Trapping Rhodamine B dye using functionalized mango (Mangifera indica) pod

Agrowaste-carbon and carbon-based nanocomposites for endocrine disruptive cationic dyes removal: A critical review

Dyes are considered to be pollutants that pose a considerable worldwide health risk, as they have been discovered as agents that affect the endocrine system. Adsorption is the most commonly used method for removing different substances since it is sustainable, flexible, affordable, and easy to use. Researchers have investigated the usage of agro-waste-based adsorbents that are ecologically friendly for the process of adsorption. This research has emphasized the potential of these adsorbents in developing carbon-based nanocomposites. Improved surface functionalization, great compatibility, and flexibility are beneficial uniqueness of carbon-based nanocomposites as well as a wide variety of applications. As a result, they are highly successful in removing cationic dyes. This paper specifically examines the environmentally friendly usage of activated carbons obtained from agricultural waste and the development of carbon-based-nanocomposites to adsorb positively charged dyes. Additionally, it offers an in-depth investigation of various cationic dyes, operating parameters, adsorption isotherms, kinetics, processes, and thermodynamic investigations. Further research is necessary to determine the effectiveness of carbon-based nanocomposites in removing new endocrine-disrupting pollutants. Additionally, these nanocomposites have the potential to be widely used in treating industrial effluents.

New recyclable and functionalized chitosan-based polyurethane foams for effective and incessant removal of Orange II (OII) and Rhodamine B (RhB) dyes from water

The development of new efficient materials for the removal of water-soluble toxic organic dyes has been one of the focused research areas in the recent past. There is a strong demand for the new materials as most of the reported techniques/materials suffer from serious limitations. In this regard, a series of flexible chitosan-based task-specific polyurethane foams (PUCS-GP, PUCS-CA-GP, PUCS-TA-GP, and PUCS-GA-GP) associated with naturally available hydroxycarboxylic acids was developed. The basis for the preparation of these task-specific and functionalized PU foams is to possess amine groups for trapping the anionic dyes (example: Orange II denoted as OII) and carboxylic acid groups for attracting the cationic dyes (example: Rhodamine B denoted as RhB) under specified pH conditions. Batch adsorption experiments were conducted to assess and improve various parametric conditions. The experimental results revealed that the adsorption kinetics closely agree with the pseudo-second-order model having a maximum sorption capacity of 38.3 mg/g at pH 3 for OII on PUCS-GP and 48.4 mg/g at pH 6 for RhB on PUCS-CA-GP. Furthermore, the adsorption process was described by isotherms, kinetic equations and thermodynamic parameters (ΔG°, ΔH° and ΔS°). Notably, the regeneration of OII and RhB dyes from the exhausted PUCS-GP and PUCS-CA-GP materials was effectively accomplished. The recovered PUCS-GP shows >90 % OII and PUCS-CA-GP displays >70 % RhB removal efficiency even after twelve adsorption-desorption processes under mild conditions, demonstrating excellent recyclability/durability. The advantages of these functionalized foam materials are facile preparation, high adsorption capacity, good reusability, and very efficient removal of organic dyes from wastewater streams.

Adsorptive removal of antibiotic pollutants from wastewater using biomass/biochar-based adsorbents

This study explores adsorptive removal measures to shed light on current water treatment innovations for kinetic/isotherm models and their applications to antibiotic pollutants using a broad range of biomass-based adsorbents. The structure, classifications, sources, distribution, and different techniques for the remediation of antibiotics are discussed. Unlike previous studies, a wide range of adsorbents are covered and adsorption of comprehensive classes of antibiotics onto biomass/biochar-based adsorbents are categorized as β-lactam, fluoroquinolone, sulfonamide, tetracycline, macrolides, chloramphenicol, antiseptic additives, glycosamides, reductase inhibitors, and multiple antibiotic systems. This allows for an assessment of their performance and an understanding of current research breakthroughs in applying various adsorbent materials for antibiotic removal. Distinct from other studies in the field, the theoretical basis of different isotherm and kinetics models and the corresponding experimental insights into their applications to antibiotics are discussed extensively, thereby identifying the associated strengths, limitations, and efficacy of kinetics and isotherms for describing the performances of the adsorbents. In addition, we explore the regeneration of adsorbents and the potential applications of the adsorbents in engineering. Lastly, scholars will be able to grasp the present resources employed and the future necessities for antibiotic wastewater remediation.

Adsorptive Removal of Rhodamine B Dye Using Carbon Graphite/CNT Composites as Adsorbents: Kinetics, Isotherms and Thermodynamic Study

The study of the adsorption efficiency of new carbon/CNT composites was undertaken to remove a cationic dye, Rhodamine B (RhB), from dye-contaminated wastewater. Indeed, we investigated the effect of different experimental parameters such as time, initial concentration of dye and temperature on the adsorption of RhB by the carbon composites (KS44-0 and KS44-20). The results showed that the adsorption uptake increased with the initial concentration and solution temperature while maintaining a relatively constant pH. The presence of the carbon nanotubes provided more active sites for dye removal and improved the adsorption behavior of Rhodamine B dye. The analysis of the experimental data was conducted using model equations, such as Langmuir, Freundlich and Temkin isotherms. As regards the Freundlich isotherm model, it was the best fit for the equilibrium data obtained from the experiments. The applicability of the pseudo-second-order equation could be explained assuming that the overall adsorption rate is limited by the rate of adsorbate transport that occurs on the pore surfaces of adsorbents. Furthermore, the intraparticle diffusion and Bangham models were used to investigate the diffusion mechanism of RhB absorption onto carbon composites. They showed that multiple adsorption stages occurred simultaneously via pore surface diffusion. Concerning the thermodynamic parameters (∆G°, ∆H°, and ∆S°), they were calculated and explained in the mean of the chemical structure of the adsorbate. Negative standard Gibbs free energy change values (ΔG°_ads) at all temperatures suggested that the adsorption process was spontaneous, and the positive values of the standard enthalpy change of adsorption (∆H°_ads) revealed the reaction to be endothermic. The values of standard enthalpy (ΔH°_ads) and activation energy (E_a) indicated that the adsorption process corresponds to physical sorption. The mechanisms for the removal of Rhodamine B dye from wastewater using carbon composite were predicted. RhB is a planar molecule that is readily adsorbed, in which adsorbed molecules are bound by hydrophobic or other weak interactions due to the π-π interactions between the dyes' aromatic backbones and the hexagonal skeleton of graphite and carbon nanotubes. Thus, the graphite carbon/carbon nanotube composite is believed to play a major role in organic pollutant reduction.