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Open AccessArticle

Analysis of Feed Inlet and Optimal Feeding Amount of Waste Ground Film Impurity Removal Equipment

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Appl. Sci. 2023, 13(17), 9905; https://doi.org/10.3390/app13179905 (registering DOI) - 01 Sep 2023

Abstract

A tumbler screen-type residual film–impurity mixture wind separator is the key equipment for the secondary utilization of farmland residual film. During its operation, the proportion of impurities in the separated waste mulch film intermittently increases, resulting in poor working stability of the device, [...] Read more.

A tumbler screen-type residual film–impurity mixture wind separator is the key equipment for the secondary utilization of farmland residual film. During its operation, the proportion of impurities in the separated waste mulch film intermittently increases, resulting in poor working stability of the device, which may hamper long-term operation. To address the above issues, the material inside the separation unit was continuously monitored, and the main factor affecting separator performance was determined to be the challenges in the effective depolymerization of some residual film-impurity mixtures. The principles of agglomeration and depolymerization of the residual film-impurity mixtures were analyzed using computational fluid dynamics (CFD) and discrete element method (DEM) flow-solid coupling simulation methods. The key factor affecting the disaggregation of the mixture was the collision force between the residual film–impurity mixture and the trommel screen. The collision force was maximum when the residual film–impurity mixture first collided with the trommel screen when it was fed into the separation device. Furthermore, simulations were carried out for different inlet structure forms; the evaluation index was the maximum collision force of the residual film–impurity mixture agglomerate on the trommel screen. The best disaggregation effect was obtained with a square feed inlet and at a feeding rate of 202 kg/h. A prototype was built using these specifications for verification. The average value of the ratio of impurities in the residual film was 6.966%, the coefficient of variation was 7.38%, and the dispersion of statistical results was small. The ratio of impurities in the residual film was kept constant during the continuous operation of the wind separator. Thus, in this study, we analyzed the agglomerate disaggregation process and provided theoretical insights for determining the optimal structures of the inlets of various cleaning devices and the feeding volumes. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessArticle

The Effect of Hydrolysis on the Antioxidant Activity of Olive Mill Waste

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Karen Attard

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Mecit Halil Oztop

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Frederick Lia

Appl. Sci. 2022, 12(23), 12187; https://doi.org/10.3390/app122312187 - 28 Nov 2022

Viewed by 842

Abstract

This study presents the effect of hydrolysis on the antioxidant activity of olive mill waste. The olive pomace samples were collected at different stages of maturity and were investigated for their phenolic content and antioxidant activity. Three different extraction procedures were employed, including [...] Read more.

This study presents the effect of hydrolysis on the antioxidant activity of olive mill waste. The olive pomace samples were collected at different stages of maturity and were investigated for their phenolic content and antioxidant activity. Three different extraction procedures were employed, including methanolic maceration extraction and two hydrolysed procedures using 6 M HCL for acid hydrolysis and 10 M NaOH for alkaline hydrolysis. The total phenolic, flavonoid and ortho-diphenolic content, metal ion reducing activity, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-Diphenyl-1-picrylhydrazyl Radical Scavenging, hydrogen peroxide and superoxide scavenging activity assays were determined for the different extracts. In this study, cultivar and maturation of olives was one of the factors that affected the phenolic content in the olive pomace samples. Results show that alkaline hydrolysis had the highest antioxidant activity with respect to total phenolic content, 2,2-Diphenyl-1-picrylhydrazyl scavenging activity, metal ion reducing activity and superoxide scavenging activity, whereas acid hydrolysis had the highest 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging activity. The correlation analysis carried out on the different phenolic classes revealed that the total phenolic, flavonoid and ortho-diphenolic content were correlated with metal ion reducing activity and Radical Scavenging activity. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessArticle

Preliminary Investigation of Geopolymer Foams as Coating Materials

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Appl. Sci. 2022, 12(21), 11205; https://doi.org/10.3390/app122111205 - 04 Nov 2022

Cited by 4 | Viewed by 903

Abstract

Various types of coatings are applied to the surface of an object or substrate to improve surface properties or extend service life, which in turn is associated with cost reductions. The main objective of this study was to develop a technique for the [...] Read more.

Various types of coatings are applied to the surface of an object or substrate to improve surface properties or extend service life, which in turn is associated with cost reductions. The main objective of this study was to develop a technique for the additive application of foamed geopolymers to existing structures and vertical surfaces. The base material was a fly ash-based geopolymer modified with sand. Hydrogen peroxide and aluminum powder were used as foaming agents. In this study, the feasibility of using an air gun with variable nozzles to apply the layers of foamed geopolymers was assessed, and the effects of nozzle diameter and the spray gun’s operating pressure were analyzed. The next stage of the study was a visual assessment of the layering of the foamed material. The foamed geopolymer layering tests verified the occurrence of the foaming process, and the applied geopolymer surface showed a reasonably good adhesive bond with the vertical wall. In addition, in this paper, we present the laser particle size results of the base materials and their oxide composition. In addition, thermal conductivity tests for the foamed geopolymer materials, compressive strength tests, and microstructure analysis via scanning electron microscopy were carried out. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessArticle

Design and Experiment of Black Soldier Fly Frass Mixture Separation through a Cylinder Sieve with Different Rotation Speeds

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Appl. Sci. 2022, 12(20), 10597; https://doi.org/10.3390/app122010597 - 20 Oct 2022

Viewed by 1783

Abstract

A differential separation trommel screener was developed to solve the problems of the impurity content in insects and the high rate of insect impurities in the separation of black soldier fly (BSF) sand mixture. Moreover, the mechanical and physical properties of the BSF [...] Read more.

A differential separation trommel screener was developed to solve the problems of the impurity content in insects and the high rate of insect impurities in the separation of black soldier fly (BSF) sand mixture. Moreover, the mechanical and physical properties of the BSF sand and its bonding contact model were examined. With the rotational speed of the trommel and the spikes and the inclination of the trommel as the experimental factors, their motion characteristics were analyzed and their value ranges were determined. In addition, the impurity content in the insects and the rate of insect impurities were selected as the test indicators. The Box–Behnken test was performed, the response surface regression model was built, and the parameters were optimized. The results indicated that the respective test factors, the impurity content and the insect rate, followed the following order of significance: the trommel rotation speed, spike teeth rotation speed, and trommel screener inclination. At the trommel rotation speed of 47.37 r/min, the speed of the spike teeth reached 24.16 r/min, the inclination angle of the trommel was 5°, the impurity content was 6.0%, and the insect rate reached 1.2%. The results of the bench test indicated that the average impurity content was 5.87% and the average insect rate was 1.20%. The results of this study provide a reference for the improvement and optimization of the separation structure of the BSF sand mixture. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessArticle

Gases Emissions during Composting Process of Agri-Food Industry Waste

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Appl. Sci. 2022, 12(18), 9245; https://doi.org/10.3390/app12189245 - 15 Sep 2022

Cited by 8 | Viewed by 1242

Abstract

The vegetable production is an important part of agriculture sector in every country. In Poland, vegetables and fruits production covering the area of no more than 3% of agricultural land, is more than 36% of plant production and 14–15% of the whole agricultural [...] Read more.

The vegetable production is an important part of agriculture sector in every country. In Poland, vegetables and fruits production covering the area of no more than 3% of agricultural land, is more than 36% of plant production and 14–15% of the whole agricultural production. The study aim was to determine the management possibilities of the selected waste from vegetable production in composting process. Laboratory tests were carried out using the bioreactor set-up with capacity of 165 dm³, respectively, for each chamber. The composting process has been tested for the following mixtures: K1—cabbage leaves, tomato dry leaves + manure and slurry additive; K2—cabbage leaves, solid fraction from biogas plant + manure and straw additive; K3—cabbage leaves, onion husk + straw additive. In all three composts the thermophilic phase occurred which indicates that the process ran correctly. In each chamber, the temperature exceeded 70 °C and its maximum value during the experiment was 77.5 °C for K2 compost. The article discusses changes in O₂, CO₂, NH₃ and H₂S emissions during composting. The carbon dioxide concentration in the exhausted gas from analyzed composts and the ratio with oxygen they testify to the decomposition of raw materials in the composting process. The results showed that the agri-food waste can be a proper substrate for composting production. Due to legal regulations and the increase in prices of mineral fertilizers, the development of the compost market should be expected. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessArticle

Perlite as a Biocarrier for Augmentation of Biogas-Producing Reactors from Olive (Olea europaea) Waste

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Appl. Sci. 2022, 12(17), 8808; https://doi.org/10.3390/app12178808 - 01 Sep 2022

Cited by 3 | Viewed by 1087

Abstract

Biogas is mainly produced by anaerobic digestion (AD), and in the EU, the widely used substrate for AD is maize silage. Due to a rise in silage prices, the intention is to gradually replace maize with lignocellulose biomass. In the Mediterranean area, the [...] Read more.

Biogas is mainly produced by anaerobic digestion (AD), and in the EU, the widely used substrate for AD is maize silage. Due to a rise in silage prices, the intention is to gradually replace maize with lignocellulose biomass. In the Mediterranean area, the olive industry produces large amounts of lignocellulose wastes, namely olive cake and pruned biomass. Still, due to its high lignin content, it is resistant to biodegradation. This issue could be resolved by adding targeted microorganisms that enhance the substrate’s primary degradation, and the cells’ attachment to suitable biocarriers could boost the augmentation process. A microbial consortium customized for biodegradation of olive cake and pruned biomass was isolated, propagated and immobilized onto the biocarrier, perlite, a naturally occurring aluminosilicate material. The perlite proved to be a suitable biocarrier with numbers of immobilized bacteria as high as 2.1 ± 0.9 × 10¹¹ and 3.4 ± 0.6 × 10¹⁰ CFU g⁻¹ when preparation was performed in aerobic and anaerobic conditions, respectively. Bioaugmentation of AD reactors significantly increased the biogas yield, but only if olive cake, not the pruned biomass, was used as a substrate. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Review

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Open AccessReview

Rare Earth Elements Recovery from Primary and Secondary Resources Using Flotation: A Systematic Review

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Pongsiri Julapong

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Apisit Numprasanthai

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Ladda Tangwattananukul

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Onchanok Juntarasakul

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Palot Srichonphaisarn

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Kosei Aikawa

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Ilhwan Park

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Mayumi Ito

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Carlito Baltazar Tabelin

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Theerayut Phengsaart

Appl. Sci. 2023, 13(14), 8364; https://doi.org/10.3390/app13148364 - 19 Jul 2023

Viewed by 478

Abstract

Rare earth minerals (REMs) contain rare earth elements (REEs) that are important in modern technologies due to their unique magnetic, phosphorescent, and catalytic properties. However, REMs are not only non-renewable resources but also non-uniformly distributed on the Earth’s crust, so the processing of [...] Read more.

Rare earth minerals (REMs) contain rare earth elements (REEs) that are important in modern technologies due to their unique magnetic, phosphorescent, and catalytic properties. However, REMs are not only non-renewable resources but also non-uniformly distributed on the Earth’s crust, so the processing of REE-bearing secondary resources via recycling is one potential route to ensure the long-term sustainability of REE supply. Flotation—a method that separates materials based on differences in their surface wettability—is a process applied for both mineral processing and recycling of REEs, especially when the particles are fine and/or a high-purity product is required. In this review, studies about rare earth flotation from 2012 to 2021 were systematically reviewed using the PRISMA guideline. It was found that most REM flotation research works focused on finding better collectors and depressants while, for recycling, studies on advanced flotation techniques like froth flotation, ion flotation, solvent sublation, electroflotation, and adsorbing colloid flotation with an emphasis on the recovery of dissolved REEs from aqueous solutions dominated. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessReview

Application of Fly Ash Obtained from the Incineration of Municipal Solid Waste in Agriculture

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Carmen Otilia Rusănescu

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Marin Rusănescu

Appl. Sci. 2023, 13(5), 3246; https://doi.org/10.3390/app13053246 - 03 Mar 2023

Viewed by 1237

Abstract

In the current context of the increase in the amount of municipal solid waste as a result of the development of urbanization, in this paper we have analyzed the impact of the use of fly ash obtained from the incineration of municipal solid [...] Read more.

In the current context of the increase in the amount of municipal solid waste as a result of the development of urbanization, in this paper we have analyzed the impact of the use of fly ash obtained from the incineration of municipal solid waste in agriculture on the development of plants as an improver of acidic soils due to the nutrients it contains. We presented ash treatment methods to reduce the content of heavy metals and salts. Based on the studies in the literature, it was found that by adding certain concentrations of fly ash to degraded soils, the quality, porosity, and texture of the soil are improved; the yield of certain crops increases; the water retention capacity of the soil and soil aeration are improved; the density of the soil bulk; the compactness of the soil is reduced; the pH value is optimized; the electrical conductivity of the soil is increased; the crust formation is reduced; and it provides micronutrients to the soil. In the context of the circular economy, by using fly ash as an organic fertilizer in agriculture, the amount of chemical fertilizers harmful to agricultural crops is reduced, the problem of ash storage is solved, and thus it no longer pollutes the environment. Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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Open AccessReview

Advanced Strategies for Mitigating Particulate Matter Generations in Poultry Houses

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Ramesh Bahadur Bist

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Lilong Chai

Appl. Sci. 2022, 12(22), 11323; https://doi.org/10.3390/app122211323 - 08 Nov 2022

Cited by 7 | Viewed by 1194

Abstract

Poultry farming plays a key role in agricultural air emissions. Particulate matter (PM) level tends to be high in broiler and cage-free layer houses, that may impair health and welfare of animals and their caretakers. To protect public health and welfare, the occupational [...] Read more.

Poultry farming plays a key role in agricultural air emissions. Particulate matter (PM) level tends to be high in broiler and cage-free layer houses, that may impair health and welfare of animals and their caretakers. To protect public health and welfare, the occupational exposure limit for PM₁₀ and PM_2.5 (i.e., PM diameters that are generally ≤10 and 2.5 μm, respectively) are suggested not to exceed 150 µg m⁻³ and 35 µg m⁻³, respectively, based on 24-h concentrations thresholds as suggested by US. EPA. However, the levels of PM₁₀ and PM_2.5 in poultry houses could be 100 times higher than that limit. For instance, PM₁₀ and PM_2.5 levels in cage-free henhouses are higher than 15,000 µg/m³ and 3500 µg/m³ in wintertime. Therefore, it is critical to identify the primary factors affecting PM generation in poultry houses and apply corresponding mitigation strategies. This review paper summarizes PM emission factors, mitigating strategies, and impacts on birds’ and caretakers’ health, and welfare. Generally, PM emissions are affected by various factors, including housing types, seasonal and diurnal variation, manure management, bedding materials, ventilation rates, and birds’ activities. High PM concentrations in poultry houses impair birds’ and caretakers’ liver, kidneys, and respiratory systems. Thus, different mitigating strategies are discussed in this study for addressing those issues. Effective mitigation strategies include frequent house cleaning, optimum light intensity, liquid spraying, bedding management, and air filtration systems. However, mitigation strategies can be cost-prohibitive and have side effects. Therefore, poultry farms should select mitigation strategies based on farm location, climate conditions, environmental policies, and available resources (government assistance programs). Full article

(This article belongs to the Special Issue Advances in Waste Treatment and Resource Utilization)

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