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[en] The adsorption on copper of 2-Mercaptobenzothiazole (2-MBT), a heterocyclic compound member of the tiazole family, has been investigated at different concentrations (1x10"-1 to 1x10"-6 M) in water, employing the Electrochemical Quartz Crystal Microbalance (EQCM). The frequency response over time was obtained for each concentration, showing a defined exponential behavior at higher concentrations (1x10"-1, 1x10"-2 and 1x10"-3 M), which was filed to the Langmuir adsorption isotherm with a good correlation coefficients (R"2=0.91 to 0.98) Surface coverage (θ) was calculated and found to be in the order of 0.50 to 0.01 for 2-MBT high concentrations. The free energy of adsorption was ΔG_ads=-5.59 kJ mol"-1, corresponding to physisorption process, probably of electrostatic nature of the interaction between 2-MBT and copper surface in aqueous solution. (Author)
[en] Highlights: • Poly(N-2-aminoethylacrylamide) was grafted magnetite nanoparticles via ATRP. • Removal of Cu(II) cations was investigated by differential pulse voltammetry (DPV). • Kinetics, thermodynamics and adsorption isotherm models were studied. • The re-usability of the prepared magnetic sorbent was investigated.
[en] Adsorption is well accepted as an effective method for perfluorinated compounds’ (PFCs) removal from water among various conventional methods. However, development of adsorbents that combine good performance of PFC removal and regenerability has not yet been realized. This work demonstrated the fabrication and application of an ammoniated magnetic adsorbent for efficient and economical PFOS and PFOA removal. Functional ammonium groups and γ-Fe2O3 were effectively incorporated in the particle with the proposed method. These fabricated magnetic particles presented superior adsorption performance for PFOS and PFOA with short equilibrium time of 120 min and high adsorption capacity. The isotherms revealed that the adsorption process belonged to multilayer sorption with their intricate interactions including anion exchange and hydrophobic interaction. The magnetic particle maintained its removal efficacy over a wide pH range of 3–9 or with coexisting substances. Moreover, the regeneration and reuse of the magnetic particle were successfully carried out with PFOS and PFOA removal efficiency sustained higher than 80% in 15 consecutive treatment cycles. Along with the efficient adsorption and easy separation of adsorbents, we expect that this ammoniated magnetic particle can serve as an excellent alternative for PFOS and PFOA removal from water.
[en] If a system described in terms of empty and filled states interacts with particles M via the following reactions: empty state + M → filled state + α empty state, filled state → M + (1-α) empty state (with α being a real number), then it may be described in terms of fractional statistics. On the other hand, provided that the states are identified with adsorption sites, this scheme may be used, according to the value assigned to α, for the description of adsorption-desorption phenomena such as the inhibition of empty sites by the adsorption of polyatomic molecules, multilayer adsorption, and the branched growth of dendrimers. Not only does the fractional statistical treatment reproduce the well-known Langmuir and Brunauer-Emmett-Teller isotherms for α = 0 and α = 1, but also it provides the adsorption isotherms for all other values of α. It is also shown that considered as a function of the parameter α the equilibrium isotherm undergoes a catastrophe at α = 1
[en] Together with increasing world population, developing technology and rapid industrialization process bring about environmental pollution. Nowadays, cleaning environment from industrial wastes and pollutants is of utmost importance. Some organic materials, produced by the majority of textile waste, cause environmental pollution. Many dyestuffs, which are hazardous for environment, can be released to environment by industrial organizations without having any precaution. Textile dyestuffs, being above certain concentrations, can cause poisoning of aquatic organisms. Dyestuffs can be classified as following: Anionic: Direct, acid and reactive dyes Cationic: Basic dyes Nonionic: Disperse dyes It can be said that most problematic group of dyes used in the textile industry is the group of reactive dyes. Analyzing performed studies shows that these views are supported. Today, adsorption techniques are gaining ground due to efficiency in removal of too stable pollutants. Adsorption is, economically, a reasonable method and we can say that it provides formation of high quality products. With the development of industry search for materials, to be used as adsorbent for removal of factory wastes and water-soluable dyestuffs from water, accelerates. In our study, from natural adsorbents diatomite(Çaldıran/VAN) is used as an adsorbent material. The removal of natural red and basic blue from aqueous solution using diatomite, was investigated with respect to the adsorbent dose (0,02 g), initial concentration (20-140 mg/L), temperature (between 25 and 450C), on batch adsorption were studied as a function of contact time. The lineer Langmuir, Freundlich and Temkin adsorption equations were applied to describe the equilibrium isotherms. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH0), Gibbs free energy (ΔG0) and entropy (ΔS0) shoved spontaneous and endothermic in nature of adsorption for both of adsorbents. (author)
[en] We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas is obtained, taking into account variations in the adsorption properties of the adsorbent in adsorption. We establish bistability and tristability of the system caused by variations in adsorption properties of the adsorbent in competitive adsorption of gas particles on it. We derive conditions under which adsorption isotherms of a binary gas mixture have two stable asymptotes. It is shown that the specific features of the behavior of the system under study can be described in terms of a potential of the known explicit form. (paper)
[en] We propose a self-consistent model taking into account the variations in adsorption properties of an adsorbent surface in the process of adsorption-desorption of gas particles on it. We introduce a dimensionless coupling parameter equal to the normalized adsorption-induced activation energy for desorption due to the substrate deformation caused by the adsorption-induced force. Bistability of the system of noninteracting adparticles is established in the case when the coupling parameter is greater than a critical value and the gas concentration belongs to a certain interval. We show that the adsorption isotherms obtained within the framework of the proposed model essentially differ from the Langmuir isotherms and we show that the Zeldovich hysteresis is possible. The kinetics of the surface coverage is analyzed in detail in the overdamped approximation. We show the possibility of a 'quasi-stationary' state of the system due to variations in adsorption properties of the surface in adsorption-desorption.
[en] Highlights: • CPO-27(Ni) is more suitable for energy storage applications with half cycle time more than 30 min. • CPO-27(Ni) outperformed other adsorbents at low evaporation temperatures. • Energy recovered from the condenser and the adsorption bed was found to be mostly dependent on the regeneration temperature. • The energy recovery from condensation and adsorption was independent of the reactor conductance except at small conductance ratio. • Recirculating the cooling water through the adsorption bed then the condenser was found to deteriorate the recovered energy from condenser 4%. - Abstract: Metal–organic framework (MOF) materials are new adsorbent materials that have high surface area and pore volume and hence high adsorption uptake. The previous exceptional properties make this class of materials have a great potential in many applications like cooling, gas separation and energy storage. However, there is very limited information on the performance of metal–organic framework materials in energy storage applications and their performance compared to conventional adsorbents. This paper aims to present an experimental characterisation of CPO-27(Ni) MOF material for water adsorption and to investigate its viability for energy storage. CPO-27(Ni) (known as MOF-74(Ni)), which is a MOF material that has high water adsorption capabilities of 0.47 g_H_2_O gads"−"1 and hydrothermally stable and can be supplied in large quantities. Firstly, the material water adsorption isotherms were predicated using Materials Studio software via the material structure information and then compared to the experimentally measured isotherms. The experimentally measured isotherms and kinetics were used to model a double bed adsorption system for energy storage application using Simulink–Matlab software coupled with Nist RefProp thermophysical routines. Finally, the performance of CPO-27(Ni) was then compared with silica gel. The CPO-27(Ni) was found to outperform silica gel at long half cycle time (more than 30 min) at low evaporating temperature making it suitable for energy storage applications. The energy stored in the condenser and the adsorption bed was found to be dependent mostly on the regeneration and the cooling temperatures. The potential of the energy recovered from the adsorption bed can be double the one recovered from the condenser. Also, the energy recovery during condensation and adsorption was found to be independent of the reactor conductance except at small conductance ratio. Finally, the adsorption unit cooling water flow strategy was found to affect the amount of the energy recovered as recirculating the cooling water through the adsorption bed and then condenser was found to decrease the recovered energy from the condenser by 4%.
[en] In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73 mg g-1, respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23 kJ/mol for BY 28 and 18.15 kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents