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Separations
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Removal of Metals or Other Toxic Substances from Wastewaters by...
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Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents

A special issue of Separations (ISSN 2297-8739). This special issue belongs to the section "Environmental Separations".

Deadline for manuscript submissions: closed (10 January 2024) | Viewed by 14088

Special Issue Editors

Dr. Ariana Pintor

E-Mail Website
Guest Editor
Laboratory of Separation and Reaction Engineering—Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
Interests: water and wastewater treatment; adsorption; low-cost materials; removal of heavy metals; nutrient recovery
Special Issues, Collections and Topics in MDPI journals
Dr. Sílvia Santos

E-Mail Website
Guest Editor
Laboratory of Separation and Reaction Engineering—Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
Interests: adsorption; wastewater treatment; natural adsorbents; toxic metalloids; metal recovery
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The last few decades have given us many technological advancements in wastewater treatment processes. However, challenges are increasing at an equally accelerating rate, with the growing detection of emerging pollutants in water reservoirs, the advent of novel chemical substances with unknown toxic effects, and the demand for resource recovery in the transition to a circular economy. In this context, adsorption remains a popular methodology for the fast, reliable, and easy-to-operate removal of specific compounds in the tertiary treatment of wastewater.

Traditionally, adsorbent materials of choice included activated carbons, clays, zeolites, and minerals, with large surface areas and high density of specific surface groups for chemical bonding. Still, research is evolving to propose alternative materials with lower prices and environmental impact. That is the case of natural sorbents derived from biomass, usually comprising byproducts or wastes from agri-food and forestry industries. Repurposing these waste flows for upcycling as adsorbents is a valuable input to reducing wastewater treatment costs and increasing the sustainability of biomass-based industrial activities.

In this Special Issue, we welcome contributions to the development and application of natural sorbents for the removal of metals and other toxic substances from wastewater, such as:

  • Novel uses for raw natural sorbents;
  • Modification of biomass for selective uptake of specific compounds;
  • Removal of emerging contaminants, especially in environmentally relevant conditions such as low concentrations;
  • Scale-up of existing applications, for instance, using real wastewaters or prototypes and pilot-scale reactors;
  • Environmental and industrial assessment of natural sorbent technology, using tools such as life-cycle analysis, cost–benefit analysis, and others.

Original research papers and review articles are equally welcome.

Dr. Ariana Pintor
Dr. Sílvia Santos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • adsorption
  • biomass
  • resource recovery
  • heavy metals
  • emerging pollutants
  • waste
  • upcycling
  • circular economy

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Published Papers (6 papers)

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Research

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12 pages, 4110 KiB  
Article
Superior Removal of Toxic Cr(VI) from Wastewaters by Natural Pine Bark
by Hanui Yang, Namgyu Kim and Donghee Park
Separations 2023, 10(8), 430; https://doi.org/10.3390/separations10080430 - 28 Jul 2023
Cited by 2 | Viewed by 987
Abstract
Hexavalent chromium (Cr(VI)) is one of the most toxic heavy metals found in industrial wastewater, so many researchers are working to develop efficient and environmentally friendly removal methods. It has been reported that natural biomass and its derivatives can be used to treat [...] Read more.
Hexavalent chromium (Cr(VI)) is one of the most toxic heavy metals found in industrial wastewater, so many researchers are working to develop efficient and environmentally friendly removal methods. It has been reported that natural biomass and its derivatives can be used to treat wastewaters containing Cr(VI). However, biomass with sufficient Cr(VI) removal performance to replace the existing chemical method, which is cheap and simple, has not been reported yet. This study reports that inexpensive, abundant, and commercially available pine bark has the highest Cr(VI) removal capacity (i.e., 376.3 mg/g) compared to biomass reported elsewhere. This value is six times higher than the theoretical value of an inorganic reducing agent (iron(II) sulfate heptahydrate). The main mechanism of Cr(VI) removal by pine bark was clearly identified through kinetic experiments, Fourier-transform infrared spectrometer, and X-ray photoelectron spectroscopy analyses, which were used to study the compositions, functional groups, and bonding states of pine bark. It was found that pine bark consists of various acidic functional groups that can act as electron donors to promote the removal of Cr(VI) through redox reactions. In conclusion, pine bark may be a promising candidate for the removal of Cr(VI) from wastewater, owing to its excellent removal capacity. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
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17 pages, 6113 KiB  
Article
Cobalt Biosorption in Fixed-Bed Column Using Greenhouse Crop Residue as Natural Sorbent
by Gabriel Blázquez, María Ángeles Martín-Lara, Irene Iáñez-Rodríguez, Inés Morales, Antonio Pérez and Mónica Calero
Separations 2022, 9(10), 316; https://doi.org/10.3390/separations9100316 - 18 Oct 2022
Cited by 3 | Viewed by 1595
Abstract
Intensive greenhouse agriculture annually produces large amounts of residues. The present work focused on the study of the dynamic adsorption of cobalt from aqueous solutions over a vegetal residue from intensive greenhouse cultivation. The influence of three operating variables, feed-flow rate, inlet concentration [...] Read more.
Intensive greenhouse agriculture annually produces large amounts of residues. The present work focused on the study of the dynamic adsorption of cobalt from aqueous solutions over a vegetal residue from intensive greenhouse cultivation. The influence of three operating variables, feed-flow rate, inlet concentration of cobalt and bed height, was analyzed. According to the results, the variable that particularly affected the percentage of cobalt adsorbed was the feed-flow rate. The results were also fitted to an adaptive neuro fuzzy system (ANFIS) model to predict cobalt adsorption from aqueous solutions and choose the most favorable operating conditions. Results were evaluated using root mean squared error (RMSE), coefficient of determination (R2) and other typical statistic factors as performance parameters. The experimental and model outputs displayed acceptable result for ANFIS, providing R2 values higher than 0.999 for both cobalt removal (%) and biosorption capacity (mg/g). In addition, the results showed that the best operating conditions to maximize the removal of cobalt were 4 mL/min of feed-flow rate, 25 mg/L of inlet concentration and 11.5 cm of bed-height. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
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Review

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25 pages, 7019 KiB  
Review
The Removal of Per- and Poly-Fluoroalkyl Substances from Water: A Review on Destructive and Non-Destructive Methods
by Natalia Malouchi, Stella Chatzimichailidou, Athanasia K. Tolkou, George Z. Kyzas, Loris Calgaro, Antonio Marcomini and Ioannis A. Katsoyiannis
Separations 2024, 11(4), 122; https://doi.org/10.3390/separations11040122 - 18 Apr 2024
Viewed by 2806
Abstract
PFAS, or per- and poly-fluoroalkyl substances, are a broad group of man-made organic compounds that are very persistent, mobile, and tend to bioaccumulate. Their removal from different environmental media is becoming increasingly important because they are associated with a multitude of (eco)toxicological effects [...] Read more.
PFAS, or per- and poly-fluoroalkyl substances, are a broad group of man-made organic compounds that are very persistent, mobile, and tend to bioaccumulate. Their removal from different environmental media is becoming increasingly important because they are associated with a multitude of (eco)toxicological effects on both humans and the environment. PFAS are detected in wastewater, groundwater, drinking water, and surface water, with the subcategories of PFOS and PFOA being the most detected. These organic compounds are divided into polymeric and non-polymeric groups. Non-polymeric PFAS are of great research interest due to their frequent detection in the environment. Numerous methods have been applied for the removal of PFAS and are divided into destructive and non-destructive (separation) techniques. Given the strength of the C–F bond, the destruction of PFAS is challenging, while for most of the separation techniques, the management of isolated PFAS requires further consideration. Most of the techniques have been applied to small-scale applications and show some limitations for larger applications, even though they are promising. Adsorption is an environmentally sustainable, economical, and high-performance technique that is applied to remove several classes of emerging pollutants from water. In this review, the use of various types of adsorbents for PFAS removal from water is reported, as well as the expected adsorption mechanisms. There are several technologies being considered and developed to manage PFAS; however, they are still in the experimental stage, with each showing its appeal for potential larger applications. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
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20 pages, 336 KiB  
Review
Enhanced Adsorption of Chromate and Arsenate Ions from Contaminated Water with Emphasis on Polyethylenimine Modified Materials: A Review
by Maria Xanthopoulou and Ioannis A. Katsoyiannis
Separations 2023, 10(8), 441; https://doi.org/10.3390/separations10080441 - 7 Aug 2023
Cited by 6 | Viewed by 1689
Abstract
Heavy metals in water pose a great threat to human health, and water treatment remains a critical issue globally. Among various water treatment techniques, adsorption has been proven to be an excellent way to remove heavy metals from water due to its advantages, [...] Read more.
Heavy metals in water pose a great threat to human health, and water treatment remains a critical issue globally. Among various water treatment techniques, adsorption has been proven to be an excellent way to remove heavy metals from water due to its advantages, like low cost, availability, profitability, ease of operation, and efficiency. Heavy metals such as chromium and arsenic are present in water in the form of anions, while many common adsorbents, such as biochar and activated carbons, cellulose, chitosan, clays, and silica, tend to acquire a negative surface charge. The surface charge of the adsorbent plays a major role in its interaction with heavy metal ions. Polyethylenimine is a polymer with a high cationic charge density. Modification of these adsorbents with polyethylenimine results in higher selectivity for these anions. The adsorption capacity is related to the efficiency of the introduction of polyethylenimine, which depends on the surface properties of the adsorbent. This review focuses on the effect of modification with polyethylenimine on the adsorption capacity of common adsorbents for the removal of heavy metal ions, such as chromate and arsenate, from water. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
18 pages, 3155 KiB  
Review
Advances in Cork Use in Adsorption Applications: An Overview of the Last Decade of Research
by João Jesus, Raquel Nunes da Silva and Ariana Pintor
Separations 2023, 10(7), 390; https://doi.org/10.3390/separations10070390 - 3 Jul 2023
Cited by 4 | Viewed by 2512
Abstract
Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a [...] Read more.
Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a raw material. This review presents these novel insights into the properties of cork, in its various forms, and how they relate to adsorption capacity. Details on new preparation methodologies and respective characteristics of cork-based activated carbons and biochars are thoroughly compared, and patterns are identified. Finally, the adsorption capacity of these materials in experimental conditions is reviewed for different compounds: heavy metals, organics, and gaseous pollutants. This review provides a complete picture of the kind and quality of different cork forms, their relative economic value, and how their conversion into activated carbons and biochars can contribute to a more circular economy by producing adsorbents that aid in the reduction of multiple pollution types. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
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32 pages, 3494 KiB  
Review
Recent Advances in Using Adsorbent Derived from Agricultural Waste for Antibiotics and Non-Steroidal Anti-Inflammatory Wastewater Treatment: A Review
by Abu Hassan Nordin, Abdul Samad Norfarhana, Siti Fadilla Md Noor, Syafikah Huda Paiman, Muhammad Luqman Nordin, Siti Muhamad Nur Husna, Rushdan Ahmad Ilyas, Norzita Ngadi, Aznizam Abu Bakar, Zuliahani Ahmad, Mohammad Saifulddin Azami, Wan Izhan Nawawi and Walid Nabgan
Separations 2023, 10(5), 300; https://doi.org/10.3390/separations10050300 - 8 May 2023
Cited by 11 | Viewed by 3834
Abstract
Antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) are among the top pharmaceutical contaminants that have been often found in the aquatic environment. The presence of these contaminants in the aquatic environment is of great concern since it has a negative impact on both ecology [...] Read more.
Antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) are among the top pharmaceutical contaminants that have been often found in the aquatic environment. The presence of these contaminants in the aquatic environment is of great concern since it has a negative impact on both ecology and human health. In contrast to other tertiary treatments, adsorption stands out as a viable treatment approach since it provides benefits such as easier operating conditions with no byproduct formation. Commercial activated carbon is widely researched as a pharmaceutical adsorbent, but its large-scale applicability is constrained by its high cost. Agricultural waste also contains a large amount of various functional groups, which may be adapted to surface modification to increase its adsorption ability. In this regard, this study is designed to review the recent progress of efficient adsorbents derived from various agricultural wastes for the removal of antibiotics and NSAIDs contaminants from water bodies. Adsorbents made from agricultural waste have important benefits over commercial activated carbon for the reduction in waste while controlling water pollution. Full article
(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)
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