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18 pages, 7244 KiB

Open AccessFeature PaperArticle

Cobalt-Modified Biochar from Rape Straw as Persulfate Activator for Degradation of Antibiotic Metronidazole

by Lei Hu, Lin Shi, Edwin Hena Dawolo, Ning Ding and Hong Liu

Processes 2024, 12(8), 1596; https://doi.org/10.3390/pr12081596 - 30 Jul 2024

Viewed by 728

Abstract

A cobalt-loaded magnetic biochar (Co-MBC) catalyst was synthesized to enhance the removal of metronidazole (MNZ). Study explored the performance and mechanism of MNZ degradation by Co-MBC activated permonosulfate (PMS). Results showed that cobalt oxides were effectively deposited onto the biochar surface, new oxygen [...] Read more.

A cobalt-loaded magnetic biochar (Co-MBC) catalyst was synthesized to enhance the removal of metronidazole (MNZ). Study explored the performance and mechanism of MNZ degradation by Co-MBC activated permonosulfate (PMS). Results showed that cobalt oxides were effectively deposited onto the biochar surface, new oxygen functional groups were added to the modified biochar, and the presence of the metallic element Co enhanced the efficiency of PMS activation in the composite. More than 90% of MNZ was removed after 60 min with a catalyst dosage of 0.2 g/L and a PS concentration of 1 mM. After four reuses, Co-MBC still showed excellent catalytic performance to degrade over 75% of MNZ. The reaction system performed well even in the presence of inorganic anions and organic macromolecules. However, the degradation rate was inhibited under alkaline conditions. The quenching experiment indicated that •SO₄⁻, •OH, ¹O₂, and •O₂⁻ synergistically degraded MNZ, and that•SO₄⁻ played a dominant role. LC-MS was applied to assess intermediate degradation products, in which CO₂, H₂O, and NO₃⁻ were the final degradation products, and potential degradation pathways were suggested. In conclusion, Co-MBC was an efficient and stable catalytic material, and its ability to activate PMS was improved to effectively degrade antibiotics, a typical priority pollutant. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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20 pages, 3431 KiB

Open AccessFeature PaperArticle

Efficient Enzymatic Hydrolysis and Polyhydroxybutyrate Production from Non-Recyclable Fiber Rejects from Paper Mills by Recombinant Escherichia coli

by Linjing Jia, Ankita Juneja, Erica L.-W. Majumder, Bandaru V. Ramarao and Deepak Kumar

Processes 2024, 12(8), 1576; https://doi.org/10.3390/pr12081576 - 27 Jul 2024

Cited by 2 | Viewed by 1048

Abstract

Non-recyclable fiber rejects from paper mills, particularly those from recycled linerboard mills, contain high levels of structural carbohydrates but are currently landfilled, causing financial and environmental burdens. The aim of this study was to develop efficient and sustainable bioprocess to upcycle these rejects [...] Read more.

Non-recyclable fiber rejects from paper mills, particularly those from recycled linerboard mills, contain high levels of structural carbohydrates but are currently landfilled, causing financial and environmental burdens. The aim of this study was to develop efficient and sustainable bioprocess to upcycle these rejects into polyhydroxybutyrate (PHB), a biodegradable alternative to degradation-resistant petroleum-based plastics. To achieve high yields of PHB per unit biomass, the specific objective of the study was to investigate various approaches to enhance the hydrolysis yields of fiber rejects to maximize sugar recovery and evaluate the fermentation performance of these sugars using Escherichia coli LSBJ. The investigated approaches included size reduction, surfactant addition, and a chemical-free hydrothermal pretreatment process. A two-step hydrothermal pretreatment, involving a hot water pretreatment (150 °C and 15% solid loading for 10 min) followed by three cycles of disk refining, was found to be highly effective and resulted in an 83% cellulose conversion during hydrolysis. The hydrolysate obtained from pretreated biomass normally requires a detoxification step to enhance fermentation efficiency. However, the hydrolysate obtained from the pretreated biomass contained minimal to no inhibitory compounds, as indicated by the efficient sugar fermentation and high PHB yields, which were comparable to those from fermenting raw biomass hydrolysate. The structural and thermal properties of the extracted PHB were analyzed using various techniques and consistent with standard PHB. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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18 pages, 2090 KiB

Open AccessFeature PaperArticle

Investigations on Amoxicillin Removal from Aqueous Solutions by Novel Calcium-Rich Biochars: Adsorption Properties and Mechanisms Exploration

by Salah Jellali, Wissem Hamdi, Majida Al-Harrasi, Malik Al-Wardy, Jamal Al-Sabahi, Hamed Al-Nadabi, Ahmed Al-Raeesi and Mejdi Jeguirim

Processes 2024, 12(8), 1552; https://doi.org/10.3390/pr12081552 - 25 Jul 2024

Viewed by 624

Abstract

This study investigates the synthesis, characterization, and environmental application for amoxicillin (AMX) removal in batch mode of three novel calcium-rich biochars. These biochars were produced from the co-pyrolysis of poultry manure, date palm wastes, and waste marble powder at temperatures of 700 °C [...] Read more.

This study investigates the synthesis, characterization, and environmental application for amoxicillin (AMX) removal in batch mode of three novel calcium-rich biochars. These biochars were produced from the co-pyrolysis of poultry manure, date palm wastes, and waste marble powder at temperatures of 700 °C (Ca-B-700), 800 °C (Ca-B-800), and 900 °C (Ca-B-900). Characterization results show that increasing the pyrolysis temperature results in improved structural, textural, and surface chemistry properties. For instance, the BET surface area of the Ca-B-900 was assessed to be 52.3 m² g⁻¹, which is 14.1 and 3.1 times higher than those observed for Ca-B-700 and Ca-B-800, respectively. Moreover, the Ca-B-900 shows higher AMX removal ability (56.2 mg g⁻¹) than Ca-B-800 (46.8 mg g⁻¹), Ca-B-700 (14.6 mg g⁻¹), and numerous other engineered biochars. The AMX removal process by these biochars is favorable under wide experimental conditions of initial pH and AMX concentrations. Additionally, the experimental and modeling data show that the AMX adsorption process includes both physical and chemical mechanisms. This study confirms that Ca-rich biochars can perform significant removal of AMX in batch mode. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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XRD analyses of Ca-B-700 (a), Ca-B-800 (b), and Ca-B-900 (c) [<a href="#B31-processes-12-01552" class="html-bibr">31</a>] (▲: CaCO3; ●: KCl; ∆: CaO; ○: Ca(OH)2). Full article ">Figure 2
N2 adsorption and desorption isotherms of the three synthesized Ca-rich biochars. Full article ">Figure 3
FTIR analyses of the three synthesized Ca-rich biochars. Full article ">Figure 4
Experimental and predicted kinetic data of AMX removal by the synthesized calcium-rich biochars at 700, 800, and 900 °C. Full article ">Figure 5
pH effect on AMX removal by Ca-B-700, Ca-B-800, and Ca-B-900. Full article ">Figure 6
Effect of the tested biochars dose on AMX removal from aqueous solutions. Full article ">Figure 7
Effect of the presence of Na2SO4 (a) and NaCl (b) on AMX removal by the tested Ca-rich biochars. Full article ">Figure 8
Isotherm experimental data of AMX removal by the synthesized Ca-rich biochars and their fitting with Freundlich, Langmuir, and D-R models. Full article ">

14 pages, 2088 KiB

Open AccessFeature PaperArticle

Recycling PVC Waste into CO₂ Adsorbents: Optimizing Pyrolysis Valorization with Neuro-Fuzzy Models

by Emilia A. Jiménez-García, Salvador Pérez-Huertas, Antonio Pérez, Mónica Calero and Gabriel Blázquez

Processes 2024, 12(3), 431; https://doi.org/10.3390/pr12030431 - 20 Feb 2024

Cited by 2 | Viewed by 1446

Abstract

Nowadays, the environmental challenges associated with plastics are becoming increasingly prominent, making the exploitation of alternatives to landfill disposal a pressing concern. Particularly, polyvinyl chloride (PVC), characterized by its high chlorine content, poses a major environmental risk during degradation. Furthermore, PVC recycling and [...] Read more.

Nowadays, the environmental challenges associated with plastics are becoming increasingly prominent, making the exploitation of alternatives to landfill disposal a pressing concern. Particularly, polyvinyl chloride (PVC), characterized by its high chlorine content, poses a major environmental risk during degradation. Furthermore, PVC recycling and recovery present considerable challenges. This study aims to optimize the PVC pyrolysis valorization process to produce effective adsorbents for removing contaminants from gaseous effluents, especially CO₂. For this purpose, PVC waste was pyrolyzed under varied conditions, and the resulting solid fraction was subjected to a series of chemical and physical activations by means of hydroxides (NaOH and KOH) and nitrogen. Characterization of the PVC-based activated carbons was carried out using surface morphology (SEM), N₂ adsorption/desorption, elemental analysis, and FTIR, and their capacity to capture CO₂ was assessed. Finally, neuro-fuzzy models were developed for the optimization of the valorization technique. The resulting activated carbons exhibited excellent CO₂ adsorption capabilities, particularly those activated with KOH. Optimal activation conditions include activations at 840 °C with NaOH at a ratio of 0.66 and at 760 °C using either NaOH or KOH with ratios below 0.4. Activations under these experimental conditions resulted in a significant increase in the adsorption capacity, of up to 25%, in the resulting samples. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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11 pages, 1464 KiB

Open AccessFeature PaperArticle

Optimal Mesh Pore Size Combined with Periodic Air Mass Load (AML) for Effective Operation of a Self-Forming Dynamic Membrane BioReactor (SFD MBR) for Sustainable Treatment of Municipal Wastewater

by Senouci Boulerial, Carlo Salerno, Fabiano Castrogiovanni, Marina Tumolo, Giovanni Berardi, Abdelkader Debab, Boumediene Haddou, Abdellah Benhamou and Alfieri Pollice

Processes 2024, 12(2), 323; https://doi.org/10.3390/pr12020323 - 2 Feb 2024

Viewed by 1053

Abstract

A self-forming dynamic membrane bioreactor (SFD MBR) is a cost-effective alternative to conventional MBR, in which the synthetic membrane is replaced by a “cake layer,” an accumulation of the biological suspension over a surface of inert, low-cost support originated by filtration itself. Under [...] Read more.

A self-forming dynamic membrane bioreactor (SFD MBR) is a cost-effective alternative to conventional MBR, in which the synthetic membrane is replaced by a “cake layer,” an accumulation of the biological suspension over a surface of inert, low-cost support originated by filtration itself. Under optimized conditions, the cake layer is easy to remove and quick to form again, resulting a “dynamic membrane.” The permeate of the SFD MBR has chemo-physical characteristics comparable to those of conventional ultrafiltration-based MBR. In this paper, two nylon meshes with pore sizes of 20 and 50 µm, respectively, were tested in a bench-scale SFD MBR in which an air mass load (AML) was periodically supplied tangentially to the filtration surface to maintain filtration effectiveness. The SFD MBR equipped with 20 µm nylon mesh coupled with 5 min of AML every 4 h showed the best performance, ensuring both a permeate with turbidity values always below 3 NTU and revealing no increases in transmembrane pressure (TMP) with manual maintenance needs. A benchmark test with the only difference of a suction break (relaxation) instead of AML was conducted under identical operating conditions for validation with an already known maintenance strategy. This latter test produced a permeate of very good quality, but it needed frequent TMP increases and consequent manual cleanings, showing that a periodic AML coupled with the use of a 20 µm mesh can be an optimal strategy for long-term operation of SFD MBR. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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21 pages, 2405 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Apple Pomace-Derived Cationic Cellulose Nanocrystals for PFAS Removal from Contaminated Water

by Luis A. Franco, T. Dwyer Stuart, Md Shahadat Hossain, Bandaru V. Ramarao, Charlene C. VanLeuven, Mario Wriedt, Michael Satchwell and Deepak Kumar

Processes 2024, 12(2), 297; https://doi.org/10.3390/pr12020297 - 30 Jan 2024

Cited by 1 | Viewed by 2296

Abstract

Per- and poly-fluoroalkyl substances (PFAS) are concerning contaminants due to their ubiquity, persistence, and toxicity. Conventional PFAS water treatments such as granular activated carbon are limited by low adsorption rates and capacities. Carbon-based nano-adsorbents with enhanced surface areas address these limitations but are [...] Read more.

Per- and poly-fluoroalkyl substances (PFAS) are concerning contaminants due to their ubiquity, persistence, and toxicity. Conventional PFAS water treatments such as granular activated carbon are limited by low adsorption rates and capacities. Carbon-based nano-adsorbents with enhanced surface areas address these limitations but are hindered by their high cost and toxicity. Cellulose nanocrystals (CNC) are promising PFAS adsorbents due to sustainable sourcing, large surface areas, and amenable surface properties. In this study, CNC was synthesized from the agro-food waste, apple pomace (APCNC), and coated with Moringa oleifera cationic protein (MOCP) aqueous extract to produce MOCP/APCNC for the removal of perfluorooctanoic acid (PFOA) from water. APCNC and MOCP/APCNC were manufactured, characterized, and utilized in PFOA batch adsorption kinetics and equilibrium trials. APCNC was successfully produced from apple pomace (AP) and determined through characterization and comparison to commercial CNC (CCNC). APCNC and MOCP/APCNC exhibited rapid PFOA adsorption, approaching equilibrium within 15 min. MOCP coatings inverted the MOCP/CNC surface charge to cationic (−15.07 to 7.38 mV) and enhanced the PFOA adsorption rate (2.65 × 10⁻³ to 5.05 × 10⁻³ g/mg/s), capacity (47.1 to 61.1 mg/g), and robustness across varied water qualities. The sustainable sourcing of APCNC combined with a green surface coating to produce MOCP/CNC provides a highly promising environmentally friendly approach to PFAS remediation. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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Process flow diagram for the isolation of APCNC from AP. Full article ">Figure 2
MOCP adsorption onto CCNC. (a) The effect of the MO loading ratio on the extract protein concentration and (b) adsorption equilibrium concentration of MOCP (Ce) vs. MOCP equilibrium uptake ratio onto CCNC (qe), fitted with the Langmuir (LANG) and Freundlich (FREUD) equilibrium models. Full article ">Figure 3
(a) X-ray diffractograms and (b) crystallinity indexes of AP, AP-cellulose, APCNC, CCNC, and MOCP/APCNC. Full article ">Figure 4
Adsorption kinetics of PFOA onto APCNC and MOCP/APCNC. Full article ">Figure 5
Adsorption equilibrium study for PFOA onto (a) APCNC, (b) MOCP/APCNC, and (c) PFOA removal efficiency for APCNC and MOCP/APCNC. Full article ">Figure 6
Schematic of the PFAS adsorption mechanism onto Moringa oleifera-derived MOCP/APCNC adsorbent. Full article ">Figure 7
The effect of solution conditions on PFOA uptake on APCNC and MOCP/APCNC. (a) The effect of solution ionic strength and (b) the effect of solution dissolved organic carbon concentration. Full article ">

14 pages, 3803 KiB

Open AccessFeature PaperArticle

The Crucial Impact of Microbial Growth and Bioenergy Conversion on Treating Livestock Manure and Antibiotics Using Chlorella sorokiniana

by Hee-Jun Kim, Sangjun Jeong, YeonA Lee, Jae-Cheol Lee and Hyun-Woo Kim

Processes 2024, 12(2), 252; https://doi.org/10.3390/pr12020252 - 24 Jan 2024

Viewed by 1374

Abstract

The residual antibiotics in livestock excreta (LE) have been regarded as a potential threat to the ecosystem and human society. Some photoautotrophic microalgae, however, were found to metabolize them during active biomass photosynthesis. This study investigates how the strength of the antibiotics impacts [...] Read more.

The residual antibiotics in livestock excreta (LE) have been regarded as a potential threat to the ecosystem and human society. Some photoautotrophic microalgae, however, were found to metabolize them during active biomass photosynthesis. This study investigates how the strength of the antibiotics impacts the overall biodiesel yield and composition of the harvested microalgal biomass grown from LE. The microalgal growth results demonstrate that increasing the concentration of residual antibiotics suppresses the microalgal growth rate from 0.87 d⁻¹ to 0.34 d⁻¹. This 61% lower biomass production rate supports the proposition that the kinetic impact of antibiotics may slow lipid synthesis. Moreover, the analytical results of fatty acid methyl ester (FAME) demonstrate that amoxicillin substantially reduces the C16:0 content by over 96%. This study evidences that the functional group similarity of amoxicillin may competitively inhibit the esterification reaction by consuming methanol. This explanation further highlights that residual antibiotics interfere with microalgal lipid synthesis and its transesterification. Moreover, it was confirmed that the presence of residual antibiotics may not affect the major nutrient removal (total nitrogen: 74.5~78.0%, total phosphorus: 95.6~96.8%). This indicates that residual antibiotics inhibit the metabolism associated with carbon rather than those associated with nitrogen and phosphorus, which is connected to the decrease in the biodiesel yield. Overall, these results reveal that the frequent abuse of antibiotics in livestock may harm the eco-friendly conversion of waste-into-bioenergy strategy. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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18 pages, 1980 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Conversion of Pistachio and Walnut Shell Waste into Valuable Components with Subcritical Water

by Maja Čolnik, Mihael Irgolič, Amra Perva and Mojca Škerget

Processes 2024, 12(1), 195; https://doi.org/10.3390/pr12010195 - 16 Jan 2024

Cited by 2 | Viewed by 2649

Abstract

Pistachio and walnut shells accumulate in large quantities as waste during food processing and represent a promising lignocellulosic biomass for the extraction of valuable components. Subcritical water technology was used as an environmentally friendly technique to study the extraction of active ingredients and [...] Read more.

Pistachio and walnut shells accumulate in large quantities as waste during food processing and represent a promising lignocellulosic biomass for the extraction of valuable components. Subcritical water technology was used as an environmentally friendly technique to study the extraction of active ingredients and other valuable degradation products from walnut and pistachio waste. Subcritical water extraction (SWE) was carried out under different process conditions (temperature (150–300 °C) and short reaction times (15–60 min)) and compared with conventional extraction using different organic solvents (acetone, 50% acetone and ethanol). The extracts obtained from pistachio and walnut shell waste are rich in various bioactive and valuable components. The highest contents of total phenols (127.08 mg GA/g extract at 300 °C for 15 min, from walnut shells), total flavonoids (10.18 mg QU/g extract at 200 °C for 60 min, from pistachio shells), total carbohydrates (602.14 mg TCH/g extract at 200 °C for 60 min, from walnut shells) and antioxidant activity (91% at 300 °C, for 60 min, from pistachio shells) were determined when the extracts were obtained via subcritical water. High contents of total phenols (up to 86.17 mg GA/g extract) were also determined in the conventional extracts obtained with ethanol. Using the HPLC method, sugars and their valuable derivatives were determined in the extracts, with glucose, fructose, furfurals (5-hydroxymethylfurfural (5-HMF) and furfural) and levulinic acid being the most abundant in the extracts obtained by subcritical water. The results show that subcritical water technology enables better exploitation of biowaste materials than conventional extraction methods with organic solvents, as it provides a higher yields of bioactive components such as phenolic compounds and thus extracts with high antioxidant activity, while at the same time producing degradation products that are valuable secondary raw materials. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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Full article ">Figure 1
Scheme of apparatus for batch SWE. Full article ">Figure 2
TGA/DSC thermogram of pistachio and walnut shells. Full article ">Figure 3
The yield of extraction of pistachio and walnut shells (PS-pistachio shells; WS-walnut shells) obtained via (a) subcritical water at different conditions and (b) conventional extraction with different solvents (ACE-acetone, EtOH-ethanol, ACE/H2O-50% acetone). Full article ">Figure 4
Antioxidant activity of pistachio and walnut shells (PS-pistachio shells; WS-walnut shells) extracts under different conditions, using (a) subcritical water and (b) conventional extraction (ACE-acetone, EtOH-ethanol, ACE/H2O-50% acetone). Full article ">Figure 5
Content of total phenols in extracts of pistachio and walnut shells (PS-pistachio shells; WS-walnut shells) obtained via (a) SWE at various temperatures and reaction times and (b) conventional extraction with ACE-acetone, EtOH-ethanol, ACE/H2O-50% acetone. Full article ">Figure 6
Content of total flavonoids in extracts of pistachio and walnut shells (PS-pistachio shells; WS-walnut shells) obtained via (a) SWE at various temperatures and reaction times and (b) conventional extraction with ACE-acetone, EtOH-ethanol, ACE/H2O-50% acetone. Full article ">Figure 7
Total carbohydrate content (TCH) in the dry extract (PS—pistachio shells; WS—walnut shells) obtained via (a) subcritical water at different reaction conditions and via (b) conventional extraction (ACE-acetone, EtOH-ethanol, ACE/H2O-50% acetone). Full article ">

16 pages, 7570 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Graphene Oxide from Graphite of Spent Batteries as Support of Nanocatalysts for Fuel Hydrogen Production

by Gabriel Sperandio, Iterlandes Machado Junior, Esteefany Bernardo and Renata Moreira

Processes 2023, 11(11), 3250; https://doi.org/10.3390/pr11113250 - 19 Nov 2023

Cited by 5 | Viewed by 1662

Abstract

The increasing production of electronic waste and the rising demand for renewable energy are currently subjects of debate. Sustainable processes based on a circular economy are required. Then, electronic devices could be the main source for the synthesis of new materials. Thus, this [...] Read more.

The increasing production of electronic waste and the rising demand for renewable energy are currently subjects of debate. Sustainable processes based on a circular economy are required. Then, electronic devices could be the main source for the synthesis of new materials. Thus, this work aimed to synthesize graphene oxide (GO) from graphite rod of spent Zn-C batteries. This was used as support for Ni/Co bimetallic nanocatalysts in the evolution of hydrogen from NaBH₄ for the first time. The graphene oxide (GO) exhibited a diffraction peak at 2θ = 9.1°, as observed using X-ray diffraction (XRD), along with the presence of oxygenated groups as identified using FTIR. Characteristic bands at 1345 and 1574 cm⁻¹ were observed using Raman spectroscopy. A leaf-shaped morphology was observed using SEM. GO sheets was observed using TEM, with an interplanar distance of 0.680 nm. Ni/Co nanoparticles, with an approximate size of 2 nm, were observed after deposition on GO. The material was used in the evolution of hydrogen from NaBH₄, obtaining an efficiency close to 90%, with a kinetic constant of 0.0230 s⁻¹ at 296.15 K and activation energy of 46.7 kJ mol⁻¹. The material showed an efficiency in seven reuse cycles. Therefore, a route of a new material with added value from electronic waste was obtained from an eco-friendly process, which can be used in NaBH₄ hydrolysis. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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Scanning Electron Microscopy of graphene oxide obtained from spent Zn-C batteries synthesized using the adapted Hummers method. Full article ">Figure 2
(a) Diffractogram of graphite and graphene oxide (GO) obtained from spent Zn-C batteries synthesized using the adapted Hummers method; (b) diffractogram of GO and Ni/Co-GO NPs (60:40 w/w). Full article ">Figure 3
Transmission Electron Microscopy images of graphene oxide obtained from spent Zn-C batteries synthesized using the adapted Hummers method. (a) Interplanar distance between the GO planes (b) Ni/Co nanoparticles decorated on the GO. Full article ">Figure 4
Hydrogen evolution from NaBH4 for different compositions of m(Ni)/m(Co) decorated in GO obtained from spent Zn-C batteries. Reaction conditions: GO support mass: 100 mg; 0.700 mmol of the catalyst; 1.00 mL of NaBH4 (0.500 mol L−1); temperature: 296.15 K. Full article ">Figure 5
(a) Hydrogen evolution from different NaBH4 concentration. (b) ln of kinetic constant vs. the ln of NaBH4 concentration. Reaction conditions: 0.700 mmol of Ni/Co NPs (60:40 w/w); GO support: 100 mg; temperature: 296.15 K. Full article ">Figure 6
(a) Hydrogen evolution from NaBH4 for different doses of catalyst Ni/Co-GO NPs. (b) ln of kinetic constant vs. the ln of catalyst dose. Reaction conditions: 0.700 mmol of Ni/Co NPs (60:40 w/w); GO support: 100 mg; 1.00 mL of NaBH4 (0.500 mol L−1); temperature: 296.15 K. Full article ">Figure 7
Catalytic efficiency of hydrogen evolution from NaBH4 in the presence of different concentrations of NaOH. Reaction conditions: 0.700 mmol of Ni/Co NPs (60:40 w/w), GO support: 100 mg; 1.00 mL of NaBH4 (0.500 mol L−1); temperature: 296.15 K. Full article ">Figure 8
Hydrogen evolution from NaBH4 catalyzed with Ni/Co-GO NPs (60:40 w/w) in different temperatures. Reaction parameters: 0.700 mmol of Ni/Co-GO NPs (60:40 w/w), GO support: 100 mg; 1.00 mL of NaBH4 (0.500 mol L−1). Inset. Arrhenius plot (lnK versus absolute temperature ratio). Data using 0.500 mol L−1 NaBH4 solution and using NP-Ni/Co-GO (60:40 w/w) as flexible at different solution temperatures. Full article ">Figure 9
Reuse of Ni/Co-GO NPs (60:40 w/w) in hydrogen evolution from NaBH4. Reaction parameters: 0.700 mmol of Ni/Co-GO NPs (60:40 w/w), GO support: 100 mg; 1.00 mL of NaBH4 (0.500 mol L−1); temperature: 296.15 K. Full article ">

22 pages, 2091 KiB

Open AccessArticle

Techno-Economic Assessment of PEM Electrolysis for O₂ Supply in Activated Sludge Systems—A Simulation Study Based on the BSM2 Wastewater Treatment Plant

by Mario Alejandro Parra Ramirez, Stefan Fogel, Sebastian Felix Reinecke and Uwe Hampel

Processes 2023, 11(6), 1639; https://doi.org/10.3390/pr11061639 - 26 May 2023

Cited by 3 | Viewed by 2706

Abstract

The conversion of renewable energy into hydrogen (H₂) by power-to-gas technologies involving electrolysis is seen today as a key element in the transition to a sustainable energy sector. Wastewater treatment plants (WWTP) could be integrated into future green H₂ networks [...] Read more.

The conversion of renewable energy into hydrogen (H₂) by power-to-gas technologies involving electrolysis is seen today as a key element in the transition to a sustainable energy sector. Wastewater treatment plants (WWTP) could be integrated into future green H₂ networks as users of oxygen (O₂) produced alongside H₂ in water electrolysis. In WWTPs, O₂ is required for biological treatment steps, e.g., in activated sludge (AS) systems. However, the production costs of electrolysis O₂ should be competitive with those of conventional O₂ production processes. In this study, mathematical models of a polymer electrolyte membrane electrolyser (PEME) plant and the WWTP of the Benchmark Simulation Model No. 2 (BSM2) were used to simulate electrolysis O₂ supply to an AS system and estimate net costs of production (NCP) for produced O₂ via a techno-economic assessment (TEA). Assuming that produced H₂ is sold to a nearby industry, NCPs for O₂ were calculated for two different PEME plant dimensions, four alternatives regarding electricity supply and costs, and three sets of assumptions regarding system performance and market conditions. The analyses were performed for 2020 as a reference year and 2030 based on forecasts of relevant data. Results of the dimensioning of the PEME show the O₂ demand of a municipal WWTP with an installed capacity of 80,000 population equivalents (PE), such as the one of the BSM2, can be covered for more than 99% of the simulated period by either a 6.4 MW PEME operated for 4073 full load hours or a 4.8 MW PEME operated for 6259 full load hours. Investment costs for the PEME stacks and the operational costs for electricity make up most of the NCP of electrolysis O₂. The projected decrease in PEME stack costs and renewable energy prices in favourable market conditions can result in a competitive NCP for electrolysis O₂ in 2030. The approach described in this study can be applied to analyse O₂ supply to biological wastewater treatment in WWTPs with different characteristics, in processes different from AS, and under different assumptions regarding economic conditions. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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Graphical representation of the modelled system. Full article ">Figure 2
Daily O2 demand from the AS system of the BSM2 plant. Average values are represented by an ×, median values by a line, the limits of the boxes are the first and third quartile, and outliers are excluded. Full article ">Figure 3
Intraday O2 demand from the AS system of the BSM2 plant. Full article ">Figure 4
Histogram of daily O2 demand from the AS system of the BSM2 plant. Full article ">Figure 5
Breakdown of (a) purchased equipment costs <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>P</mi> <mi>E</mi> <mi>C</mi> </mrow> </msub> </mrow> </semantics></math>; (b) fixed costs of investment <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>F</mi> <mi>C</mi> <mi>I</mi> </mrow> </msub> </mrow> </semantics></math>; (c) capital expenditures <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>C</mi> <mi>A</mi> <mi>P</mi> <mi>E</mi> <mi>X</mi> </mrow> </msub> </mrow> </semantics></math>; (d) variable costs of production <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>V</mi> <mi>C</mi> <mi>P</mi> </mrow> </msub> </mrow> </semantics></math>; (e) fixed costs of production <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>F</mi> <mi>C</mi> <mi>P</mi> </mrow> </msub> </mrow> </semantics></math> and; (f) net costs of production <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>N</mi> <mi>C</mi> <mi>P</mi> </mrow> </msub> </mrow> </semantics></math> for scenario 1 in 2020, neutral economic conditions, and PV electricity supply. Full article ">

15 pages, 1126 KiB

Open AccessArticle

Techno-Economic Evaluation of the Thermochemical Energy Valorization of Construction Waste and Algae Biomass: A Case Study for a Biomass Treatment Plant in Northern Greece

by Georgios Manthos, Dimitris Zagklis, Sameh S. Ali, Constantina Zafiri and Michael Kornaros

Processes 2023, 11(5), 1549; https://doi.org/10.3390/pr11051549 - 18 May 2023

Cited by 3 | Viewed by 1328

Abstract

Biomass treatment for energy production is a promising way for achieving fossil fuel replacement and environmental relief. Thermochemical processes are a common way of processing biomass, but their potential economic benefits are not always clear to investors. In this work, three basic thermochemical [...] Read more.

Biomass treatment for energy production is a promising way for achieving fossil fuel replacement and environmental relief. Thermochemical processes are a common way of processing biomass, but their potential economic benefits are not always clear to investors. In this work, three basic thermochemical processes (combustion, gasification, and pyrolysis) are examined in terms of their theoretical yields and their products, as well as their economic viability. The goal of this analysis was to look into the total amount of available biomass streams and compare business plans in terms of sustainability from a technical and economic perspective. The estimation of the fixed capital investment was based on ready−made solutions that are already available on the market. The analysis showed that the gasification unit has the optimum sustainability results since the total amount of gross income was EUR 0.13/kg of biomass while the treatment cost was estimated at EUR 0.09/kg of biomass. The internal rate of return of the investment was calculated at 9%, establishing a promising alternative solution to sustainable “green” energy production. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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14 pages, 5472 KiB

Open AccessEditor’s ChoiceArticle

Candidatus Scalindua, a Biological Solution to Treat Saline Recirculating Aquaculture System Wastewater

by Federico Micolucci, Jonathan A. C. Roques, Geoffrey S. Ziccardi, Naoki Fujii, Kristina Sundell and Tomonori Kindaichi

Processes 2023, 11(3), 690; https://doi.org/10.3390/pr11030690 - 24 Feb 2023

Cited by 3 | Viewed by 2480

Abstract

Recirculating aquaculture systems (RAS) are promising candidates for the sustainable development of the aquaculture industry. A current limitation of RAS is the production and potential accumulation of nitrogenous wastes, ammonium (NH₄⁺), nitrite (NO₂⁻) and nitrate (NO₃ [...] Read more.

Recirculating aquaculture systems (RAS) are promising candidates for the sustainable development of the aquaculture industry. A current limitation of RAS is the production and potential accumulation of nitrogenous wastes, ammonium (NH₄⁺), nitrite (NO₂⁻) and nitrate (NO₃⁻), which could affect fish health and welfare. In a previous experiment, we have demonstrated that the marine anammox bacteria Candidatus Scalindua was a promising candidate to treat the wastewater (WW) of marine, cold-water RAS. However, the activity of the bacteria was negatively impacted after a direct exposure to RAS WW. In the current study, we have further investigated the potential of Ca. Scalindua to treat marine RAS WW in a three-phase experiment. In the first phase (control, 83 days), Ca. Scalindua was fed a synthetic feed, enriched in NH₄⁺, NO₂⁻ and trace element (TE) mix. Removal rates of 98.9% and 99.6% for NH₄⁺ and NO₂⁻, respectively, were achieved. In the second phase (116 days), we gradually increased the exposure of Ca. Scalindua to nitrogen-enriched RAS WW over a period of about 80 days. In the last phase (79 days), we investigated the needs of TE supplementation for the Ca. Scalindua after they were fully acclimated to 100% RAS WW. Our results show that the gradual exposure of Ca. Scalindua resulted in a successful acclimation to 100% RAS WW, with maintained high removal rates of both NH₄⁺ and NO₂⁻ throughout the experiment. Despite a slight decrease in relative abundance (from 21.4% to 16.7%), Ca. Scalindua remained the dominant species in the granules throughout the whole experiment. We conclude that Ca. Scalindua can be successfully used to treat marine RAS WW, without the addition of TE, once given enough time to acclimate to its new substrate. Future studies need to determine the specific needs for optimal RAS WW treatment by Ca. Scalindua at pilot scale. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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Full article ">Figure 1
The conventional nitrogen removal process in RAS, with nitrification and denitrification compartments (A); the nitritation (partial nitrification)/anammox process (B). Full article ">Figure 2
Schematic drawing of the up-flow column reactor. Full article ">Figure 3
Concentration of NH4+, NO2− and NO3− in the influent (filled circles) and effluent (open circles) throughout the experiment. Full article ">Figure 4
Anammox performance in the reactor. (A) NH4+ (closed diamonds) and NO2− (open triangles) removal efficiencies. (B) Nitrogen loading and removal rates (filled and open circles, respectively). Dotted lines and open circle indicate changes in operational phase (artificial seawater or RAS WW, the presence of TE). RAS, recirculating aquaculture system WW; TE, trace element solutions. Purple arrows indicate biomass sampling on days 83, 200, and 280. Full article ">Figure 5
Microbial community composition at the end of each experimental phase (days 83, 200 and 280), based on 16S rRNA gene amplicon sequencing. Red percentages correspond to the relative abundance of the marine anammox Ca. Scalindua. Full article ">Figure 6
FISH micrographs of biomass collected from the column reactor at days 83 (A), 200 (B) and 280 (C). FISH was performed with Alexa Fluor 647-labelled EUB338mix probe (cyan) for all bacteria, and an Alexa Fluor 555-labelled Sca1129b probes (red) for Ca. Scalindua. Ca. Scalindua appears magenta and other bacteria appear blue. Scale bars represent 10 μm. Full article ">

Review

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39 pages, 3760 KiB

Open AccessFeature PaperReview

Quaternary Treatment of Urban Wastewater for Its Reuse

by Jakub Jurík, Barbora Jankovičová, Ronald Zakhar, Nikola Šoltýsová and Ján Derco

Processes 2024, 12(9), 1905; https://doi.org/10.3390/pr12091905 - 5 Sep 2024

Viewed by 1045

Abstract

In today’s ongoing rapid urban expansion, deforestation and climate changes can be observed mainly as unbalanced rain occurrence during the year, long seasons without any rain at all and unordinary high temperatures. These adverse changes affect underground water levels and the availability of [...] Read more.

In today’s ongoing rapid urban expansion, deforestation and climate changes can be observed mainly as unbalanced rain occurrence during the year, long seasons without any rain at all and unordinary high temperatures. These adverse changes affect underground water levels and the availability of surface water. In addition, quite a significant proportion of drinking water is used mainly for non-drinking purposes. With several EU countries increasingly suffering from droughts, reusing quaternary treated urban wastewater can help address water scarcity. At the European level, Regulation 2020/741 of the European Parliament and of the Council of 25 May 2020 on minimum requirements for water reuse was adopted. This regulation foresees the use of recycled wastewater mainly for agricultural irrigation. This article provides an overview of various processes, such as filtration, coagulation, adsorption, ozonation, advanced oxidation processes and disinfection, for quaternary treatment of urban wastewater in order to remove micropollutants and achieve the requirements for wastewater reuse. According to the literature, the most effective method with acceptable financial costs is a combination of coagulation, membrane filtration (UF or NF) and UV disinfection. These processes are relatively well known and commercially available. This article also helps researchers to identify key themes and concepts, evaluate the strengths and weaknesses of previous studies and determine areas where further research is needed. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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11 pages, 497 KiB

Open AccessFeature PaperReview

Crude Oil Bioremediation: From Bacteria to Microalgae

by Rosa Paola Radice, Vincenzo De Fabrizio, Antonietta Donadoni, Antonio Scopa and Giuseppe Martelli

Processes 2023, 11(2), 442; https://doi.org/10.3390/pr11020442 - 1 Feb 2023

Cited by 11 | Viewed by 5496

Abstract

Crude oil is one of the major pollutants present. Its extraction and processing generate processing waters contaminated by hydrocarbons which are harmful to both human health and the flora and fauna that come into contact with it. Hydrocarbon contamination can involve soil and [...] Read more.

Crude oil is one of the major pollutants present. Its extraction and processing generate processing waters contaminated by hydrocarbons which are harmful to both human health and the flora and fauna that come into contact with it. Hydrocarbon contamination can involve soil and water, and several technologies are used for recovery. The most used techniques for the recovery of spilt oil involve chemical-physical methods that can remove most of the pollutants. Among these, must consider the bioremediation by microorganisms, mostly bacterial capable of degrading many of the toxic compounds contained within the petroleum. Microalgae participate in bioremediation indirectly, supporting the growth of degrading bacteria, and directly acting on contaminants. Their direct contribution is based on the activation of various mechanisms ranging from the production of enzymes capable of degrading hydrocarbons, such as lipoxygenases, to the attack through the liberation of free radicals. The following review analyzed all the works published in the last ten years concerning the ability of microalgae to remove hydrocarbons, intending to identify in these microorganisms an alternative technology to the use of bacteria. The advantages of using microalgae concern not only their ability to remove toxic compounds and release oxygen into the atmosphere but their biomass could then be used in a circular economy process to produce biofuels. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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31 pages, 2223 KiB

Open AccessReview

Life Cycle Assessment and Its Application in Wastewater Treatment: A Brief Overview

by Siti Safirah Rashid, Siti Norliyana Harun, Marlia M. Hanafiah, Khalisah K. Razman, Yong-Qiang Liu and Duratul Ain Tholibon

Processes 2023, 11(1), 208; https://doi.org/10.3390/pr11010208 - 9 Jan 2023

Cited by 21 | Viewed by 9907

Abstract

This paper provides a brief review on wastewater treatment system and the application of life cycle assessment (LCA) for assessing its environmental performance. An extensive review regarding the geographical relevance of LCA for WWTPs, and the evaluation of sustainable wastewater treatment by LCA [...] Read more.

This paper provides a brief review on wastewater treatment system and the application of life cycle assessment (LCA) for assessing its environmental performance. An extensive review regarding the geographical relevance of LCA for WWTPs, and the evaluation of sustainable wastewater treatment by LCA in both developed and developing countries are also discussed. The objective of the review is to identify knowledge gap, for the improvement of the LCA application and methodology to WWTPs. A total of 35 published articles related to wastewater treatment (WWT) and LCA from international scientific journals were studied thoroughly and summarised from 2006 to 2022. This review found that there is lack of studies concerning LCA of WWTPs that consider specific local criteria especially in the developing countries. Thus, it is important to: (1) assess the influence of seasonality (i.e., dry and wet seasons) on the environmental impact of WWT, (2) investigate environmental impacts from WWTPs in developing countries focusing on the site-specific inventory data, and (3) evaluate environmental sustainability of different processes for upgrading the wastewater treatment system. The environmental impact and cost assessment aspects are crucial for the sustainable development of WWTP. Therefore, environmental impacts must be thoroughly assessed to provide recommendation for future policy and for the water industry in determining environmental trade-offs toward sustainable development. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

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