Preparation of graphene oxide-doped silica aerogel using supercritical method for efficient removal of emerging pollutants from wastewater

Innovative Sorbents for the Removal of Micropollutants from Water

This review summarizes the current knowledge in the field of preparing new and/or innovative materials that can be advantageously used for the sorption of emerging pollutants from water. This paper highlights new innovative materials such as transition metal-modified biochar, zeolites, clays, carbon fibers, graphene, metal organic frameworks, and aerogels. These materials have great potential for the removal of heavy metals from water, particularly due to their large surface area, nanoscale size, and availability of various functionalities; moreover, they can easily be chemically modified and recycled. This paper not only highlights the advantages and ever-improving physicochemical properties of these new types of materials but also critically points out their shortcomings and suggests possible future directions.

Facile synthesis of reduced graphene oxide/carbon/calcium alginate aerogel for the removal of pharmaceutical pollutants

Pharmaceuticals are the new emerging challenge pollutants to removal from the aquatic environments. In this study, a series of reduced graphene oxide/carbon/calcium alginate (rGO/C/CA) aerogel was fabricated using an environmentally friendly freeze-drying method. The surface properties including surface textures, elemental contents, crystal structures, and functional groups of rGO/C/CA aerogel were investigated. The aerogels were utilized for the adsorptive removal of oxytetracycline (OTC) and amitriptyline HCl (AMT) drugs in contaminated aquatic environments. Results showed that rGO/C/CA aerogel had much higher adsorption efficiency of OTC and AMT compared to other pristine and binary aerogels due to the enhanced surface properties and synergetic effect of functional groups. The equilibrium data were best fitted to the Toth isotherm model for both OTC and AMT and the mathematical interpretation of fitting data suggests a monolayer adsorption for both drugs. The results demonstrated that rGO/C/CA aerogel could be a reusable adsorbent for eliminating wastewater related pharmaceutical pollutants.

Chitosan-glutaraldehyde graphene oxide aerogel for extraction of polybrominated and -chlorinated carbazoles in lotus root

Halogenated carbazoles (HCZs) are prevalent in sediments, pose a risk of entering the human food chain via lotus roots. However, starch, protein, and fat in lotus root complicate determination of HCZs in this food. This study introduces a straightforward, sensitive, and rapid method for detecting four HCZs in lotus roots. The method employs a conical monolithic extraction column (MEC) containing chitosan-glutaraldehyde-graphene oxide aerogel (CS-GA-GOA) material. The CS-GA-GOA - MEC successfully achieved extraction of four HCZs in spiked lotus root samples in under 5 min. The method was rapid (15 min) compared with alternatives, as well as being sensitivity (0.08-0.27 ng/g), accurate (89.7 %-104.2 %), and more cost-effective. This work contributes to the exploration of advanced adsorbents but also broadens the applicability of graphene oxide aerogels in extraction processes, paving the way for the development of rapid and accurate analytical methods for HCZs in foods.

Facile synthesis of a 3D magnetic graphene oxide/Fe3O4/banana peel-derived cellulose composite aerogel for the efficient removal of tetracycline

Many initiatives have incorporated graphene oxide (GO) and biomass into aerogels for wastewater treatment. We report on the facile fabrication of a magnetic GO/Fe3O4/banana peel-derived cellulose (bio-cellulose) aerogel using an ultrasound-assisted mechanical mixing method and freeze-drying technique for the removal of tetracycline (TC). The component materials and composite aerogel were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen adsorption-desorption analysis, and vibrating sample magnetometry (VSM). The effects of solution pH and adsorbent dose on the adsorption performance of the synthesized adsorbents were investigated. The adsorption behavior at the equilibrium of the GO/Fe3O4/bio-cellulose aerogel was studied and analyzed using four well-known non-linear models: Langmuir, Freundlich, Sips, and Temkin. The results showed that the experimental data fitted well with the Freundlich and Sips isotherm models. The maximum adsorption capacity achieved from the Sips model was 238.7 mg g-1. The adsorption kinetics were studied and proved to follow the Elovich kinetic model with an initial rate of 0.89 g g-1 min-1. These results confirm the favorable adsorption of TC on the heterogeneous surface that exhibits a wide range distribution of adsorption energies of the desired GO/Fe3O4/bio-cellulose aerogel. The experimental findings demonstrate that the aerogel possesses the notable features of environmental friendliness, cost-effectiveness, and comparatively high TC adsorption capacity. Therefore, utilizing biomass to develop the structure of the magnetic GO-based composite aerogel is significantly promising for antibiotic-containing wastewater treatments.

Optimization of methyl orange decolorization by bismuth(0)-doped hydroxyapatite/reduced graphene oxide composite using RSM-CCD

In the current study, the catalyst for the decolorization of methyl orange (MO) was developed HAp-rGO by the aqueous precipitation approach. Then, bismuth(0) nanoparticles (Bi NPs), which expect to show high activity, were reduced on the surface of the support material (HAp-rGO). The obtained catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The parameters that remarkably affect the decolorization process (such as time, initial dye concentration, NaBH4 amount, and catalyst amount) have been examined by response surface methodology (RSM), an optimization method that has acquired increasing significance in recent years. In the decolorization of MO, the optimum conditions were identified as 2.91 min, Co: 18.85 mg/L, NaBH4 amount: 18.35 mM, and Bi/HAp-rGO dosage: 2.12 mg/mL with MO decolorization efficiency of 99.60%. The decolorization process of MO with Bi/HAp-rGO was examined in detail kinetically and thermodynamically. Additionally, the possible decolorization mechanism was clarified. The present work provides a new insight into the use of the optimization process for both the effective usage of Bi/HAp-rGO and the catalytic reduction of dyes.

An Updated Overview of Silica Aerogel-Based Nanomaterials

Silica aerogels have gained much interest due to their unique properties, such as being the lightest solid material, having small pore sizes, high porosity, and ultralow thermal conductivity. Also, the advancements in synthesis methods have enabled the creation of silica aerogel-based composites in combination with different materials, for example, polymers, metals, and carbon-based structures. These new silica-based materials combine the properties of silica with the other materials to create a new and reinforced architecture with significantly valuable uses in different fields. Therefore, the importance of silica aerogels has been emphasized by presenting their properties, synthesis process, composites, and numerous applications, offering an updated background for further research in this interdisciplinary domain.