Ultra‐Rapid Removal of Pb(II) Ions by a Nano‐MoS₂ Decorated Graphene Aided by the Unique Combination of Affinity and Electrochemistry

Abstract

co-precipitation, [11] cloud point extraction, [12] flocculation, [13] reverse osmosis, [14] and adsorption, [15,16] the adsorption-based removal methodology is one of the most promising and widely applied methods to remove pollutants from the environment due to its cost-effectiveness, simple operation, and environmental friendliness. [17] However, the efficiency of adsorption in the removal of toxic metal ions such as Pb (II) depends on the selectivity of the materials used toward the particular ions because of the presence of other pollutants and common metal ions in relatively higher concentrations in water and the very low (safe) level of Pb (II) that need to be achieved. [16] For past decades, various adsorbents have been explored to remove heavy metal ions, which included activated carbon [18,19] from various sources and methods, zeolites, [20,21] clays, [22,23] and polymers [24,25] which exhibited lower removal efficiency for Pb (II) due to the weak binding affinity toward Pb (II) and lack of selectivity.Recently, ultrathin 2D nanomaterials such as graphene (Gr), and Gr-based compounds, molybdenum disulfide (MoS 2 ), [26,27] boron nitride, etc., have gained immense attention as adsorption materials due to their higher theoretical surface area (SA), enhanced catalytic and other unique properties. [28][29][30][31] With its high theoretical SA (≈2630 m 2 g −1 ), chemical stability, and outstanding physicochemical properties, Gr has shown high adsorption capacities for toxic metal ions [32] compared to the other commonly studied adsorbents. [33][34][35][36] Similarly, MoS 2 exhibits higher SA in its nanoforms and, in addition, can exhibit a significant advantage in the adsorption of heavy metal ions such as Hg (II), Ag (I), Cd (II), and Pb (II) because of the affinity toward S 2ions. [37][38][39][40] A previous work from our group utilized MoS 2 -HNR for the removal of toxic metal ions, and it demonstrated simultaneous removal of toxic metal ions: Hg (II), Pb (II), and Ag (I) from groundwater and seawater samples with adsorption capacities as high as ≈1991, 1350, and 1267 mg g −1 for Hg (II), Ag (I), and Pb (II). Even though the maximum adsorption capacity of MoS 2 -HNR toward Pb (II) was higher, the MoS 2 -HNR required ≤30 min to decrease the [Pb (II)] to the safe level (≤10 ppb) in water. The results were able to be explained based on affinity and electrochemistry mechanism. Cost-effective adsorbent materials with high Pb(II) removal efficiency and selectivity are considered necessary for successfully removing Pb(II) contamination from drinking water because of their high-level toxicity and the ultralow safe level of ≤10 ppb in water. This study demonstrates the synthesis and the ultrafast Pb(II) removal capability of a partially reduced graphene oxide-nano-molybdenum disulfide composite (prGO-MoS 2 ). The prGO-MoS 2 exhibits thin sheets of prGO covered more or less uniformly with nano-MoS 2 , and the open architecture gives enhanced accessibility to the S 2and oxygen moieties present in prGO-MoS 2 . A singl...

Trace-Level Detection of Pb(II) and Cd(II) Aided by MoS2 Nanoflowers and Graphene Nanosheet Combination

“…In our previous report, the ultra-rapid and selective adsorption of Pb(II) by prGO-MoS 2 was explained based on the combination of affinity (between Pb(II) and the S 2− and O moieties) and the electrochemistry mechanism (imparted by the electron-rich prGO). 28 There, it was observed that MoS 2 In this study, the presence of oxidation peaks observed in DPV for Pb(II) and Cd(II) on prGO-MoS 2 (Figure 3A) is evident in the EC mechanism, i.e., the spontaneous reduction of Pb(II)/ Cd(II) to Pb(0)/Cd(0), by prGO-MoS 2 . The absence of these peaks in both MoS 2 and pm-prGO+MoS 2 (Figure 3B) indicates the absence of an EC mechanism in these materials.…”

“…The detailed synthesis procedure of prGO-MoS 2 is reported elsewhere by our group; GO, sodium molybdate, and thioacetamide were used as the precursor, and a simple hydrothermal route was followed. 28 The synthesis procedures followed to obtain prGO-MoS 2 are elaborated in the Supporting Information (Page No. S1).…”

“…4,14,15 In EC sensing, electrodes play the most significant part, which decides the efficiency of the sensor; different nanomaterials such as reduced graphene oxide (rGO), 16 multiwalled carbon nanotubes (MWCNTs), Au nanoparticles, 7 metal−organic frameworks (MOFs), 17 metal oxides, 18 SnS decorated with Bi 2 O 3 nanosheets, 19 poly(glutamic acid) and carboxylated carbon nanosheets, 8 N-doped-carbon nanosheets, 20 Ru−GO nanocomposite, 21 boron nitride (h-BN), etc., have gained immense attention as electrode materials because of their properties such as possible higher specific surface area (SA), enhanced catalytic activity, structural flexibility, inertness, and biocompatibility. 22−27 A previous report from our group revealed the benefits of combining Gr and nano-MoS 2 (a partially reduced graphene oxide-MoS 2 composite (prGO-MoS 2 )) for the ultrafast adsorption of Pb(II) from wastewater, 28 and another report of pGr-MoS 2 made from Gr obtained by pulverization of graphite imparted ultraselective sensing toward dopamine (DA), 29 whereas in both cases, the respective properties were not observed in the starting materials: prGO, GO, pGr, or nano-MoS 2 . The remarkable adsorption performance of Pb(II) by prGO-MoS 2 motivated us to explore the EC sensing of toxic metal ions by prGO-MoS 2 , especially Pb(II).…”

Comparison of Kinetics of Adsorption of Permanganate on Co-Al-Layered Double Hydroxide and MoS2 Nanocompounds

“…During recent years, researchers used MoS 2 and its composites as efficient adsorbents. [72][73][74][75][76] As reported in our previous work, 2 the regions of adsorption isotherms of MnO -4 on MoS 2 and their boundaries under different conditions were analyzed by the ARIAN model and were shown in Table S2. Using data of this Table, the appropriate initial concentrations of MnO -4 were determined for carrying out adsorption kinetic tests.…”

Dimethyl 2‐Methylglutarate (Iris): A Green Platform for Efficient Liquid‐Phase Exfoliation of 2D Materials

“…The emergence of 2D materials [1][2][3][4][5][6][7][8] had a tremendous impact on the scientific research, in consideration of the unique properties and their broad technological prospect in photonics, [9] flexible electronics, [10] nanocomposites, [11,12] (photo)electrocatalysis, [13][14][15] supercapacitors, [16,17] functional coatings, [18] (bio)sensors, [19] and desalination. [11,[20][21][22]…”