
Keywords: Biosorption; Heavy metal; Marine algae; Biosorption heat; Wastewater; Desorption; Desorbent
Use of biopolymers for the removal of heavy metals produced by the oil industry—A feasibility study by N. A. Pérez; G. Rincón; L. A. Delgado; N. González (pp. 279-286).
The possibility of using lignin from the paper industry’s black liquor to absorb nickel (Ni) and vanadium (V), was studied. The work comprised two stages: first, the identification of lignin’s main functional groups and the surface characterization of the solid; second, an experimental study of lignin’s behavior towards the Ni and V cations. Results revealed the presence of aromatic groups as well as substituted methoxy groups on the lignin’s surface. This explains lignin’s adsorptive capacity exhibited in the experimental evaluations. The removal of Ni and V ions was higher than expected solely through the physical adsorption mechanism. This higher capacity is associated with a proposed complex formation on the surface of the lignin. For Ni(II), lignin showed a higher adsorption compared to commercial adsorbents. In the case of V, the behavior is reversed, in order to elucidate this result, further research is recommended.
Keywords: Adsorption; Lignin; Nickel; Vanadium; Revaluation