scholarly journals Sorption of Organic Pollutants onto Soils: Surface Diffusion Mechanism of Congo Red Azo Dye

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1639 ◽  
Author(s):  
Camelia Smaranda Bețianu ◽  
Petronela Cozma ◽  
Mihaela Roșca ◽  
Elena-Diana Comăniță Ungureanu ◽  
Ioan Mămăligă ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Congo Red ◽  
Diffusion Mechanism ◽  
Sorption Process ◽  
Intraparticle Diffusion ◽  
Complex Nature ◽  
Film Diffusion ◽  
Rate Limiting Step ◽  
Diffusion Analysis ◽  
Pass Through

For the protection of human and ecological receptors from the effects of soil pollution with chemical compounds, we need to know the behavior and transport of pollutants in soil. This work investigated the Congo red (CR) acid dye sorption on three natural soils collected from central and northeastern regions of Romania, symbolized as IS-65, IS-T, and MH-13. To define the mechanism of sorption and identify the rate governing step, various diffusion models such as Weber–Morris intraparticle diffusion, Boyd, film and pores diffusion, and mass transfer analysis have been verified. The intraparticle diffusion analysis of Congo red sorption onto soils has been described by a multi-linear plots, showing that the sorption process takes place by surface sorption and intraparticle diffusion in macro, meso, and micropores. The values of intraparticle diffusion coefficient kid increased with any rise of the initial concentration of pollutant. The results show that the values of pore diffusion coefficient (Dp) and film diffusion coefficient (Df) are found to be from 10−8 to 10−10 cm2 s−1, indicating that film diffusion influences the sorption rate limiting step. The intraparticle diffusion analysis shows that the plots did not pass through the origin and have two distinct parts, confirming that intraparticle diffusion is not the single determining mechanism involved in the sorption of Congo red on soils IS-65, IS-T, and MH-13. The results revealed that the sorption process has a complex nature, since both external diffusion and internal diffusion are involved in the sorption of CR from solution onto the investigated soils.

Kinetics of removal of zinc ions from aqueous solutions by a modified acrylnitrile copolymer

1999 ◽  
Vol 39 (8) ◽  
pp. 139-146
Author(s):  
R. Y. Stefanova
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Sorption Process ◽  
Intraparticle Diffusion ◽  
Zinc Ions ◽  
Sorption System ◽  
Modified Polymer ◽  
Rate Limiting Step ◽  
High Sorption ◽  
Kinetics Of

The kinetics of removal of zinc ions from aqueous solutions by a modified acrylnitrile copolymer containing carboxyl and amino groups has been investigated. The dependence of the rate of removal on the intensity of stirring, the size of the sorbent's particles, the initial concentration of metal ions and the temperature of the solution have been established. Attempts have been made to identify the rate limiting step and to determine the batch kinetic parameters. The limiting conditions of the transition from external to intraparticle diffusion step of mass transfer in a sorption system have been determined. The coefficients of intraparticle diffusion and the energy of activation of the sorption process have been established. The data obtained in this work show that the modified polymer with a high sorption capacity and very good kinetic characteristics can be successfully used for removal of heavy metal ions from water solutions and industrial wastewaters.

scholarly journals Kinetics and Thermodynamics of Adsorption Process Using A Spent-FCC Catalyst

2018 ◽  
Vol 7 (4.5) ◽  
pp. 284
Author(s):  
Zakir Hussain ◽  
Rakesh Kumar ◽  
Deepa Meghavathu
Keyword(s):  
Intraparticle Diffusion ◽  
Batch Adsorption ◽  
Sudden Increase ◽  
Dye Molecules ◽  
Film Diffusion ◽  
Linear Set ◽  
Intraparticle Diffusion Model ◽  
Rate Determining Step ◽  
Straight Line ◽  
Pass Through

Adsorption is potentially an attractive technique for the treatment of wastewater containing dyes. In the present work, spent fluid catalytic cracking catalyst (SFCC), a petroleum refinery waste was explored as a novel adsorbent and report its adsorption capability for the first time in the literature. Batch adsorption studies were carried out to remove methylene blue (MB) dye using SFCC. The equilibrium data was modeled using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. Also, the van’t Hoff equation was used to obtain the thermodynamic contributions of the process. Results show that the plot of intraparticle diffusion model (considering only film diffusion) has less R2 value (0.887); it seems that the plot is nonlinear. Hence, the data points were represented by a double linear set of equations (lines) considering both pore & film diffusion. In the first straight line, the sudden increase in slope signifies that the dye molecules were transported to the external surface of the adsorbent through film diffusion. The second straight line signifies that the dye molecules diffused through the pores. The portion which does not pass through the origin indicates that the pore diffusion is the only rate-determining step for the transport of MB onto SFCC.  

1H NMR characterisation of the diffusional properties of methanogenic granular sludge

1999 ◽  
Vol 39 (7) ◽  
pp. 187-194 ◽  
Author(s):  
P. Lens ◽  
F. Vergeldt ◽  
G. Lettinga ◽  
H. Van As
Keyword(s):  
Diffusion Coefficient ◽  
Relaxation Time ◽  
Bacterial Cell ◽  
Granular Sludge ◽  
T2 Relaxation ◽  
Self Diffusion ◽  
Diffusion Analysis ◽  
S Matrix ◽  
Granular Matrix ◽  
Pfg Nmr

The diffusive properties of mesophilic methanogenic granular sludge have been studied using diffusion analysis by relaxation time separated pulsed field gradient nuclear magnetic resonance (DARTS PFG NMR) spectroscopy. NMR measurements were performed at 22°C with 10 ml granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Spin-spin relaxation (T2) time measurements indicate that three 1H populations can be distinguished in methanogenic granular sludge beds, corresponding to water in three different environments. The T2 relaxation time measurements clearly differentiate the extragranular water (T2 ≈ 1000 ms) from the water present in the granular matrix (T2 = 40-100 ms) and bacterial cell associated water (T2 = 10-15 ms). Self-diffusion coefficient measurements at 22°C of the different 1H-water populations as the tracer show that methanogenic granular sludge does not contain one unique diffusion coefficient. The observed distribution of self-diffusion coefficients varies between 1.1 × 10−9 m2/s (bacterial cell associated water) and 2.1 × 10−9 m2/s (matrix associated water).

scholarly journals Methanesulphonic acid movement in solid ice cores

2004 ◽  
Vol 39 ◽  
pp. 540-544 ◽  
Author(s):  
Barbara T. Smith ◽  
Tas D. Van Ommen ◽  
Mark A. J. Curran
Keyword(s):  
Diffusion Coefficient ◽  
Biological Activity ◽  
Sea Ice ◽  
Diffusion Mechanism ◽  
Ice Core ◽  
Ice Cores ◽  
East Antarctica ◽  
The Core ◽  
Central Value

AbstractMethanesulphonic acid (MSA) is an important trace-ion constituent in ice cores, with connections to biological activity and sea-ice distribution. Post-depositional movement of MSA has been documented in firn, and this study investigates movement in solid ice by measuring variations in MSA distribution across several horizontal sections from an ice core after 14.5 years storage. The core used is from below the bubble close-off depth at Dome Summit South, Law Dome, East Antarctica. MSA concentration was studied at 3 and 0.5 cm resolution across the core widths. Its distribution was uniform through the core centres, but the outer 3 cm showed gradients in concentrations down to less than half of the central value at the core edge. This effect is consistent with diffusion to the surrounding air during its 14.5 year storage. The diffusion coefficient is calculated to be 2 ×10–13 m2 s–1, and the implications for the diffusion mechanism are discussed.

Molecular Dynamics Simulation Study of the Effect of Ni, Fe, Cu on Cryolite Molten Salt System 78% Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%-Al2O3

2021 ◽  
Vol 1026 ◽  
pp. 39-48
Author(s):  
Han Bing He ◽  
Yu Si Wang ◽  
Ze Xiang Luo ◽  
Jing Zeng
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Molten Salt ◽  
Diffusion Mechanism ◽  
Research Work ◽  
Dynamics Simulation ◽  
Salt System ◽  
Electrolyte System ◽  
Aluminum Composite ◽  
Molten Salt System

The effect of different additives Ni, Fe, Cu on the structure and properties of electrolyte system 78% Na3AlF6- -9.5%AlF3-5.0%CaF2-7.5%Al2O3 at 1200K and 1.01Mpa was studied by molecular dynamics method. The radial distribution function, coordination number, diffusion coefficient, conductivity, and viscosity of the system were discussed in detail. The results demonstrated that the order of the self-diffusion coefficient of ions in the electrolyte system is: Na+ > F- > O2- > Ca2+ >Al3+. The addition of Ni and Fe connected the free aluminum composite ion groups in the system through fluorine bridges, which enhanced the interaction between Al3+ and Al3+. The addition of Cu weakened the interaction between Al3 + and Al3+ and the F-. The interaction between Al3+ and Na+, [AlF7]4- ionic groups might appeared in the melt system. After adding NiO, Fe2O3, and Cu, the electrical conductivity of the system increased, and the viscosity decreased. The research work revealed the influence of Ni, Fe, Cu on the ion existence form, mobility, inter-ion interaction and diffusion mechanism of cryolite molten salt system, which has important guiding significance for aluminum electrolysis production.

Surface Separation Equilibria and Dynamics of Cationic Dye Loaded onto Citric Acid and Sodium Hydroxide Treated Eggshells

2018 ◽  
Vol 17 (1) ◽  
Author(s):  
Elisha A. Adeniji ◽  
Temitope O. Abodunrin ◽  
Temitope A. Ogunnupebi ◽  
Babatunde A. Koiki ◽  
Abimbola M. Olatunde ◽  
...  
Keyword(s):  
Citric Acid ◽  
Diffusion Mechanism ◽  
Experiment Data ◽  
Surface Separation ◽  
Rate Limiting Step ◽  
Monolayer Adsorption ◽  
Delta G ◽  
Rate Limiting ◽  
Best Fit ◽  
Adsorption Systems

AbstractThis research enthusiastically highlights the bio-adsorption of methylene blue (MB) by local, poultry, NaOH and citric acid modified ubiquitous eggshell (LES, NLES, CLES, PES, NPES and CPES) adsorbents. The microstructures of these adsorbents indicated that they had some surface functional moieties that were responsible for the adsorption of MB. The Langmuir isotherm and PSO model best fit the experiment data. The largest Langmuir monolayer adsorption capacity${q_{max}}$, was 242.47 mg/g, with the largest MB initial concentration of 400 mg/L. This was a clear indication and a confirmation that MB adsorption by the powdered eggshells was chemisorptive. Moreover, the values of$F$, the thickness of the boundary layer/film were$\gt 0$, showing that the rate limiting step for the adsorption process was controlled by more than one diffusion mechanism. The values of$\Delta {G^\circ }$for the adsorption of MB by the adsorbents indicated that the adsorption reactions were all non-feasible and non-spontaneous. The values for$\Delta {S^\circ }$(J/K/mol) for LES, NLES and CPES for the uptake of MB showed decrease in the chaos or degree of randomness of the adsorption reactions, and the reverse was the case for PES, NPES and CLES for the uptake of MB, which showed increase in the chaos or degree of randomness of the adsorption. The adsorption of MB by LES, NLES and CPES gave$\Delta {H^\circ }$(kJ/mol) values which were indicative of endothermic nature of the adsorption systems, and the reverse was the case for the uptake of MB by PES, NPES and CLES, which was indicative of the exothermic nature of the adsorption systems.

Biosorption of Eosin by Chemically Modified Peanut Husk

2011 ◽  
Vol 233-235 ◽  
pp. 439-443
Author(s):  
Ying Hua Song ◽  
Sheng Ming Chen
Keyword(s):  
Freundlich Isotherm ◽  
Sorption Process ◽  
Intraparticle Diffusion ◽  
Transfer Model ◽  
Experimental Conditions ◽  
Isotherm Equation ◽  
Chemically Modified ◽  
Pseudo Second Order ◽  
Uptake Studies ◽  
Rate Controlling Step

The sorption of eosin by peanut husk, which was chemically modified by formaldehyde in acidic medium was studied with variation in the parameters of contact time, pH, initial eosin concentration and temperature. They were used for equilibrium sorption uptake studies with eosin. The results indicate that sorption equilibrium could be well described by the Freundlich isotherm equation. The sorption followed the pseudo-second order model. The mass transfer model as intraparticle diffusion was applied to the experimental data to examine the mechanisms of the rate controlling step. It was found that the intraparticle diffusion is becoming the significant controlling step under the experimental conditions. The thermodynamic constants of the sorption process were also evaluated, which suggest an endothermic physical sorption process which runs spontaneously.

Modeling the Diffusion Mechanism and the Reaction Kinetics for the Photocatalytic Degradation of Acid Red 151 Aqueous Solutions by ZnO: Comparison of Linear and Non-Linear Methods

2007 ◽  
Vol 10 (2) ◽  
Author(s):  
K. Vasanth Kumar ◽  
K. Porkodi
Keyword(s):  
Aqueous Solution ◽  
Diffusion Coefficient ◽  
Aqueous Solutions ◽  
Photocatalytic Degradation ◽  
Reaction Kinetics ◽  
Diffusion Mechanism ◽  
Batch Processes ◽  
Average Diffusion Coefficient ◽  
Diffusion Controlled ◽  
Average Diffusion

AbstractBatch processes were carried out for the photocatalytic degradation of Acid Red 151 from its aqueous solution using ZnO catalyst at different initial dye concentrations. The process was found to be diffusion controlled for the first 15-20 minutes (before irradiation) with an average diffusion coefficient of 6.759 × 10

scholarly journals Microstructures of SiO2 Scales Formed on MoSi2

2006 ◽  
Vol 522-523 ◽  
pp. 595-602 ◽  
Author(s):  
Kazuya Kurokawa ◽  
Daichi Goto ◽  
Jyunichi Kuchino ◽  
Akira Yamauchi ◽  
Tamaki Shibayama ◽  
...  
Keyword(s):  
Growth Rate ◽  
Diffusion Coefficient ◽  
Oxide Scale ◽  
Oxidation Rate ◽  
Diffusion Mechanism ◽  
Lattice Diffusion ◽  
Oxide Scales ◽  
Amorphous Sio2 ◽  
O2 Diffusion ◽  
Diffusion Coefficient Of Oxygen

The microstructures of oxide scales formed on MoSi2 at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO3 and crystallization of amorphous SiO2 scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO2 with small amounts of fine MoO3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO2. Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO2. It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O2 diffusion to lattice diffusion of O2- through SiO2. In addition, the diffusion coefficient of oxygen was estimated from the growth rate of SiO2 scale.

scholarly journals Chlorates(VII) removal on Dowex™PSR-2 resin

2016 ◽  
Vol 71 (1) ◽  
pp. 105
Author(s):  
Dorota Kołodyńska ◽  
Aleksandra Łyko ◽  
Marzena Gęca ◽  
Zbigniew Hubicki
Keyword(s):  
Solution Concentration ◽  
Intraparticle Diffusion ◽  
Optimum Conditions ◽  
Order Model ◽  
Experimental Conditions ◽  
Freundlich Model ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Pseudo Second Order ◽  
Rate Limiting

<p>Lately there has been observed the increased presence of chlorates(VII) in the natural environment which can affect human health negatively. Therefore the removal of chlorate(VII) ions using the gel type resin functionalized with the tri-n-butyl ammonium (Dowex<sup>™</sup>PSR-2) from waters was studied. The main aim was to evaluate the effects of experimental conditions including contact time, initial solution concentration, pH and temperature on chlorate(VII) ions removal as well as the anion exchanger properties on chlorate(VII) ions sorption. It was found that only the pseudo second order model described the experimental data well and the intraparticle diffusion was not the rate-limiting step. According to the Freundlich model, the q<sub>e</sub> value was to be 69.26 mg/g at optimum conditions (pH 7.0 at 25 <sup>o</sup>C).<strong></strong></p>

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