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The discharge of diethylenetriamine (DETA) into aqueous environment poses a threat to public health and environment. Therefore, it is imperative to take effective measures to remove DETA from water. The elimination of DETA from water may be realized via the way of adsorption with activated carbon. In this paper, the adsorption of DETA from water by activated carbon originated from coconut shell has been explored in batchwise operation. The effects of stirring speed, temperature, pH, DETA concentration, carbon dosage and particle size on DETA adsorption have been determined by experiment. The adsorption results exhibit that the DETA adsorption rate increases with its concentration in the aqueous solution and temperature. However, the amount of DETA adsorbed on the carbon at equilibrium decreases slightly with temperature. The DETA adsorbed increases with pH changing from 8 to 11 and remains constant if pH rising over 11. The kinetic study shows that DETA adsorption on the activated carbon is in good agreement with the pseudo-second-order kinetic model with a correlation coefficient of 0.999. The DETA removal from the solution increases with the carbon dosage. The Langmuir equilibrium isotherm model has been found to provide a better fitting of the adsorption data than the Freundlich equilibrium isotherm model with a maximum adsorption of 90.50 mg g−1. The thermodynamic parameters evaluated from the experiments are ΔS 14.49 J∙mol−1∙K−1, ΔH −11.32 kJ mol−1 and ΔG changing from −15.71 from −16.15 kJ mol−1with the temperature rising from 30°C to 60°C. The thermodynamic study suggests the exothermic and spontaneous natures of DETA sorption on activated carbon. [ABSTRACT FROM AUTHOR]

In this study, the adsorption experiments of water vapour on deep reservoir were conducted. The thermodynamics for water vapour adsorption were analysed. Results illustrate that primary binding centres have stronger affinity than secondary binding centres. Water molecule will be preferentially trapped at primary binding centres in low-pressure region. In high-pressure region, secondary adsorption predominates. Primary adsorption spontaneity increases with pressure. At secondary binding centres and total binding centres, the spontaneity degree quickly improves and then slowly decreases as pressure increases. The transfer of water molecules from the more energetic binding centres to the less binding centres leads to the initial reduction in entropy loss (ΔS) and isosteric heat of adsorption (Qst). The late enhancement in ΔS and Qst is caused by the growing water clusters. Water vapour adsorption can promote CH4 desorption. By occupying adsorption sites and reducing pore connectivity, water vapour adsorption causes an unfavourable effect on CO2 sequestration. [ABSTRACT FROM AUTHOR]

Waste residue of Chinese prickly ash seeds were simply treated with aqueous ZnCl2 to prepared the high-performed activated carbon. It was characterized by the methods of XRD, SEM, EDX, FT-IR, BET and XPS. The synergetic adsorption performance of Chinese prickly ash seeds activated carbon for Pb2+, Ni2+ and Acid Orange IΙ (AO) was studied. In the single-component system, the adsorption capacity of Pb2+, Ni2+ and AO were 15.1, 10.7 and 188.4 mg/g, respectively. In the AO-Pb2+ system, the maximum adsorption capacity of Pb2+ and AO were 79.40 and 332.68 mg/g under temperature of 30°C and pH of 5.0, respectively. For AO-Ni2+ system, it was 375.6 and 38.3 mg/g, respectively. The adsorption kinetics was satisfactorily fitted by the pseudo-second-order model. The synergic adsorption process can be smoothly described by the non-modified Sips isotherm. [ABSTRACT FROM AUTHOR]

The adsorption characteristic and mechanism of poly(N1,N1,N3,N3-tetraallylpropane-1,3-diaminium chloride) (PTAPDAC) toward Cr(VI) ions were systematically investigated. Results showed that the removal efficiency of PTAPDAC toward Cr(VI) could reach above 98% at pH = 3–6. The equilibrium data of Cr(VI) adsorbed by PTAPDAC fitted the Langmuir model well, and the maximum sorption capacity deduced from the Langmuir model at 293 K was 273.17 mg g−1. The adsorption of PTAPDAC toward Cr(VI) was rapid and reached equilibrium within 60 min, and the adsorption kinetic process was relevant to the pseudo-second-order kinetic model. Moreover, the activation energy Ea was calculated as −22.505 kJ mol−1. The adsorption processes were spontaneous and exothermic driven by an increase in entropy, which involved electrostatic attraction, ion exchange, and redox reactions. The X-ray photoelectron spectroscopy analysis revealed that approximately 64.5% of Cr(VI) reduced to be Cr(III), and 24.29% of –C–NH+ deprotonated. The combination of reduced Cr(III) with tertiary amine groups resulted in a positively charged tertiary amine group, which further promoted Cr(VI) adsorption, thereby increasing the adsorption capacity of PTAPDAC toward Cr(VI). Therefore, PTAPDAC has a broad application prospect in removing Cr(VI) ions in wastewater. [ABSTRACT FROM AUTHOR]

This paper describes instrumentation of a spectrophotometric system and its application for in-situ, real-time measurement of adsorption thermodynamics in aqueous solution by use of laboratory-constructed fiber-optic measurements. A measurement vessel was assembled from an adsorption bag, stirring and thermostatic devices, and a fiber-optic dipping probe. A macroporous adsorption resin and rutin were selected as the model adsorbent and adsorbate. In-situ liquid phase adsorption measurement of the system was achieved through monitoring of the absorption by dipping the probe in a broad range of concentrations. In-situ measurement of the AB-8 resin adsorption at temperatures from 303 K to 323 K was systematically carried out, showing that temperature was an influencing factor for the adsorption capacity and initial adsorption rate. The adsorption thermodynamic parameters for AB-8 indicated that the results well fitted the Freundlich model. In addition, a favorable, exothermic, spontaneous, physical process of rutin was demonstrated on AB-8. The obtained results showed that this method was successful at keeping the adsorption temperature constant. The application of fiber-optic sensing to the in-situ measurement of liquid phase adsorption enables automated and real-time monitoring of adsorption thermodynamics. [ABSTRACT FROM AUTHOR]

A series of functional hyper-cross-linked resins were successfully synthesized by incorporating anhydride, sulfoacid and menthanone groups into post-cross-linked polymer. They were evaluated for adsorption of 2-amino-4-methylbenzothiazole (2A4MBT) from aqueous solution. The five resins were efficient for adsorption of 2A4MBT from aqueous solution. The adsorption process includes both physical adsorption and irreversible chemical adsorption. The absolute value of adsorption enthalpy had an order of PRLMR (3.24 kJ mol−1) < IDLMR (7.96 kJ mol−1) < TMAMR (9.72 kJ mol−1) < PAMR (−13.1 kJ mol−1) < SAMR (21.8 kJ mol−1). Phthalic anhydride-modified resin could be regenerated by 10% HCl/methanol solution after adsorption equilibrium. [ABSTRACT FROM AUTHOR]

In this study, Monascus pigments were separated from the extractive fermentation broth by the combination of reverse micellar extraction and macroporous resins (MACR) adsorption with the alkalizing S-8 MACR (S-8 ALR). A 95.07% pigment adsorption was achieved together with a relative low Triton X-100 co-adsorption that was only 2.53%. The liquid intraparticle diffusion and film diffusion limit the pigment adsorption rate. A 79.48-84.03% of the pigment could be eluted from the resin using the methanol solution containing a 0.5% (w/v) hydrochloric acid. The S-8 ALR could be recovered for cycle use without a deficit of the adsorption or desorption efficiency. Abbreviations: ACR—Acidified resin; ALR—Alkalizing resin; HPLC—High performance liquid chromatography; PSM—pigment- surfactant micelle; TEM—Transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The adsorption of the anticoagulant warfarin onto unmodified (UMS) and modified (phenyl (PhMS), methyl (MMS), mercaptopropyl (MPMS)) mesoporous silica materials was studied at pH 1.6 and 7.4 and in the temperature range of 293–325 K. The silica materials were prepared by sol-gel method for further characterization by FTIR spectroscopy, N2adsorption/desorption method, transmission electron microscopy and zeta potential measurements. The effects of medium pH, temperature and surface modification of mesoporous silica material on their adsorption characteristics (adsorption capacity, thermodynamic parameters of adsorption) relative to anticoagulant warfarin were investigated. It was found that medium acid–base properties strongly affect the adsorption of warfarin due to the pH-dependent structural diversity of the drug and ionization state of the silica surfaces. The adsorption capacity of the silica materials at pH 1.6 decreases in the order: MMS > MPMS > UMS > PhMS. The influence of various non-covalent interactions on the adsorption capacity of the silica materials and energy of the drug-silica interactions is discussed. These results may be useful for the development of a novel delivery system of warfarin. [ABSTRACT FROM PUBLISHER]

The binderless 5A zeolite has higher economy when used in adsorption process to improve utilization efficiency of naphtha. Adsorption isotherms of n-pentane, n-hexane, n-heptane and n-octane on binderless 5A zeolite pellets were determined gravimetrically and analyzed in the temperature ranging from 423 to 573 K. Adsorption thermodynamic parameters were extracted from multisite Langmuir (MSL) model. Heats of adsorption for n-paraffins on 5A zeolite show an increasing trend with carbon number. At small degree of sites filling, the heats of adsorption of n-paraffins on binderless pellets increase from 53.19 kJ mol-1 for n-pentane to 72.34 kJ mol-1 for n-octane. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate the influence of various experimental parameters viz. initial pH (pH0), adsorbent dose, contact time, initial concentration and temperature on the adsorptive removal of furfural from aqueous solution by commercial grade activated carbon (ACC). Optimum conditions for furfural removal were found to be pH0 ≈ 5.9, adsorbent dose ≈ 10 g/l of solution and equilibrium time ≈ 6.0 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural was of the order of 10-13 m2/s. Furfural adsorption onto ACC was found to be best represented by the Redlich-Peterson isotherm. A decrease in the temperature of the operation favorably influenced the adsorption of furfural onto ACC. The positive values of the change in entropy (ΔS0); and the negatived value of heat of adsorption (ΔH0) and change in Gibbs free energy (ΔG0) indicated feasible, exothermic, and spontaneous nature of furfural adsorption onto ACC. [ABSTRACT FROM AUTHOR]

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (pH0), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be pH0 ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10-13 m2/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS0) and heat of adsorption (ΔH0) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG0) indicates the feasible and spontaneous adsorption of furfural on BFA. [ABSTRACT FROM AUTHOR]

The ability of Japanese cedar (Cryptomeria japonica) bark to remove Cr(VI) from aqueous solutions was investigated. The research parameters included the solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and adsorbate concentration dependent, and mainly governed by physicochemical adsorption under the weak acidic conditions studied (initial solution pH ≥ 3). However, the reduction of Cr(VI) to Cr(III) occurred extensively at low solution pH (initial solution pH ≤ 2). The equilibrium data at different temperatures fit well in the Langmuir isotherm model. The endothermic nature of the adsorption was confirmed by the positive value of enthalpy change (18.9 kJ mol−1). The positive value of entropy change (65.2 J mol−1 K−1) suggested the increased randomness at the solid–solution interface during the adsorption. The studies showed that Japanese cedar bark can be used as a cost-effective adsorbent for the removal of Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

A study on the interactions between silica and elastomers typically used in tire tread production has been carried out by inverse gas chromatography (IGC) and image analysis aided transmission electron microscopy (TEM/AIA). At infinite dilution, IGC has been performed using precipitated silica as the stationary phase to determine its surface properties and to calculate the adsorption free energy and enthalpy of low molecular weight analogues of elastomers, used as the eluates. Vulcanized samples based on different matrices employed in tire formulations, i.e., natural rubber, butadiene rubber, and styrene-butadiene rubber, have been investigated by TEM/AIA to determine the dispersion of the filler within the matrix as well as to achieve quantitative information on aggregate size and shape distribution of silica and, consequently, on the polymer-filler interactions. A comparison between thermodynamic predictions deduced by IGC and the results from morphological analysis concerning filled compounds shows a very satisfactory agreement. [ABSTRACT FROM AUTHOR]

In this paper the effect of additives on adsorption of sodium oleate on kaolinite in aqueous solution is examined. Kaolinite with specific surface area 20.2 m[SUP2] /g and zero point of charge 2.0 is used as adsorbent. Adsorption of sodium oleate on kaolinite has been investigated with or without additives such as NaCI, n-butanol, npenanol, PHPAM (partially hydrolyzed polyacrylamide) and AEO (a nonionic polyoxyethylene surfactant. The adsorption isotherm of sodium oleate, which is different from that of other anionic surfactants on kaolinite, showed two plateaus (i.e. LS type). But it is interesting that an adsorption maximum is found in the isotherms when these additives are added in the liquid/solid adsorption system. Basically, three different adsorption behaviors have been found when the additives are added. The adsorbed amount of sodium oleate decreases considerably when alcohols are added to the solution, while the amount increases when NaCI or PHPAM is added; only a slight alteration is observed when AEO is added to the solution. The adsorption process on kaolinite is found to follow a two-step first-order kinetic rate equation with two different (k[SUB1] and k[SUB2]) rates constants. Values of the energy of activation Ea[SUB1] and Ea[SUB2] are calculated from the slope of the linear plot of - Ink against 1/T for different systems. The enthalpies of activation (ΔH), entropies of activation (ΔS) and free energies of activation (ΔG) are calculated by using thermodynamic equations. It is found that there is an entropy-enthalpy compensation effect in the adsorption process from the values of ΔH and ΔS. These results are usefull in controlling the surfactant's adsorbent loss in tertiary oil recovery. [ABSTRACT FROM AUTHOR]