Rational Synthesis, Characterization, and Application of Environmentally‐Friendly (Polymer‐Carbon Dot) Hybrid Composite Film for Fast and Efficient UV Assisted Cd2+ removal from water

Abstract

Carbon-dots (CDs) are of particular interest in numerous applications. However, their efficiency for heavy metal removal from wastewater was not yet reported. Herein, we rationally synthesized CDs from petroleum-coke-waste via hydrothermal treatment in the presence of ammonia.This drove the formation of outstanding photoluminescent, water-soluble, biocompatible, and high yield of monodispersed sub-5 nm CDs. The CDs are co-doped with high 10 % of N and 0.2 % of S. The as-prepared CDs possess unprecedented photoluminescent properties over broad pH range making these dots unique efficient pH sensors. Chitosan (CH)-CDs hybrid hydrogel nanocomposite film was further prepared as a platform membrane for the removal of Cd2+ metal from wastewater. The prepared CH-CDs membranes show a relatively good mechanical properties, based on stressresistantance and flexibility in order to facilitate handling. The equilibrium state was reached within 5 minutes. Intriguingly, the UV-light illuminations enhanced the Cd2+ removal efficiency of the photoluminescent CDs substantially by four times faster. It was found that adsorption followed pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity at 25̊ C was found to be 112.4 mg g-1 at pH 8. This work paves the way to new applications of CDs in water treatment.

Photoluminescent Carbon Dot-Intercalated Bentonite: A Light Responsive Nanohybrid for Lead Removal

“…The UV-Vis absorption of B-CDs nanocomposite (Fig. 4a), displays two absorption peak centered at 380 and 450 nm, assigned to π → π* transition and n → π* transition, similar to previously reported carbon quantum dots-based materials 7,12 . The photoluminescence properties of the nanocomposites were also evaluated with the help of photoluminescence spectroscopy.…”

“…In order to obtain nitrogen dopped carbon quatum dots (CDs), 4 g of graphite waste was initially grinded then dissolved in sulfuric and nitric acids under stirring/refluxing, as previously described 7 , the as obtained CDs was introduced to bentonite clay(BP) suspension, in order to obtain the (BP-CDs )nanocomposite through cation exchange reaction, 1g of BP (negatively charged) was mixed with 20 wt.% of CDs (positively charged), the mixture was kept under mechanical stirring at room temperature for 24 h, centrifuged, washed and dried at 60̊ C. The as prepared material (B-CDs) was used hereafter as hybrid platform for heavy metal removal, heater for led removal.…”

“…5b, and the maximum adsorption capacity, was equal to 400 mg/g toward PB (II) removal, at room temperature and pH=8 and under light conditions. As shown in Table 3, the B-CDs nanohybrid presents superior adsorption capacity compared to other adsorbents, due to the formation of strong complex between the free carboxylic, N and sulfur groups present in CDs and Pb 2+ ions from one side 7,22 , and the cation exchange reaction from the other side, that may happen between the Na + present in bentonite clay galleries and the Pb 2+ metal present in solution as shown in Fig. 6.…”