Functional Ionic Liquid-Capped Graphene Quantum Dots for Chromium Removal from Chromium Contaminated Water

Abstract

New functional ionic liquid (IL) capped graphene quantum dot (GQD) was synthesized as an adsorbent for the removal of toxic heavy metal chromium(VI) ion (Cr 6+ ). The physicochemical properties of the adsorbent (IL-GQD) were investigated by Fourier transform infrared, Xray diffraction, atomic force microscopy, Raman, scanning electron microscopy, energy dispersive X-rays, and transmission electron microscopy analyses. The adsorption parameters, namely equilibrium time, solution pH, competing co-ions, dosage, and initial chromium concentration, were optimized for maximum Cr 6+ adsorption. The maximum adsorption capacity reached 934.62 mg/g at 40 min in neutral pH; this is much better than most of the other adsorbents reported earlier. In addition, the effect of pH in solution was investigated in the range of 3.0−12.0. The result showed that the lower pH value was found to favor the adsorption. The adsorption kinetics and isotherms fitted well with Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic studies indicated that the chromium adsorption process followed a spontaneous and endothermic model. This new functionalization of ionic liquid moieties into graphene quantum dot provides excellent results for the removal of toxic Cr 6+ . This can be utilized for field applications to reduce the chromium concentration to below the tolerance limit (>0.05 mg L −1 ).

Efficient Biosorption of Hexavalent Chromium from Water with Human Hair

“…The data suggests that the adsorption follows the Freundlich isotherm model ( R 2 = 0.99). The value of adsorption intensity ( n = 1.80) lying in the range of 1–10 confirms the favorable conditions for adsorption . The mean biosorption energy ( E ) was evaluated using the D–R isotherm which gives crucial information on predicting the type of biosorption process.…”

“…The value of adsorption intensity ( n = 1.80) lying in the range of 1–10 confirms the favorable conditions for adsorption. 43 The mean biosorption energy ( E ) was evaluated using the D–R isotherm which gives crucial information on predicting the type of biosorption process. If E is less than 8 kJ/mol, the biosorption process is controlled by physisorption, whereas if E > 16 kJ/mol, chemisorption is followed.…”

“…Experiments for the study of desorption were conducted in the batch mode. The 50 mg/L concentration of Cr(VI)-saturated adsorbents was treated with 50 mL of water at pH 12, for 6 h. 54 Separated human hair was washed with distilled water. It was further regenerated on addition of 1 N HCl.…”

Dicarboxylic acid cross-linked metal ion decorated bentonite clay and chitosan for fluoride removal studies

“…The sd values of diffusion-based and reaction based models of CeBC-A@CS nanocomposite were calculated and are summarized in Table 3. Intra-particle diffusion 45 and pseudo-second-order models 46 possessed lower sd values than the pseudo-rstorder model. Hence, the pseudo-second-order kinetic models were recognized as the well tted kinetic models for the uoride ions onto the adsorbent because the rate of this system will depends on both adsorbent and adsorbate.…”

Green Synthesis of Carbon Dots for Rapid Selective Detection and Photoreduction of Cr(VI) under Sunlight

“…According to previous reports, the ionic liquid (IL) was modified on CDs using EDC and NHS as coupling reagents. 33 Initially, 10 mg of EDC was mixed into 5 mL of CD (1 mg/mL) solution and stirred for 60 min. Then, 20 mL of 0.1 M phosphate buffer solution (PBS) (pH 7.4) was mixed with the above solution.…”