scholarly journals Cd(II) Adsorption on Different Modified Rice Straws under FTIR Spectroscopy as Influenced by Initial pH, Cd(II) Concentration, and Ionic Strength

2019 ◽  
Vol 16 (21) ◽  
pp. 4129
Author(s):  
Shuai Wang ◽  
Wanhong Li ◽  
Xinhua Yin ◽  
Nan Wang ◽  
Shuai Yuan ◽  
...  
Keyword(s):  
Citric Acid ◽  
Ionic Strength ◽  
Ion Exchange ◽  
Adsorption Capacity ◽  
Rice Straw ◽  
Ph Value ◽  
Sorption Process ◽  
Oh Groups ◽  
Chemical Structures ◽  
Adsorption Amount

Rice straw is a kind of low-cost biosorbent. Through mechanical crushing, pyrolysis, incineration, and citric acid (CA) modification, it could be converted to rice straw powder (Sp), biochar (Sb), ash (Sa), and modified rice straw (Ms) accordingly. Using rice straw as an adsorbent, the influence of pH value (2, 4, and 9), initial Cd(II) concentration (0, 200, and 800 mg/L), and ionic strength (0, 0.2, to 0.6 mg/L) on the adsorption capacity for Cd(II) were examined with three replicates, and the relevant mechanisms were explored using Fourier transform infrared (FTIR) technology. Results showed that the modifications could improve the adsorption capacity of Cd(II) by changing their chemical structures. The products (Sb and Sa) of the pyrolysis and incineration of rice straw contained fewer hydroxyl and alkyl groups, but more Si–O groups. Citric acid modification removed a portion of silica in rice straw, increased its carboxylic content, and made more –OH groups exposed. Compared with Sp, Sb, Sa, and Ms were more likely to act as π donors in the Cd(II) sorption process and exhibited more carboxyl binding. The bands of C = C, –O–CH3, and the O–H, carboxyl, Si–O–Si or Si–O groups were involved in the Cd(II) sorption process. The adsorption amount of Cd(II) by the four adsorbents increased with the increase in the pH value of the solution and the initial Cd(II) concentration. Affected by pH in a solution, ion exchange, surface complexation, and precipitation were the major adsorption mechanisms. Further, under the influence of the initial Cd(II) concentration, electrostatic attraction played a leading role. With no interference by ionic strength, all the adsorbents had the greatest adsorption amount of Cd(II), and the intensity of O–H vibration was also the weakest; ion exchange was the most important mechanism in this process. Regardless of the influencing factors, Sa, with the greatest specific surface area, had an absolute advantage in the adsorption capacity of Cd(II) over Sp, Sb, and Ms.

scholarly journals Characterization and Interpretation of Cd (II) Adsorption by Different Modified Rice Straws under Contrasting Conditions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Shuai Wang ◽  
Nan Wang ◽  
Kai Yao ◽  
Yuchuan Fan ◽  
Wanhong Li ◽  
...  
Keyword(s):  
Citric Acid ◽  
Ionic Strength ◽  
Adsorption Capacity ◽  
Rice Straw ◽  
Contact Time ◽  
Ph Value ◽  
Batch Adsorption ◽  
Acid Modification ◽  
Adsorption Capacities ◽  
Straw Ash

AbstractRice straw can adsorb Cd(II) from wastewater, and modification of rice straw may improve its adsorption efficiency. The rice straw powder (Sp) from the direct pulverization of rice straw was used as the control, the rice straw ash (Sa), biochar (Sa), and modified rice straw (Ms) were prepared by ashing, pyrolysis and citric acid modification, respectively, and all of them were examined as adsorbents for Cd(II) in this study. Batch adsorption experiments were adopted to systematically compare the adsorption capacities of rice straw materials prepared with different modification methods for Cd(II) from aqueous solution under different levels of initial Cd(II) concentration (0–800 mg·L−1), temperature (298, 308, and 318 K), contact time (0–1440 min), pH value (2–10), and ionic strength (0–0.6 mol·L−1). The results indicated that the modification method affected the adsorption of Cd(II) by changing the specific surface area (SSA), Si content, surface morphology, and O-containing functional group of rice straw. Compared with Sp, Ms held more surface O–H, aliphatic and aromatic groups, while Sa had more phenolic, C–O (or C–O–C), and Si–O groups, and Sb held more C–O (or C–O–C) and Si–O groups; besides, Sa, Sb, and Ms had larger SSA than Sp. Adsorption capacity of the four adsorbents for Cd(II) increased and gradually became saturated with the increase in the initial Cd(II) concentration (0–800 mg·L−1). The adsorption capacity of Cd(II) was significantly higher at 318 K than 298 K and 308 K, regardless of the adsorbent type. Sa had the largest SSA (192.38 m2·g−1) and the largest adsorption capacity for Cd(II). When the initial Cd2+ concentration was at 800 mg·L−1, the Cd(II) adsorption amount reached as high as 68.7 mg·g−1 with Sa at 318 K. However, the SSA of Sp was only 1.83 m2·g−1, and it had the least adsorption capacity for Cd(II). Only the adsorption of Cd(II) upon Sb at 298 K was spontaneous, and surprisingly, all other adsorptions were nonspontaneous. These adsorptions were all chemical, and were favorable, exothermic and order-increasing processes. The pseudo-second-order model showed a strong fit to the kinetics of Cd(II) adsorption by the four adsorbents. The adsorption capacities of Cd(II) by the adsorbents were less at low pH, and all were enhanced with the increase of initial pH value (2–10) in the solution. The inhibiting effect on Cd(II) adsorption due to the increase in ionic strength was greater with Sa, Sb, and Ms than that under Sp. The rice straw ash prepared by ashing unexpectedly had greater adsorption capacity for Cd(II) than the biochar and citric acid modified rice straw. The optimum condition for Cd(II) adsorption was established as the temperature of 318 K, initial Cd(II) concentration of 800 mg·L−1, contact time of 240 min, and no Na(I) interference regardless of absorbent. In conclusion, rice straw ash shows the greatest potential of being applied to paddy fields for the remediation of Cd(II) pollution so as to reduce the risk of Cd(II) enrichment in rice grains and straws.

Effect of Modification with Nitric Acid and Hydrogen Peroxide on Chromium (VI) Adsorption by Activated Carbon Fiber

2012 ◽  
Vol 518-523 ◽  
pp. 2099-2103
Author(s):  
Guang Zhou Qu ◽  
Hai Bing Ji ◽  
Ran Xiao ◽  
Dong Li Liang
Keyword(s):  
Hydrogen Peroxide ◽  
Activated Carbon ◽  
Nitric Acid ◽  
Carbon Fiber ◽  
Adsorption Capacity ◽  
Adsorption Kinetics ◽  
Ph Value ◽  
Activated Carbon Fiber ◽  
Order Kinetic ◽  
Adsorption Amount

The activated carbon fiber (ACF) was treated by different concentration nitric acid (HNO3) and hydrogen peroxide (H2O2) oxidization to enhance its adsorption capacity to hexavalent chromium (Cr6+) ion. The adsorption amount and adsorption kinetics of Cr6+ion on ACFs, and the surface chemical groups were investigated. The results showed that the modified ACFs with 1% HNO3and 10% H2O2had a better adsorption capacity, respectively. The adsorption amount of ACFs was affected strongly solution pH value, and decreased significantly with increasing of the pH value. The adsorption kinetics indicated that the adsorption rates of Cr6+ ion on different modified ACFs were well fitted with the pseudo-second-order kinetic model. After 1% HNO3and 10% H2O2modification, respectively, the total acidic oxygen-containing groups on ACFs surface had an increase obviously, which might be enhance the adsorption amount of Cr6+ion on ACFs.

scholarly journals Batch and Fixed-Bed Biosorption of Pb (II) Using Free and Alginate-Immobilized Spirulina

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 466
Author(s):  
Maria Villen-Guzman ◽  
Carlos Jiménez ◽  
Jose Miguel Rodriguez-Maroto
Keyword(s):  
Ionic Strength ◽  
Adsorption Capacity ◽  
Dose Response ◽  
Ph Value ◽  
Fixed Bed ◽  
Alginate Beads ◽  
Breakthrough Curves ◽  
Pressure Drops ◽  
Removal Capacity ◽  
Biosorption Process

The valorization of Spirulina as a potential biosorption material to treat contaminated wastewater was evaluated. Batch experiments were conducted to study the influence of pH value and ionic strength on the biosorption capacity of Spirulina. Higher removal capacity was observed at pH 5.2, while higher ionic strength was found to result in lower adsorption capacity, which suggests that ion exchange is a relevant mechanism for Pb (II) adsorption on Spirulina. The immobilization of Spirulina on alginate beads was found not only to increase the adsorption capacity, but also to overcome limitations such as unacceptable pressure drops on column systems. The Langmuir model was the most appropriate model to describe the biosorption equilibrium of lead by free and immobilized Spirulina. The experimental breakthrough curves were evaluated using the Thomas, Bohart-Adams, and dose-response models. The experimental results were most properly described by the dose-response model, which is consistent with previous results. The adsorption capacity of Spirulina was found to increase linearly with the influent lead concentration (in the range 4–20 mg L−1) at 1.6 mL min−1 flow rate. Batch and column experiments were compared to better understand the biosorption process. The promising results obtained indicate the potential use of Spirulina immobilized on alginate beads to treat industrial wastewater polluted with toxic metals.

Adsorption Behavior of Phenol in Aqueous Solution on MCM-41 Grafted by Different Functional Groups

2014 ◽  
Vol 955-959 ◽  
pp. 74-79
Author(s):  
Xiao Jun Sun ◽  
Xiao Chun Yan ◽  
Yu Jie Feng ◽  
Xian Bin Liu
Keyword(s):  
Aqueous Solution ◽  
Adsorption Capacity ◽  
Functional Groups ◽  
Ph Value ◽  
Nitrogen Adsorption ◽  
Adsorption Behaviors ◽  
Prepared Material ◽  
Adsorption Amount ◽  
Adsorption Desorption ◽  
Mcm 41

Four types of organo-functionalized mesoporous silicas were synthesized by post-grafting method, and characterized by powder X-ray diffraction, nitrogen adsorption/desorption and fourier transform infrared spectroscopy. In addition, adsorption behaviors of the prepared material modified with different functional groups were studied by adsorption of phenol in aqueous solution. When the concentration of phenol was 800 mg/L, the equilibrium adsorption capacity of N-aminoethyl-γ-aminopropyl-MCM-41, aminopropyl-MCM-41, mercaptopropyl-MCM-41 and propyl-MCM-41 was respectively as 2.5 times, 2.2 times, 1.9 times, and 1.7 times as that of MCM-41. It was due to the introduction of organo-functional groups, changing the polarity of the channel surface, and increasing the hydrophobic properties. N-aminoethyl-γ-aminopropyl and aminopropyl groups could generate acid-base interactions with phenol, therefore, their adsorption capacity increased much more. Besides, the pH value of the solution could significantly affect the adsorption amount of phenol on samples. The result showed that with the increase of pH, the adsorption amount of phenol increased at first, and then decreased. The maximum adsorption amount of all the prepared materials occurred at about pH value of 6.

Study on Adsorption of Uranium in Wastewater by Clay

2012 ◽  
Vol 209-211 ◽  
pp. 2081-2085 ◽  
Author(s):  
Shi You Li ◽  
Shui Bo Xie ◽  
Cong Zhao ◽  
Jin Xiang Liu ◽  
Hui Ling ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Uranium Concentration ◽  
Ph Value ◽  
Sorption Process ◽  
Order Kinetic ◽  
Adsorption Data ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Langmuir And Freundlich Models ◽  
Adsorption Capability

The effectives of pH value, contact time，sorbent dose and different initial concentration were analyzed to study the properties of the adsorption of uranium in wastewater by clay. The results show the highest adsorption capacity was obtained around neutral pH.The amount adsorbed of uranium on clay increase rapidly with increasing initial uranium concentration, but the removal rates of uranium are declined.Clay has a good adsorption capability to uranium with 18.25mg/g of adsorption capacity. The adsorption data on clay are followed by both Langmuir and Freundlich models and the results are well described by Langmuir isotherm. The pseudo-second-order kinetic model is more appropriate for the sorption process.

Technology of Modified Orange Peel Adsorption Treatment in Wastewater Containing Zinc

2012 ◽  
Vol 610-613 ◽  
pp. 1540-1545
Author(s):  
Rui Yu Jia ◽  
You Hong Lin ◽  
Wei Zhang
Keyword(s):  
Adsorption Capacity ◽  
Ph Value ◽  
Orange Peel ◽  
Sorption Process ◽  
Optimal Conditions ◽  
Adsorption Time ◽  
Initial Concentration ◽  
Ph Values ◽  
Wide Range ◽  
Adsorption Treatment

Using modified flavedo as the adsorbent , the sorption process of Zn2+Superscript text by modified flavedo in wastewater containing heavymetals was studied. The effects of various factors in Zn2+Superscript text adsorption , such as adsorbtion time , temperature , pH value , initial Zn2+ concentration , and pretreatment,were analyzed. The results showed that the pretreatment of modified raised adsorption capacity , and the adsorption capacity was suitable for wastewater with a wide range of pH values. The rate of removal of Zn2+Superscript text reached 98% when the Zn2+ initial concentration was under 100mg/L. The optimal conditions for Zn2 + adsorptionSuperscript text by Modified orange peel were a wastewater pH value of 5.5 , at 25 °C, an adsorption time of 60 minutes , and a dosage of modacrylic flavedo of 2 g/ L.

scholarly journals Preparation of Slow-Release Insecticides from Biogas Slurry: Effectiveness of Ion Exchange Resin in the Adsorption and Release of Ammonia Nitrogen

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1461
Author(s):  
Quanguo Zhang ◽  
Zexian Liu ◽  
Francesco Petracchini ◽  
Chaoyang Lu ◽  
Yameng Li ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Adsorption Capacity ◽  
Exchange Resin ◽  
Slow Release ◽  
Ph Value ◽  
Nitrogen Concentration ◽  
Ion Exchange Resin ◽  
Ammonia Nitrogen ◽  
Biogas Slurry ◽  
Adsorption Effect

The insecticidal ingredient in a biogas solution being fully utilized by cation exchange resin to produce slow-release insecticide is of great social value. In this work, the feasibility of ammonia nitrogen in a biogas slurry loaded on resin as a slow-release insecticide was evaluated by studying the effect of adsorption and the slow release of ammonia nitrogen by resin. The effects of the ammonia nitrogen concentration, resin dosage, adsorption time and pH value on the ammonia nitrogen adsorption by the resin were studied. The results showed that the ion exchange resin had a good adsorption effect on the ammonia nitrogen. With the increase of the resin dosage, time and ammonia nitrogen concentration, the adsorption capacity increased at first and then stabilized. The ammonia nitrogen adsorption capacity reached its maximum value (1.13 mg) when the pH value was 7. The adsorption process can be fitted well by the Langmuir isothermal adsorption equation and quasi-second-order kinetic model. Additionally, the release rate of the ammonia nitrogen increased with the increasing sodium chloride concentration. The adsorption capacity of ammonia nitrogen by the D113 (resin type) resin decreased by 15.8% compared with the ammonium chloride solution. The report shows that the ion exchange resin has a good adsorption effect on ammonia nitrogen, which is of guiding significance for expanding the raw materials for slow-release insecticides, improving the utilization rate of biogas slurry and cleaner production of slow-release insecticides from biogas slurry. Additionally, all variables showed statistical differences (p < 0.05).

Adsorption Mechanism of Humic Acid on Attapulgite Based on Stumm-Schindle Surface Complexation Model

2012 ◽  
Vol 630 ◽  
pp. 99-105 ◽  
Author(s):  
Nan Sun ◽  
Shui Li Yu
Keyword(s):  
Humic Acid ◽  
Ionic Strength ◽  
Zeta Potential ◽  
Adsorption Capacity ◽  
Adsorption Mechanism ◽  
Ph Value ◽  
Surface Complexation ◽  
Practical Significance ◽  
Surface Complexation Model ◽  
Coordination Reaction

Attapulgite from Xuyi in Jiangsu was characterized by X-ray spectrometer and FT-IR spectrophotometer, the coordination reaction degree of attapulgite/water interface and adsorption mechanism of humic acid(HA) on attapulgite was analyzed by Stumm-Schindle(SS) surface complexation model. The results showed that the main component of attapulgite is magnesia-alumina acid salt, the surface charge on attapulgite adapted from hydrolysates of Si-O and Al-O broken bond. After adsorption, zeta potential decreased firstly and then increased with ionic strength increasing, reduced with a pH value increasing. The zero point charge (pHzpc) of attapulgite was about 4~5, zeta potential and adsorption capacity reached the maximum values when pH= 4 and the minimum values when pH=12. The adsorption capacity increased with ionic strength rising. SS surface complexation model could well explain attapulgite / water interfacal coordination reaction, ionic strength can promote the interfacial coordination reaction and reduce electrostatic repulsion effects on adsorption, which has a definite theoretical and practical significance for guiding adsorption experiment and application of attapulgite in water-treatment technology.

scholarly journals Electrochemical Removal of Cesium Ions via Capacitive Deionization Using an Ion-Exchange Layer Coated on a Carbon Electrode

2021 ◽  
Vol 11 (21) ◽  
pp. 10042
Author(s):  
Sang-Hun Lee ◽  
Mansoo Choi ◽  
Jei-Kwon Moon ◽  
Songbok Lee ◽  
Jihoon Choi ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Adsorption Capacity ◽  
Ph Value ◽  
Carbon Electrode ◽  
Capacitive Deionization ◽  
Exchange Layer ◽  
Ph Values ◽  
Influent Water ◽  
Electrochemical Removal ◽  
Cs Ions

This study was conducted to evaluate the feasibility of using electrosorption to remove cesium (Cs+) ions from aqueous solutions using the membrane capacitive deionization (MCDI) process. The electrochemical properties were analyzed using cyclic voltammetry (CV) and impedance spectroscopy (EIS). The activated carbon electrode coated by a polymer layer showed higher specific adsorption capacity (SAC) and removal efficiency of Cs+ than the AC electrode. The effects of potential, flow rate, initial Cs+ concentration, and pH values were investigated to optimize the electrosorption performance. The electrosorption capacity increased with an increase in the applied potential and the concentration of Cs+ in the influent water. The pH value is an important parameter on electrosorption performance. The removal of Cs+ ions was affected by the pH of the influent water because H+ ions acted as competing ions during the electrosorption process. Cs+ was preferentially adsorbed to the electrode in the early stages of adsorption but was later replaced by H+. A higher presence of H+ ions could reduce the adsorption capacity of Cs+ ions. The ion-exchange layer coated AC electrode was shown to be favorable for the removal of Cs+, despite the limited electrosorption ability in a highly acidic solution.

scholarly journals Removal of Cd2+ from Water Containing Ca2+, Mg2+ using Titanate Nanotubes Modified by Carbon

2021 ◽  
Author(s):  
Mingda Wu ◽  
Linghong Lu ◽  
Tao Zhou ◽  
Yi Ma ◽  
Zhengsong Weng
Keyword(s):  
Electron Microscope ◽  
Ion Exchange ◽  
Adsorption Capacity ◽  
Titanate Nanotubes ◽  
Exchange Property ◽  
Spectra Analysis ◽  
Xps Spectra ◽  
Carbon Modification ◽  
Transmission Electron ◽  
Adsorption Amount

Abstract Ca2+ and Mg2+ usually exist in natural water. When Cd2+ is removed from water by adsorption, it will be inhibited by these two ions. Titanate nanotubes (TNTs) have an effective adsorption capacity for Cd2+ due to extraordinary ion-exchange property. However, TNTs also adsorb Ca2+ and Mg2+ in water. In this study, carbon-modified TNT (TNT/C or TNT/HC) was synthesized by hydrothermal synthesis. The transmission electron microscope (TEM) images show that TNT/C or TNT/HC still keep nanotube morphology. The experimental results show the order of adsorption amount to Cd2+ is TNT > TNT/C > TNT/HC when there is no Ca2+ or Mg2+. But when there is Ca2+ or Mg2+ in the water, the order of Cd2+ adsorption capacity becomes TNT/HC > TNT/C > TNT. It indicates that the surface carbon-modification can alleviate the hindrance of Ca2+ or Mg2+ to Cd2+ removal. This is because the carbon on the surface of TNT captured part of Ca2+ or Mg2+, it made more Cd2+ be successfully absorbed by TNT through ion exchange. This mechanism was confirmed by XPS spectra analysis. The results of this paper can provide ideas for the adsorption and removal of Cd2+ in water in the presence of Ca2+ or Mg2+.

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