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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: 30 June 2025 | Viewed by 8521

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Prof. Dr. Eva Chmielewská

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Guest Editor

Department of Environmental Ecology and Landscape Management, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, Mlynská dolina B2, 842 15 Bratislava, Slovakia
Interests: environmental qality (water, soil, and biota) monitoring; water and solid waste treatment by physico-chemical and biological method (bioremediation techniques); environmental policy; natural zeolites
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Craig Williams

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Guest Editor

School of Applied Sciences, University of Wolverhampton, Wolverhampton WV1 1LY, UK
Interests: zeolites; microporous and mesoporous materials; pollution remediation

Special Issue Information

Dear Colleagues,

Mankind is currently facing urgent challenges in meeting rising demands for clean water as the available supplies of freshwater are decreasing due to population growth and extended water pollution. This also includes inadequate water treatment infrastructure due to global climate change and increasing consumption of ultrahigh-quality water from various modern and sophisticated industrial branches. The protection of water treatment systems against potential chemical and biological contamination, in the time of increasing diversity, is also becoming a critical issue in water resources planning. Environmental requirements are becoming of great importance in today´s society, since there is an increased interest in the industrial use of renewable resources. Biomimetics and bioinspiration is one of the most progressive, recently developed sciences, which deals with nature and living systems in order to provide sustainable life for future generations. With a more complex insight into living organisms and an understanding of their functions, the ability to mimic nature has increased dramatically over several decades and, thus, nature-driven solutions have brought technological progress to a higher level. Nevertheless, the above-mentioned discipline offers then a substantial scientific portfolio for the development of current material chemistry, specifically for novel nanoscale adsorbent synthesis. It is supposed that basic constructional processes of matter like biomineralisation, biomimetics, supramolecular preorganisation or interfacial molecular recognition (templating), and other recent techniques and new advanced nanomaterials contribute to a certain portfolio for potential Green Synthesis or Processing of the future. Moreover, there is a gradual insistence that clean industrial production, water reuse and solid waste recycling can provide sustainable living for the next generations.

Municipal solid waste (MSW) management can be defined as the discipline associated with the generation, storage, collection, transfer, processing, and disposal of MSW, in a way which is governed by the best principles of public health, economics, engineering, aesthetics, and other environmental considerations. Waste utilization management is explored in the context of the dominant principle of the circular economy: waste should be processed into secondary resources, reducing environmental risks. It is emphasized that separate waste collection is an important condition for creating a responsible "garbage culture" in society. Secondary methods (recycling) are the next stage, with mechanical, chemical, and thermal techniques used on the waste for processing in order to obtain an usable end result.

The main objective of the contributions for this Special Issue of Processes is to provide a view of the state of the art and the future prospects of Green Synthesis (Processing), with special emphasis on environmentally friendly, biocompatible nanoadsorbents and using natural renewable products or resources in order to support their valorization in environmental protection and sustainable development.

Prof. Dr. Eva Chmielewská
Prof. Dr. Craig Williams
Guest Editors

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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. Processes 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 2400 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

bioinspiration and biomimetics
sustainable life
reuse and recycling of water and human goods
green processing
nanomaterials
circular economy

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Published Papers (8 papers)

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Research

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14 pages, 3121 KiB

Open AccessArticle

Internet of Things-Driven Waste Management: Paving the Way for Sustainable Smart Cities

by Khadija Salim Al Yarubi, Sallam O. F. Khairy, S. M. Emdad Hossain and Gasim Hayder

Processes 2025, 13(4), 1140; https://doi.org/10.3390/pr13041140 - 10 Apr 2025

Viewed by 529

Abstract

Rapid urban growth around the globe has created major waste management challenges, particularly in locations that have experienced rapid urban expansion, such as Oman. In the following study, Al-Duqm as Oman’s primary economic zone is investigated, where outdated waste management practices are at odds with the national Sustainable Development Goals. In order to address this problem, we present a system that includes the use of Internet of Things sensors, combined with GPS tracking features and artificial intelligence capabilities. With this waste collection system, we aim to achieve enhanced speed and cost effectiveness and environmental sustainability. Ultrasonic sensors with AI-based route planning installed in waste bins enable the system to minimize unnecessary waste collection rounds by trucks. Laboratory evaluations of our system demonstrated a 28% reduction in fuel consumption and a 15% decrease in operational expenses, achieving collection performance levels that improved by more than 41.5%. The unique quality of this approach consists of aligning multifaceted technologies to fulfill Al-Duqm’s special requirements for its dry climate and expanding infrastructure. The combination of sensor-generated data enables trucks to navigate empty container spaces, thus saving time and lowering emission levels. The findings of this study aid Oman in reaching its 2040 targets, in addition to Global Sustainable Development Goal 11, while simultaneously enhancing environmentally friendly initiatives in urban areas. The results of this study demonstrate how modern smart systems transform expensive waste management services into an intelligent environmental tool, thus providing examples for other areas that seek to achieve sustainable development through urban growth. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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15 pages, 2224 KiB

Open AccessArticle

Fe³⁺ and Mn²⁺ Removal from Water Solutions by Clinoptilolite Zeolites as a Potential Treatment for Groundwater Wells

by William D. Arenhardt, Felipe Ketzer, João H. C. Wancura, Janaina Seraglio, Fabio L. Carasek, Guilherme Zin, Jean F. F. Calisto, Clovis A. Rodrigues, Alessandra C. de Meneses, José Vladimir Oliveira and Jacir Dal Magro

Processes 2025, 13(4), 1060; https://doi.org/10.3390/pr13041060 - 2 Apr 2025

Viewed by 451

Abstract

This study presents data on the water quality of the Guarani Aquifer based on samples collected from distinct groundwater wells in the western region of Santa Catarina State, Brazil. Among the analyses performed, the results indicated the need for treatment to ensure suitability for human consumption, particularly concerning Fe³⁺ and Mn²⁺ ions. Accordingly, natural (NCLIN) and activated clinoptilolite (ACLIN) zeolites were evaluated for ion removal from synthetic aqueous solutions through adsorption. NCLIN demonstrated excellent performance in adsorbing Fe³⁺ and Mn²⁺ ions, achieving removal efficiencies of over 98% and 95%, respectively, at a controlled pH of 6.0 (NCLIN) or 4.0 (ACLIN). A non-linear approach to modeling adsorption kinetics indicated that the pseudo-second-order model best represented the experimental data. This finding suggests that the interaction between the adsorbent and Fe³⁺ and Mn²⁺ ions occur through electron sharing and chemisorption. Equilibrium modeling analysis revealed that adsorption on NCLIN occurred in a monolayer, whereas adsorption on ACLIN followed a multilayer pattern. This behavior is attributed to the activation process with H₂SO₄, which led to dealumination and the formation of HSO₃⁻ groups on the adsorbent surface. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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17 pages, 10201 KiB

Open AccessArticle

The Separation and Recovery of Barium from Barium Slag by Using Shaking Table Gravity Concentration Method

by Yang Wan, Bo Zhang, Xing Yang, Xin Song, Guocui Li, Siqi Zhang and Wen Ni

Processes 2025, 13(4), 1012; https://doi.org/10.3390/pr13041012 - 28 Mar 2025

Viewed by 370

Abstract

Barium slag, classified as HW47 hazardous waste, is produced in large quantities and has a high accumulation with heavy metal Ba ions that are significantly above the standard levels, posing a serious threat to the ecological environment and the growth of flora and fauna. Before barium slag can be stored, it must undergo harmless treatment, which is costly, and with the current large volume of accumulated barium slag, storage facilities are strained. There is an urgent need for new technologies to extract barium elements from barium slag while achieving reduction in volume. This study first treats the barium slag to reduce its oxidation state and then utilizes the density differences to separate barium-rich compounds through shaking table concentration. Macro and microanalytical methods such as XRD (X-ray diffraction), XRF (X-ray fluorescence), and SEM&EDS (Scanning Electron Microscopy & Energy-dispersive X-ray Spectroscopy) were employed. The results show that barium in the slag is evenly distributed, and after sufficient crushing, it can be separated by gravity concentration. The barium content can be enriched from 20% to over 80%. This research provides theoretical support for the separation of barium compounds from barium slag. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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16 pages, 3324 KiB

Open AccessArticle

Research on the Harmless Treatment of Barium Slag Using Flue Gas Desulfurization Gypsum

by Yang Wan, Zhou Chen, Xiaohui Cao, Xin Song, Yu Zhan, Chunting Ma, Siqi Zhang and Wen Ni

Processes 2025, 13(1), 55; https://doi.org/10.3390/pr13010055 - 30 Dec 2024

Viewed by 909

Abstract

This study proposes an innovative method for the harmless treatment of barium slag using the industrial by-product Flue Gas Desulfurization Gypsum. Barium slag is a by-product of the barium carbonate production process, and due to its high content of barium ions and corrosive properties, it poses a significant threat to the environment and human health. It is classified as barium-containing hazardous waste (code HW47) in China. In this study, barium slag was optimally combined with FGD gypsum, utilizing a synergistic precipitation mechanism to solidify the easily leachable barium ions and form stable sulfate minerals. Mechanical and heavy metal leaching tests showed that the harmlessly treated barium slag had a certain compressive strength, and the concentration of barium ions in the leachate was below the national hazardous waste identification standards (100 mg/L) and the drinking water quality standards (0.7 mg/L). Microstructural analysis using X-ray diffraction, Fourier Transform Infrared Spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy indicated that FGD gypsum promotes the solidification of barium slag, and through the synergistic precipitation mechanism, low-solubility barium sulfate minerals are formed. This treatment method also has a low cost and good potential for resource utilization, providing effective technical support for the green treatment of industrial waste. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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21 pages, 7683 KiB

Open AccessArticle

Coffee-Waste-Based ZnCl₂ Activated Carbon in High-Performance Supercapacitor Electrodes: Impact of Graphitization, Surface Morphology, Porosity and Conductivity

by Sami Mukhiemer, Allan Daraghmah, Heba Nassar, Shahzad Hussain, Hanyi Lim, Hyobin Han, Tae Woo Kim, Ameed N. Amireh and Hikmat S. Hilal

Processes 2024, 12(12), 2832; https://doi.org/10.3390/pr12122832 - 10 Dec 2024

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Abstract

Activated carbon (AC) electrodes from coffee waste (CW) were earlier assessed in supercapacitors but showed lower supercapacitor performance in terms of specific capacity (C_s), specific power (P_s) or both, compared to other biowastes. This work describes how CW-based AC electrode performance may be improved if carefully prepared. Careful processing yields higher graphitization, carbon content (aromaticity), conductivity and porosity free of any residues. Thus, AC electrodes will exhibit higher C_s and P_s simultaneously. CW was first pyrolyzed (C_Pyrol) and then chemically activated by ZnCl₂ (AC_Chem). Both materials were characterized using SEM, TEM, BET, FT-IR spectra, Raman spectra and XRD. The AC_Chem exhibited much higher graphitization, crystallinity, specific surface area (SSA), porosity and conductivity. From cyclic voltammetry, the AC_Chem electrode exhibited a C_s of 261 F/g, an energy density of 18.3 Wh/kg and a P_s of 360 W/kg at 0.33 A/g. From galvanostatic charge–discharge, there was a stable C_s of 150 F/g at 0.33 A/g over 5000 charge–discharge cycles. From electrochemical impedance spectroscopy, the Cs was ~180 F/g, with a low equivalent series resistance (ESR) of 0.56 Ω at a frequency of 0.01 Hz, compared to the literature. The AC_Chem electrode was superior to the C_Pyrol electrode and to earlier CW-based AC counterparts, with much lower resistance. Moreover, the electrode competed with other biowaste-based electrodes. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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15 pages, 4471 KiB

Open AccessArticle

Plasma Gasification of a Simulated Low-Level Radioactive Waste: Co, Cs, Sr, and Ce Retention Efficiency

by Juan Ariel Pullao, Franco Emmanuel Benedetto, Gian Franco Binetti Basterrechea, Leonardo Andrés Neira Poblete, Diana Carolina Lago and Miguel Oscar Prado

Processes 2024, 12(9), 1919; https://doi.org/10.3390/pr12091919 - 6 Sep 2024

Cited by 2 | Viewed by 1065

Abstract

Thermal plasma is a versatile technology that can be used to treat various types of wastes, including vegetal and mineral oils, solvents, plastics, paper and cardboard, glasses, bricks and rocks, metals, clothes, and mixtures of these materials. In this study, we utilized a commercial plasma cutter as a thermal plasma source to decrease the volume of a simulated low-level radioactive mixed solid waste. The simulated waste included papers, plastics, clothes, gloves, metals, and stable Co, Cs, Sr, and Ce additives as surrogates of ⁶⁰Co, ¹³⁷Cs, ⁹⁰Sr, and ¹⁴⁴Ce, respectively, the latter being typical contaminants in nuclear LLW. As a result of the process, two products were obtained: a solid phase, on which we focused this work, and a gaseous phase. To retain as many as surrogates as possible in the solid final phase, crushed glass from broken bottles was included as a vitrification additive to the original waste. After undergoing heat treatment, a dense vitreous slag was produced along with ashes. The process resulted in a volume reduction of 70%, indicating the successful gasification of organic excess materials. The surrogate elements were retained in the process and were found in the ashes composition: Co (3.4% w/w), Cs (37.7% w/w), and Ce (0.6% w/w) and in the glass matrix composition of Co, Cs, Sr and Ce: 72.4 ± 14.7, 32 ± 18.2, 125.3 ± 31.6, 80 ± 13.1% w/w, respectively. For the actual experimental conditions, retention efficiencies were estimated for cobalt (Co) at 72.4 ± 14.7%, cerium (Ce) at 80 ± 13.1%, strontium (Sr) at 125.3 ± 31.6%, and notably cesium (Cs) at 32 ± 18.2%. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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16 pages, 2045 KiB

Open AccessArticle

Plant-Based Substrates for the Production of Iron Bionanoparticles (Fe-BNPs) and Application in PCB Degradation with Bacterial Strains

by Marcela Tlčíková, Hana Horváthová, Katarína Dercová, Michaela Majčinová, Mariana Hurbanová, Katarína Turanská and Ľubomír Jurkovič

Processes 2024, 12(8), 1695; https://doi.org/10.3390/pr12081695 - 13 Aug 2024

Cited by 1 | Viewed by 1352

Abstract

Removing polychlorinated biphenyls (PCBs) from the environment is an important process for the protection of biota. This work examines three different approaches to the degradation of such contaminants. The first involves the use of iron bionanoparticles (Fe-BNPs) prepared through green synthesis from selected plant matrices. The second approach entails the use of the bacteria Stenotrophomonas maltophilia (SM) and Ochrobactrum anthropi (OA) isolated from a PCB-contaminated area, Strážsky canal, located in the Slovak republic, which receives efflux of canal from Chemko Strážske plant, a former producer of PCB mixtures. The third approach combines these two methods, employing a sequential hybrid two-step application of Fe-BNPs from the plant matrix followed by the application of bacterial strains. Fe-BNPs are intended to be an eco-friendly alternative to synthetic nanoscale zero-valent iron (nZVI), which is commonly used in many environmental applications. This work also addresses the optimization parameters for using nZVI in PCB degradation, including the pH of the reaction, oxygen requirements, and dosage of nZVI. Pure standards of polyphenols (gallic acid, GA) and flavonoids (quercetin, Q) were tested to produce Fe-BNPs using green synthesis at different concentrations (0.1, 0.3, 0.5, 0.8, and 1 g.L⁻¹) and were subsequently applied to the PCB degradation experiments. This step monitored the minimum content of bioactive substances needed for the synthesis of Fe-BNPs and their degradation effects. Experimental analysis indicated that among the selected approaches, sequential nanobiodegradation appears to be the most effective for PCB degradation, specifically the combination of Fe-BNPs from sage and bacteria SM (75% degradation of PCBs) and Fe-BNPs from GA (0.3 g.L⁻¹) with bacteria OA (92% degradation of PCBs). Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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Review

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25 pages, 1583 KiB

Open AccessReview

Biosand Reactors for Municipal and Industrial Wastewater Treatment: Status Quo, Challenges and Opportunities

by Pamela Jean Welz

Processes 2024, 12(4), 641; https://doi.org/10.3390/pr12040641 - 23 Mar 2024

Cited by 4 | Viewed by 1651

Abstract

Biosand reactors (BSRs), alternatively known as slow or biological sand filters, are passive systems that are used to remove contaminants from domestic wastewater, industrial wastewater and drinking water. This review focuses specifically on their application for remediation of industrial effluent and sewage-containing municipal and household effluent. The relationships between the physicochemical characteristics of the sand grains (size, size distribution, shape, chemical composition) and the hydraulic conductivity of the sand employed in BSFs are critically discussed in relationship to the achievable loading rates and hydraulic retention times. The modes of operation and influence of the functional microbial biomass as well as biodegradable and recalcitrant particulates on these parameters is comprehensively reviewed. Finally, the bioremediation of sewage-based and industrial wastewater is examined. This includes an account of the biotic and abiotic removal mechanisms and the limitations of BSRs for removal of pollutants such as phosphorus/phosphate and nitrates/nitrites. The removal mechanisms and removal efficiencies of macronutrients, micropollutants, fecal indicators and other microorganisms such as antibiotic-resistant bacteria in BSRs are discussed. Full article

(This article belongs to the Special Issue Advances in Wastewater and Solid Waste Treatment Processes)

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