Contribution of the Basal Planes to Carbon Basicity: An Ab Initio Study of the H3O+−π Interaction in Cluster Models

Groundwater solutes influence the adsorption of short-chain perfluoroalkyl acids (PFAA) to colloidal activated carbon and impact performance for in situ groundwater remediation

Subsurface injection of colloidal activated carbon (CAC) is an in situ remediation strategy for perfluoroalkyl acids (PFAA), but the influence of groundwater solutes on longevity is uncertain, particularly for short-chain PFAA. We quantify the impact of inorganic anions, dissolved organic matter (DOM), and stabilizing polymer on PFAA adsorption to a commercial CAC. Surface characterization supported PFAA chain-length dependent adsorption results and mechanisms are provided. Inorganic anions decreased adsorption for short-chain PFAA (<7 perfluorinated carbons) due to competitive effects, while long-chain PFAA (≥ 7 perfluorinated carbons) were less impacted. DOM decreased adsorption of all PFAA in a chain-length dependent manner. High DOM concentrations (10 mg/L, ∼5 mg OC/L) decreased PFOA adsorption by a factor of 2, PFPeA by one order of magnitude, and completely hindered PFBA adsorption. High MW DOM has less impact on short-chain PFAA than low MW DOM, possibly due to differences in the ability to access CAC micropores. Low DOM concentrations (1 mg/L, ∼0.5 mg OC/L) did not impact adsorption. CMC (90 kDa average MW) had negligible impact on PFAA adsorption likely due to minimal CAC surface coverage. Longevity modeling demonstrated that groundwater solutes limit the capacity for PFAA in a CAC barrier, particularly for short-chain PFAA.

Towards the valorisation of glycerol by designing the surface chemistry of carbon xerogels by doping and oxygen functionalization

Research on innovative approaches to the valorisation of glycerol as a subproduct of biodiesel production has acquired an increasing demand in the development of a circular economy around energy generation, especially, in the line of improvement of the heterogeneous metallic catalysts used. In this regard, carbon xerogels have gained importance due to their stability and modifiability, while transition metals such as copper stand out as a cost-effective alternative, resulting in a technology where surface engineering plays a crucial role in achieving competitive catalytic activity. Building upon this, current research evaluates doped xerogels (Si, N, or GO) as supports of Cu and catalysts by themselves for glycerol oxidation. Benefits from the incorporation of oxygenated functional groups (OFG) were also evaluated. Results showed a consistently higher selectivity towards lactic acid (LA) across all catalysts and competitive catalytic conversion. In this performance, dopants played a crucial role in surface acid-base characteristics, while oxygenated functional groups (OFG) influenced copper adsorption, dispersion, and reducibility. Notably, the Cu/CXN-f catalyst demonstrated the highest LA yield by combining the effect of N as a doping species, with the presence of OFG and the formation of appropriated metallic Cu domains. This research underscores the potential of carbon xerogels in the tailored catalyst design, contributing to sustainable chemical production through their customizable textural and chemical properties.

Steric Interaction of Polyglycerol-Functionalized Detonation Nanodiamonds

Detonation nanodiamonds have found numerous potential applications in a diverse array of fields such as biomedical imaging and drug delivery. Here, we systematically characterized non-functionalized and polyglycerol-functionalized detonation nanodiamond particles (DNPs) dispersed in aqueous suspensions at different ionic strengths (∼1.0 × 10^-7 to 1.0 × 10^-2 M) via dynamic light scattering and cryogenic transmission electron microscopy. For these colloidal suspensions, the total potential energies of interactions between a pair of DNPs were theoretically calculated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory plus the fitting of the Boltzmann distribution to the interparticle spacing distribution of the colloidal DNPs. These investigations revealed that the non-functionalized DNPs are dispersed in aqueous media through the long-range (>10 nm) and weak (<7 k_BT) electrical double-layer repulsive interaction, while the driving force on dispersion of polyglycerol-functionalized DNPs is mostly derived from the short-range (<2 nm) and strong (∼55 k_BT) steric repulsive potential barrier generated by the polyglycerol. Moreover, our results show that the truly monodispersed and individually dispersed DNP colloids, forming no aggregates in aqueous suspensions, are available by both functionalizing DNPs by polyglycerol and increasing ionic strength of suspending media to ≳1.0 × 10^-2 M.

Reactive Mesoporous pH-Sensitive Amino-Functionalized Silica Nanoparticles for Efficient Removal of Coomassie Blue Dye

In this work, new smart mesoporous amine-functionalized silica nanoparticles were prepared from hydrolyzing microgels based on N-isopropyl acrylamide-co-vinyltrimethoxysilane microgels with tetraethoxysilicate and 3-aminopropyltriethoxysilane by sol-gel method. The thermal stability and Fourier transform infrared were used to determine the amine contents of the silica nanoparticles. The pH sensitivity of the synthesized silica nanoparticles in their aqueous solutions was evaluated by using dynamic light scattering (DLS) and zeta potential measurements. The porosity of the amine-functionalized silica nanoparticles was evaluated from a transmittance electron microscope and Brunauer-Emmett-Teller (BET) plot. The results have positively recommended the pH-sensitive amine-functionalized silica nanoparticles as one of the effective nano-adsorbent to remove 313 mg·g⁻¹ of CB-R250 water pollutant.

Structural Characterization of Graphene Oxide: Surface Functional Groups and Fractionated Oxidative Debris

The purpose of this work is the structural analysis of graphene oxide (GO) and by means of a new structural model to answer the questions arising from the Lerf–Klinowski and the Lee structural models. Surface functional groups of GO layers and the oxidative debris (OD) stacked on them were investigated after OD was extracted. Analysis was performed successfully using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), X-ray photoemission spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy (SSNMR), standardized Boehm potentiometric titration analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The analysis showed that graphene oxide layers, as well as oxidative debris contain different functional groups such as phenolic –OH, ketone, lactone, carboxyl, quinone and epoxy. Based on these results, a new structural model for GO layers is proposed, which covers all spectroscopic data and explains the presence of the other oxygen functionalities besides carboxyl, phenolic –OH and epoxy groups.

Tailoring the self-assembly of a tripeptide for the formation of antimicrobial surfaces

The accumulation of bacteria on surfaces is currently one of the greatest concerns for the management of proper healthcare systems, water and energy. Here, we describe the mechanism by which a single peptide forms two pH-dependent supramolecular particles that resist bacterial contamination. By using NMR and molecular dynamics (MD), we determined the structures of the peptide monomers and showed the forces directing the self-assembly of each structure under different conditions. These peptide assemblies change the characteristics of bare glass and confer it with the ability to prevent biofilm formation. Furthermore, they can adsorb and release active compounds as demonstrated with an anticancer drug, antibiotic and enzyme. This synergism and the detailed understanding of the processes are necessary for developing new sterile surfaces for healthcare systems, water purification devices, food packaging or any environment that suffers from biocontamination.

Efficient mercury removal from wastewater by pistachio wood wastes-derived activated carbon prepared by chemical activation using a novel activating agent

Ammonium nitrate (NH₄NO₃) with explosive characteristics at high temperatures was used as a novel activating reagent to prepare a surface-engineered activated carbon derived from pistachio wood wastes (PWAC). PWAC was characterized and compared with commercial activated carbon (CAC) by textural and morphological properties, surface chemistry, crystal structure, and surface elemental composition. The results indicated that the optimal conditions of PWAC preparation to obtain the highest mercury adsorption capacity were pyrolysis temperature (800 °C), pyrolysis time (2 h), and impregnation ratio (5%). PWAC was of highly regular-shaped and well-developed pores and possessed a large surface area (1448 m²/g) and high total pore volume (0.901 cm³/g). The batch experiments indicated that the adsorption process of Hg(II) was strongly dependent on the solution pH and reached fast equilibrium at approximately 30 min. PWAC (202 mg/g) exhibited a significantly higher maximum adsorption capacity than commercial activated carbon (66.5 mg/g). Adsorbent-adsorbate dispersion interaction plays a major role in the adsorption mechanism, compared to the minor role played by pore filling and reduction mechanism. Overall, ammonium nitrate can be considered a newer activating reagent to prepare promising and low-cost PWAC for effectively Hg(II) removal from water media.

Chemical activation of biochar for energy and environmental applications: a comprehensive review

Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.

Positive zeta potential of nanodiamonds

In this paper, the origin of positive zeta potential exhibited by nanodiamond particles is explained. Positive zeta potentials in nano-structured carbons can be explained by the presence of graphitic planes at the surface, which leave oxygen-free Lewis sites and so promotes the suppression of acidic functional groups. Electron Microscopy and Raman Spectroscopy have been used to show that positive zeta potential of nanodiamond is only exhibited in the presence of sp² carbon at the surface.

Enhanced Recyclable Magnetized Palm Shell Waste-Based Powdered Activated Carbon for the Removal of Ibuprofen: Insights for Kinetics and Mechanisms

A novel preparation method of magnetized palm shell waste-based powdered activated carbon (MPPAC, avg. size 112 μm) was developed. The prepared MPPAC was assessed by several physicochemical analyses, and batch tests were performed for ibuprofen (IBP) removal. Field emission scanning electron microscopy (FESEM) and N2 gas isotherms revealed that magnetite and maghemite were homogeneous and deposited mostly on the surface of PPAC without a significant clogging effect on the micropores. Isotherm results showed that 3.8% Fe (w/w) impregnated PPAC [MPPAC-Fe(3.8%)] had about 2.2-fold higher maximum sorption capacity (157.3 mg g-1) and a 2.5-fold higher sorption density (0.23 mg m-2) than pristine PPAC. Both Fourier-transform infrared spectroscopy (FTIR) and isotherm data indicated that the high sorption capacity and density of IBP by MPPAC was primarily attributable to donor-acceptor complexes with the C = O group and dispersive π-π interactions with the carbon surface. Based on kinetic and repeated adsorption tests, pore diffusion was the rate-limiting step, and MPPAC-Fe(3.8%) had about 1.9~2.8- and 9.1~15.8-fold higher rate constants than MPPAC-Fe(8.6%) and palm shell-waste granular activated carbon (PGAC, avg. size 621 μm), respectively. MPPAC showed almost eight fold greater re-adsorption capacity than PPAC due to a thermal catalytic effect of magnetite/maghemite.

The effect of the carbon surface chemistry and electrolyte pH on the energy storage of supercapacitors

Combined effect of electrolyte pH and surface chemistry of oxidized carbon xerogels on the electrochemical response of supercapacitors.

Adsorption of triton X-100 on silica gel: effects of temperature and alcohols

Adsorption of Triton X-100 (TX-100) on silica gel has been studied as a function of temperature (308–328 K) and composition for mixtures of water with ethanol or t-butanol. The adsorption capacity of silica gel for TX-100 decreases with increase in alcohol content. Adsorption isotherms of TX-100 on silica gel are four-region and were analyzed using the ARIAN (adsorption isotherm regional analysis) model. Data in regions 2, 3 and 4 were fitted to the Temkin, bilayer and reverse desorption isotherms, respectively. The results show that adsorption of TX-100 on silica gel in water and alcohol-water binary mixtures occurs mainly through formation of monolayer surface aggregates or low bilayer coverage.

Adsorption behavior of multiwall carbon nanotube/iron oxide magnetic composites for Ni(II) and Sr(II)

Multiwall carbon nanotube (MWCNT)/iron oxide magnetic composites were prepared, and were characterized by scan electron microscopy using a field emission scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. The adsorptions of Ni(II) and Sr(II) onto MWCNT/iron oxide magnetic composites were studied as a function of pH and ionic strength. The results show that the adsorptions of Ni(II) and Sr(II) on the magnetic composites is strongly dependent on pH and ionic strength. The adsorption capacity of the magnetic composites is much higher than that of MWCNTs and iron oxides. The solid magnetic composites can be separated from the solution by a magnetic process. The Langmuir model fits the adsorption isotherm data of Ni(II) better than the Freundlich model. Results of desorption study shows that Ni(II) adsorbed onto the magnetic composites can be easily desorbed at pH<2.0. MWCNT/iron oxide magnetic composites may be a promising candidate for pre-concentration and solidification of heavy metal ions and radionuclides from large volumes of aqueous solution, as required for remediation purposes.

Waste-derived activated carbons for removal of ibuprofen from solution: role of surface chemistry and pore structure

The removal of a widespread used drug (i.e., ibuprofen) from water was investigated using high valuable carbon adsorbents obtained from chemical and physical activation of a bioresource (cork) and a municipal waste (plastic). The waste-derived carbons outperformed the adsorption capacity of commercial carbonaceous adsorbents due to their adequate features for the removal of the targeted compound. Regarding the adsorption mechanism, the results obtained point out that ibuprofen retention is favored in activated carbons with basic surface properties. On the other hand, the textural features also play an important role; the presence of a transport pores network (i.e., mesopores) is crucial to ensure the accessibility to the inner porosity, and the microporosity must be large enough to accommodate the ibuprofen molecule. Specifically, adsorbents with a large fraction of ultramicropores (pore widths <0.7 nm) are not adequate to effectively remove ibuprofen.

A study of the static and dynamic adsorption of Zn(II) ions on carbon materials from aqueous solutions

The effect of surface oxidation, solution pH, and ionic strength on the adsorption of Zn(II) ions from aqueous solution under static conditions was studied using commercial activated carbons in the form of grains and cloth. In addition, the effects of surface oxidation and the presence of dissolved natural organic matter (tannic acid) were studied under dynamic conditions using activated carbon cloth column beds. Under static conditions, surface oxidation largely increased Zn2+ uptake and two H+ ions were displaced from the oxidized carbon surface per Zn(II) ion adsorbed. It is proposed that adsorption of Zn(II) on the as-received basic carbons was due to C(pi)-cation interactions. An increase in solution pH in the range 3-6 increased Zn(II) uptake, whereas an increase in ionic strength decreased Zn(II) uptake because of the screening effect of the added salt. In the experiments carried out with carbon column beds, the oxidized activated carbon cloth was also more effective than the as-received carbon to remove Zn(II) ions. In this case, the presence of tannic acid decreased the efficiency of the oxidized activated carbon cloth bed to remove Zn(II) ions. An increase in the tannic acid initial concentration had a greater effect on the removal of tannic acid than on the removal of Zn(II) by the column bed. This may be a consequence of the greater size of tannic acid molecules and their low affinity for oxidized carbon surfaces.

Adsorption of Cr(III) on ozonised activated carbon. Importance of Cpi-cation interactions

The adsorption of Cr(III) in aqueous solution was investigated on a series of ozonised activated carbons, analysing the effect of oxygenated surface groups on the adsorption process. A study was carried out to determine the adsorption isotherms and the influence of the pH on the adsorption of this metal. The adsorption capacity and affinity of the adsorbent for Cr(III) increased with the increase in oxygenated acid groups on the surface of the activated carbon. These findings imply that electrostatic-type interactions predominate in the adsorption process, although the adsorption of Cr(III) on the original (basic) carbon indicates that other forces also participate in the adsorption process. Thus, the ionic exchange of protons in the -Cpi-H3O(+) interaction for Cr(III) accounts for the adsorption of cationic species in basic carbons with positive charge density. Study of the influence of pH on the adsorption of Cr(III) showed that, in each system, the maximum adsorption occurred when the charge of the carbon surface was opposite that of the species of Cr(III) present at the pH of the experiment. These results confirmed that electrostatic interactions predominate in the adsorption process.

Mechanism of the reductive half-reaction in cellobiose dehydrogenase

The extracellular flavocytochrome cellobiose dehydrogenase (CDH; EC ) participates in lignocellulose degradation by white-rot fungi with a proposed role in the early events of wood degradation. The complete hemoflavoenzyme consists of a catalytically active dehydrogenase fragment (DH(cdh)) connected to a b-type cytochrome domain via a linker peptide. In the reductive half-reaction, DH(cdh) catalyzes the oxidation of cellobiose to yield cellobiono-1,5-lactone. The active site of DH(cdh) is structurally similar to that of glucose oxidase and cholesterol oxidase, with a conserved histidine residue positioned at the re face of the flavin ring close to the N5 atom. The mechanisms of oxidation in glucose oxidase and cholesterol oxidase are still poorly understood, partly because of lack of experimental structure data or difficulties in interpreting existing data for enzyme-ligand complexes. Here we report the crystal structure of the Phanerochaete chrysosporium DH(cdh) with a bound inhibitor, cellobiono-1,5-lactam, at 1.8-A resolution. The distance between the lactam C1 and the flavin N5 is only 2.9 A, implying that in an approximately planar transition state, the maximum distance for the axial 1-hydrogen to travel for covalent addition to N5 is 0.8-0.9 A. The lactam O1 interacts intimately with the side chains of His-689 and Asn-732. Our data lend substantial structural support to a reaction mechanism where His-689 acts as a general base by abstracting the O1 hydroxyl proton in concert with transfer of the C1 hydrogen as hydride to the re face of the flavin N5.