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4 pages, 192 KiB

Open AccessEditorial

Green Chemistry: From Wastes to Value-Added Products

by Alazne Gutiérrez and Roberto Palos

Processes 2023, 11(7), 2131; https://doi.org/10.3390/pr11072131 - 17 Jul 2023

Cited by 1 | Viewed by 1579

Abstract

The concept of “From wastes to value-added products” sums up the essence of the circular economy and its transformative potential [...] Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

Research

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12 pages, 2087 KiB

Open AccessArticle

Single-Chamber Microbial Fuel Cell with Multiple Plates of Bamboo Charcoal Anode: Performance Evaluation

by Chikashi Sato, N. Evelin Paucar, Steve Chiu, Muhammad Z. I. M. Mahmud and John Dudgeon

Processes 2021, 9(12), 2194; https://doi.org/10.3390/pr9122194 - 6 Dec 2021

Cited by 18 | Viewed by 4966

Abstract

In this study, three single-chamber microbial fuel cells (MFCs), each having Pt-coated carbon cloth as a cathode and four bamboo charcoal (BC) plates as an anode, were run in a fed-batch mode, individually and in series. Simulated potato-processing wastewater was used as a [...] Read more.

In this study, three single-chamber microbial fuel cells (MFCs), each having Pt-coated carbon cloth as a cathode and four bamboo charcoal (BC) plates as an anode, were run in a fed-batch mode, individually and in series. Simulated potato-processing wastewater was used as a substrate for supporting the growth of a mixed bacterial culture. The maximum power output increased from 0.386 mW with one MFC to 1.047 mW with three MFCs connected in series. The maximum power density, however, decreased from 576 mW/m² (normalized to the cathode area) with one MFC to 520 mW/m² with three MFCs in series. The experimental results showed that power can be increased by connecting the MFCs in series; however, choosing low resistance BC is crucial for increasing power density. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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15 pages, 1666 KiB

Open AccessArticle

Synergistic Dual Catalytic System and Kinetics for the Alcoholysis of Poly(Lactic Acid)

by Fabio M. Lamberti, Andy Ingram and Joseph Wood

Processes 2021, 9(6), 921; https://doi.org/10.3390/pr9060921 - 24 May 2021

Cited by 11 | Viewed by 3253

Abstract

Plastic pollution is a global issue that is approaching crisis levels as plastic production is projected to reach 1.1 GT annually by 2050. The bioplastic industry along with a circular production economy are solutions to this problem. One promising bioplastic polylactic acid (PLA) [...] Read more.

Plastic pollution is a global issue that is approaching crisis levels as plastic production is projected to reach 1.1 GT annually by 2050. The bioplastic industry along with a circular production economy are solutions to this problem. One promising bioplastic polylactic acid (PLA) has mechanical properties comparable to polystyrene (PS), so it could replace PS in its applications as a more environmentally sustainable material. However, since the bioplastic PLA also suffers from long biodegradation times in the environment, to ensure that it does not add to the current pollution problem, it should instead be chemically recycled. In this work, PLA was chemically recycled via alcoholysis, using either methanol or ethanol to generate the value-added products methyl lactate and ethyl lactate respectively. Two catalysts, zinc acetate dihydrate (ZnAc) and 4-(dimethylamino)pyridine (DMAP), were tested both individually and in mixtures. A synergistic effect was exhibited on the reaction rate when both catalysts were used in an equal ratio. The methanolysis reaction was determined to be two-step, with the activation energy estimated to be 73 kJ mol⁻¹ for the first step and 40.16 kJ mol⁻¹ for the second step. Both catalysts are cheap and commercially available, their synergistic effect could be exploited for large-scale PLA recycling. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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16 pages, 42508 KiB

Open AccessArticle

Recovery of Valuable Materials from the Waste Crystalline-Silicon Photovoltaic Cell and Ribbon

by Wei-Sheng Chen, Yen-Jung Chen, Cheng-Han Lee, Yi-Jin Cheng, Yu-An Chen, Fan-Wei Liu, Yi-Chung Wang and Yu-Lun Chueh

Processes 2021, 9(4), 712; https://doi.org/10.3390/pr9040712 - 17 Apr 2021

Cited by 38 | Viewed by 6376

Abstract

With the dramatic increase of photovoltaic (PV) module installation in solar energy-based industries, the methods for recovering waste solar generators should be emphasized as the backup of the PV market for environmental protection. Crystalline-silicon accounts for most of the worldwide PV market and [...] Read more.

With the dramatic increase of photovoltaic (PV) module installation in solar energy-based industries, the methods for recovering waste solar generators should be emphasized as the backup of the PV market for environmental protection. Crystalline-silicon accounts for most of the worldwide PV market and it contains valuable materials such as high purity of silicon (Si), silver (Ag), copper (Cu), tin (Sn), and lead (Pb). This study can provide an efficient recycling process for valuable materials resourced from waste crystalline-silicon PV module, including Si in the PV cell, and Ag, Cu, Pb, Sn, in PV ribbon. As tempered glass and Ethylene Vinyl Acetate (EVA) resin were removed, the module was separated into two materials, PV ribbon and PV cell. For PV cell purification, Si with purity at 99.84% was recovered by removing impurities such as aluminum (Al) and Ag by two-step leaching and dissolving the impurities. For PV ribbon recovering, purified metal or metal oxide was obtained through the processes of leaching/polishing, extraction, and chemical precipitation. In the polishing process, 99.5% of copper wire was collected. The purities of final products are 99.7% for CuO, 99.47% for PbO, 99.68% for SnO₂, and 98.85% for Ag respectively. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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15 pages, 2418 KiB

Open AccessFeature PaperArticle

Pretreatment of Switchgrass for Production of Glucose via Sulfonic Acid-Impregnated Activated Carbon

by Yane Ansanay, Praveen Kolar, Ratna Sharma-Shivappa, Jay Cheng and Consuelo Arellano

Processes 2021, 9(3), 504; https://doi.org/10.3390/pr9030504 - 11 Mar 2021

Cited by 9 | Viewed by 2475

Abstract

In the present research, activated carbon-supported sulfonic acid catalysts were synthesized and tested as pretreatment agents for the conversion of switchgrass into glucose. The catalysts were synthesized by reacting sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid with activated carbon. The characterization of [...] Read more.

In the present research, activated carbon-supported sulfonic acid catalysts were synthesized and tested as pretreatment agents for the conversion of switchgrass into glucose. The catalysts were synthesized by reacting sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid with activated carbon. The characterization of catalysts suggested an increase in surface acidities, while surface area and pore volumes decreased because of sulfonation. Batch experiments were performed in 125 mL serum bottles to investigate the effects of temperature (30, 60, and 90 °C), reaction time (90 and 120 min) on the yields of glucose. Enzymatic hydrolysis of pretreated switchgrass using Ctec2 yielded up to 57.13% glucose. Durability tests indicated that sulfonic solid-impregnated carbon catalysts were able to maintain activity even after three cycles. From the results obtained, the solid acid catalysts appear to serve as effective pretreatment agents and can potentially reduce the use of conventional liquid acids and bases in biomass-into-biofuel production. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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12 pages, 1634 KiB

Open AccessFeature PaperArticle

An Expedient Catalytic Process to Obtain Solketal from Biobased Glycerol

by Fabrizio Roncaglia, Luca Forti, Sara D’Anna and Laura Maletti

Processes 2021, 9(1), 141; https://doi.org/10.3390/pr9010141 - 12 Jan 2021

Cited by 4 | Viewed by 2323

Abstract

Developing simple and effective chemistry able to convert industrial waste streams into valuable chemicals is a primary contributor to sustainable development. Working in the context of biodiesel production, we found that plain bisulfate on silica (SSANa, 3.0 mmol/g) proved to be an optimal [...] Read more.

Developing simple and effective chemistry able to convert industrial waste streams into valuable chemicals is a primary contributor to sustainable development. Working in the context of biodiesel production, we found that plain bisulfate on silica (SSANa, 3.0 mmol/g) proved to be an optimal catalyst to convert glycerol into solketal. With the assistance of a proper anhydrification technique, isolated yields of 96% were achieved working in mild conditions, on 100 g scale. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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11 pages, 2707 KiB

Open AccessArticle

Case Study of Anaerobic Digestion Process Stability Detected by Dissolved Hydrogen Concentration

by Daniela Platošová, Jiří Rusín, Jan Platoš, Kateřina Smutná and Roman Buryjan

Processes 2021, 9(1), 106; https://doi.org/10.3390/pr9010106 - 7 Jan 2021

Cited by 4 | Viewed by 2386

Abstract

The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process [...] Read more.

The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process was run in a Terrafors IS rotary drum bioreactor for 230 days. The substrate dosed on weekdays was food leftovers from the university canteen. At an average temperature of 37 °C, an organic loading of volatiles of 0.858 kg m⁻³ day⁻¹ and a theoretical retention time of 259 days, biogas production of 0.617 Nm³ kg VS⁻¹ was achieved with a CH4 content of 51.7 vol. %. The values of the established FOS/TAC stability indicator ranged from 0.26 to 11.4. The highest value was reached when the reactor was overloaded. The dissolved hydrogen concentration measured by the amperometric microsensor ranged from 0.039–0.425 mg dm⁻³. Data were statistically processed using Pearson’s correlation coefficient. The correlation of the hydrogen concentration with other parameters such as the concentration of organic acids was evaluated. The value of Pearson’s correlation coefficient was 0.331 and corresponded to a p-value of 0. The results confirmed a very low limit of the hydrogen concentration at which the microbial culture, especially methanogens, was already overloaded. The amperometric microsensor proved to be rather unsuitable for operational applications due to insufficient sensitivity and short service life. The newly designed ratio of dissolved hydrogen concentration to neutralizing capacity was tested but did not work significantly better than the established FOS/TAC stability indicator. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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Review

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27 pages, 433 KiB

Open AccessFeature PaperReview

Microbial Fuel Cell for Energy Production, Nutrient Removal and Recovery from Wastewater: A Review

by N. Evelin Paucar and Chikashi Sato

Processes 2021, 9(8), 1318; https://doi.org/10.3390/pr9081318 - 29 Jul 2021

Cited by 42 | Viewed by 6245

Abstract

The world is facing serious threats from the depletion of non-renewable energy resources, freshwater shortages and food scarcity. As the world population grows, the demand for fresh water, energy, and food will increase, and the need for treating and recycling wastewater will rise. [...] Read more.

The world is facing serious threats from the depletion of non-renewable energy resources, freshwater shortages and food scarcity. As the world population grows, the demand for fresh water, energy, and food will increase, and the need for treating and recycling wastewater will rise. In the past decade, wastewater has been recognized as a resource as it primarily consists of water, energy-latent organics and nutrients. Microbial fuel cells (MFC) have attracted considerable attention due to their versatility in their applications in wastewater treatment, power generation, toxic pollutant removal, environmental monitoring sensors, and more. This article provides a review of MFC technologies applied to the removal and/or recovery of nutrients (such as P and N), organics (COD), and bioenergy (as electricity) from various wastewaters. This review aims to provide the current perspective on MFCs, focusing on the recent advancements in the areas of nutrient removal and/or recovery with simultaneous power generation. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

24 pages, 5359 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Trends in Sustainable Remediation of Pb-Contaminated Shooting Range Soils: Rethinking Waste Management within a Circular Economy

by María T. Gómez-Sagasti, Mikel Anza, June Hidalgo, Unai Artetxe, Carlos Garbisu and José M. Becerril

Processes 2021, 9(4), 572; https://doi.org/10.3390/pr9040572 - 25 Mar 2021

Cited by 5 | Viewed by 3087

Abstract

Soil metal contamination in recreational shooting ranges represents a widespread environmental problem. Lead (Pb) is the primary component of traditional ammunition, followed by metalloids such as antimony (Sb) and arsenic (As). Lead-based bullets and pellets deposited on the soil surface are subject to [...] Read more.

Soil metal contamination in recreational shooting ranges represents a widespread environmental problem. Lead (Pb) is the primary component of traditional ammunition, followed by metalloids such as antimony (Sb) and arsenic (As). Lead-based bullets and pellets deposited on the soil surface are subject to steady weathering; hence, metal(loid)s are released and accumulated in the underlying soil, with potential adverse consequences for ecosystem function and human health. Amongst the currently available environmentally-safe technologies for the remediation of metal-contaminated soils, chemical immobilization is recognized as the most practical and cost-effective one. This technology often uses inorganic and organic amendments to reduce metal mobility, bioavailability and toxicity (environmental benefits). Likewise, amendments may also promote and speed up the re-establishment of vegetation on metal-affected soils, thus facilitating the conversion of abandoned shooting ranges into public green spaces (social benefit). In line with this, the circular economy paradigm calls for a more sustainable waste management, for instance, by recycling and reusing by-products and wastes in an attempt to reduce the demand for raw materials (economic benefit). The objective of this manuscript is to present a state-of-the-art review of the different industrial and agro-food by-products and wastes used for the remediation of metal-contaminated shooting range soils. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products)

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