Xiushen Ye

Competitive adsorption of Li, Na, K, Rb and Cs ions onto calcium alginate–potassium tetraphenylborate composite adsorbent

In this study, the calcium alginate–potassium tetraphenylborate (Ca(ALG)2–KB(C6H5)4) composite adsorbent was synthesized using potassium tetraphenylborate (KB(C6H5)4) as the adsorption-active component and calcium alginate (Ca(ALG)2) as the matrix material. Different techniques were used for characterization of the adsorbent such as SEM, EDS, XRD, laser particle size analysis and moisture analysis. Competitive adsorption of Li, Na, K, Rb, Cs ions onto the adsorbent was investigated through kinetic curves, adsorption isotherms and column techniques at 25 °C. The equilibrium adsorption capacities were compared in the single-element and multi-element systems. The equilibrium adsorption amount was in the sequence Cs+ > Rb+ ≫ Na+ ∼ Li+, and Li and Na ions were hardly adsorbed. The separation factor was found to follow the order βCs/Li > βRb/Li > βNa/Li under both the noncompetitive and competitive adsorption conditions. In the kinetic experiments for competitive adsorption, the adsorption reached equilibrium in about 24 h. The equilibrium sorption data were described by the Langmuir and Freundlich isotherm models and the results showed that the Langmuir model with determination coefficients of 0.997 and 0.981 for Cs+ and Rb+ respectively could describe the competitive system at room temperature more correctly. Lower breakthrough ratio and higher adsorption amount were observed for Cs+ in the column experiments for competitive adsorption. Ion-exchange was deduced as the mechanism for selective adsorption of Rb+ and Cs+ ions onto the composite on the basis of EDS and XRD analysis of the adsorbent before and after adsorption. The tetraphenylborate anion (B(C6H5)4−) had different affinity to different alkali metal ions following the order Cs+ > Rb+ > K+ due to the order of the solubility product Ksp (CsBph4) < Ksp (RbBph4) < Ksp (KBph4).

Rubidium and Cesium Ion Adsorption by a Potassium Titanium Silicate-Calcium Alginate Composite Adsorbent

In this work, a composite spherical adsorbent, which employs potassium titanium silicate as an adsorption active component, and calcium alginate as a carrier, was successfully prepared. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the adsorbent. The kinetics and thermodynamics of rubidium and cesium ions adsorption were investigated comprehensively, by considering the effects of initial concentration, temperature, solution pH, and coexisting NaCl. According to the determination coefficients, the pseudo second-order kinetic model provided an impressive and comparable correlation, and the second-order rate constant and the initial adsorption rate increase with increasing temperature. In general, the equilibrium adsorption amount increases with the increasing initial metal ion concentration, but decreases with increasing coexisting NaCl. The adsorption capacity keeps constant in the pH value range 3-12 and slightly fades when the temperature increases from 25 to 55°C. Under similar conditions, rubidium and cesium show the similar adsorption amount. The adsorbent has a fast adsorption rate and an adsorption capacity of about 1.55 mmol g−1 for rubidium and 1.47 mmol g−1 for cesium when the initial metal ion concentration is 0.10 mol L−1. The composite adsorbent is effective for the adsorption of rubidium or cesium ions from simulated brines.

Competitive adsorption of Li, K, Rb, and Cs ions onto three ion-exchange resins

Abstract Adsorption is one of the effective methods to recover or remove alkali metal ions from aqueous solutions. Current studies on the adsorption of alkali metal ions are mainly focused on the adsorption of one alkali metal ion. However, under natural conditions, alkali metal ions are usually coexisted. During separation processes, they compete with each other. In this study, competitive and noncompetitive adsorption of Li, K, Rb, and Cs ions onto three ion-exchange resins (D001, LSC-100, and LSC-500) of sodium form was investigated in batch experiments at 25oC. Compared with the noncompetitive adsorption, competitive adsorption of different alkali metal ions present with larger differences, in general. The adsorption from single and multiple solutions presents similar preference. Under both the noncompetitive and competitive adsorption conditions, for D001 resin, the separation factor was found to follow the order of β Cs/Li > β Rb/Li > β K/Li, on the contrary, for both LSC-100 and LSC-500 resins, it ...

Iodide Adsorption onto Three Organic-Inorganic Composite Adsorbents

Composite adsorbents, Ca(ALG)2–Cu2O, Ca(ALG)2–AgCl and Ca(ALG)2–Ag, were prepared using Cu2O, AgCl and Ag as the adsorption-active components and calcium alginate as the matrix material. The adsorption of iodide from aqueous solutions onto these adsorbents was investigated as a function of initial solution pH, temperature and co-existing NaCl. The loading of the adsorption-active components in the composite adsorbents is much higher than that in the reported composite adsorbents. In neutral solutions, the equilibrium adsorption amount follows the order of Ca(ALG)2–AgCl <> Ca(ALG)2–Ag >> Ca(ALG)2–Cu2O. The adsorption by Ca(ALG)2–AgCl is insensitive to pH, while the adsorption by Ca(ALG)2–Cu2O and Ca(ALG)2–Ag is pH dependent. The effect of temperature on the adsorption is more pronounced for Ca(ALG)2–Cu2O than for Ca(ALG)2–AgCl and Ca(ALG)2–Ag. The co-existing NaCl does not affect the adsorption by Ca(ALG)2–AgCl very much; however, it suppresses the adsorption by Ca(ALG)2–Ag, and especially, Ca(ALG)2–Cu2O. Chemical adsorption is the main mechanism for all the three adsorbents. Ca(ALG)2–AgCl was found to be the best adsorbent owing to its highest adsorption capacity, suitable adsorption rate and insensitivity to solution pH, temperature and co-existing NaCl.

Iodide adsorption from aqueous solutions by bis(trimethoxysilylpropyl)amine polycondensate/silver chloride composites

Abstract Composite adsorbents for iodide were prepared with AgCl as an adsorption active component and bis(trimethoxysilylpropyl)amine (TSPA) as a gel precursor. The prepared composite adsorbents were used to adsorb iodide from aqueous solutions by considering the effects of initial iodide concentration, temperature, initial solution pH, and coexisting NaCl. The loading of AgCl in the prepared composite adsorbents was 5.5 mmol/g, much higher than that in the reported silver or silver chloride-impregnated activated carbon (around 0.097 mmol/g). The high AgCl loading ensures that the prepared composite adsorbents have a high adsorption capacity. At the initial adsorption stage of 0–12 h, the adsorption rate increases with increasing initial iodide concentration from 2 to 8 mmol/L. When the initial iodide concentration further increases from 8 to 14 mmol/L, the adsorption rate does not have an obvious increase. Pseudo-second-order model fits the experimental kinetic data quite well. The initial adsorption ra...

Comparative Study of the Competitive Adsorption of Mg, Ca and Sr Ions onto Resins

Existing studies on the adsorption of alkaline earth metal ions have mainly focused on the adsorption of one alkaline earth metal ion. However, under natural conditions, alkaline earth metal ions usually co-exist. While separating them using an adsorbent, they compete with each other for adsorption onto the adsorbent. In this work, comparative and competitive adsorption of Mg, Ca and Sr ions onto four resins (D001, DJH003, LSC-100 and LSC-500) of sodium form were investigated in batch experiments at 25 °C. Our results showed that in all the experiments, the equilibrium point was attained in approximately 4 hours. In general, the pseudo-first-order model is more suitable to describe the adsorption kinetic data than the pseudo-second-order model. For both D001 and DJH003 resins, there are bigger differences in the adsorption amounts of Mg, Ca and Sr ions for the competitive adsorption than for the non-competitive adsorption. Under competitive adsorption conditions, the separation factor follows the order of βSr/Mg > βCa/Mg, and the order of preference for adsorption is Sr2+ > Ca2+ > Mg2+. Therefore, it can be seen that there is a clear inhibitory effect for the adsorption of Mg ions owing to the competition of other ions. However, for both LSC-100 and LSC-500 resins, the competitive adsorption of Mg, Ca and Sr ions does not show obvious differences. The competitive adsorption results for all the resins were explained by considering hydration of the metal ions, electrostatic attractions and complexation between the metal ions and the resins. The results obtained would be helpful for understanding the competitive adsorption processes and the recovery or removal of one or more alkaline earth metal ions from aqueous solutions.

Influence of Sol Compositions on Boron Adsorption by Boron-Selective Hybrid Gels

Hybrid gels with boron-chelating groups were prepared using bis(trimethoxysilylpropyl)amine (TSPA) and the precursors synthesized from (3-glycidoxypropyl)trimethoxysilane (GPTMS) and N-methylglucamine (MG). Boron adsorption by the hybrid gels and a commercial boron-selective resin D564 were compared. The experimental results demonstrated that sol compositions have a great effect on the boron adsorption by the hybrid gels. Changing the sol compositions is a convenient way to adjust the adsorption capacity of the hybrid gels. The highest boron adsorption amount of the hybrid gels was found to be 1.54 mmol g-1, higher than that of the commercial resin D564 (1.39 mmol g-1). The hybrid gels reported in this study are easy to prepare, having a higher adsorption capacity and a good mechanical strength.

Preparation of Fe3O4-octadecyltrichlorosilane for removal of methyl orange and methylene blue: Influence of pH and ionic strength on competitive adsorption

Fe3O4-octadecyltrichlorosilane (Fe3O4-OTS) was synthesized and used to remove dyes in a competitive system. Fe3O4-OTS was prepared by slow hydrolysis of OTS in cyclohexane on the surface of Fe3O4 obtained through coprecipitation method. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and contact angle analyzer (CA) were used to analyze the properties of Fe3O4-OTS. Methyl orange (MO) and methylene blue (MB) were selected as model molecules to study the influence mechanism of pH and ionic strength on competitive adsorption. The results of EDS and CA indicated that Fe3O4 was modified successfully with OTS on the surface. Silicon appeared and carbon content increased obviously on the surface of adsorbent. Contact angle of adsorbent increased from 0° to 107° after being modified by OTS. Fe3O4-OTS showed good separation for MO and MB in competitive system, which has potential to separate dyes in sewage. Separation factor (βBO) changed from 18.724 to 0.017, when pH changed from 7 to 12, revealing that MO and MB could be separated almost thoroughly by Fe3O4-OTS. pH could change the surface charge of Fe3O4-OTS and structure of dyes, and thus change the interactions of competitive system indirectly. Even though hydrophobic interaction was enhanced, ionic strength reduced the difference of electrostatic interaction between dyes and Fe3O4-OTS. So it is unfavorable to separate dyes with opposite charges when ionic strength increases. These findings may provide theoretical guidances to separate two-component dye pollutants.

Electrochemical performance of LiNi0.5Mn1.5O4 doped with la and its compatiblity with new electrolyte system

Cathode materials LiNi0.5Mn1.5O4 and LiNi0.5 − x/2LaxMn1.5 − x/2O4 (x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNi0.5Mn1.5O4 material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L−1 lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L−1 LiPF6-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNi0.45La0.1Mn1.45O4/Li cell performed better than LiNi0.5Mn1.5O4/Li cell at cycle performance, median voltage, and efficiency.

Adsorption of boron by CA@KH-550@EPH@NMDG (CKEN) with biomass carbonaceous aerogels as substrate

This research reports an innovative boron adsorbent of CA@KH-550@EPH@NMDG (CKEN) via the modification of N-methyl-d-glucosamine (NMDG) on the surface of biomass carbonaceous aerogel, which is environmentally friendly, economically inexpensive, has simple preparation process and good regenerability. SEM and FT-IR characterization results indicate that CKEN has a 3D cross-staggered structure with lots of hydroxyl groups and pore structure, which are beneficial to the diffusion of boron and the chelation interaction between boron and CKEN. The adsorption behavior of CKEN for boron was evaluated. Various parameters affecting adsorption properties, viz., pH, ionic strength, initial concentration of boron, temperature and contact time were investigated. The adsorption kinetics is fitted with pseudo-second-order kinetics model better and the adsorption of boron on CKEN is an exothermic process. The adsorption equilibrium reached within 15 h with the maximum adsorption amount of 1.42 mmol/g (298 K). Moreover, CKEN also showed excellent reusability by consecutive five cycles of adsorption-desorption. It can be used as a potential recyclable adsorbent for efficient enrichment of boron from aqueous solution.