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The present work synthesized two new materials of functionalized multi-walled carbon nanotubes (MWCNT-OH and MWCNT-COOH) impregnated with magnetite (Fe 3 O 4 ) using solution precipitation methodology. The resulting MWCNT-OH-Mag and MWCNT-COOH-Mag materials were characterized by scanning electron microscopy coupled with energy dispersion X-ray spectroscopy, Fourier transform infrared, X-ray diffraction, atomic force microscopy, and electrical force microscopy. The characterization results indicate that the -OH functional groups in the MWCNT interact effectively with magnetite iron favoring impregnation and indicating the regular distribution of nanoparticles on the surface of the synthesized materials. The adsorption efficiency of the MWCNT-OH-Mag and MWCNT-COOH-Mag materials was tested using the pollutants 2,4-D and Atrazine. Over batch studies carried out under different pH ranges, it was found that the optimal condition for 2,4-D adsorption was at pH 2, while for Atrazine, it was found at pH 6. The rapid adsorption kinetics of 2,4-D and Atrazine reaches equilibrium within 30 min. The pseudo-first-order model described 2,4-D adsorption well. The General-order model described better atrazine adsorption. The magnetically doped adsorbent functionalized with -OH surface groups (MWCNT-OH-Mag) demonstrated superior adsorption performance and increased Fe-doped sites. The Sips model described the adsorption isotherms accurately. MWCNT-OH-Mag presented the greatest adsorption capacity at 51.4 and 47.7 mg g -1 for 2,4-D and Atrazine, respectively. Besides, electrostatic forces and complexation rule the molecular interactions between metals and pesticides. The leaching and regeneration tests of the synthesized materials indicate high stability in an aqueous solution. Furthermore, experiments with wastewater samples contaminated with the model pollutants indicate that the novel adsorbents are highly promising for enhancing water purification by adsorptive separation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this work, a novel and effective hydrochar was prepared by hydrothermal treatment of Prunus serrulata bark to remove the pesticide atrazine in river waters. The hydrothermal treatment has generated hydrochar with a rough surface and small cavities, favoring the atrazine adsorption. The adsorption equilibrium time was not influenced by different atrazine concentrations used, being reached after 240 min. The Elovich adsorption kinetic model presented the best adjustment to the kinetic data. The Langmuir model presented the greatest compliance to the isotherm data and indicated a higher affinity between atrazine and hydrochar, reaching a maximum adsorption capacity of 63.35 mg g -1 . Thermodynamic parameters showed that the adsorption process was highly spontaneous, endothermic, and favorable, with a predominance of physical attraction forces. In treating three real river samples containing atrazine, the adsorbent showed high removal efficiency, being above 70 %. The hydrochar from Prunus serrulata bark waste proved highly viable to remove atrazine from river waters due to its high efficiency and low precursor material cost., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The residual bark of the tree species Campomanesia guazumifolia was successfully modified with H2SO4 and applied to remove the toxic herbicide 2.4-dichlorophenoxyacetic (2.4-D) from aqueous solutions. The characterization techniques made it possible to observe that the material maintained its amorphous structure; however, a new FTIR band emerged, indicating the interaction of the lignocellulosic matrix with sulfuric acid. Micrographs showed that the material maintained its irregular shape; however, new spaces and cavities appeared after the acidic modification. Regardless of the herbicide concentration, the system tended to equilibrium after 120 min. Using the best statistical coefficients, the Elovich model was the one that best fitted the kinetic data. The temperature increase in the system negatively influenced the adsorption of 2.4-D, reaching a maximum capacity of 312.81 mg g−1 at 298 K. The equilibrium curves showed a better fit to the Tóth model. Thermodynamic parameters confirmed the exothermic nature of the system (ΔH0 = −59.86 kJ mol−1). As a residue obtained from urban pruning, the bark of Campomanesia guazumifolia treated with sulfuric acid is a promising and highly efficient alternative for removing the widely used and toxic 2.4-D herbicide from aqueous solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Activated carbon (AC) from araçá fruit husks for atrazine adsorption. • It was a microporous material with a surface area of 431 m2 g−1. • The adsorption capacity was 35.67 mg g−1 at 328 K, and ΔH0 was 129.5 kJ mol−1. • Adsorption occurs due to electrostatic, H-bonds, π–π and n–π interactions. • The "araça" derived AC was promising in removing atrazine from aqueous solutions. The residual husks of the edible fruits of Psidium cattleianum were carbonized with FeCl 3 as an activating agent and used as an adsorbent to remove the toxic herbicide. After the carbonization step, changes in the material's structure were found. Activated carbon showed characteristics of microporous materials with a pore volume of 0.280 cm3 g−1 and surface area of 431 m2 g−1. Micrographs revealed the emergence of new cavities with a uniform and circular shape. The FTIR spectra showed the disappearance of some bands, remaining bands belonging to functional groups containing carbon, oxygen, and hydrogen. The XRD patterns confirmed the amorphous structure of the material even after the carbonization step, composed of amorphous graphitic carbon. EDS analysis showed that the carbon percentage increased and the oxygen decreased after the carbonization. The experiments were performed at neutral pH using 1 g L−1 of adsorbent. In equilibrium isotherms, the temperature played a considerable role in the adsorption capacity, increasing from 26.39 mg g−1 to 35.67 mg g−1 when the temperature varied from 298 to 328 K. The Liu isotherms were the ones that best fit the isotherm data. The changes in the adsorption enthalpy were endothermic (ΔH° 129.5 kJ mol−1). The general order kinetic model was the most adequate for kinetic data, presenting the lowest values of the Bayesian Information Criterion. Thus, activated carbon developed from the residues of the "araça" fruit showed promise in removing atrazine from aqueous solutions, with the great advantage of its high efficiency under neutral pH solutions and mild temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microporous activated carbon (Hd-AC) from Hovenia dulcis for atrazine adsorption. • The maximum adsorption capacity was 58 mg g−1 at 328 K. • Satisfactory isothermal fit to the Freundlich model. • The LDF model represented the adsorption kinetics. • Hd-AC showed 70% removal efficiency from river water contaminated with atrazine. The species Hovenia dulcis has become a major issue for the Brazilian biome due to its high adaptation and accelerated propagation, putting the local biodiversity at risk. In this sense, this study sought to generate a new purpose for the fruits of this peculiar species. They were carbonized with ZnCl 2 to produce porous activated carbon, which was used to remove the herbicide atrazine from aqueous solutions. The Hovenia dulcis activated carbon (Hd -AC) presented a surface area of 898.4 m2/g, with narrow pores with an average diameter of 1.24 nm and a pore volume of 0.296 cm3 g−1. Hd -AC for atrazine adsorption was efficient at a pH of 6.0 for an adsorbent dosage of 0.5 g/L, where the adsorption capacity was 58 mg g−1 at 328 K. The isothermal curves showed a good adjustment to the Freundlich isotherm. The thermodynamic results indicated that herbicide adsorption was spontaneous, favorable, and endothermic (ΔH° = 8.21 kJ mol−1). Besides, the linear driving force model (LDF) was used satisfactorily to describe the kinetic behavior of atrazine. Also, in treating a sample of river water contaminated with atrazine, Hd -AC showed high performance, reaching the removal of 70 % of the emerging pollutant. Therefore, using the residual fruits of the Hovenia dulcis as biomass to prepare a highly porous adsorbent reveals a promising alternative. [ABSTRACT FROM AUTHOR]

[Display omitted] • High surface area activated carbon derived from Diospyros kaki fruit waste; • Remarkable adsorption capacity for aqueous-phase atrazine; • Linear driving force (LDF) model provides good fit to kinetic data; • Activated carbon efficient to remove atrazine in real river samples. In this work, Diospyros kaki fruit waste was employed as a precursor material to develop a high surface area activated carbon, which efficiently removed the toxic herbicide atrazine (ATZ) from synthetic water solutions and river waters. The alternative activated carbon presented excellent characteristics and structure, including high values of specific surface area (1067 m2 g−1) and pore volume (0.530 cm3 g−1) and some important functional groups on the surface. The temperature positively influenced the adsorption capacity, from 194.20 to 211.51 mg g−1. The Freundlich model was the proper one to represent the equilibrium data. Thermodynamic parameters confirmed the endothermic nature of the adsorption process. Kinetic studies confirmed that equilibrium was reached until 240 min, regardless of ATZ initial concentration. The LDF model adjusted well to the kinetic data, resulting in a diffusion coefficient ranging from 0.89x10-9 to 1.63x10-9 cm2 s−1 as the ATZ concentration increased. The activated carbon also decreased 85% of the ATZ concentration in a river water sample. Overall, the activated carbon developed from Diospyros kaki fruit waste presented an efficient ATZ removal from aqueous matrices. [ABSTRACT FROM AUTHOR]