Measurements of Metal Adsorption in Oxide-Clay Mixtures: “Competitive-Additivity” Among Mixture Components

1992 ◽  
Vol 294 ◽  
Author(s):  
V. S. Tripathi ◽  
M.D. Siegel ◽  
Z. S. Kooner
Keyword(s):  
Surface Complexation ◽  
Particle Interactions ◽  
Complexation Constants ◽  
Lead Adsorption ◽  
Adsorption Sites ◽  
Adsorption Behaviors ◽  
Limited Success ◽  
Ph Dependent ◽  
Waste Repositories ◽  
Zinc Adsorption

ABSTRACTAn important question concerning the transport of radionuclides from nuclear waste repositories is whether the adsorption of metals by rocks and soils can be predicted from the properties of the constituent minerals. Attempts by previous researchers to use sorption models based on linear adsorption or weighted "sorptive additivity" have met with limited success. In this study, a “competitive-additivity” model based on surface complexation theory was used to model the pH-dependent adsorption of lead by goethite/Ca-montmorillonite mixtures using complexation constants obtained from single sorbent systems. Measurements of lead adsorption by goethite, Ca-montmorillonite, and goethite-Ca-montmorillonite mixtures (and similar studies of copper and zinc adsorption) demonstrate that the two adsorbents compete for adsorption of metals over wide ranges of pH and concentrations of adsorbents and metals. The adsorption behaviors of the mixtures are determined by the relative concentrations of the adsorbents and their respective affinities for the adsorbate metal. Particle-particle interactions such as heterocoagulation of the oxide and clay do not appear to be significant for the majority of the adsorption sites in this system.

scholarly journals Effects of Cu(II) on the Adsorption Behaviors of Cr(III) and Cr(VI) onto Kaolin

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Juanjuan Liu ◽  
Xiaolong Wu ◽  
Yandi Hu ◽  
Chong Dai ◽  
Qin Peng ◽  
...  
Keyword(s):  
Distribution Coefficient ◽  
Adsorption Capacity ◽  
Removal Efficiency ◽  
Saturation Index ◽  
Surface Complexation ◽  
Maximum Adsorption Capacity ◽  
Positive Correlation ◽  
Adsorption Sites ◽  
Ph Values ◽  
Adsorption Behaviors

The adsorption of Cr(III) or Cr(VI) in the absence and presence of Cu(II) onto kaolin was investigated under pH 2.0–7.0. Results indicated that the adsorption rate was not necessarily proportional to the adsorption capacity. The solutions’ pH values played a key role in kaolin zeta potential(ζ), especially the hydrolysis behavior and saturation index of heavy metal ions. In the presence of Cu(II),qmixCr(III)reached the maximum adsorption capacity of 0.73 mg·g−1at pH 6.0, while the maximum adsorption capacity for the mixed Cr(VI) and Cu(II) system (qmixCr(VI)) was observed at pH 2.0 (0.38 mg·g−1). Comparing the adsorption behaviors and mechanisms, we found that kaolin prefers to adsorb hydrolyzed products of Cr(III) instead of Cr3+ion, while adsorption sites of kaolin surface were occupied primarily by Cu(II) through surface complexation, leading to Cu(II) inhibited Cr(VI) adsorption. Moreover, Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficientKd. Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficientKdand that of adsorption affinities of Cr(III) or Cr(VI) on kaolin was found to beKdCr(III) <KdCr(III)-Cu(II) andKdCr(VI) >KdCr(VI)-Cu(II).

Sorption Mechanism of Carbon-14 by Hardened Cement Paste

1995 ◽  
Vol 412 ◽  
Author(s):  
K. Noshita ◽  
T. Nishi ◽  
M. Matsuda ◽  
T. Izumida
Keyword(s):  
Electrostatic Force ◽  
Cementitious Materials ◽  
Hardened Cement ◽  
Sorption Mechanism ◽  
Carbon 14 ◽  
Adsorption Sites ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Positively Charged

AbstractCarbon-14 sorption by cementitious materials should be enhanced to ensure the long term safety of radioactive waste repositories. The sorption mechanism of inorganic C- 14 (CO32- was investigated using batch sorption experiments and zeta potential measurements. The results suggested that C-14 was adsorbed onto the cement surface by an electrostatic force, due to the reaction between SiO2 and CaO contained in the cementitious composition. That is, SiO2 was originally negatively charged (SiO-) in cement, but became positively charged through the interaction of Ca2+. These positive sites on the SiO2 surface adsorbed inorganic C-14. Ordinary Portland cement (OPC) did not contain enough SiO2 compared with its CaO content to produce sufficient numbers of C-14 adsorption sites. The C-14 distribution coefficient (Kd) was increased from 2,000 to 7,000 mL/g by adding SiO2 to OPC.

Comparative adsorption of Eu(iii) and Am(iii) on TPD

2015 ◽  
Vol 17 (9) ◽  
pp. 1634-1640 ◽  
Author(s):  
Q. H. Fan ◽  
X. L. Zhao ◽  
X. X. Ma ◽  
Y. B. Yang ◽  
W. S. Wu ◽  
...  
Keyword(s):  
Surface Complexation ◽  
Surface Complexation Model ◽  
Adsorption Behaviors

Comparative adsorption behaviors of Eu(iii) and Am(iii) on thorium phosphate diphosphate (TPD), i.e., Th4(PO4)4P2O7, have been studied using a batch approach and surface complexation model (SCM) in this study.

scholarly journals Comparative Study on the Adsorption Capacities of the Three Black Phosphorus-Based Materials for Methylene Blue in Water

2020 ◽  
Vol 12 (20) ◽  
pp. 8335
Author(s):  
Juanhong Wang ◽  
Zhaocheng Zhang ◽  
Dongyang He ◽  
Hao Yang ◽  
Dexin Jin ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Adsorption Capacity ◽  
Black Phosphorus ◽  
Adsorption Effect ◽  
Adsorption Sites ◽  
Surface Areas ◽  
Adsorption Behaviors ◽  
Adsorption Capacities ◽  
Reduced Graphene ◽  
Black Phosphorene

Dye effluent has attracted considerable attention from worldwide researchers due to its harm and toxicity in recent years; as a result, the treatment for dye has become one of the focuses in the environmental field. Adsorption has been widely applied in water treatment owing to its various advantages. However, the adsorption behaviors of the new materials, such as the 2D black phosphorus (BP), for pollution were urgently revealed and improved. In this work, BP, black phosphorene (BPR), and sulfonated BPR (BPRS) were prepared by the vapor phase deposition method, liquid-phase exfoliating method, and modification with sulfonation, respectively. The three BP-based materials were characterized and used as adsorbents for the removal of methylene blue (MB) in water. The results showed that the specific surface areas (SSAs) of BP, BPR, and BPRS were only 6.78, 6.92, and 7.72 m2·g−1, respectively. However, the maximum adsorption capacities of BP, BPR, and BPRS for MB could reach up to 84.03, 91.74, and 140.85 mg·g−1, which were higher than other reported materials with large SSAs such as graphene (GP), nanosheet/magnetite, and reduced graphene oxide (rGO). In the process of BP adsorbing MB, wrinkles were generated, and the wrinkles would further induce adsorption. BPR had fewer layers (3–5), more wrinkles, and stronger adsorption capacity (91.74 mg·g−1). The interactions between the BP-based materials and MB might cause the BP-based materials to deform, i.e., to form wrinkles, thereby creating new adsorption sites between layers, and then further inducing adsorption. Although the wrinkles had a certain promotion effect, the adsorption capacity was limited, so the sulfonic acid functional group was introduced to modify BPR to increase its adsorption sites and promote the adsorption effect. These findings could provide a new viewpoint and insight on the adsorption behavior and potential application of the BP-based materials.

A surface complexation model for cadmium and lead adsorption onto diatom surface

2006 ◽  
Vol 88 (1-3) ◽  
pp. 110-113 ◽  
Author(s):  
A. Gélabert ◽  
O.S. Pokrovsky ◽  
C. Reguant ◽  
J. Schott ◽  
A. Boudou
Keyword(s):  
Surface Complexation ◽  
Lead Adsorption ◽  
Surface Complexation Model ◽  
Cadmium And Lead
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