An
approach is reported for the exclusive production of CdTe magic-size
clusters (MSCs) that exhibit an optical absorption doublet peaking
at 385/427 nm, with an explanation of the synthesis procedure. The
MSCs, defined as dMSC-427, were produced from the reaction of cadmium
oleate (Cd(OA)2) and tri-n-octylphosphine
telluride in octadecene at 100 °C, with the addition of acetic
acid (HOAc) or acetate (M(OAc)2) during the prenucleation
stage (40 °C). Without such an addition or when it was performed
in the postnucleation stage (100 °C), quantum dots (QDs) developed.
The production of dMSC-427 or QDs is hypothesized to be related to
the solubility of the Cd precursor, such as Cd(OA)1(OAc)1 or Cd(OA)2, respectively. Also, the reactions
that lead to Cd(OA)1(OAc)1 are proposed. The
present study provides an in-depth understanding of the two-pathway
model proposed for the prenucleation stage of binary colloidal QDs,
as well as of the formation of MSCs and/or QDs.
Vanadium (V) and chromium (Cr) co-exists in the whole process of V extraction from the vanadium titano-magnetite ore in China. It remains a challenge to remove trace V(V) from Cr(VI) in a simple way. Based on facile pretreatment of transforming Cr(VI) selectively, a novel method to remove V(V) from Cr(VI) by anion exchange resin Dex-V has been established. The influence of operation parameters including pH, contact time and temperature on adsorption ratio has been investigated. The Langmuir model and Henry model were successfully applied to describe the adsorption behavior of V by the Dex-V resin. It is shown that V is adsorbed chemically in monolayer and the Dex-V resin presents a homogeneous nature. Kinetics of V adsorption was analyzed with the pseudo-second order model, the Richenberg model and the Weber-Morris model. Results show that the rate of V adsorption is controlled by film diffusion in initial 70 min and the intra-particle diffusion contributes to the rate-controlling after 70 min. The proposed method was applied to remove V from real waste water and the removal ratio as high as 96% was obtained, with Cr recovery of 95%, which validates the effectiveness and efficiency of the novel method. This work has thus provided new insights into separation and recovery of analogue metals in aqueous.
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