Graphene Composites for Lead Ions Removal from Aqueous Solutions

Effective adsorptive removal of Pb2+ ions from aqueous solution using functionalized agri-waste biosorbent: New green mediation via Seidlitzia rosmarinus extract

Currently, the use of natural adsorbent for the elimination of pollutants, such as heavy metals, from water has been extensively investigated. However, the low adsorption capacity of these natural adsorbents has led researchers towards the use of synthetic surfactants, which themselves can become environmental pollutants. In this research, an investigation was conducted to examine the impact of a surfactant obtained from the Seidlitzia rosmarinus plant on the adsorption properties of Pumpkin seed shell (PSS), a natural adsorbent. As a result, a modified version of PSS, known as functionalized Pumpkin seed shell (FPSS), was developed, and the effect of these two adsorbents on the elimination of Pb2+ has been investigated. FESEM, EDS, FTIR, and BET analyses were conducted to get detailed information of the adsorbent. Additionally, the effects of contact time, dosage of the adsorbent, pH of the solution, and temperature on the adsorbent were studied. The experimental data was fitted using Langmuir, Freundlich, Temkin, and Jovanovic isotherms. The PSS adsorbent was fitted best with the Langmuir isotherm, showing an adsorption capacity of 160.80 mg g-1, while the FPSS adsorbent was fitted with the Jovanovic isotherm, exhibiting an adsorption capacity of 553.57 mg g-1. Furthermore, kinetic modeling results indicated that the data for these adsorbents follow pseudo-second-order kinetic. Finally, the impact of coexisting ions and reusability was examined, with the FPSS adsorbent outperforming PSS. Therefore, the investigation of all these aspects demonstrated that the use of this natural surfactant significantly improves the performance of the adsorbent.

Graphene oxide@Fe3O4-decorated iota-carrageenan composite for ultra-fast and highly efficient adsorption of lead (II) from water

The aggravated problem of lead pollution, especially in aquatic environments, necessitates the development of eminent adsorbents that could radically solve this environmental problem. Hence, a new composite was constructed based on iota carrageenan (i.Carr), graphene oxide (GO) and magnetite (Fe3O4) for removing noxious Pb2+ ions. The GO@Fe3O4-i.Carr composite was characterized by VSM, SEM, XPS, XRD, FTIR and Zeta potential. The removal of Pb2+ ions attained a quick equilibrium of almost 30 min with a removal efficiency reaching 93.68 %. The removal of Pb2+ was boosted significantly, in the order of GO@Fe3O4-i.Carr(1:1) > GO@Fe3O4-i.Carr(1:3) > GO@Fe3O4-i.Carr(3:1). Moreover, acquired experimental data fitted the pseudo 2nd order kinetic model and Freundlich isotherm model with a maximal monolayer adsorption capacity reached 440.05 mg/g. Notably, after five adsorption runs, the composite maintained its removal efficiency exceeding 74 %. The assumed adsorption mechanisms of Pb2+ onto GO@Fe3O4-i.Carr were complexation, precipitation, Lewis acid-base, and electrostatic attraction forces. Overall, the GO@Fe3O4-i.Carr composite elucidated the auspicious adsorbent criteria, comprising fast adsorption with high performance, ease-separation and tolerable recyclability, advising its feasible use to decontaminate water bodies from hazardous heavy metals.

Preconcentration and Removal of Pb(II) Ions from Aqueous Solutions Using Graphene-Based Nanomaterials

Direct determination of lead trace concentration in the presence of relatively complex matrices is often a problem. Thus, its preconcentration and separation are necessary in the analytical procedures. Graphene-based nanomaterials have attracted significant interest as potential adsorbents for Pb(II) preconcentration and removal due to their high specific surface area, exceptional porosities, numerous adsorption sites and functionalization ease. Particularly, incorporation of magnetic particles with graphene adsorbents offers an effective approach to overcome the separation problems after a lead enrichment step. This paper summarizes the developments in the applications of graphene-based adsorbents in conventional solid-phase extraction column packing and its alternative approaches in the past 5 years.

Removal of toxic metals from wastewater environment by graphene-based composites: A review on isotherm and kinetic models, recent trends, challenges and future directions

Access to clean water has reduced in recent years due to pollution and man-made activities. Wastewater treatment regimens are many such as electrocoagulation, adsorption, ozonation, membrane and advanced oxidation processes. Owing to economical, resource availability and ease of operation adsorption has upper hand over all other methods employed in wastewater treatment. Graphene based adsorbents attracted researchers due to their ability to play dual role as adsorbent and photo-catalysts. When it comes to removal of heavy metals and dyes graphene-based aerogels are successful. Graphene composites were predominantly synthesized by top-down and bottom-up approach methods. Graphene composites are mesoporous and have microporous structure on surface. Graphene has copper desorption efficiency of 90 % upon 10th consecutive cycle. Graphene based adsorbents have adsorption efficiency of 367, 246 and 106.3 mg^-1 for lead, zinc and cadmium respectively. Though graphene possesses numerous applications, this review was devoted towards heavy metals removal from aqueous environment. In detail, the synthesis routes and interaction mechanism were explained and also the adsorption isotherms, kinetics were added. This review will serve as support for future research directions on removal of wastewater contaminants (heavy metals).

Green synthesis, characterization, application and functionality of nitrogen-doped MgO/graphene nanocomposite

A facile, feasible, and green synthesis via an electrochemical exfoliation process was applied to synthesize nitrogen-doped MgO/graphene nanocomposite (N-MgO/G). The N-MgO/G nanocomposite was characterized by several analytical techniques including X-ray photoelectron spectroscopy, X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, selected area electron diffraction, and elemental mapping analysis. N-MgO/G nanocomposite was then applied to adsorb lead metal ions (Pb²⁺) from aqueous solutions. The N-MgO/G nanocomposite demonstrated a remarkably high Langmuir maximum adsorption capacity (294.12 mg/g) for Pb²⁺ ions under the optimum experimental conditions at a pH of 5.13, time of 35 min, dose of 0.025 g, the concentration of 400 mg/L, and a temperature of 36 °C. Adsorption kinetics results fitted with a pseudo-second-order model and a thermodynamic study showed that Pb²⁺ adsorption is an endothermic process. The practical application of N-MgO/G was also investigated to test its applicability in real water samples collected from different sources such as deionized water, tap water, wastewater, and river water.