Diesel exhaust soot (DES), a hazardous by-product of incomplete diesel combustion, was valorized into activated nanocarbon (ANC) through phosphoric acid activation for phenol removal from water. The synthesized ANC was characterized by FTIR, XRD, FE-SEM, TEM, EDX, and AFM. The results revealed predominantly spherical nanoparticles with an average size below 30 nm, a turbostratic carbon structure, and oxygen-containing surface functional groups favorable for adsorption. The adsorption performance was evaluated as a function of adsorbent dosage, contact time, initial phenol concentration, and temperature. The optimum adsorbent dosage and equilibrium time were 0.1 g and 90 min, respectively, while the highest removal efficiency was obtained at an initial phenol concentration of 10 mg L−1. The equilibrium data were best described by the Langmuir model (R2 = 0.999), with a maximum adsorption capacity of 23.98 mg g−1, indicating predominantly monolayer adsorption. Thermodynamic analysis confirmed that phenol adsorption was spontaneous (ΔG = −22.42 to −25.79 kJ mol−1) and endothermic (ΔH = +11.43 kJ mol−1), with a positive entropy change (ΔS° = +113.47 J mol−1 K−1). These findings demonstrate the potential of DES as a low-cost precursor for functional nanocarbon adsorbents and provide a sustainable approach for converting combustion waste into a value-added material for water purification.
Graphite (stacked graphene layers) has been modified in several ways to enhance its potential properties/utilities. One approach is to convert graphite into a unique 'nano-graphite' form. Nano-graphite consists of few-layered graphene, multi-layered graphene, graphite nanoplatelets, and other graphene aggregates. Graphite can be converted to nano-graphite using physical and chemical methods. Nano-graphite, similar to graphite, has been reinforced in conducting polymers/thermoplastics/rubbery matrices to develop high-performance nanocomposites. Nano-graphite and polymer/nano-graphite nanomaterials have characteristics that are advantageous over those of pristine graphitic materials. This review basically highlights the essential features, design versatilities, and applications of polymer/nano-graphite nanocomposites in solar cells, electromagnetic shielding, and electronic devices.
Oil spills necessitate the development of effective methods for preventing their damaging effects on the environment. A number of physical, chemical, thermal, and biological methods are used to combat oil spills. Among them, sorption is considered to be efficient in removing thin oil films from water surfaces. Currently, there is an urgent need for simple methods of obtaining oil sorbents that include a magnetosensitive component to optimize the process of removing oil from the water surface. The purpose of the work is to obtain and research oil sorbents resistant to destruction, with increased bulk density and complex magnetosensitivity, based on thermally expanded graphite (TEG) with the inclusion of micro- and nano-particles of iron and its oxides. The structure and composition of the new composite material was characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometry, thermogravimetric analysis, and laser diffraction particle sizing. The composite sorbent comprised TEG with the inclusion of iron-containing magnetosensitive particles. Metal-carbon nanoparticles (MCN) were used as the magnetosensitive component; they had a magnetosensitive iron core covered with a carbon shell. We used two methods of synthesis, namely (i) mechanical mixing of the TEG flakes and MCN particles, and (ii) applying a thermal shock (microwave processing) to the mixture of graphite intercalated with sulphuric acid and micro- and nanoparticles of iron and iron oxides. In the first case, MCN particles were fixed on the faces, edges, and other surface defects of the TEG flakes due to intermolecular forces, coordinate bonds, and electrostatic interaction. The strong adhesion of magnetosensitive iron/iron oxide and TEG particles in the second case was due to the mutual dissolution of iron and carbon components during the thermal shock, which formed an interfacial layer in which iron carbide is present. The presence of magnetosensitive components in the structure of the proposed oil sorbents allows the use of magnetic separation for the localization and removal of oil spills, increases the density of sorbents, and, accordingly, leads to a decrease in windage while retaining the advantageous properties of thermally expanded graphite. According to the results of laboratory studies, the efficiency of removing oil from the water surface is not lower than 95–96%.
In this study, activated carbons derived from walnut shells (CA-N) and apple wood (CA-M) were used as adsorbents to remove cobalt(II) and strontium(II) ions from aqueous solutions. The novel materials were obtained using nitric acid (CA-Mox) and nitric acid/urea mixture (CA-Mox-u, CA-Nox-u) as oxidizing agents. The physical–chemical characteristics of activated carbons were determined from nitrogen sorption isotherms, SEM-EDX, FTIR, pH metric titrations, the Boehm titration method and elemental analysis. The results of batch experiments indicate that maximum adsorption can be achieved in broad pH ranges: 4–8 for Co(II) and 4–10 for Sr(II). The maximum adsorption capacities of Co(II) and Sr(II) on oxidized activated carbons at pH = 4 are: CA-Mox, 0.085 and 0.076 mmol/g; CA-Mox-u, 0.056 and 0.041 mmol/g; and CA-Nox-u, 0.041 and 0.034 mmol/g, respectively. The mathematical models (pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models, and Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin–Pyzhev isotherm models) were used to explain the adsorption kinetics, to study the adsorption mechanism and predict maximum adsorption capacity of the adsorbents. The adsorption mechanisms of toxic metal ions on activated carbons were proposed.
Global warming and climate changes are among the biggest modern-day environmental problems, the main factor causing these problems is the greenhouse gas effect. The increased concentration of carbon dioxide in the atmosphere resulted in capturing increased amounts of reflected sunlight, causing serious acute and chronic environmental problems. The concentration of carbon dioxide in the atmosphere reached 421 ppm in 2022 as compared to 280 in the 1800s, this increase is attributed to the increased carbon dioxide emissions from the industrial revolution. The release of carbon dioxide into the atmosphere can be minimized by practicing carbon capture utilization and storage methods. Carbon capture utilization and storage (CCUS) has four major methods, namely, pre-combustion, post-combustion, oxyfuel combustion, and direct air capture. It has been reported that applying CCUS can capture up to 95% of the produced carbon dioxide in running power plants. However, a reported cost penalty and efficiency decrease hinder the wide applicability of CCUS. Advancements in the CCSU were made in increasing the efficiency and decreasing the cost of the sorbents. In this review, we highlight the recent developments in utilizing both physical and chemical sorbents to capture carbon. This includes amine-based sorbents, blended absorbents, ionic liquids, metal-organic framework (MOF) adsorbents, zeolites, mesoporous silica materials, alkali-metal adsorbents, carbonaceous materials, and metal oxide/metal oxide-based materials. In addition, a comparison between recently proposed kinetic and thermodynamic models was also introduced. It was concluded from the published studies that amine-based sorbents are considered assuperior carbon-capturing materials, which is attributed to their high stability, multifunctionality, rapid capture, and ability to achieve large sorption capacities. However, more work must be done to reduce their cost as it can be regarded as their main drawback.
