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Natural-Based Sorbents for Water Remediation

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Physical Chemistry".

Deadline for manuscript submissions: closed (30 November 2025) | Viewed by 3366

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Special Issue Editors

Dr. Stefano Salvestrini

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Guest Editor

Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, Caserta, Italy
Interests: adsorption; water remediation; advanced oxidation processes; heterogeneous catalysis; kinetic reaction mechanisms; thermodynamics
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Dr. Yannice Tatiane da Costa Santos

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Guest Editor Assistant

Federal Institute of Education, Science and Technology of Ceará—Campus Juazeiro do Norte, Av. Plácido Aderaldo Castelo, 1646, Juazeiro do Norte, Ceará 63040-540, Brazil
Interests: adsorption of toxic metals; wastewater treatment; water treatment; natural adsorbents; adsorption kinetics; adsorption isotherms; adsorption thermodynamics

Dr. Hiago de Oliveira Gomes

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Guest Editor Assistant

Federal Institute of Education, Science and Technology of Ceará—Campus Iguatu, Iguatu, Brazil
Interests: adsorption; water treatment; emerging contaminants; biosorbent; adsorption equilibrium; thermodynamics; chromatographic methods; validation

Special Issue Information

Dear Colleagues,

Due to persistent industrialization and anthropic action, water remediation will always be a challenge. It is therefore crucial to develop new technologies for the treatment of contaminated water resources. Sorption, as an efficient and well-structured method for the remediation of water resources, requires the development of new sorbents highly efficient at removing different classes of contaminants, given the increasingly complex composition of waste discharged into water resources. It is desirable, however, to use natural-based sorbents, specifically those that promote the reuse of waste and discharged materials, as opposed to conventional/synthetic sorbents that are relatively expensive and laborious to produce and less environmentally friendly. Recent published papers have demonstrated the good performance and versatility of natural-based sorbents for removing a large variety of contaminants. It is therefore advisable to further explore the knowledge on this kind of material.

In this regard, the present Special Issue focuses on experimental studies concerning the preparation and use of natural-based sorbents and that cover the following topics: (a) natural sorbents, e.g., from mineral waste and vegetal or animal biomass, with or without physical and chemical modification; (b) removal of organic or inorganic contaminants from water; (c) physical and chemical characterization of the sorbent; (d) kinetic and equilibrium sorptive tests with the aim of verifying the optimum conditions for pollutant uptake, exploring the effect of reaction time, pH, sorbent dosage, concentration, and temperature; (e) evaluation of thermodynamic and kinetic parameters; and (f) determination of the actual sorption mechanism.

Dr. Stefano Salvestrini
Guest Editor

Dr. Yannice Tatiane da Costa Santos
Dr. Hiago de Oliveira Gomes
Guest Editor Assistants

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Keywords

natural sorbents
removal of organic or inorganic contaminants from water
physical and chemical characterization of the sorbent
kinetic and equilibrium sorptive tests
evaluation of thermodynamic and kinetic parameters
determination of the actual sorption mechanism

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Published Papers (4 papers)

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Research

23 pages, 1550 KB

Open AccessArticle

Kinetics and Isotherm Study of Ceftriaxone Removal Using Functionalized Biochar Combined with Photocatalysis

by Luísa Cruz-Lopes, Rodrigo Araújo, Ana Rita Lopes, Samuel Moles, Francisca Romero-Sarria and Bruno Esteves

Molecules 2025, 30(21), 4291; https://doi.org/10.3390/molecules30214291 - 5 Nov 2025

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Abstract

The increasing presence of antibiotics such as cephalosporins in wastewater represents a significant environmental risk. These compounds are excreted in large quantities, and conventional wastewater treatment plants are often ineffective at their removal. Consequently, the development of more sustainable and efficient treatment technologies is essential. In this study, the removal of cephalosporins from aqueous solutions was evaluated through adsorption using pine bark biochar, photocatalysis with TiO₂, and a combination of both processes. Kinetic experiments were conducted with cephalosporin solutions (15 mg/L), employing 150 mg/L of biochar, 100 mg/L TiO₂, or their combination, under continuous stirring and/or UV-vis irradiation. Samples were collected at 0 and 120 min and analyzed via UV-vis spectrophotometry. Adsorption isotherms were established for initial cephalosporin concentrations ranging from 5 to 50 mg/L. The biochar alone achieved a removal efficiency of 94.2% after 120 min. Photocatalysis with TiO₂ alone resulted in 75% removal, while the combined approach reached 95.9%, indicating a synergistic effect between adsorption and photodegradation mechanisms. Kinetic data fitted the pseudo-second-order model, and the Langmuir isotherm provided the best correlation, suggesting monolayer adsorption. These findings demonstrate that pine bark biochar, whether used independently or in combination with TiO₂, constitutes an eco-friendly, effective, and low-cost alternative for the removal of antibiotics from wastewater, while simultaneously contributing to the valorization of forestry residues. Full article

(This article belongs to the Special Issue Natural-Based Sorbents for Water Remediation)

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23 pages, 4400 KB

Open AccessArticle

Assessment of Hydrochar and Porous Carbon from Tectona Grandis Seeds for Removal of Acridine Dyes

by Shubham Chaudhary, Monika Chaudhary, Sarita Kushwaha, Vaishali Tyagi, Shivangi Chaubey, Isabel Pestana da Paixão Cansado, Evgeny Galunin and Suhas

Molecules 2025, 30(19), 3989; https://doi.org/10.3390/molecules30193989 - 4 Oct 2025

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Abstract

This study explores the use of lignocellulosic Tectona grandis seeds (TGs), hydrochar (HC-230-4), and activated carbon (AC-850-5) produced via hydrothermal carbonization and followed by CO₂ activation for removing acridine yellow G (AYG) and acridine orange 14 (ABO) from water. HC-230-4 showed a rich presence of surface functional groups and irregular morphology with some sphere-like structures. In contrast, AC-850-5 exhibited a much higher surface area (729.7 m²/g), though with fewer surface functional groups than HC-230-4. The batch method was used to study the effects of contact time, pH, dye concentration, and temperature. Among the materials, AC-850-5 showed the highest adsorption capacity of 198 mg/g for AYG and 171 mg/g for ABO at 25 °C, around 12% higher than commercial activated carbon. The adsorption process was spontaneous and endothermic, fitting well to the Langmuir isotherm model, suggesting monolayer coverage. The adsorption kinetics followed the pseudo-second-order model, indicating that the rate depends on the surface site availability. Intraparticle diffusion analysis further confirmed a multi-step adsorption process. These findings show the strong potential of TG-derived activated carbon as an effective and sustainable material for removing acridine dyes from polluted water. Full article

(This article belongs to the Special Issue Natural-Based Sorbents for Water Remediation)

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21 pages, 4562 KB

Open AccessArticle

The Influence of the Plant Biomass Pyrolysis Conditions on the Structure of Biochars and Sorption Properties

by Bernadetta Kaźmierczak, Jolanta Drabik, Paweł Radulski, Anna Kaczmarczyk and Edyta Osuch-Słomka

Molecules 2025, 30(14), 2926; https://doi.org/10.3390/molecules30142926 - 10 Jul 2025

Viewed by 722

Abstract

The aim of this work was to obtain biochar materials from plant biomass and to determine the changes occurring under the conditions of the pyrolysis process and physical activation, as well as to characterize the physicochemical characteristics of the produced products in terms of their practical use. The pyrolysis process was carried out at a temperature of 700 °C, under the flow of a protective gas, i.e., carbon dioxide, at a rate of 5.0 L/min. The pyrolysis processes were carried out in the absence and presence of an activating agent. For ecological safety, physical activation using water vapor was chosen. In the next stage of the work, biochars were produced and subjected to detailed physicochemical analysis. A scanning electron microscope with energy-dispersive SEM/EDS was used to determine the microstructure and changes in the chemical composition of the biochars. FTIR spectrophotometry was used to identify the functional groups present in the structures of biochars and to indicate changes occurring in the biomass during pyrolysis. Meanwhile, Raman spectroscopy was used to assess the ordering of the biochar structures based on the identification of spectral signals. The description of the specific surface areas of the biochars was made possible by studies conducted using a physical and chemical adsorption analyzer. Based on the obtained research results, the elementary structure, surface development, presence of functional groups on the surfaces of biochars and changes in the structure before and after activation with water vapor were determined. It was found that the biochars had functional groups, a well-developed specific surface area that increased after activation with water vapor, micropores and mesopores, as well as changes in structure under the influence of physical activation. It has been shown that the presence of functional groups influences the hydrogen sulfide sorption capacity. Full article

(This article belongs to the Special Issue Natural-Based Sorbents for Water Remediation)

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18 pages, 3108 KB

Open AccessArticle

Removal of Azoxystrobin and Deltamethrin from Water Using Activated Biochar from Moringa oleifera L. Wood: Synthesis, Characterization, and Adsorption Study

by Hiago Gomes, Ellen Bento, Maria Dayrine Tavares, Yannice Santos, José Galberto da Costa, Ronaldo do Nascimento, Stefano Salvestrini and Raimundo Teixeira

Molecules 2025, 30(13), 2757; https://doi.org/10.3390/molecules30132757 - 26 Jun 2025

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Abstract

The aim of this study was to evaluate the efficiency of activated biochar produced from Moringa oleifera L. wood for removing azoxystrobin (fungicide) and deltamethrin (insecticide) from water. The adsorption of pesticides on activated carbon was studied using batch tests evaluating the influence of contact time (1–180 min), concentration (5–50 mg L⁻¹), and temperature (283, 298 and 313 K). The highest removal percentage obtained was 94.39% for azoxystrobin and 91.96% for deltamethrin, considering an initial concentration of 10 mg L⁻¹ and adsorbent dosage of 5.0 g L⁻¹. FTIR spectra confirmed H-bonding in the adsorption process, SEM analysis revealed homogeneous surface area characteristics, and BET results confirmed a highly superficial area for the activated carbon, all of which favor pesticide adsorption. The Boyd model showed that the intraparticle diffusion stage is determinant for both compounds in the initial stages of the adsorption process. The Sips model was the isotherm with the best fit to the experimental data, possibly indicating cooperativity between adsorbate molecules at low temperatures. The thermodynamic study showed a favorable adsorption at all the temperatures investigated, given the negative value of ΔG°. In addition, this study revealed good adsorption capacities for the material indicating that Moringa oleifera wood activated carbon is a viable alternative for removing azoxystrobin and deltamethrin from water. Full article

(This article belongs to the Special Issue Natural-Based Sorbents for Water Remediation)

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