Relative Contribution Of Adsorption Research Articles

Fe(III) Reduction and U(VI) Immobilization by Paenibacillus sp. Strain 300A, Isolated from Hanford 300A Subsurface Sediments

A facultative iron-reducing [Fe(III)-reducing] Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes [Fe(III)-nitrilotriacetic acid and Fe(III)-citrate] but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 μM) of either of the electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 μM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We also found that Paenibacillus sp. 300A could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ∼7:3 in PIPES [piperazine-N,N'-bis(2-ethanesulfonic acid)] and ∼1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments.

Sorption and biodegradation of sulfonamide antibiotics by activated sludge: Experimental assessment using batch data obtained under aerobic conditions

This study investigated the adsorption, desorption, and biodegradation characteristics of sulfonamide antibiotics in the presence of activated sludge with and without being subjected to NaN 3 biocide. Batch experiments were conducted and the relative contributions of adsorption and biodegradation to the observed removal of sulfonamide antibiotics were determined. Three sulfonamide antibiotics including sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamonomethoxine (SMM), which had been detected in the influent and the activated sludge of wastewater treatment plants (WWTP) in Taiwan, were selected for this study. Experimental results showed that the antibiotic compounds were removed via sorption and biodegradation by the activated sludge, though biodegradation was inhibited in the first 12 h possibly due to competitive inhibition of xenobiotic oxidation by readily biodegradable substances. The affinity of sulfonamides to sterilized sludge was in the order of SDM > SMM > SMX. The sulfonamides existed predominantly as anions at the study pH of 6.8, which resulted in a low level of adsorption to the activated sludge. The adsorption/desorption isotherms were of a linear form, as well described by the Freundlich isotherm with the n value approximating unity. The linear distribution coefficients ( K d ) were determined from batch equilibrium experiments with values of 28.6 ± 1.9, 55.7 ± 2.2, and 110.0 ± 4.6 mL/g for SMX, SMM, and SDM, respectively. SMX, SMM, and SDM desorb reversibly from the activated sludge leaving behind on the solids 0.9%, 1.6%, and 5.2% of the original sorption dose of 100 μg/L. The sorbed antibiotics can be introduced into the environment if no further treatments were employed to remove them from the biomass.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate

Infinite dilution activity coefficients γ 1 ∞ and gas–liquid partition coefficients K L of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulphur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO 3] were determined by gas–liquid chromatography at five temperatures in the range from 318.15 to 353.15 K. Relative contribution of adsorption at gas–liquid interphase to the overall solute retention, as examined by varying sample size and IL loading in the column, was found negligible. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the γ 1 ∞ values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the K L values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. Comparison to [EMIM][NO 3] studied previously revealed [MeSO 3] − anion to have still greater hydrogen bond basicity than that found for [NO 3] −. In addition, similarly to [EMIM][NO 3], promising potential of [EMIM][MeSO 3] for applications in solvent-aided separation processes was identified, the selectivities of [EMIM][MeSO 3] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons ranking among the highest ever observed with ILs or molecular solvents.

Activity Coefficients at Infinite Dilution of Organic Solutes in the Ionic Liquid 1-Ethyl-3-methyl-imidazolium Nitrate

Infinite dilution activity coefficients gamma(1)(infinity) and gas-liquid partition coefficients K(L) of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulfur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium nitrate [EMIM][NO(3)] were determined by gas-liquid chromatography at five temperatures in the range from 318.15 to 353.15 K. Relative contribution of adsorption at gas-liquid interphase to the overall solute retention, as examined by varying sample size and IL loading in the column, was found negligible. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the gamma(1)(infinity) values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. In addition, the promising potential of [EMIM][NO(3)] for applications in solvent-aided separation processes was identified, the selectivities of [EMIM][NO(3)] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons ranking among the highest ever observed with ILs or molecular solvents.

Composition distribution separation of methyl methacrylate-methacrylic acid copolymers by normal-phase gradient elution high-performance liquid chromatography

The characterization of copolymers requires the determination of chemical composition distribution in addition to molecular mass ( M) distribution. Techniques commonly applied to copolymer analysis provide either average bulk composition or a convolution of M and composition distributions. The application of gradient elution adsorption chromatography, under appropriate conditions, allows the separation of copolymers based solely upon their chemical composition in a M-independent mode. Separation independent of M requires the elimination of size-exclusion effects with the porous adsorbent and the minimization of precipitation contributions. For separation over a wide copolymer composition range, the relative contributions of adsorption and precipitation retention mechanisms change with solvent composition. Under gradient elution conditions where adsorption retention dominates, composition fractionation can be combined with subsequent size-exclusion chromatography to provide a complete composition/ M map of the copolymer.

Relative contribution of adsorption and absorption effects to the strength loss of metal-polymer bonds

The adhesion of a polymer to a metal, characterized by the stress required to destroy the adhesion bond, is one of the principal criteria for predicting the behavior of metal-polymer materials and structures under various conditions. In most cases the materials are exposed to liquid media or vapors (moist air, water, electrolytes, solvents, etc.). The relative humidity of the atmosphere rarely falls below 70%. Under these conditions the strength of adhesion bonds, including polymer--metal bonds, usually decreasesp and the bonds are sometimes observed to fail spontaneously [I, 2].