Haining Liu

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.

Some physicochemical aspects of water-soluble mineral flotation

Some physicochemical aspects of water-soluble mineral flotation including hydration phenomena, associations and interactions between collectors, air bubbles, and water-soluble mineral particles are presented. Flotation carried out in saturated salt solutions, and a wide range of collector concentrations for effective flotation of different salts are two basic aspects of water-soluble mineral flotation. Hydration of salt ions, mineral particle surfaces, collector molecules or ions, and collector aggregates play an important role in water-soluble mineral flotation. The adsorption of collectors onto bubble surfaces is suggested to be the precondition for the association of mineral particles with bubbles. The association of collectors with water-soluble minerals is a complicated process, which may include the adsorption of collector molecules or ions onto such surfaces, and/or the attachment of collector precipitates or crystals onto the mineral surfaces. The interactions between the collectors and the minerals include electrostatic and hydrophobic interactions, hydrogen bonding, and specific interactions, with electrostatic and hydrophobic interactions being the common mechanisms. For the association of ionic collectors with minerals with an opposite charge, electrostatic and hydrophobic interactions could have a synergistic effect, with the hydrophobic interactions between the hydrophobic groups of the previously associated collectors and the hydrophobic groups of oncoming collectors being an important attractive force. Association between solid particles and air bubbles is the key to froth flotation, which is affected by hydrophobicity of the mineral particle surfaces, surface charges of mineral particles and bubbles, mineral particle size and shape, temperature, bubble size, etc. The use of a collector together with a frother and the use of mixed surfactants as collectors are suggested to improve flotation.

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...

Selective precipitation of water-soluble proteins using designed polyelectrolyte

By using lysozyme, hemoglobin (bovine), and pepsin as the model proteins and copolymer F1110 containing reactive functional groups of amido, sulfonate, and carboxylic acid groups as the flocculating agents, selective precipitation of proteins was performed by using two chemical processes. The experiment shows that the surface charge of copolymer F1110 is closely related to the pH value in solution. The flocculation behaviors of proteins with F1110 can be controlled completely by adjusting pH value in solution, which realizes the selective separation of mixed proteins. In addition, the selective precipitation of the proteins is promoted by a “modified flocculation” process, in two steps with a combination of F1110 and polyacrylamide. The characterization of modified flocculation is closely related to the property of the protein. These studies show a great prospect for selectively separating proteins from a mixture solution using designed polyelectrolytes containing reactive functional groups.

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.

Research progress in the preparation of rare earth alloys by molten salt electrolysis method

Rare earth alloys can be prepared through the methods of melting, metallothermic reduction, and molten salt electrolysis. Compared to the former two methods, the molten salt electrolysis method has several advantages: the production cost is lower, the composition of the rare earth alloys is uniform and easy control, and the quality of the rare earth alloys is good. The rare earth alloys can be prepared easily and continuously on industrial scale. In this paper, the research progress in the molten salt electrolysis preparation of the rare earth alloys of magnesium, aluminum, iron, cobalt, nickel, and copper is reviewed by considering the rare earth alloy applications in structural, magnetic, and hydrogen storage materials. The prospects of the related research works are discussed.

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.