Display omitted
•Organic acids sorption–desorption to minerals were examined by batch experiments.•Interaction mechanisms were evaluated using ATR-FTIR spectroscopy.•Overall, carboxylic acids ...sorption and retention were higher than amino acids.•Minerals with variable charge (Fe oxides) sorbed more carboxylic acids.•Permanently charged minerals showed greater potential to sorb amino acids.
Batch experiments were conducted to evaluate the sorption–desorption behaviour of 14C-labelled carboxylic acids (citric and oxalic) and amino acids (glutamic, alanine, phenylalanine and lysine) on pure minerals (kaolinite, illite, montmorillonite, ferrihydrite and goethite). The sorption experiments were complemented by ATR-FTIR spectroscopy to gain possible mechanistic insight into the organic acids–mineral interactions. In terms of charge, the organic solutes ranged from strongly negative (i.e., citric) to positively charged solutes (i.e., lysine); similarly the mineral phases also ranged from positively to negatively charged surfaces. In general, sorption of anionic carboxylic and glutamic acids was higher compared to the other compounds (except lysine). Cationic lysine showed a stronger affinity to permanently charged phyllosilicates than Fe oxides. The sorption of alanine and phenylalanine was consistently low for all minerals, with relatively higher sorption and lower desorption of phenylalanine than alanine. Overall, the role of carboxylic functional groups for the sorption and retention of these carboxylic and amino acids on Fe oxides (and kaolinite) and of amino group on 2:1 phyllosilicates was noticeable. Mineral properties (surface chemistry, specific surface area), chemistry of the organic compounds (pKa value, functional groups) and the equilibrium pH of the system together controlled the differences in sorption–desorption patterns. The results of this study aid to understand the effects of mineralogical and chemical factors that affect naturally occurring low molecular weight organic compounds sorption under field conditions.
Sequestration of anthropogenic antibiotics by biochars from waters may be a promising strategy to minimize environmental and human health risks of antibiotic resistance. This study investigated the ...long-term sequestration of lincomycin by 17 slow-pyrolysis biochars using batch sorption experiments during 365 days. Sorption kinetics were well fitted to the Weber-Morris intraparticle diffusion model for all tested biochars with the intraparticle diffusion rate constant (kid) of 25.3–166 μg g−1 day−0.5 and intercept constant (Cid) of 39.0–339 μg g−1, suggesting that the sorption kinetics were controlled by fast initial sorption and slow pore diffusion. The quasi-equilibrium sorption isotherms became more nonlinear with increasing equilibration time at 1, 7, 30, and 365 days, likely due to increasing abundance of heterogeneous sorption sites in biochars over time. Intriguingly, low-temperature (300 °C) and high-temperature (600 °C) biochars had faster sorption kinetics than intermediate-temperature (400–500 °C) biochars at the long term, which was attributed to greater specific surface area and pore volume of high-temperature biochars and the substantial and continuous release of dissolved organic carbon (DOC) from low-temperature biochars, respectively. DOC release enhanced lincomycin sorption by decreasing biochar particle size and/or increasing the accessibility of sorption sites and pores initially blocked by DOC. Additionally, a large fraction (>75%) of sorbed lincomycin in biochars after a 240-day equilibration could not be extracted by the acetonitrile/methanol extractant. The strong sorption and low extraction recovery demonstrated the great potential of biochars as soil amendments for long-term sequestration of antibiotics in-situ.
Display omitted
•Lincomycin sorption to biochars was controlled by pore diffusion in the long term.•Quasi-equilibrium sorption isotherms of lincomycin became more nonlinear over time.•Release of dissolved organic carbon from biochars enhanced lincomycin sorption.•Lincomycin sequestered in biochar pores was highly resistant to extraction.
Arsenic adsorption on amorphous aluminum and iron oxides was investigated as a function of solution pH, solution ionic strength, and redox state. In this study in situ Raman and Fourier transform ...infrared (FTIR) spectroscopic methods were combined with sorption techniques, electrophoretic mobility measurements, and surface complexation modeling to study the interaction of As(III) and As(V) with amorphous oxide surfaces. The speciation of As(III) and As(V) in aqueous solution was examined using Raman and attenuated total reflectance (ATR)-FTIR methods as a function of solution pH. The position of the As–O stretching bands, for both As(III) and As(V), are strongly pH dependent. Assignment of the observed As–O bands and their shift in position with pH was confirmed using semiempirical molecular orbital calculations. Similar pH-dependent frequency shifts are observed in the vibrational bands of As species sorbed on amorphous Al and Fe oxides. The mechanisms of As sorption to these surfaces based on the spectroscopic, sorption, and electrophoretic mobility measurements are as follows: arsenate forms inner-sphere surface complexes on both amorphous Al and Fe oxide while arsenite forms both inner- and outer-sphere surface complexes on amorphous Fe oxide and outer-sphere surface complexes on amorphous Al oxide. These surface configurations were used to constrain the input parameters of the surface complexation models. Inclusion of microscopic and macroscopic experimental results is a powerful technique that maximizes chemical significance of the modeling approach.
13C CP-MAS nuclear magnetic resonance (NMR) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies were compared for evaluating their potential to characterise the influence of ...land use change on organic carbon (OC) chemistry of particulate organic matter (POM) and mineral associated OM (MOM) fractions of different soil types. Surface soil samples of Ferralsol, Luvisol, Vertisol and Solonetz were collected from native and crop lands and isolated into different density fractions. NMR and DRIFT showed distinct OC composition for all the soil fractions of two land uses. In NMR spectra, greater proportion of carbohydrate and aromatic C was observed in POM, while MOM fractions were rich in carbohydrate, amino groups and aliphatic C. DRIFT spectra showed greater carboxylic, aromatic C and amide N in MOM than corresponding POM. NMR spectroscopy detected charred aromatic C in both fractions, which was not feasible with DRIFT. The overall effect of land use in both techniques appeared similar on the composition of POM- OC, i.e., increased aromaticity and decreased alkyl C:O-alkyl C ratio. However, differences of land use impact were observed in MOM-OC, e.g., overall decreased aromaticity and increased alkyl C:O-alkyl C for all soils in NMR, and in DRIFT, it varied with soil type (aromaticity: Ferralsol, Vertisol > Luvisol, Solonetz). However, these trends were inconsistent and indistinct among fractions of four soils. Discrepancy in NMR and DRIFT results was ascribed to the sensitivity limitations of the two techniques in characterising soil OM in mineral rich fractions, and sample pre-treatment effect in NMR. We conclude that combination of NMR and DRIFT spectroscopy, preferably supplemented by other techniques e.g., mass spectroscopy and XPS, would improve the proficiency in elucidating small changes in soil OM composition with land use conversion.
Display omitted
•NMR spectroscopy detected charred C in soil fractions, but DRIFT could not.•C composition variation trend was inconsistent among organic matter (OM) fractions•C chemistry in NMR & DRIFT: mostly varied (due to land use) for mineral associated OM•Both techniques had sensitivity limitation in characterising soil (mineral rich) OM•Combining NMR & DRIFT can improve their ability in elucidating soil OM composition
This study tests the influence of a diverse set of biochar properties on As(V), Se(IV), Cd(II), Cu(II), Ni(II), Pb(II), or Zn(II) removal from solution at pH 4.5. Six commercial biochars produced ...using different feedstock and pyrolysis conditions were extensively characterized using physical, chemical, and spectroscopic techniques, and their properties were correlated to anion and cation removal using multiple linear regression. H/total organic C (TOC) ratio and volatile matter were positively correlated to cation removal from solution, which indicate interactions between metals and non-aromatic C. Defining the correlation of ion removal with specific OC functional groups was hindered by the inherent limitations of the spectroscopic techniques, which was exacerbated by the heterogeneity of the biochars. Ash was negatively correlated to Se(IV) and positively correlated to Cd(II), Cu(II), and Ni(II) removal from solution. Interference from soluble P in biochars may partly explain the low Se(IV) removal from solution; and Ca-, P-, and Fe- containing compounds likely sorbed or precipitated Pb(II), Cd(II), Cu(II), Ni(II) and Zn(II). Furthermore, Ca-oxalate identified using X-ray diffraction in willow, may be responsible for willow's increased ability to remove Cd(II), Ni(II), and Zn(II) compared to the other 5 biochars. It was clear that both OC and inorganic biochar components influenced metal(loid) and Se(IV) removal from solution. The non-aromatic and volatile OC correlated to removal from solution may be readily available for microbial degradation, while Mg, N, P, and S are required for biological growth. Biological metabolism and uptake of these compounds may inhibit or destabilize their interaction with contaminants.
Display omitted
•Properties of biochars were related to removal of metal(loid)s and Se from solution.•All biochars efficiently scavenged dissolved Pb and Cu under acidic conditions.•Phosphates negatively correlated to anion but positively correlated to cation removal.•Ca and volatile matter were positively correlated to Cd, Cu, Ni removal.•Oxalate in willow biochar was responsible for greater Cd and Ni removal.
Display omitted
•Irreversible adsorption of sulfamethoxazole from water by zeolite Y, mordenite, and ZSM-5.•Medium-weak zeolite-antibiotic host–guest cooperative interactions.•Sulfamethoxazole ...molecules localization into zeolite porosities by Rietveld analysis of XRD data.
Sulfonamide antibiotics are persistent pollutants present in surface and subsurface waters in both agricultural and urban environments. Sulfonamides are of particular concern in the environment because they are known to induce high levels of bacterial resistance. Adsorption of sulfamethoxazole sulfonamide antibiotic into three high silica zeolites (Y, mordenite, and ZSM-5) with pore opening sizes comparable to sulfamethoxazole dimensions is reported. Sulfamethoxazole was almost completely removed from water by zeolite Y and MOR in a few minutes. Adsorption onto ZSM-5 showed an increased kinetics with increasing temperature. Antibiotic sorption was largely irreversible with little antibiotic desorbed. Sulfamethoxazole incorporation and localization into the pore of each zeolite system was defined along with medium-weak and cooperative host–guest interactions in which water molecules play a certain role only in zeolite Y and mordenite.
Surfactant-polymer flooding is an effective process in extracting most of the original oil in place remained after conventional water flooding process. However, this technique is complicated and ...involves extensive screening and numerous experiments to find the optimum chemical composition, salinity, etc. Surfactant-polymer flood modeling can facilitate the optimization of the process, however, the inherently large parameter space results in great uncertainty and poor predictive capability. Here, by means of a novel approach using global sensitivity analysis, we reduce the parameter space of a typical surfactant-polymer flood model to facilitate model calibration and history matching process.
To inform our analysis, we performed three Berea coreflood experiments with different slug designs and salinity profiles. The results from our coreflood experiments revealed and quantified the high sensitivity to salinity, underlying the importance of accurate phase behavior modeling. In addition to coreflood experimental data, we used an extensive set of laboratory data including polymer rheology, surfactant phase behavior, polymer permeability reduction, and capillary desaturation along with results from sensitivity analysis to build a mechanistic surfactant-polymer flood model.
After modeling of sub-processes such as polymer flood model or phase behavior of our surfactant/oil/water system, through a multi-stage calibration algorithm, coreflood experimental data was used to build a thorough surfactant-polymer flood model where cumulative oil production and pressure profile were history matched simultaneously. Finally, we showed that our surfactant-polymer flood model has predictive capabilities with no need for ad hoc tuning of the model parameters by modeling two additional coreflood experiments where cumulative oil production and pressure profile matched those of experiments.
Polymeric flocculation represents a widely used approach to accelerate consolidation of fluid fine tailings (FFTs), generated by mining bitumen from oil sands. Questions remain, however, regarding ...the structure produced by polymer addition, and its evolution over time. Dynamic strain amplitude sweep tests on undisturbed specimens show that flocculation leads to an improvement in stiffness and strength, delays yield, and modifies the damping properties. These effects are attributed to the percolated network formed as the polymer aggregates mineral particles, and further bridges these aggregates. This structure dominates the response of the material and controls the solid-to-fluid transition, which has characteristics typical of a highly networked system. Increasing disturbance causes rapid and irreversible degradation of the response, evidence of the sensitivity of the structure. The data for FFTs from two tailings ponds demonstrate the uniqueness of these materials with differences observed in the response before and after flocculation, and in the water release process.
The paper examines the effect of the presence of small percentages (1–5%) by dry mass of the sand of laponite – a synthetic nanoclay with plasticity index exceeding 1000% – on the cyclic response of ...sand with relative density in the 15–25% range. The work is based on cyclic triaxial tests performed on specimens prepared pluviating sand and laponite under dry conditions and then permeated with water. 1% laponite impacts all stages of the cyclic tests, from the response during the first loading cycle to liquefaction, increasing the cyclic resistance. Further benefits are observed with a longer pre-shear aging period or higher dosages (3–5%) of laponite.
The observed behavior is associated with reduced mobility of the sand particles during cyclic loading, which can be ascribed to two mechanisms: (1) bonding/bridging at the particle contacts due to the charged laponite fines which are attracted to the sand grains; and (2) formation of a pore fluid with solid like properties. The first appears to control the behavior with 1% laponite, while it is proposed that the second is responsible for the response with higher dosages of laponite.
The results presented provide new insight into the effects of high plastic fines on the cyclic response of sands, the “extreme” effects of the plasticity of the fines, and are significant in light of the possible use of laponite for liquefaction mitigation, an idea first put forth by the authors.
•1% laponite impacts all stages of the cyclic response of sand.•It causes an order of magnitude increase in number of cycles to liquefaction.•Higher dosages (3-5%) of laponite produce further increase in cyclic resistance.•The increase in cyclic resistance is due to a reduction in particle mobility.•Inter-particle bonding and pore fluid with solid like properties control behavior.
PDF
