a b s t r a c tDate palm fiber (DPF) was demonstrated in the present issue as a potential low cost adsorbent for the removal of hexavalent chromium [Cr(VI)] from aqueous solution. A series of batch tests were conducted and the influence of initial metal ion concentration, contact time, pH of the solution and adsorbent dosage was investigated. The adsorbent was characterized by Fourier Transformed Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) to confirm the surface properties of the DPF adsorbent. The adsorption process was found to be strongly pH dependent. The adsorption isotherm data were fitted with Langmuir equation and the adsorption process was found to be followed pseudo-second-order rate kinetics. Chromium showed peculiar activities in aqueous solution due to its transition properties and the mechanism of Cr(VI) adsorption onto the DPF solid surface exhibited physisorption due to intermolecular bonding. Therefore, DPF can be employed as an efficient cost-effective adsorbent for the removal of Cr(VI) as a model component for heavy metals present in industrial wastewater.
Organic redox-active molecules are promising materials
for charge
storage in redox-flow batteries (RFBs); however, the development of
all-organic RFBs is hindered by material crossover, limited energy
density, and poor stability of active materials. Here, ester-substituted
bispyridinylidenes are reported as the first examples of intrinsic
bipolar molecules that exhibit basically concerted double two-electron
redox activity at a potential difference of 1.01 V. All three oxidation
states of the pentylester derivative exhibited excellent temporal
stability and good solubility in the electrolyte. Testing this active
material in symmetric cells, which alleviates crossover issues, revealed
good cyclability (fade of 0.025% and 0.35% per cycle for static and
flow cells, respectively), capacities of up to 89% of the theoretical
value, and Coulombic efficiencies above 99%. Considering previous
evidence for active material solubility limits of ∼2 M, and
the benefits of a symmetric design, such double concerted multielectron
bipolar active materials will be key to developing energy dense organic
RFBs.
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