scholarly journals Application of Functionalized DVB-co-GMA Polymeric Microspheres in the Enhanced Sorption Process of Hazardous Dyes from Dyeing Baths

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5247
Author(s):  
Monika Wawrzkiewicz ◽  
Beata Podkościelna ◽  
Przemysław Podkościelny
Keyword(s):  
Dye Adsorption ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Sorption Process ◽  
Polymeric Microspheres ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Intensive Development ◽  
Acid Violet ◽  
Huge Challenge

Intensive development of many industries, including textile, paper, plastic or food, generate huge amounts of wastewaters containing not only toxic dyes but also harmful auxiliaries such as salts, acid, bases, surfactants, oxidants, heavy metal ions. The search for effective pollutant adsorbents is a huge challenge for scientists. Synthesis of divinylbenzene copolymer with glycidyl methacrylate functionalized with triethylenetetramine (DVB-co-GMA-TETA) resin was performed and the obtained microspheres were evaluated as a potential adsorbent for acid dye removal from dyeing effluents. The sorption capacities were equal to 142.4 mg/g for C.I. Acid Green 16 (AG16), 172 mg/g for C.I. Acid Violet 1 (AV1) and 216.3 mg/g for C.I. Acid Red 18 (AR18). Non-linear fitting of the Freundlich isotherm to experimental data was confirmed rather than the Langmuir, Temkin and Dubinin-Radushkevich. The kinetic studies revealed that intraparticle diffusion is the rate-limiting step during dye adsorption. Auxiliaries such as Na2SO4 (5–25 g/L), CH3COOH (0.25–1.5 g/L) and anionic surfactant (0.1–0.5 g/L) present in the dyeing baths enhance the dye adsorption by the resin in most cases. Regeneration of DVB-co-GMA-TETA is possible using 1 M NaCl-50% v/v CH3OH.

Removal of Mg from spring water using natural clinoptilolite

Clay Minerals ◽  
2012 ◽  
Vol 47 (1) ◽  
pp. 81-92 ◽  
Author(s):  
S. Tomić ◽  
N. Rajić ◽  
J. Hrenović ◽  
D. Povrenović
Keyword(s):  
Ion Exchange ◽  
Kinetic Studies ◽  
Spring Water ◽  
Zeolite A ◽  
Zeolitic Tuff ◽  
Rate Limiting Step ◽  
Intra Particle Diffusion ◽  
Pseudo Second Order ◽  
Natural Clinoptilolite ◽  
Rate Limiting

AbstractNatural zeolitic tuff from Brus (Serbia) consisting mostly of clinoptilolite (about 90%) has been investigated for the reduction of the Mg concentration in spring water. The sorption capacity of the zeolite is relatively low (about 2.5 mg Mg g-1for the initial concentration of 100 mg Mg dm-3). The zeolitic tuff removes Mg from water solutions by ion exchange, which has been demonstrated by energy dispersive X-ray analysis (EDS). The extent of ion exchange was influenced by the pH and the initial Mg concentration. Kinetic studies revealed that Lagergen's pseudo-second order model was followed. Intra-particle diffusion of Mg2+influenced the ion exchange, but it is not the rate-limiting step. Rather than having to dispose of the Mg-loaded (waste) zeolite, a possible application was tested. Addition to a wastewater with a low concentration of Mg showed that it could successfully make up for the lack of Mg micronutrient and, accordingly, enabled the growth of phosphate-accumulating bacteriaA. Junii, increasing the amount of phosphate removed from the wastewater.

Removal of Pb (II) from Aqueous Solution by Blast-Furnace Slags

2013 ◽  
Vol 726-731 ◽  
pp. 2736-2741
Author(s):  
Ming Da Liu ◽  
Ge Tian ◽  
Liang Jie Zhao ◽  
Yao Sheng Wang ◽  
Lei Guo ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Blast Furnace ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Sorption Process ◽  
Second Order ◽  
Order Model ◽  
Pseudo Second Order ◽  
Solution Kinetic ◽  
Second Order Model

Five blast-furnace slags were used as adsorbents to remove Pb (II) from aqueous solution. Kinetic studies showed that the sorption process was best described by pseudo-second-order model. Among Langmuir, Freundlich and Temkin isotherms, the Freundlich isotherm had a better fit with the simulation of the adsorption of Pb (II).

scholarly journals Rate-Limiting Steps of Dye Degradation over Titania-Silica Core-Shell Photocatalysts

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 583 ◽  
Author(s):  
Ariane Giesriegl ◽  
Jakob Blaschke ◽  
Shaghayegh Naghdi ◽  
Dominik Eder
Keyword(s):  
Dye Degradation ◽  
Sol Gel ◽  
Dye Adsorption ◽  
Thin Layers ◽  
Continuous Change ◽  
Uv Illumination ◽  
Rate Limiting Step ◽  
Sol Gel Process ◽  
Rate Limiting ◽  
Positively Charged

In this work, we employed a step-by-step sol-gel process to controllably deposit ultra-thin layers of SiO2 on anatase nanoparticles in the range between 0 and 1 nm. The deposition was confirmed by TEM, EDX, and ATR-FTIR (e.g., Ti-O-Si band at 960 cm-1). Zeta potential measurements unravelled a continuous change in surface charge density with increasing silica shell thickness. The photocatalysts were evaluated towards adsorption and degradation of positively-charged and negatively-charged dyes (methylene blue, methyl orange) under UV illumination. The growth mechanism follows the Stranski–Krastanov model with three thickness regimes: (a) Flat islands (first step), (b) mono/bilayers (second/third step), and (c) regular thick films (fourth/fifth step). The results suggest different rate limiting processes for these regimes: (a) For the thinnest scenario, acidic triple-phase boundaries (TPBs) increase the activity for both dyes with their accessibility being the rate limiting step; (b) for continuous mono/bilayers, dye adsorption on the negatively-charged SiO2 shells becomes the rate liming step, which leads to a stark increase in activity for the positively-charged MB and a decrease for MO; (c) for thicker shells, the activity decreases for both dyes and is limited by the charge transport through the isolating shells.

Parametric and adsorption kinetic studies of methylene blue removal from simulated textile water using durian (Durio zibethinus murray) skin

2015 ◽  
Vol 72 (6) ◽  
pp. 896-907 ◽  
Author(s):  
S. M. Anisuzzaman ◽  
Collin G. Joseph ◽  
D. Krishnaiah ◽  
A. Bono ◽  
L. C. Ooi
Keyword(s):  
Methylene Blue ◽  
Adsorption Capacity ◽  
Dye Adsorption ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
Durio Zibethinus

In this study, durian (Durio zibethinus Murray) skin was examined for its ability to remove methylene blue (MB) dye from simulated textile wastewater. Adsorption equilibrium and kinetics of MB removal from aqueous solutions at different parametric conditions such as different initial concentrations (2–10 mg/L), biosorbent dosages (0.3–0.7 g) and pH solution (4–9) onto durian skin were studied using batch adsorption. The amount of MB adsorbed increased from 3.45 to 17.31 mg/g with the increase in initial concentration of MB dye; whereas biosorbent dosage increased from 1.08 to 2.47 mg/g. Maximum dye adsorption capacity of the durian skin was found to increase from 3.78 to 6.40 mg/g, with increasing solution pH. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. The sorption equilibrium was best described by the Freundlich isotherm model with maximum adsorption capacity of 7.23 mg/g and this was due to the heterogeneous nature of the durian skin surface. Kinetic studies indicated that the sorption of MB dye tended to follow the pseudo second-order kinetic model with promising correlation of 0.9836 < R2 < 0.9918.

scholarly journals Coupling of kenaf Biochar and Magnetic BiFeO3 onto Cross-Linked Chitosan for Enhancing Separation Performance and Cr(VI) Ions Removal Efficiency

2020 ◽  
Vol 17 (3) ◽  
pp. 788 ◽  
Author(s):  
Daixi Zhou ◽  
Guangyu Xie ◽  
Xinjiang Hu ◽  
Xiaoxi Cai ◽  
Yunlin Zhao ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Adsorption Process ◽  
Reaction System ◽  
Freundlich Isotherm ◽  
Fractional Factorial ◽  
Separation Performance ◽  
Initial Concentration ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Competing Ions

Cr(VI) contamination has posed great threat to both the ecosystem and human health for its carcinogenic and mutagenic nature. A highly effective adsorbent for the removal of Cr(VI) was prepared and its adsorption mechanism was thoroughly discussed in this study. In detail, magnetic BiFeO3 and kenaf biochar were loaded on cross-linked chitosan to obtain chitosan-kenaf biochar@BiFeO3 (CKB) for improving adsorption capacity towards Cr(VI). The adsorption process of Cr(VI) onto CKB was evaluated as a function of the pH, the existence of competing ions, the initial concentration of Cr(VI) and contact time. The results show that CKB exhibits the highest adsorption capacity under the optimal pH 2.0. The presence of competing ions such as Ca2+, NO3−, SO42−, and Cl− decreases the adsorption capacity; among them, Ca2+ and NO3− show the greatest hindrance. By studying the effect of initial Cr(VI) concentration on the adsorption capacity, it was found that CKB in the solution was enough to remove Cr(VI) for all treatments (10–200 mg/L). The adsorption experimental data were well fitted with pseudo-first-order model, suggesting that chemisorption is not the dominant rate-limiting step. Freundlich isotherm model can better explain the adsorption process, indicating a non-ideal adsorption towards Cr(VI) on a heterogeneous surface of CKB. A 25-1 Fractional Factorial Design (FFD) showed that pH and initial concentration of Cr(VI) have significant influence on Cr(VI) adsorption in our reaction system. In general, excellent adsorption efficiency of CKB indicates that it may be a good candidate for the remediation of Cr(VI)-contaminating wastewater.

scholarly journals Kinetic studies of formate dehydrogenase

1970 ◽  
Vol 120 (4) ◽  
pp. 763-769 ◽  
Author(s):  
D. Peacock ◽  
D. Boulter
Keyword(s):  
Carbon Dioxide ◽  
Formate Dehydrogenase ◽  
Kinetic Studies ◽  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Reverse Reaction ◽  
Enzyme Form ◽  
Rate Limiting Step ◽  
Measurable Rate ◽  
Rate Limiting

1. The kinetic mechanism of formate dehydrogenase is a sequential pathway. 2. The binding of the substrates proceeds in an obligatory order, NAD+ binding first, followed by formate. 3. It seems most likely that the interconversion of the central ternary complex is extremely rapid, and that the rate-limiting step is the formation or possible isomerization of the enzyme–coenzyme complexes. 4. The secondary plots of the inhibitions with HCO3− and NO3− are non-linear, which suggests that more than one molecule of each species is able to bind to the same enzyme form. 5. The rate of the reverse reaction with carbon dioxide at pH6.0 is 20 times that with bicarbonate at pH8.0, although no product inhibition could be detected with carbon dioxide. The low rate of the reverse reaction precluded any steady-state analysis as the enzyme concentrations needed to obtain a measurable rate are of the same order as the Km values for NAD+ and NADH.

Photoenhancement of Gas-Solid Reactions by Surface Excitation

1983 ◽  
Vol 29 ◽  
Author(s):  
Carol I. H. Ashby
Keyword(s):  
Thermal Effects ◽  
Kinetic Studies ◽  
Wavelength Dependence ◽  
Reaction Rates ◽  
Thermal Reaction ◽  
Subsequent Formation ◽  
Rate Limiting Step ◽  
Surface Excitation ◽  
Rate Limiting ◽  
Reactive Excited State

ABSTRACTUltraviolet irradiation of the surface of graphite leads to the enhancement of the reaction of graphite with hydrogen to form methane under conditions where photo-induced thermal effects are negligible. Wavelength dependence of the photoenhancement correlates with excitation of the π-valence to π-conduction transition of graphite centered at 260 nm. Subsequent formation of some reactive excited state species leads to enhanced reaction rates. Likely candidates for such reactive species have been identified by comparative kinetic studies of the thermal and the photoenhanced reactions. For example, at low temperatures (< 500 K), the rate-limiting step of the thermal reaction is addition of H to surface CH3 groups, and the observed photoenhancement can be explained by activation of these CH3 groups.

Removal of toxic elements from aqueous solution using bentonite modified with l-histidine

2014 ◽  
Vol 70 (12) ◽  
pp. 2022-2030 ◽  
Author(s):  
E. N. Bakatula ◽  
E. M. Cukrowska ◽  
I. M. Weiersbye ◽  
L. Mihaly-Cozmuta ◽  
H. Tutu
Keyword(s):  
Aqueous Solution ◽  
Freundlich Isotherm ◽  
Batch Mode ◽  
Operating Variables ◽  
Ph Values ◽  
Surface Areas ◽  
Rate Limiting Step ◽  
Thermodynamic Constants ◽  
Pseudo Second Order ◽  
Rate Limiting

This study proposes the use of bentonite modified with l-histidine for the removal of Cu, Co, Cr, Fe, Hg, Ni, U and Zn from aqueous solutions such as those impacted by acidic drainage. The surface areas of natural bentonite and bentonite–histidine were 73.8 and 61.2 m2 g−1, respectively. Elemental analysis showed an increase in the amount of carbon (0.258%) and nitrogen (0.066%) for the bentonite–histidine. At a fixed solid/solution ratio, the operating variables affecting the adsorption of metal ions from aqueous solution such as pH, initial concentration, contact time and temperature were studied in batch mode. The Freundlich isotherm model yielded a better fit than the Langmuir for the adsorption of Cu, Co, Ni and Zn, implying adsorption on a heterogeneous surface. Adsorption kinetics followed a pseudo-second-order model, suggesting chemisorption as the rate-limiting step. The apparent activation energy was greater than 40 kJ mol−1 for Cu, Zn, Ni, Co and U, which is characteristic of a chemically controlled reaction. Thermodynamic constants ΔG and ΔH showed that the adsorption of metals was endothermic and spontaneous. Adsorption of heavy metals onto bentonite–histidine was efficient at low pH values, meaning that the adsorbent could be useful for remediating acid mine water.

scholarly journals Removal of Dye Acid Red 1 from Aqueous Solutions Using Chitosan-iso-Vanillin Sorbent Material

2020 ◽  
Vol 5 (3) ◽  
pp. 352-365
Author(s):  
Eman Al Abbad ◽  
Fadi Alakhras
Keyword(s):  
Aqueous Solutions ◽  
Low Cost ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Sorption Process ◽  
Modified Chitosan ◽  
Sorbent Material ◽  
Removal Capacity ◽  
Rate Determining Step ◽  
Acid Red 1

Sorption of Acid Red 1 (AR1) from aqueous solutions utilizing low-cost sorbent material; (chitosan-iso-vanillin) is studied under batch conditions. The remaining concentrations of the azo dye are measured at λmax = 546 nm by UV spectrophotometric method. Langmuir data reveal that the maximum removal capacity was 555.556 mg/g at pH 3. Freundlich isotherm represents the best fitting model on the removal of AR1 using chemically modified chitosan verifying the sorption takes place on heterogeneous surfaces with multilayer adsorption. Kinetic studies of the sorption process revealed that intraparticle diffusion is not only the rate-determining step but also a chemical reaction takes place as well. The results indicate that high sorption rapidness with almost 90% achieved within 90 min. Thermodynamic investigations suggest that the process favours an exothermic nature. The polymer utilized in the present study is being considered as a feasible sorbent material for the removal of AR1 from waste effluent.

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