Bio-based functionalized adsorptive polymers for sustainable water decontamination: A systematic review of challenges and real-world implementation.

The overwhelming concerns of water pollution, industrial discharges and environmental deterioration by various organic and inorganic substances, including dyes, heavy metals, pesticides, pharmaceuticals, and detergents, intrinsically drive the search for urgent and efficacious decontamination techniques. This review illustrates the various approaches to remediation, their fundamentals, characteristics and demerits. In this manner, the advantageous implementation of nature-based adsorbents has been outlined and discussed. Different types of lignocellulosic compounds (cellulose, lignin, chitin, chitosan, starch) have been introduced, and the most used biopolymeric materials in bioremediation have been highlighted; their merits, synthesis methods, properties and performances in aqueous medium decontamination have been described. The literature assessment reveals the genuine interest and dependence of academic and industrial fields to valorize biopolymers in the adsorption of various hazardous substances. Yet, the full potential of this approach is still confined by certain constraints, such as the lack of reliable, substantial, and efficient extraction of biopolymers, as well as their modest and inconsistent physicochemical properties. The futuristic reliance on such biomaterials in all fields, rather than adsorption, is inherently reliable on in-depth investigations and understanding of their features and mechanisms, which can guarantee a real-world application and green technologies.

Adsorption of cationic and anionic dyes onto coffee grounds cellulose/sodium alginate double-network hydrogel beads: Isotherm analysis and recyclability performance.

This work describes the preparation of new eco-friendly adsorbents with a simple method. Gel beads of coffee grounds cellulose (CGC) and sodium alginate (SA) were prepared for wastewater treatment. Upon their synthesis, the physicochemical properties, performances and efficiency were analyzed by means of various structural and morphological characterizations. Kinetic and thermodynamic adsorption approaches evaluated the removal capacity of these beads which reached equilibrium in 20 min for Methylene Blue (MB) and Congo Red (CR). Also, the kinetics shows that the results can be explained by the pseudo-second-order model (PSO). Furthermore, the isotherm assessments showed that Langmuir-Freundlich can fit the adsorption data of both contaminants. Accordingly, the maximum adsorption capacities reached by the Langmuir-Freundlich model are 400.50 and 411.45 mg/g for MB and CR, respectively. It is interesting to note that the bio-adsorption capabilities of MB and CR on bead hydrogels decreased with temperature. Besides, the results of the thermodynamic study evidenced that the bio-adsorption processes are favorable, spontaneous and exothermic. The CGC/SA gel beads are therefore outstanding bio-adsorbents, offering a great adsorptive performance and regenerative abilities.

Theoretical and experimental studies on the carbon-nanotube surface oxidation by nitric acid: interplay between functionalization and vacancy enlargement.

The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or carboxylic groups. At room temperature, this reaction takes place on the most reactive carbon atoms. At higher temperatures a different mechanism would operate, as evidenced by the difference in activation energies. Experimental data can be partially related to first-principles calculations, showing a multistep functionalization mechanism. The theoretical aspects of the present article have led us to propose the most efficient pathway leading to carboxylic acid functional groups on the surface. Starting from mono-vacancies, it ends up with the synergistic formation of dangling -COOH groups and the enlargement of the vacancies.

Hydrogenation of p-chloronitrobenzene over nanostructured-carbon-supported ruthenium catalysts.

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been used for the first time to support ruthenium nanoparticles for the hydrogenation of p-chloronitrobenzene (p-CNB) to produce selectively p-chloroaniline. The preparation of well-dispersed ruthenium catalysts from the [Ru(3)(CO)(12)] precursor required activation of the purified supports by nitric acid oxidation. The supports, purified and functionalized, and the supported catalysts have been characterized by a range of techniques. The catalytic activity of these materials for the hydrogenation of p-CNB at 35 bar and 60 °C is shown to reach as high as 18 mol(p-CNB)g(Ru)(-1) h(-1), which is one order of magnitude higher than a commercial Ru/Al(2)O(3) catalyst. Selectivities between 92 and 94 % are systematically obtained, the major byproduct being aniline.