Adsorption of industrial dyes on functionalized and nonfunctionalized asphaltene: A combined molecular dynamics and quantum mechanics study

Theoretical investigation of asphaltene molecules in crude oil viscoelasticity enhancement

Understanding the mechanisms of viscosity enhancement in crude oil phases is crucial for optimizing extraction and transportation processes. The enhanced viscosity mechanism of crude oil phase can be attributed to the intricate intermolecular interactions between asphaltene molecules. However, the molecular mechanism of the viscosification of asphaltene molecules in crude oil is not yet to be fully understood. In this work, molecular dynamics simulations were employed to investigate the dynamic behavior and viscosification mechanism of asphaltene molecules in complex oil phases. Research suggests that the neutral surface of asphaltenes features abundant positive and negative electrostatic potential regions, facilitating complementary pairing between these areas. This significantly augments electrostatic interactions among asphaltene molecules. Besides, the expansive nonpolar expanse on the normal asphaltene surface facilitates interactions between asphaltenes and crude oil molecules. This leads the crude oil viscosity of the system containing normal asphaltene is higher than that of the system containing acidic asphaltene under the same mass fraction (382 μ Pa·s for AAsp and 416 μ Pa·s for NAsp). This work provides insight into the viscosity enhancement mechanisms in crude oil phases and is helpful in improving the efficiency of crude oil extraction and transportation.

High potential for biomass-degrading CAZymes revealed by pine forest soil metagenomics

The undisturbed environment in Netarhat, with its high levels of accumulated lignocellulosic biomass, presents an opportunity to identify microbes for biomass digestion. This study focuses on the bioprospecting of native soil microbes from the Netarhat forest in Jharkhand, India, with the potential for lignocellulosic substrate digestion. These biocatalysts could help overcome the bottleneck of biomass saccharification and reduce the overall cost of biofuel production, replacing harmful fossil fuels. The study used metagenomic analysis of pine forest soil via whole genome shotgun sequencing, revealing that most of the reads matched with the bacterial species, very low percentage of reads (0.1%) belongs to fungal species, with 13% of unclassified reads. Actinobacteria were found to be predominant among the bacterial species. MetaErg annotation identified 11,830 protein family genes and 2 metabolic marker genes in the soil samples. Based on the Carbohydrate Active EnZyme (CAZy) database, 3,996 carbohydrate enzyme families were identified, with family Glycosyl hydrolase (GH) dominating with 1,704 genes. Most observed GH families in the study were GH0, 3, 5, 6. 9, 12. 13, 15, 16, 39, 43, 57, and 97. Modelling analysis of a representative GH 43 gene suggested a strong affinity for cellulose than xylan. This study highlights the lignocellulosic digestion potential of the native microfauna of the lesser-known pine forest of Netarhat.Communicated by Ramaswamy H. Sarma.

Using functionalized asphaltenes as effective adsorbents for the removal of chromium and lead metal ions from aqueous solution

For the first time, functionalized asphaltene has been designed, synthesized, and used for the removal of heavy metals from the water. Asphaltene was separated from the crude oil with the addition of n-alkanes. Asphaltene having a complex chemical structure including multilayered and clustered aromatic fused rings bearing aliphatic chains. Asphaltene also contains heteroatoms like N, S, and O atoms along with Ni and V as prominent trace metals. On functionalization of asphaltene with nitric acid, the aliphatic chains and some of the naphthenic rings broke down and developed -COOH, -CO, C-O, and other oxygen functional groups which are playing key roles as surface-active agents in the removal of the heavy metals via chemisorption. The study was conducted using different parameters such as dose, time, pH, and concentration. The adsorption efficiency for this material at pH 4 is excellent for the removal of chromium and lead. The Langmuir, Freundlich and Temkin adsorption isotherm models as well as Lagergren pseudo second-order kinetic model were investigated. The positive enthalpies ΔHs confirm that the adsorption process is endothermic and the negative free energies ΔGs confirm the spontaneity of the process. The good efficiency of the adsorption implies the efficacy in the removal of the heavy metal ions, as well as the good efficiency in desorption, which implies the excellent recovery of the adsorbent. The effective reusability of this adsorbent makes it applicable for industrial water treatment from contaminants.

Study on the adsorption properties of multiple-generation hyperbranched collagen fibers towards isolan-series acid dyes

In the present study, collagen fibers derived from leather solid wastes were used and modified as insoluble vectors and successfully employed as adsorbents for the removal of acid dyes. A “one-step” method was applied to synthesis effective adsorbents, which provided a sustainable way to reuse leather solid wastes via multifunctional modification. The adsorption properties of amino-terminated hyperbranched polymer (HBPN)-modified collagen fibers for the removal of different kinds of acid dyestuff from aqueous solutions were studied. The adsorption capacities of the second generation of modified collagen fibers (CF-HBPN-II) toward Isolan Black 2S-LD, Supralan Yellow, Isolan Grey K-PBL 02, Isolan Dark Blue 2S-GL 03, and Isolan Brown NHF-S were determined to be 224.87, 340.14, 287.36, 317.80, and 251.25 mg g⁻¹, respectively. Three kinetic models, namely, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were used to analyze the kinetic data. The fitting result indicated that the adsorption process of Isolan Black 2S-LD on CF-HBPN-II followed a pseudo-second-order rate model. The adsorption equilibrium of amino-terminated hyperbranched polymer-modified collagen fibers (CF-HBPN) was analyzed using the Langmuir, Freundlich and Temkin isotherm models. The Langmuir isotherm was suitable to describe the adsorption process of Isolan Black 2S-LD. R_L was observed to be in the range of 0–1. The values of ΔH, ΔS and ΔG suggest that adsorption is an endothermic and spontaneous process. The adsorbed dye from the modified collagen fiber was successfully desorbed by 0.1 M NaOH. This research provides theoretical guidance for the engineering and recycling application of bio-based adsorbents.

Collagen fibers extracted from leather wastes were modified by amino-terminated hyperbranched polymers to prepare CF-HBPN-I and CF-HBPN-II. The adsorption process of CF-HBPN-II toward Isolan Black 2S-LD is in accordance with the pseudo-second-order and Langmuir model.