Analysis Of Kinetic Data Research Articles

Kinetic analysis of continuous reaction data for RAFT and free radical copolymerization with acrylic and styrenic monomers

Free radical (FR) and Reversible Addition Fragmentation Chain Transfer (RAFT) copolymerization rates for styrenic monomers in bulk and aqueous reactions were accelerated by acrylic comonomers, whose own rates were both delayed and decreased. The effect was found with styrenics as low as 0.6% by mole, and is directly observable from Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) data. Rapid radical transfer from acrylic to styrenic comonomer, through lower energy radical resonance stabilization in styrenics, was the suspected cause. FR and RAFT rates were equal, suggesting that FR termination controlled radical concentrations and rates. Despite strongly changing concentrations of initiator and comonomer radicals during reactions, the Quasi-Steady-State Approximation was demonstrated to hold. While rates were identical, molecular weights showed the characteristic increase with conversion for RAFT and decrease for FR. A new, generalized method for reactivity ratio determination was found and acceleration/deceleration behavior was consistently interpreted within a penultimate model.

Kinetics of heat-induced changes in foods: A workflow proposal

The goal of kinetic modeling is twofold: i) to increase scientific understanding of the process under study, and ii) to predict product properties in product and process design and shelf life. Reviewing food science literature shows that classical two-step kinetic analysis is most common, by first deriving rate constants for an assumed order of reaction (possibly after linearization to make linear regression possible) and then deriving Arrhenius parameters via linear regression, again after log-linearization. This two-step approach is not without problems and this article proposes an alternative general workflow on the untransformed data using nonlinear, global regression. The basic elements consist of: i) a full statistical analysis of the order of the reaction per temperature, ii) a global analysis of all data simultaneously to estimate Arrhenius parameters while characterizing a possibly varying order via multilevel modeling, iii) evaluation of the resulting model and parameters in terms of fitting and, even more importantly, predictive capacity. The proposed workflow is illustrated with a case study on thermal degradation of carnitin (described in literature as a first-order reaction). A Bayesian approach was used to obtain probability distributions of parameters rather than point estimates, but the common standard frequentist approach can also be applied. Kinetic analysis of the carnitin data for each temperature separately showed that the order varied with temperature between 0.9 and 1.6. Multilevel modeling on all data simultaneously was used to better characterize this variation along with the common Arrhenius parameters. Due to the nature of the Arrhenius equation, reparameterization and rescaling is necessary to avoid strong parameter correlation and numerical difficulties during nonlinear regression. Multilevel modeling of all data showed that the variation of the order with temperature was not that strong as suggested from the separate analyses but it did show that the global order was higher than one. The outcome of the suggested workflow was compared to that of the classical two-step kinetic analysis and showed considerable differences in Arrhenius parameters; this appeared to be due to linearization by taking logarithms of concentration data, at least for this case study. Furthermore, it is illustrated that Bayesian regression leads to better insight into behaviour of parameters and models than least-squares regression in terms of density distributions, parameter correlations and joint confidence intervals. Even more importantly, testing of predictive capacity of kinetic models can be done much more rigorously using the Bayesian approach. • Estimation of uncertainty in reaction order from kinetic data gives insight in reactions. • Multilevel modeling allows variation of reaction order per temperature. • Global regression leads to less uncertainty in model predictions. • Bayesian estimation gives more insight in regression parameters than least-squares. • Logarithmic transformation in Arrhenius regression leads to biased estimates.

MUCOADHESIVE BUCCAL FILMS: A NOVEL APPROACH FOR THE DELIVERY OF ANTI-HYPERTENSIVE DRUGS

The buccal drug delivery system is a prominent route of administration for drug delivery through the buccal mucosa. It is rich in blood supply with more surface area for rapid absorption as well as provides direct entry of drugs from the site of application into the systemic circulation through the jugular vein. Buccal drug delivery systems consist of various approaches such as lozenges, wafers, gels, microparticles, patches or films from which mucoadhesive buccal film is an attractive dosage form in terms of flexibility and high systemic bioavailability. Since most of the antihypertensive drugs show first-pass metabolism which leads to less oral bioavailability generally up to 20–50%. Thus, incorporation of antihypertensive drugs in mucoadhesive buccal films using mucoadhesive polymers can provide higher systemic bioavailability. The films can be formulated using various techniques such as solvent casting method and hot extrusion melt method. These films can be evaluated based on various characteristics to determine their efficacy and performance such as tensile strength, mucoadhesion residence time, and kinetic release data analysis. They have various advantages over conventional solid oral dosage forms, hence are preferable for the preparation of antihypertensive drug-loaded buccal films. Mucoadhesive buccal films of antihypertensive drugs can also provide controlled drug delivery with enhanced bioavailability.

A Novel High-Throughput FLIPR Tetra-Based Method for Capturing Highly Confluent Kinetic Data for Structure-Kinetic Relationship Guided Early Drug Discovery.

Target engagement by small molecules is necessary for producing a physiological outcome. In the past, a lot of emphasis was placed on understanding the thermodynamics of such interactions to guide structure-activity relationships. It is becoming clearer, however, that understanding the kinetics of the interaction between a small-molecule inhibitor and the biological target [structure-kinetic relationship (SKR)] is critical for selection of the optimum candidate drug molecule for clinical trial. However, the acquisition of kinetic data in a high-throughput manner using traditional methods can be labor intensive, limiting the number of molecules that can be tested. As a result, in-depth kinetic studies are often carried out on only a small number of compounds, and usually at a later stage in the drug discovery process. Fundamentally, kinetic data should be used to drive key decisions much earlier in the drug discovery process, but the throughput limitations of traditional methods preclude this. A major limitation that hampers acquisition of high-throughput kinetic data is the technical challenge in collecting substantially confluent data points for accurate parameter estimation from time course analysis. Here, we describe the use of the fluorescent imaging plate reader (FLIPR), a charge-coupled device (CCD) camera technology, as a potential high-throughput tool for generating biochemical kinetic data with smaller time intervals. Subsequent to the design and optimization of the assay, we demonstrate the collection of highly confluent time-course data for various kinase protein targets with reasonable throughput to enable SKR-guided medicinal chemistry. We select kinase target 1 as a special case study with covalent inhibition, and demonstrate methods for rapid and detailed analysis of the resultant kinetic data for parameter estimation. In conclusion, this approach has the potential to enable rapid kinetic studies to be carried out on hundreds of compounds per week and drive project decisions with kinetic data at an early stage in drug discovery.

Removal of methylene blue dye by adsorption onto Natural Muscovite Clay: experimental, theoretical and computational investigation

ABSTRACT The ability of Natural Muscovite Clay (NMC) to adsorb Methylene Blue (MB) as a dye widely used in the industrial sector was investigated, and the adsorption process was interpreted at the molecular scale through computational modelling. After the characterisation of NMC, the effect of adsorbent mass (5–40 mg), contact time (1–60 min), solution pH (3.7-11.78), stirring speed (100–900 rpm), initial MB concentration (15–80 mg.L-1), and temperature (293.15-333.15 K) on the adsorption efficiency were inspected in the batch mode. The results showed that the basic pH, high stirring speed, and low temperature were the favourable conditions for the MB adsorption onto NMC. The adsorbed quantity Qe,exp of MB dye was found to be 59.828 mg.g-1 for the initial concentration of 80 mg.L-1 at 293.15 K using an NMC mass of 20 mg. The obtained values of thermodynamic parameters suggested that the removal of the MB dye was exothermic, and physical in nature. The adsorption isotherm of the MB/NMC system was analysed according to the statistical physics approach using the Levenberg-Marquardt iterating algorithm and showed a best fitting with the monolayer model with one energy. The analysis of kinetic data showed that the external diffusion and intra-particle diffusion steps have occurred simultaneously and contributed to the control of the adsorption rate of the MB dye onto NMC. The computational modelling of interactions between the MB molecule and the muscovite, kaolinite, and quartz minerals were examined according to the Monte Carlo simulation (MCS) and showed an ability of the dye molecule to be adsorbed onto the surface of these minerals. The calculated adsorption energies ranged between -2.23×104 and -1.10×104 Kcal.mol-1 reflected the stability and the spontaneity of the adsorption process. So, the surface of clay minerals (i.e. muscovite and kaolinite) was more favourable to the adsorption of the MB molecule.

Design, characterization and evaluation of Ce-modified cobalt catalysts supported on alpha alumina in the abatement of methane emissions from natural gas engines

This work deals with the optimisation of Ce-promoted Co3O4 catalysts supported on alpha alumina for the oxidation of traces amounts of methane. Ten Co-Ce samples were synthesised by incipient wetness coimpregnation with the aim of analysing the influence of the Ce/Co molar ratio and the Co3O4 loading on the physico-chemical properties and resultant catalytic behaviour. Textural, structural, morphological and redox properties along with bulk/surface composition were thoroughly characterised. Lattice distortion provoked by insertion of controlled amounts of Ce increased the abundance of Co3+ and improved consequently the redox properties and the mobility of lattice oxygen species of the Co-Ce catalysts. Analysis of kinetic data in the 200−600 °C temperature range evidenced that the optimal catalyst formulation was 10 %Co3O4wt. with a Ce/Co molar ratio of 0.05. In addition, this sample showed a reasonable stability with time on stream under cycled dry/humid conditions.

Individual tuning of solvent parameters – from organic solvents to ionic liquids

For more than 20 years, we have investigated electron transfer reactions of various types and under various conditions. According to the Marcus theory, solvent parameters have a significant influence on the observed kinetics. Temperature-dependent measurements, such as those used to obtain activation parameters, are especially strongly affected by these influences. Typically, all solvent parameters (e.g., viscosity, density, refractive index, dielectric constant) change systematically as the temperature changes. Therefore, the analysis of kinetic data is difficult. One way to overcome this difficulty is to apply solvent mixtures. In this paper, a detailed description is provided of how one single solvent parameter can be changed while the all others are kept nearly constant. Three different approaches were taken: First, the viscosity was altered at a constant temperature while maintaining the refractive index and dielectric constant. Second, dielectric constant was altered at a constant temperature while maintaining a constant viscosity and refractive index. Finally, all parameters were maintained while the temperature was varied. The latter approach offers the possibility to study activation parameters, e.g., by applying the Arrhenius equation, regardless of the viscosity changes that occur when the reaction temperature increases.

Thermogravimetric Studies of Dehydration of the Cellulose Acetate Layer in UAM-100, UAM-150, and MGA-95 Composite Films

This paper presents an analytical overview of the study of the kinetic and physicochemical characteristics of composite membrane films. UAM-100, UAM-150, and MGA-95 composite films have been studied using thermogravimetry in the temperature range from 30 to 300°C. A kinetic analysis of experimental data by the Freeman–Carroll method is carried out. It was found that hydrated water for all the studied semi-permeable films evaporates in the temperature range from ~95 to ~180°C. Comparison of the ratios of the amount of removed water in the film samples correlates with the geometric parameters of the pores. The values of the activation energy and the pre-exponential factor (E = 26.9 kJ/mol and ln(A ≈ 6.3 (min–1)) in the range 0.2 < α < 0.7 of the degree of dehydration indicate the same regularity in the distribution of water molecules in the polymolecular layer for all composite films. The high dehydration values, e.g., for a sample of a composite semipermeable film MGA-95 at the temperature of the maximum on the thermogravimetry curve (Tmax = 169.6°C) indicate that water molecules form hydrogen bonds both with ionogenic groups of cellulose acetate and with each other.

Design of Copper Microfabricated Potentiometric Sensor for in‐line Monitoring of Neostigmine Degradation Kinetics

AbstractThe quality of pharmaceutical products is critical for human health. Drug development requires tools to assess the presence of degradation products and contaminants during the manufacturing and storage processes. Accelerated stress degradation and kinetic studies play a vital role in predicting final product stability. This work describes the design of potentiometric sensor based on copper microfabricated electrodes for in‐line tracking the degradation kinetics of neostigmine. The proposed electrochemical technique provides a continuous profile for the hydrolysis of NEO under different temperatures and pH. The hydrolysis activation energy was found to be 18.88 kcal mol−1 which was aligned with the reported hydrolysable ester values. Consequently, the kinetic data analysis is crucial to predict the optimum analysis and storage conditions.

Toward Molecular Cooperation by De Novo Peptides.

Theoretical models of the chemical origins of life depend on self-replication or autocatalysis, processes that arise from molecular interactions, recruitment, and cooperation. Such models often lack details about the molecules and reactions involved, giving little guidance to those seeking to detect signs of interaction, recruitment, or cooperation in the laboratory. Here, we develop minimal mathematical models of reactions involving specific chemical entities: amino acids and their condensation reactions to form de novo peptides. Reactions between two amino acids form a dipeptide product, which enriches linearly in time; subsequent recruitment of such products to form longer peptides exhibit super-linear growth. Such recruitment can be reciprocated: a peptide contributes to and benefits from the formation of one or more other peptides; in this manner, peptides can cooperate and thereby exhibit autocatalytic or exponential growth. We have started to test these predictions by quantitative analysis of de novo peptide synthesis conducted by wet-dry cycling of a five-amino acid mixture over 21days. Using high-performance liquid chromatography, we tracked abundance changes for >60 unique peptide species. Some species were highly transient, with the emergence of up to 17 new species and the extinction of nine species between samplings, while other species persisted across many cycles. Of the persisting species, most exhibited super-linear growth, a sign of recruitment anticipated by our models. This work shows how mathematical modeling and quantitative analysis of kinetic data can guide the search for prebiotic chemistries that have the potential to cooperate and replicate.

Titrationanalysis: A Tool for High-throughput Analysis of Binding Kinetics Data for Multiple Label-Free Platforms

Label-free techniques such as Surface Plasmon Resonance (SPR) and Biolayer Interferometry (BLI) are powerful biophysical tools widely used in academia and biopharmaceutical industry for the characterization of biomolecular interactions. Here we have built a new tool named the TitrationAnalysis as a package for the Mathematica programming system to analyze biomolecular interaction kinetics data. The core function of the TitrationAnalysis tool utilizes the non-linear curve-fitting module available in the Mathematica programming system.

Extraction of Nb and Ta from a coltan ore from South Kivu in the DRC by alkaline roasting – thermodynamic and kinetic aspects

An alkaline roasting of a coltan bearing ore from the Numbi deposit (South Kivu, the DRC) was investigated with particular focus on the extraction kinetics of Ta and Nb. Isothermal roasting experiments were carried out to study the effects from KOH to ore mass ratio, particle size and roasting temperature on the degree of Ta and Nb recoveries. The roasting efficiency was found to be affected by all the parameters being studied with their optimal values being found as following: particle size range +75–45 µm, KOH to ore ratio 3/1, roasting temperature 550 °C and roasting duration of 1 h. Under these conditions, 80% of Ta and 87% of Nb were recovered from the ore. The kinetic data analysis by different kinetic models indicated that the caustic potash roasting of the Numbi coltan ore is governed by a chemical reaction at particle surface. The apparent activation energies for Ta and Nb were estimated as 40.9 and 46.1 kJ.mol-1 respectively. The obtained results demonstrated that it is possible to bring Ta and Nb into solution without using hydrofluoric acid and deliver a pregnant leach solution (PLS) suitable for downstream treatment.

Mapping Distinct Sequences of Structure Formation Differentiating Multiple Folding Pathways of a Small Protein

To determine experimentally how the multiple folding pathways of a protein differ, in the order in which the structural parts are assembled, has been a long-standing challenge. To resolve whether structure formation during folding can progress in multiple ways, the complex folding landscape of monellin has been characterized, structurally and temporally, using the multisite time-resolved FRET methodology. After an initial heterogeneous polypeptide chain collapse, structure formation proceeds on parallel pathways. Kinetic analysis of the population evolution data across various protein segments provides a clear structural distinction between the parallel pathways. The analysis leads to a phenomenological model that describes how and when discrete segments acquire structure independently of each other in different subensembles of protein molecules. When averaged over all molecules, structure formation is seen to progress as α-helix formation, followed by core consolidation, then β-sheet formation, and last end-to-end distance compaction. Parts of the protein that are closer in the primary sequence acquire structure before parts separated by longer sequence.

Removal of Rhodamine 6G from Industrial Wastewater Using Combination Approach of Adsorption Followed by Sonication

The present work reports a combination approach involving adsorption followed by ultrasonic degradation for the treatment of Rhodamine 6G (R6G) containing wastewater. The main benefit of the combination treatment approach is that adsorption concentrates the effluent which is treated in the subsequent step of ultrasonic degradation in a cost-effective manner based on lower treatment volumes. In the adsorptive removal, INDION 225Na Resin has been used as adsorbent. A study into the effect of different adsorption parameters revealed that the optimum contact time required for the equilibrium was 20 min. It was also established that the optimum values of pH and resin loading for maximum dye removal as 77.6% were 12 and 6 g L−1, respectively. Analysis of different adsorption isotherm models for equilibrium established that the Langmuir model is the best-fitted model with the correlation coefficient value (R2) as 0.99. Similarly, kinetic data analysis revealed that pseudo-second-order model explained the system precisely based on a higher value of R2. For the case of ultrasonic degradation, it was established that a pH of 12 and a temperature of 50 °C were the best treatment conditions. Overall, it was demonstrated that the proposed combination of adsorption and sonication is an efficient approach for the treatment of R6G containing wastewater.

Проблеми аварійної динаміки теплогідравлічних процесів у перспективних реакторах із надкритичними параметрами легководного теплоносія

A complex of scientific and technical problems directly related to the priority of ensuring the operational safety and reliability of the cores of promising power nuclear reactors with supercritical thermodynamic parameters of a light-water coolant is systematized. The problems of implementation of effective heat removal from the surface of fuel elements and ensuring reliable calculation of thermal and hydrodynamic processes in turbulent flows of a supercritical coolant are considered. The main attention in the consideration of thermohydraulic processes in the near-critical region is paid to the conditionality of the physical nature of these processes by the regularities of transformation of the thermophysical properties of the coolant with changes in its temperature. It is noted that these phenomena have not been sufficiently studied and that modern designers of nuclear reactors with supercritical parameters practically do not have physically substantiated adequate ideas about the physical nature of an emergency mode of deteriorated heat transfer, which can arise unpredictably on the surface of a fuel element even if it is continuously cooled by a coolant with supercritical parameters. It is only known that the main physical sign of the occurrence of this emergency mode is a significant deterioration in heat transfer, which becomes abnormally low, but the physical reasons for such a dangerous anomaly are currently unknown. Based on the analysis of the molecular kinetics data of the near-wall coolant layer, it was proposed to consider such facts of an emergency decrease in the heat transfer intensity due to the appearance of an unknown pseudo-film boiling regime on the fuel element surface. In this context, it is shown that under the conditions under study, macromolecular assemblies in the form of pseudo-vapor formations can appear on the heat exchange surface, as a result of which the heat transfer on the fuel element surface is disturbed. Using experimental data, it is shown that there is a rather deep physical analogy between heat transfer in a supercritical thermodynamic system and the subcooled boiling process at subcritical parameters of the coolant. The dynamics of changes in the characteristics of the experimental spectra of acoustic emission of pseudo-boiling with a sequential increase in the thermal load is analyzed and it is shown that these phenomena can, in principle, be used in promising systems for diagnostic monitoring of reactors with supercritical parameters for early detection of the initial phases of pseudo-boiling and prompt prevention of the occurrence of emergency modes of deteriorated heat transfer

Enhanced accessibility and hydrophobicity of amyloidogenic intermediates of the β2-microglobulin D76N mutant revealed by high-pressure experiments

β2-Microglobulin (β2m) is the causative protein of dialysis-related amyloidosis. Its unfolding mainly proceeds along the pathway of NC →UC ⇄ UT, whereas refolding follows the UT → IT (→NT) →NC pathway, in which N, I, and U are the native, intermediate, and unfolded states, respectively, with the Pro32 peptidyl-prolyl bond in cis or trans conformation as indicated by the subscript. It is noted that the IT state is a putative amyloidogenic precursor state. Several aggregation-prone variants of β2m have been reported to date. One of these variants is D76N β2m, which is a naturally occurring amyloidogenic mutant. To elucidate the molecular mechanisms contributing to the enhanced amyloidogenicity of the mutant, we investigated the equilibrium and kinetic transitions of pressure-induced folding/unfolding equilibria in the wild type and D76N mutant by monitoring intrinsic tryptophan and 1-anilino-8-naphthalene sulfonate fluorescence. An analysis of kinetic data revealed that the different folding/unfolding behaviors of the wild type and D76N mutant were due to differences in the activation energy between the unfolded and the intermediate states as well as stability of the native state, leading to more rapid accumulation of IT state for D76N in the refolding process. In addition, the IT state was found to assume more hydrophobic nature. These changes induced the enhanced amyloidogenicity of the D76N mutant and the distinct pathogenic symptoms of patients. Our results suggest that the stabilization of the native state will be an effective approach for suppressing amyloid fibril formation of this mutant.

Large-Grained Cylindrical Block Copolymer Morphologies by One-Step Room-Temperature Casting.

We report a facile method of ordering block copolymer (BCP) morphologies in which the conventional two-step casting and annealing steps are replaced by a single-step process where microphase separation and grain coarsening are seamlessly integrated within the casting protocol. This is achieved by slowing down solvent evaporation during casting by introducing a nonvolatile solvent into the BCP casting solution that effectively prolongs the duration of the grain-growth phase. We demonstrate the utility of this solvent evaporation annealing (SEA) method by producing well-ordered large-molecular-weight BCP thin films in a total processing time shorter than 3 min without resorting to any extra laboratory equipment other than a basic casting device, i.e., spin- or blade-coater. By analyzing the morphologies of the quenched samples, we identify a relatively narrow range of polymer concentration in the wet film, just above the order–disorder concentration, to be critical for obtaining large-grained morphologies. This finding is corroborated by the analysis of the grain-growth kinetics of horizontally oriented cylindrical domains where relatively large growth exponents (1/2) are observed, indicative of a more rapid defect-annihilation mechanism in the concentrated BCP solution than in thermally annealed BCP melts. Furthermore, the analysis of temperature-resolved kinetics data allows us to calculate the Arrhenius activation energy of the grain coarsening in this one-step BCP ordering process.

Scale-Invariant Structure of the Seismic Kinetics in Strongly Nonequilibrium Medium

Results of the scaling analysis of the waiting time series for seismic events of the 2019 Ridgecrest earthquake sequence in East California have been presented. It has been shown that the waiting time series before a strong earthquake with a magnitude of M = 7.1 acquires a scale-invariant structure. A reason for the appearance of the statistical self-similarity in the waiting time series is the transition of the medium in the focal region to a strongly nonequilibrium state. The result can be interpreted as the appearance of a temporal dissipative structure in the process of seismic kinetics. It has been proposed to use the scaling analysis of the seismic kinetic data to monitor the current state of the seismogenerating medium.

Ethosomal Gel Formulation of Alpha Phellandrene for the Transdermal Delivery in Gout.

Purpose: Purpose was to improve the skin compatibility and permeability of alpha phellandrene through an ethosomal gel formulation for the treatment of gout; as the oral use of the drug is reported to cause gastrointestinal disturbances and toxicities. Methods: Alpha phellandrene loaded ethosomal formulation (APES) was prepared by cold method for the treatment of gout. APES were loaded into carbopol gel (APEG) by dispersion method. Physico-chemical characterizations of the APES were done by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) etc. In vitro release, permeation, haemo-compatibility and anti-inflammatory studies were conducted. Results: APES showed a particle size of 364.83 ± 45.84 nm. The entrapment efficiency of the optimized formulation is found as 95.06 ± 2.51%. Hemolysis data indicated that APES does not cause any significant hemolysis. In vitro drug release studies were carried out using dialysis membrane technique and the amount of drug released from APES & APEG is found to be 95% and 94.21% respectively after 5 and6 hours. Kinetic data analysis revealed that APES & APEG follows first order and zero order release kinetics, respectively. The anti-inflammatory activity studies of the formulation are done by estimating its inhibitory effects on cyclooxygenase II (COX) II, lipoxygenase-5 (LOX-5), Myeloperoxidase (MPO), Inducible nitric oxide synthase (INOS) & cellular nitrite level using RAW 264.7 cells. The significant inhibition in the activities of the enzymes implies the anti-inflammatory activity of the formulations. Skin permeation study was carried out using porcine skin and revealed that the permeation of alpha phellandrene is increased from APES & APEG when compared with alpha-phellandrene solution (APS). Skin deposition study of APS, APES & APEG revealed better drug deposition from APEG (48.799 ± 1.547µg/cm2 ) after 24 hours when compared with APS & APES. Conclusion: Overall results indicate that the ethosomal formulation of alpha phellandrene through transdermal route is an effective alternative for oral use of the drug.

Enhanced arsenate removal by Fe-impregnated canola straw: assessment of XANES solid-phase speciation, impacts of solution properties, sorption mechanisms, and evolutionary polynomial regression (EPR) models.

The impact of arsenic (As) contamination of water is an ongoing concern worldwide with As released from anthropogenic activities including mining and agriculture. Biosorption is a promising As treatment methodology used currently for arsenate (As(V)) sorption from water. The biosorbent was developed by a simple and inexpensive treatment of coating of canola straw particles with iron hydroxides. The modification procedure was optimized with consideration of the concentration of iron solution, pH of modification process, and sonication time. A higher concentration of iron and lower pH led to an improved sorption capacity of the iron-loaded canola straw (ICS), while impacts of sonication time were not conclusive. Pareto analyses indicated that the magnitude of the effect of the pH was higher than that of the iron concentration. Overall, the maximum As(V) sorption capacity of the ICS was 5.5 mg/g for an 0.25 M FeCl3 solution concentration at pH 3. Analysis of kinetic data showed that the sorption processes of As(V) followed pseudo-second order and Elovich mechanisms, while sorption isotherm data were best represented by Freundlich and Temkin isotherm models. Studying the effect of ionic strength using NaCl suggested that the inner-sphere complex was the probable sorption mechanism. The thermodynamic parameters including ΔS°, ΔH°, and ΔG° showed that the As(V) sorption was thermodynamically favorable and spontaneous. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that no reaction to As(III) occurred during the sorption of As(V) using the optimum ICS biosorbent. The evolutionary polynomial regression (EPR) approach was able to closely match predicted vs. experimental sorption capacities (R2 = 0.95). Overall, the improved understanding of the biosorbent's capability for removal of As(V) will be beneficial for assessment of its use for treatment of various water and wastewater matrices. In addition, knowledge gained from this research can assist in the understanding of sorption capacities of a variety of other biosorbents.