Unexpected Selective Absorption of Lithium in Thermally Reduced Graphene Oxide Membranes

Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate of spent lithiumion batteries. Conventional wisdom shows that Li^(+) with low valence states has a much weaker adsorption(and absorption energy) with graphene than multivalent ions such as Mg^(2+). Here, we show the selective adsorption of Li^(+) in thermally reduced graphene oxide(rGO) membranes over other metal ions such as Mg^(2+), Co^(2+), Mn^(2+),Ni^(2+), or Fe^(2+). Interestingly, the adsorption strength of Li^(+) reaches up to 5 times the adsorption strength of Mg^(2+),and the mass ratio of a mixed Mg^(2+)/Li^(+) solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg^(2+)/Li^(+) separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cation–π interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes.

Hierarchically Porous Carbon Membranes Derived from PAN and Their Selective Adsorption of Organic Dyes

Porous carbon membranes were favorably fabricated through the pyrolysis of polyacrylonitrile（PAN） precursors, which were prepared with a template-free technique-thermally induced phase separation. These carbon membranes possess hierarchical pores, including cellular macropores across the whole membranes and much small pores in the matrix as well as on the pore walls. Nitrogen adsorption indicates micropores（1.47 and 1.84 nm） and mesopores（2.21 nm） exist inside the carbon membranes, resulting in their specific surface area as large as 1062 m2/g. The carbon membranes were used to adsorb organic dyes（methyl orange, Congo red, and rhodamine B） from aqueous solutions based on their advantages of hierarchical pore structures and large specific surface area. It is particularly noteworthy that the membranes present a selective adsorption towards methyl orange, whose molecular size（1.2 nm） is smaller than those of Congo red（2.3 nm） and rhodamine B（1.8 nm）. This attractive result can be attributed to the steric structure matching between the molecular size and the pore size, rather than electrostatic attraction. Furthermore, the used carbon membranes can be easily regenerated by hydrochloric acid, and their recovery adsorption ratio maintains above 90% even in the third cycle. This work may provide a new route for carbon-based adsorbents with hierarchical pores via a template-free approach, which could be promisingly applied to selectively remove dye contaminants in aqueous effluents.

Design of Neutral Carrier for Solvent Polymeric Membrane Iodide Electrode With High Selectivity

Anion-selective electrodes based on dissociated ion-exchangers such as lipophilicquaternary ammonium or phosphonium species always display classical Hofmeister be-havior in the following order: ClO4-】SCN-】I-】Br-】NO2-】Cl-】SO42-.A new sol-vent polymeric membrane electrode based on Schiff base complexes of Co（Ⅱ）[Co（Ⅱ）S]and showing excellent selectivity toward iodide ion is for the first time prepared inour work. The resulting electrodes exhibit fairly low detection limits andpotentiometric anion-selectivity sequences deviated from the Hofmeister pattern.Bis（salicylaldehyde） ethylenediiminecobalt（Ⅱ） [Co（Ⅱ）（salen）], bis（salicylaldehyde）-phenyldiiminecobalt（Ⅱ） [Co（Ⅱ）（salophen）],

Transport and selectivity of indium through polymer inclusion membrane in hydrochloric acid medium

In the present paper, a polymer inclusion membrane （PIM） containing polyvinyl chloride （PVC）, and bis-（2-ethylhexyl） phosphate （D2EHPA） which was used as extracting agent was used for the recovery of In（Ⅲ） ions in hydrochloric acid medium. The effects of carrier concentration, feed phase pH, strip phase HCI concentration, temperature on the transport, and the membrane＇s stability and thickness were examined. And the conditions for the selective separation of In（Ⅲ） and CU（Ⅱ） were optimized. The results showed that the transport of In（Ⅲ） across PIM was consistent with the first order kinetics equation, and also it was controlled by both the diffusion of the metal complex in the membrane and the chemical reaction at the interface of the boundary layers. The transport flux （J0） was inversely proportional to the membrane thickness, however, the transport stability improved as the membrane thickness increased. The transport flux of In（Ⅲ） and CU（Ⅱ） was decreased by excessive acidity of feed phase and high concentration of Cl^- . The selectivity separation coefficient of In（Ⅲ）/Cu（Ⅱ） was up to 34.33 when the original concentration of both In（Ⅲ） and Cu（Ⅱ） was 80 mg· L^ -1 as well as the pH of the feed phase and the concentration of Cl^- in the adjusting context were 0.6 and 0.5 mol· L^-1, respectively. Within the range of pH = 1-3, the separation selectivity of In（Ⅲ）/Cu（Ⅱ） reached the peak in the case when the Cl^- concentration was 0.7 mol·L^ -1.

Cable-like Au@SiO2 Janus composite nanorods

Cable-like Au@SiO2 Janus composite nanorods with PS and PEG grafting on both ends respectively are fabricated by skiving in combination of a post favorable modification. The cable-like Au@SiO2 composite nanofibers are synthesized in the channel of porous anodic aluminium oxide （AAO） membrane. After skiving, the corresponding composite nanorods are obtained. Following, PEG-SH and PS-SH are conjugated onto the two ends of the nanorods by a selective partial modification, respectively. Length and diameter of the Au@SiO2 Janus composite nanorods can be tuned controllably. It can be extended to fabricate a variety of different Janus nanorods with different compositions and microstructures.