scholarly journals Interactions between adsorbents and adsorbates in aqueous solutions

2020 ◽  
Vol 92 (10) ◽  
pp. 1655-1662
Author(s):  
Zhijian Wu ◽  
Xiushen Ye ◽  
Haining Liu ◽  
Huifang Zhang ◽  
Zhong Liu ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Adsorption Capacity ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Solution Ph ◽  
Electrostatic And Hydrophobic Interactions

AbstractAdsorption is one of the most widely used processes in physicochemical operations. To design an adsorbent for a specific adsorbate, it is important to understand the interactions between adsorbents and adsorbates, which are very important for both adsorption capacity and selectivity. Electrostatic interactions, hydrogen bonding, hydrophobic interactions, complexation, and precipitation are comprehensively discussed. Adjusting solution pH and ionic strength is an effective method to improve the adsorption, especially when electrostatic and hydrophobic interactions are main interactions. With the increase in ionic strength, the hydrophobic interactions between adsorbents and adsorbates increase, while the electrostatic interactions decrease.

scholarly journals Adsorptive and Coagulative Removal of Trace Metals from Water Using Surface Modified Sawdust-Based Cellulose Nanocrystals

J ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 193-205
Author(s):  
Opeyemi A. Oyewo ◽  
Sam Ramaila ◽  
Lydia Mavuru ◽  
Taile Leswifi ◽  
Maurice S. Onyango
Keyword(s):  
Trace Metals ◽  
Adsorption Capacity ◽  
Cellulose Nanocrystals ◽  
Inductively Coupled Plasma ◽  
Electrostatic Interactions ◽  
Natural Waters ◽  
Maximum Adsorption Capacity ◽  
Solution Ph ◽  
Major Drawback ◽  
Surface Modified

The presence of toxic metals in surface and natural waters, even at trace levels, poses a great danger to humans and the ecosystem. Although the combination of adsorption and coagulation techniques has the potential to eradicate this problem, the use of inappropriate media remains a major drawback. This study reports on the application of NaNO2/NaHCO3 modified sawdust-based cellulose nanocrystals (MCNC) as both coagulant and adsorbent for the removal of Cu, Fe and Pb from aqueous solution. The surface modified coagulants, prepared by electrostatic interactions, were characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive spectrometry (SEM/EDS). The amount of coagulated/adsorbed trace metals was then analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). SEM analysis revealed the patchy and distributed floccules on Fe-flocs, which was an indication of multiple mechanisms responsible for Fe removal onto MCNC. A shift in the peak position attributed to C2H192N64O16 from 2θ = 30 to 24.5° occurred in the XRD pattern of both Pb- and Cu-flocs. Different process variables, including initial metal ions concentration (10–200 mg/L), solution pH (2–10), and temperature (25–45 °C) were studied in order to investigate how they affect the reaction process. Both Cu and Pb adsorption followed the Langmuir isotherm with a maximum adsorption capacity of 111.1 and 2.82 mg/g, respectively, whereas the adsorption of Fe was suggestive of a multilayer adsorption process; however, Fe Langmuir maximum adsorption capacity was found to be 81.96 mg/g. The sequence of trace metals removal followed the order: Cu > Fe > Pb. The utilization of this product in different water matrices is an effective way to establish their robustness.

scholarly journals Kinetic and Equilibrium Studies on the Zinc Adsorption-desorption Characteristics of Some Promising Biochars in Aqueous Solutions

2021 ◽  
Author(s):  
Masoumeh Faryadi Shahgoli ◽  
Adel Reyhanitabar ◽  
Nosratollah Najafi ◽  
Shahin Oustan
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Rice Straw ◽  
Pyrolysis Temperature ◽  
Ph Effect ◽  
Solution Ph ◽  
Equilibrium Studies ◽  
Batch Technique ◽  
Adsorption Desorption ◽  
Zinc Adsorption

Abstract The present research aimed at investigating zinc (Zn) sorption capacity of the biochars derived from apple wood (WB) and rice straw (RB) feedstocks at two 300 and 600°C pyrolysis temperatures (WB300, WB600, RB300 and RB600, respectively) in aqueous solutions. Kinetic and equilibrium sorption experiments were conducted via batch technique. In equilibrium adsorption experiments, the study used the concentration range of 5-200 mg Zn L− 1 and focused on the solution pH effect on Zn adsorption in biochars under the following conditions: unadjusted and adjusted pH (4 and 6) and three ionic strength levels (0.01, 0.03, 0.1 M KNO3). Zinc desorption experiments were conducted under all above mentioned conditions but without pH adjustment at five separate stages. Kinetic data analysis indicated that Zn adsorption in biochars reached the near steady state within 24 hours with the sorption rate order of WB300 < WB600 < RB300 < RB600. The best fitness was superior to both Elovich and exponential rate models. Also, Zn adsorption isotherms in the studied biochars were shown to fit quite well to Langmuir, Freundlich and Dubinin-Radushkevich models. Zn sorption maxima were found to be 4.3, 16.4, 17.9 and 33.3 mg g− 1, on average, for WB300, WB600, RB300, and RB600, respectively. The initial increased pH solution from 4 to 6 caused an increase in Zn adsorption in RB600, RB300 and WB600, however the sorption maxima in WB300 was detected at pH 4. The rise in solution ionic strength from 0.01 M to 0.1 M dropped the Zn adsorption capacity in all the studied biochars. Findings suggested that rice straw derived biochars showed a better performance than woody biochars in Zn sorption and retention from aqueous solutions. In addition, this ability increased with increasing pyrolysis temperature in both types of biochars. Finally, the study revealed that rice straw biochars, produced at high pyrolysis temperatures, can serve as economical and efficient absorbents for Zn removal from aqueous solutions.

scholarly journals Effect of Praestol as a Coagulant-Aid to Improve Coagulation-Flocculation in Dye containing Wastewaters

2015 ◽  
Vol 18 (1) ◽  
pp. 38-46 ◽  
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Removal Efficiency ◽  
Dye Removal ◽  
Settling Time ◽  
Solution Ph ◽  
Polyaluminum Chloride ◽  
Flocculation Process ◽  
Flocculation Time

<div> <p>This study was conducted to investigate the effect of praestol, as a coagulant-aid, to improve coagulation-flocculation process in the removal of disperse red 60 from aqueous solutions. The effect of various parameters including coagulants dose (10-1000 mg l<sup>-1</sup>), praestol dose (0-1000 mg l<sup>-1</sup>), solution pH (3-11), initial dye concentration (100-500 mg l<sup>-1</sup>), flocculation speed (30-60 rpm), flocculation time (15-30 min), settling time (5-60 min) and ionic strength (0-6 mg l<sup>-1</sup>) was evaluated on the dye removal. The dye removal efficiency was substantially increased by using praestol in the concentration of 80 mg l<sup>-1 </sup>and 400 mg l<sup>-1 </sup>for coagulation with alum and polyaluminum chloride (PACl), respectively. The maximum dye removal by alum coupled with praestol (Al-P) and PACl coupled with praestol (PA-P) was found to be 97.8% and 98.7%, respectively that were occurred at pH 7. The results showed that the application of PA-P or Al-P can be effectively used to remove disperse red 60 (DR 60) in aqueous solutions.</p> </div> <p>&nbsp;</p>

scholarly journals Potential of Kale and Lettuce Residues as Natural Adsorbents of the Carcinogen Aflatoxin B1 in a Dynamic Gastrointestinal Tract-Simulated Model

Toxins ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 771
Author(s):  
Alma Vázquez-Durán ◽  
María de Jesús Nava-Ramírez ◽  
Daniel Hernández-Patlán ◽  
Bruno Solís-Cruz ◽  
Víctor Hernández-Gómez ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Gastrointestinal Tract ◽  
Aflatoxin B1 ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Maximum Adsorption Capacity ◽  
Promising Alternative ◽  
Simulated Model ◽  
Dipole Interactions ◽  
Natural Adsorbents

Adsorption of the carcinogen aflatoxin B1 (AFB1) onto agro-waste-based materials is a promising alternative over conventional inorganic binders. In the current study, two unmodified adsorbents were eco-friendly prepared from kale and lettuce agro-wastes. A dynamic gastrointestinal tract-simulated model was utilized to evaluate the removal efficiency of the sorptive materials (0.5%, w/w) when added to an AFB1-contaminated diet (100 µg AFB1/kg). Different characterization methodologies were employed to understand the interaction mechanisms between the AFB1 molecule and the biosorbents. Based on adsorption results, the biosorbent prepared from kale was the best; its maximum adsorption capacity was 93.6%, which was significantly higher than that of the lettuce biosorbent (83.7%). Characterization results indicate that different mechanisms may act simultaneously during adsorption. Non-electrostatic (hydrophobic interactions, dipole-dipole interactions, and hydrogen bonding) and electrostatic interactions (ionic attractions) together with the formation of AFB1-chlorophyll complexes appear to be the major influencing factors driving AFB1 biosorption.

scholarly journals Core-Shell Structured Magnetic Carboxymethyl Cellulose-Based Hydrogel Nanosorbents for Effective Adsorption of Methylene Blue from Aqueous Solution

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3054
Author(s):  
Yiming Zhou ◽  
Te Li ◽  
Juanli Shen ◽  
Yu Meng ◽  
Shuhua Tong ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Aqueous Solutions ◽  
Adsorption Capacity ◽  
Carboxymethyl Cellulose ◽  
Chemical Properties ◽  
Polymer Nanocomposite ◽  
Core Shell ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
Solution Ph

This article reports effective removal of methylene blue (MB) dyes from aqueous solutions using a novel magnetic polymer nanocomposite. The core-shell structured nanosorbents was fabricated via coating Fe3O4 nanoparticles with a layer of hydrogel material, that synthesized by carboxymethyl cellulose cross-linked with poly(acrylic acid-co-acrylamide). Some physico-chemical properties of the nanosorbents were characterized by various testing methods. The nanosorbent could be easily separated from aqueous solutions by an external magnetic field and the mass fraction of outer hydrogel shell was 20.3 wt%. The adsorption performance was investigated as the effects of solution pH, adsorbent content, initial dye concentration, and contact time. The maximum adsorption capacity was obtained at neutral pH of 7 with a sorbent dose of 1.5 g L−1. The experimental data of MB adsorption were fit to Langmuir isotherm model and Pseudo-second-order kinetic model with maximum adsorption of 34.3 mg g−1. XPS technique was applied to study the mechanism of adsorption, electrostatic attraction and physically adsorption may control the adsorption behavior of the composite nanosorbents. In addition, a good reusability of 83.5% MB recovering with adsorption capacity decreasing by 16.5% over five cycles of sorption/desorption was observed.

scholarly journals Molecular Recognition by Pillar[5]arenes: Evidence for Simultaneous Electrostatic and Hydrophobic Interactions

Pharmaceutics ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 60
Author(s):  
Borja Gómez-González ◽  
Luis García-Río ◽  
Nuno Basílio ◽  
Juan C. Mejuto ◽  
Jesus Simal-Gandara
Keyword(s):  
Molecular Recognition ◽  
Inclusion Complexes ◽  
Electrostatic Interactions ◽  
Alkyl Chain ◽  
Hydrophobic Interactions ◽  
Binding Constants ◽  
Ionic Interactions ◽  
Hydrophobic Effects ◽  
Hydrophobic Character ◽  
Electrostatic And Hydrophobic Interactions

The formation of inclusion complexes between alkylsulfonate guests and a cationic pillar[5]arene receptor in water was investigated by NMR and ITC techniques. The results show the formation of host-guest complexes stabilized by electrostatic interactions and hydrophobic effects with binding constants of up to 107 M−1 for the guest with higher hydrophobic character. Structurally, the alkyl chain of the guest is included in the hydrophobic aromatic cavity of the macrocycle while the sulfonate groups are held in the multicationic portal by ionic interactions.

Adsorption of Cr(VI) onto Cetylpyridinium Bromide Modified Zeolites: Effect of Surfactant Loading, Solution pH, Ionic Strength and Coexisting Anions

2011 ◽  
Vol 183-185 ◽  
pp. 1772-1776
Author(s):  
Jian Wei Lin ◽  
Yan Hui Zhan ◽  
Yun Qing Xing ◽  
Yu Liu
Keyword(s):  
Ionic Strength ◽  
Adsorption Capacity ◽  
Natural Zeolite ◽  
Cetylpyridinium Bromide ◽  
Solution Ph ◽  
Bicarbonate Ions ◽  
Competing Anions ◽  
Chloride Sulfate ◽  
Modified Zeolites ◽  
Monolayer Coverage

Surfactant-modified zeolites (SMZ) with different coverage types were prepared by loading the cetylpyridinium bromide (CPB) onto the surface of the natural zeolite collected from Jinyun County, Zhejiang Province, China. The adsorption behavior of Cr(VI) on SMZ was investigated. Natural zeolite and SMZ with CPB monolayer coverage were inefficient for the removal of Cr(VI) from aqueous solution. However, SMZ with CPB patchy bilayer or bilayer coverage was efficient in the removal of Cr(VI) and the Cr(VI) adsorption capacity of SMZ increased with its CPB loading. The Cr(VI) adsorption capacity of SMZ showed a maximum at pH 3-6 and decreased with increasing pH from 6 to 11. The presence of competing anions such as chloride, sulfate and bicarbonate ions reduced the Cr(VI) adsorption capacity of SMZ. The adsorption process was strongly dependent on ionic strength, indicating that anionic exchange and electrostatic interaction were the main mechanisms that govern the adsorption of Cr(VI) on SMZ.

scholarly journals Examination of the Effectiveness of Physical and Chemical Activation of Natural Bentonite for the Removal of Heavy Metal Ions from Aqueous Solutions

2002 ◽  
Vol 20 (2) ◽  
pp. 151-167 ◽  
Author(s):  
Fawzi Banat ◽  
Sameer Al-Asheh ◽  
Leena Abu-Aitah
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Adsorption Capacity ◽  
Chemical Activation ◽  
Sodium Dodecyl ◽  
Batch Adsorption ◽  
Initial Material ◽  
Solution Ph ◽  
Experimental Conditions ◽  
Activated Bentonite

The ability of physically and chemically activated bentonite to adsorb copper and nickel ions from aqueous solutions was examined under various experimental conditions. Physically activated bentonite was obtained by thermal treatment of the initial material in an oven at 700°C (T-bentonite), while chemically activated bentonite was obtained in two ways, either by treatment of the initial material with sodium dodecyl sulphate (SDS) as an anionic surfactant to give SDS-bentonite or with aluminium hydroxypolycation as a pillaring agent to give Al-bentonite. Batch adsorption tests were undertaken to study the removal of Cu2+ and Ni2+ ions from aqueous solutions using the above-mentioned types of activated bentonite. The adsorption capacity of the bentonites towards both Cu2+ and Ni2+ ions followed the order: Al-bentonite > SDS-bentonite > T-bentonite > natural bentonite. The initial metal concentration, solution pH, temperature and salinity of the solution affected the adsorption capacity towards both metal ions. The uptake of Cu2+ ions increased with an increase in temperature (25–45°C) as well as with an increase in the initial pH of the solution (3–5). The uptake of Cu2+ and Ni2+ ions decreased significantly with an increase in the NaCl and KCl concentrations present in the aqueous solution. Sulphuric acid of 0.1 M concentration was found to be an effective desorbent for bentonite laden with heavy metals.

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