Unsteady state diffusion-adsorption-reaction. Selectivity of consecutive reactions on porous catalyst particles

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Juan Rafael García ◽  
Claudia María Bidabehere ◽  
Ulises Sedran
Keyword(s):  
Adsorption Capacity ◽  
Transient State ◽  
Fluid Phase ◽  
Concentration Profiles ◽  
Adsorption Effect ◽  
Porous Catalyst ◽  
Diffusion Limitations ◽  
Consecutive Reactions ◽  
Secondary Reactions ◽  
The Relationship

Abstract The simultaneous processes of diffusion, adsorption and chemical reaction, considering the transient nature of the concentration profiles in the porous catalyst particles as applied to the analysis of consecutive reactions A → B → C, where reactant and products are subjected to diffusion limitations, are analyzed. The concentrations of the desired intermediate product B, both the average in the catalytic particles and the observed in the fluid phase, initially increase as a function of time until reaching a maximum value and then decline due to the consumption in the secondary reaction. Due to the diffusion restrictions and the adsorption effect, the observed selectivities, calculated from the concentrations in the fluid phase, are always lower than the true selectivities, which also include the amounts accumulated in the particles. Besides depending on the rates of the primary and secondary reactions, the observed yield of product B also depends on the system adsorption capacity, i.e., the relationship between the capacities of the particles and the external fluid phase to accumulate the reactant species. For a given relationship between the intrinsic rates of the primary and secondary reactions, the higher the system adsorption capacity, the lower the observed yield of B as a function of conversion. The relationship between the observed yield of B and the observed conversion of A, calculated considering the transient state of the concentration profiles in the particles, is coincident with that predicted by classical models, which assume the steady state in the particles, when the system adsorption capacity is extremely small.

Adsorption of Cu(II) Ions from an Aqueous Solution by Cross-Linked Carboxymethyl Konjac Glucomannan

2011 ◽  
Vol 239-242 ◽  
pp. 2310-2316 ◽  
Author(s):  
Chun Mei Niu ◽  
Shao Ying Li ◽  
Dong Huang
Keyword(s):  
Adsorption Capacity ◽  
Copper Nitrate ◽  
Konjac Glucomannan ◽  
Ion Adsorption ◽  
Adsorption Time ◽  
Isotherm Equation ◽  
Langmuir Isotherm Equation ◽  
Effects Of Ph ◽  
The Relationship ◽  
Carboxymethyl Konjac Glucomannan

Crosslinked Carboxymethyl Konjac Glucomannan(CMKGM) with substitution degrees ofcarboxymethyl group（DS）0.265, 0.457 and 0.586 were prepared through reaction of monochloroacetic acid, konjac glucomannan(KGM) and epichlorohydrin and used to adsorb Cu(II) from the aqueous solutions of copper nitrate. The effects of pH, adsorbent dose, initial concentration of Cu(II), adsorption time and temperature on adsorption capacity were investigated. The results showed that adsorption capacity increased with an increasing DS of the carboxymethyl groups. Equilibrium adsorption time was 20 min or so and was independent on DS. The adsorption followed Langmuir isotherm equation. Ligand ion adsorption between carboxymethyl group and Cu(II) was thought to be predominate in the process of adsorption according to the relationship between DS and thermodynamic parameters. CMKGM can be used as cheaper and more effective adsorbents.

Robot end effector based on electrostatic adsorption for manipulating garment fabrics

2021 ◽  
pp. 004051752110418
Author(s):  
Wenqian Feng ◽  
Yanli Hu ◽  
Xin rong Li ◽  
Lidong Liu
Keyword(s):  
Adsorption Capacity ◽  
Structural Parameters ◽  
Garment Industry ◽  
Industrial Robots ◽  
Force Model ◽  
Adsorption Effect ◽  
Electrostatic Adsorption ◽  
End Effector ◽  
Application Range ◽  
Capacity Model

To improve the effectiveness of industrial robots in the textile and garment industry, it is necessary to expand the application range of electrostatic adsorption end effectors and solve the problem of automatically grasping and transferring fabrics during garment processing. Taking weft-knit fabric as an example, this paper begins by analyzing the factors that influence the electrostatic adsorption capacity, and then constructing an electrostatic adsorption capacity model based on the fabric characteristics. Next, the shape arrangement and structural parameters of the electrode plate are optimized by taking the electrostatic adsorption force model and maximizing the adsorption force per unit area. Finally, the adsorption effect of the electrostatic adsorption end effector is verified by simulation and experiment. The verification results show that the electrode with a comb-shaped arrangement and optimized structural parameters can adsorb clothing fabric well and meets the requirements of clothing automated production lines. This study provides a new method for solving the problem of automatically grasping and transferring fabrics and provides technical support for improving automation in the garment industry.

Synthesis of Mesoporous Silica and its Adsorption Properties for Chloride Ions

2019 ◽  
Vol 956 ◽  
pp. 282-293
Author(s):  
Guo Jun Ke ◽  
Tian Shi Liu ◽  
Peng Fei Yang ◽  
Xiao Lin Tang
Keyword(s):  
Mesoporous Silica ◽  
Specific Surface ◽  
Adsorption Capacity ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Adsorption Properties ◽  
Adsorption Effect ◽  
Silica Materials ◽  
Mesoporous Silica Materials ◽  
Mcm 41

A series of mesoporous silica materials (SBA-15, MCM-41, KIT-6) with different pore structures and properties were synthesized and characterized by means of small angle X-ray scattering, transmission electron microscopy, infrared spectroscopy and nitrogen adsorption-desorption. The adsorption properties of three mesoporous silica materials for chlorine ions in aqueous solution were investigated. The results show that SBA-15, MCM-41 with two-dimensional hexagonal structure has a better adsorption effect on chloride ion than KIT-6 With cubic core structure, and MCM-41 with larger specific surface area and smaller pore size has better adsorption effect on chloride ion than on SBA-15. The specific surface area of MCM-41 is 1036 m2/g, and the The adsorption kinetics accords with the pseudo-second-order kinetic model, and the adsorption isotherm is more consistent with the Langmuir isotherm model. The optimum operating conditions for MCM-41 to adsorb chloride ions are as follows: temperature 55 °C, pH 6, adsorption time 2 h, Cl- concentration 0.01 mol/L (584 mg/L) and adsorbent concentration 1.0 g/L. Under these conditions, the adsorption capacity of MCM-41 to chloride ions is greatly enhanced, and the maximum adsorption capacity is 188.18 mg/g.

Insights into the mechanism of methylene blue removed by novel and classic biochars

2019 ◽  
Vol 79 (8) ◽  
pp. 1561-1570
Author(s):  
Wei Chen ◽  
Fengting Chen ◽  
Bin Ji ◽  
Lin Zhu ◽  
Hongjiao Song
Keyword(s):  
Methylene Blue ◽  
Adsorption Capacity ◽  
Ph Value ◽  
Low Cost ◽  
Underlying Mechanism ◽  
Maximum Adsorption Capacity ◽  
Experimental Conditions ◽  
Average Pore ◽  
Adsorption Effect ◽  
Magnolia Grandiflora

Abstract The adsorption behavior and the underlying mechanism of methylene blue (MB) sorption on biochars prepared from different feedstocks at 500 °C were evaluated. The biochar feedstocks included Magnolia grandiflora Linn. leaves biochar (MBC), pomelo (Citrus grandis) peel biochar (PBC) and badam shell biochar (BBC). The results of characterizing and analyzing the samples showed that different biochars had different effects on the adsorption of MB. It could be found that MBC had the best adsorption effect on MB due to its largest average pore diameter of 5.55 nm determined by Brunauer-Emmett-Teller analysis. Under the optimal conditions, the maximum adsorption capacities of BBC, PBC and MBC were 29.7, 85.15 and 99.3 mg/g, respectively. The results showed that the amount of adsorption was affected by the pH value. The maximum adsorption capacity of MBC was 46.99 mg/g when it was at pH of 3, whereas for the same experimental conditions the maximum adsorption capacity of BBC and PBC was 25.29 mg/g at pH of 11 and 36.08 mg/g at pH of 7, respectively. Therefore, MBC was found to be a most efficient low-cost adsorbentl for dye wastewater treatment compared with BBC and PBC, and it had the best removal effect under acidic conditions.

scholarly journals Effect of chemical aging of Alternanthera philoxeroides-derived biochar on the adsorption of Pb(II)

2019 ◽  
Vol 80 (2) ◽  
pp. 329-338
Author(s):  
Xuan Wang ◽  
Yande Jing ◽  
Yongqiang Cao ◽  
Shuo Xu ◽  
Lidong Chen
Keyword(s):  
Adsorption Capacity ◽  
Structural Changes ◽  
Aging Treatment ◽  
Alternanthera Philoxeroides ◽  
Order Kinetic ◽  
Adsorption Effect ◽  
Chemical Aging ◽  
Adsorption Capacities ◽  
Order Kinetic Model ◽  
Pseudo Second Order

Abstract In this study, biochar was prepared from Alternanthera philoxeroides (AP) under O2-limited condition at 350 °C (LB) and 650 °C (HB) and treated with aging by HNO3/H2SO4 oxidation. Structural changes of the biochar after aging treatment and the treatment's effect on Pb(II) absorption were explored. The results showed that oxygen-containing functional groups, aromatic structure and surface area of the biochar increased after the aging treatment. However, the integrity of the tubular structure was broken into fragments. The adsorption process of Pb(II) was in accordance with the pseudo-second-order kinetic model and fitted by the Langmuir model. With the increase of pH, the adsorption capacities of Pb(II) increased gradually, and the adsorption effect was best at pH 5. The aged HB presented a decrease of the carboxyl group, which caused less adsorption capacity of Pb(II) than that of aged LB. The maximum adsorption capacities of Pb(II) on fresh biochar at 350 °C and 650 °C were 279.85 and 286.07 mg·g−1 and on aged biochar were 242.57 and 159.82 mg·g−1, respectively. The adsorption capacity of HB for Pb(II) was higher than that of LB, and the adsorption capacity of aged biochar for Pb(II) decreased obviously, which might be attributable to changes in physicochemical properties of biochar after the aging treatment.

scholarly journals CH4/N2 Adsorptive Separation on Zeolite X/AC Composites

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Cai Long Xue ◽  
Wen Ping Cheng ◽  
Wen Ming Hao ◽  
Jing Hong Ma ◽  
Rui Feng Li
Keyword(s):  
Adsorption Capacity ◽  
Micropore Volume ◽  
Zeolite X ◽  
Adsorption Selectivity ◽  
Adsorptive Separation ◽  
Capacity Loss ◽  
Pressure Swing ◽  
Polar Functional Groups ◽  
Adsorption Desorption ◽  
The Relationship

A series of zeolite X/activated carbon (AC) composites were prepared from the same starting materials at various activation time. The corresponding modified samples were obtained by being treated with diluted NH4Cl solution. The relationship between porosity development, surface properties, and CH4/N2 adsorption performance was investigated. The increase of micropore volume is beneficial to the improvement of CH4 and N2 adsorption capacity, but more sensitive for CH4. In addition, the polar functional groups of zeolite X/AC composites may enhance CH4 adsorption capacity. More importantly, both developing micropore structure and surface modification contributed to enhance the adsorption selectivity αCH4/N2. As the optimum sample of these studies, HZAC(24) showed CH4 adsorption capacity of 17.3 cm3/g and the highest adsorption selectivity αCH4/N2 of 3.4. The CH4 and N2 adsorption isotherms of all samples can be well fitted by the Langmuir–Freundlich model. HZAC(24) showed an excellent cyclability of adsorption/desorption of CH4 with a neglectable capacity loss after subsequent cycles. Moreover, HZAC(24) displayed relatively rapid adsorption kinetics. These properties of zeolite X/AC composites are essential for the adsorptive separation of CH4 from N2 in the pressure swing adsorption (PSA) process.

Topotactic replacement of augite by omphacite in a blueschist rock from north-west Turkey

1978 ◽  
Vol 42 (324) ◽  
pp. 435-438 ◽  
Author(s):  
M. A. Carpenter ◽  
A. Okay
Keyword(s):  
Fluid Phase ◽  
Partial Replacement ◽  
Cation Ordering ◽  
North West ◽  
Space Groups ◽  
Transmission Electron ◽  
Ordering Schemes ◽  
Antiphase Domains ◽  
The Relationship ◽  
Symmetry Change

SummaryPartial replacement of original igneous augite crystals by omphacite during blueschist metamorphism of a dolerite from the Mihalliççik area of north-west Turkey has been studied by transmission electron microscopy. The replacement occurred topotactically, apparently by ion exchange with a fluid phase, which left the basic pyroxene structure unchanged. Cation ordering in the omphacite caused a symmetry change fromC-face centred to primitive with the formation of fine-scale antiphase domains. Selected-area diffraction provides evidence forP2andP2/cspace groups for the ordered omphacite though the best ordered areas show a tendency towardsP2/n(reflections violating then-glide are very weak) and also contain fine, wavy, disordered precipitates approximately parallel to (too).It is suggested that the replacement temperature was below the cation-ordering temperature and that the omphacite grew in a metastable, disordered state. Subsequent ordering occurred under irreversible conditions via a series of intermediate structures. The ordering sequence may illustrate the relationship between different ordering schemes in other blueschist pyroxenes.

Adsorption Effect of NO3-, SO42- and PO43- about As (V) on the Porous Biomorph-Genetic Composite of Fe2O3/Fe3O4/C with Eucalyptus Wood Template

2014 ◽  
Vol 522-524 ◽  
pp. 473-476
Author(s):  
Li Wei Xie ◽  
Bin Huang ◽  
Yan Hua Huang ◽  
Shuang Cao ◽  
Zong Qiang Zhu ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Competitive Adsorption ◽  
The Novel ◽  
Adsorption Effect ◽  
Adsorption Phenomenon ◽  
Eucalyptus Wood ◽  
Change Trend ◽  
Wood Template

The adsorption effect of NO3-, SO42- or PO43- about As (V) on the novel porous biomorph-genetic composite of Fe2O3/Fe3O4/C was prepared with eucalyptus wood template (PBGC-Fe/C) was analyzed and considered. The results show that NO3-, SO42- and PO43- have different change trend onto the PBGC-Fe/C adsorbent under initial As (V) concentration of 5, 10, 50mg/L, the competitive adsorption capacity is: PO43-> NO3-> SO42-. And with increasing of NO3-, SO42- and PO43- concentration, the competitive adsorption phenomenon is more violent.

scholarly journals Transient Dynamics of the Lorenz System with a Parameter Drift

2021 ◽  
Vol 31 (02) ◽  
pp. 2150029
Author(s):  
Julia Cantisán ◽  
Jesús M. Seoane ◽  
Miguel A. F. Sanjuán
Keyword(s):  
Lorenz System ◽  
Scaling Law ◽  
Transient State ◽  
Rate Of Change ◽  
Transient Dynamics ◽  
Change Rate ◽  
The Lorenz System ◽  
Sudden Transition ◽  
The Relationship

Nonautonomous dynamical systems help us to understand the implications of real systems which are in contact with their environment as it actually occurs in nature. Here, we focus on systems where a parameter changes with time at small but non-negligible rates before settling at a stable value, by using the Lorenz system for illustration. This kind of systems commonly show a long-term transient dynamics previous to a sudden transition to a steady state. This can be explained by the crossing of a bifurcation in the associated frozen-in system. We surprisingly uncover a scaling law relating the duration of the transient to the rate of change of the parameter for a case where a chaotic attractor is involved. Additionally, we analyze the viability of recovering the transient dynamics by reversing the parameter to its original value, as an alternative to the control theory for systems with parameter drifts. We obtain the relationship between the paramater change rate and the number of trajectories that tip back to the initial attractor corresponding to the transient state.

Sign in / Sign up

Export Citation Format

Share Document