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Recovery of Waste Materials: Technological Research and Industrial Scale-Up

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 39829

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Dr. Franco Medici

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Department of Chemical Engineering, Materials and Environmental, “Sapienza” University of Roma, Roma, Italy
Interests: industrial waste; hazardous material; recovery; circular economy; treatment; industrial plants; process development
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

The circular economy already allows the recycling of many wastes from either the domestic cycle or the demolition of civil structures; however, the recovery of industrial wastes appears more difficult and demanding. Industrial wastes come from processing and nonprocessing industries, as well as utilities such as packaging materials, food wastes, spoiled metal, plastic and textiles, fuel burning residuals, and spent processing chemicals.

Heavy metals can be recovered from industrial residues, such as rare earths from the waste of fluorescent lamps, precious metals from end-of-life photovoltaic panels or cellular electronic cards; moreover, agri-food wastes can be used as heavy metal adsorbents.

Low-cost and reduced environmental impact technologies have been studied in the research area in the last twenty years; hence, development technological applications at an industrial scale are now necessary.

For this reason, it is my pleasure to invite you to submit a manuscript for this Special Issue; full papers, communications and reviews are welcome aiming to propose technological solutions or consider recovery as a non-problem for the global community.

Prof. Eng. Franco Medici
Guest Editor

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

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

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

Keywords

waste materials
recycling
recovery
valuable materials
technological research
scale-up
chemical operations
process engineering
pilot plant
case study

Published Papers (13 papers)

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Editorial

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3 pages, 186 KiB

Open AccessEditorial

Recovery of Waste Materials: Technological Research and Industrial Scale-Up

by Franco Medici

Materials 2022, 15(2), 685; https://doi.org/10.3390/ma15020685 - 17 Jan 2022

Cited by 3 | Viewed by 1590

Abstract

An increase in population, booming economy, rapid urbanization and the rise in living standards have exponentially accelerated waste production [...] Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

Research

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12 pages, 1045 KiB

Open AccessArticle

Recovery of Waste Polyurethane from E-Waste. Part II. Investigation of the Adsorption Potential for Wastewater Treatment

by Vincenzo Santucci and Silvia Fiore

Materials 2021, 14(24), 7587; https://doi.org/10.3390/ma14247587 - 10 Dec 2021

Cited by 7 | Viewed by 1864

Abstract

This study explored the performances of waste polyurethane foam (PUF) derived from the shredding of end-of-life refrigerators as an adsorbent for wastewater treatment. The waste PUF underwent a basic pre-treatment (e.g., sieving and washing) prior the adsorption tests. Three target pollutants were considered: methylene blue, phenol, and mercury. Adsorption batch tests were performed putting in contact waste PUF with aqueous solutions of the three pollutants at a solid/liquid ratio equal to 25 g/L. A commercial activated carbon (AC) was considered for comparison. The contact time necessary to reach the adsorption equilibrium was in the range of 60–140 min for waste PUF, while AC needed about 30 min. The results of the adsorption tests showed a better fit of the Freundlich isotherm model (R² = 0.93 for all pollutants) compared to the Langmuir model. The adsorption capacity of waste PUF was limited for methylene blue and mercury (K_f = 0.02), and much lower for phenol (K_f = 0.001). The removal efficiency achieved by waste PUF was lower (phenol 12% and methylene blue and mercury 37–38%) compared to AC (64–99%). The preliminary results obtained in this study can support the application of additional pre-treatments aimed to overcome the adsorption limits of the waste PUF, and it could be applied for “rough-cut” wastewater treatment. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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14 pages, 2051 KiB

Open AccessArticle

Recovery of Waste Polyurethane from E-Waste—Part I: Investigation of the Oil Sorption Potential

by Vincenzo Santucci and Silvia Fiore

Materials 2021, 14(21), 6230; https://doi.org/10.3390/ma14216230 - 20 Oct 2021

Cited by 8 | Viewed by 1604

Abstract

The shredding of end-of-life refrigerators produces every year in Italy 15,000 tons of waste polyurethane foam (PUF), usually destined for energy recovery. This work presents the results of the investigation of the oil sorption potential of waste PUF according to ASTM F726–17 standard. Three oils (diesel fuel and two commercial motor oils) having different densities (respectively, 0.83, 0.87, and 0.88 kg/dm³) and viscosities (respectively, 3, 95, and 140 mm²/s at 40 °C) were considered. The waste PUF was sampled in an Italian e-waste treatment plant, and its characterization showed 16.5 wt% particles below 0.71 mm and 13 wt% impurities (paper, plastic, aluminum foil), mostly having dimensions (d) above 5 mm. Sieving at 0.071 mm was applied to the waste PUF to obtain a “coarse” (d > 0.71 mm) and a “fine” fraction (d < 0.71 mm). Second sieving at 5 mm allowed an “intermediate” fraction to be obtained, with dimensions between 0.71 and 5 mm. The oil sorption tests involved the three fractions of waste PUF, and their performances were compared with two commercial oil sorbents (sepiolite and OKO-PUR). The results of the tests showed that the “fine” PUF was able to retain 7.1–10.3 g oil/g, the “intermediate” PUF, 4.2–7.4 g oil/g, and the “coarse” PUF, 4.5–7.0 g oil/g, while sepiolite and OKO-PUR performed worse (respectively, 1.3–1.6 and 3.3–5.3 g oil/g). In conclusion, compared with the actual management of waste PUF (100 wt% sent to energy recovery), the amount destined directly to energy recovery could be limited to 13 wt% (i.e., the impurities). The remaining 87 wt% could be diverted to reuse for oil sorption, and afterward directed to energy recovery, considered as a secondary option. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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14 pages, 1522 KiB

Open AccessArticle

A Study of Treatment of Industrial Acidic Wastewaters with Stainless Steel Slags Using Pilot Trials

by Mattia De Colle, Rahul Puthucode, Andrey Karasev and Pär G. Jönsson

Materials 2021, 14(17), 4806; https://doi.org/10.3390/ma14174806 - 25 Aug 2021

Cited by 3 | Viewed by 1304

Abstract

Different stainless steel slags have been successfully employed in previous experiments, for the treatment of industrial acidic wastewaters. Although, before this technology can be implemented on an industrial scale, upscaled pilot experiments need to be performed. In this study, the parameters of the upscale trials, such as the volume and mixing speeds, are firstly tested by dispersing a NaCl tracer in a water bath. Mixing time trials are used to maintain constant mixing conditions when the volumes are increased to 70, 80 and 90 L, compared to the 1 L laboratory trials. Subsequently, the parameters obtained are used in pH buffering trials, where stainless steel slags are used as reactants, replicating the methodology of previous studies. Compared to laboratory trials, the study found only a minor loss of efficiency. Specifically, in previous studies, 39 g/L of slag was needed to buffer the pH of the acidic wastewaters. To reach similar pH values within the same time span, upscaled trials found a ratio of 43 g/L and 44 g/L when 70 and 90 L are used, respectively. Therefore, when the kinetic conditions are controlled, the technology appears to be scalable to higher volumes. This is an important finding that hopefully promotes further investments in this technology. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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11 pages, 3582 KiB

Open AccessArticle

Initial Conditioning of Used Cigarette Filters for Their Recycling as Acoustical Absorber Materials

by Valentín Gómez Escobar, Celia Moreno González, María José Arévalo Caballero and Ana Mᵃ Gata Jaramillo

Materials 2021, 14(15), 4161; https://doi.org/10.3390/ma14154161 - 27 Jul 2021

Cited by 8 | Viewed by 2445

Abstract

Used cigarette butts represent a major and problematic form of waste, due to their abundance, toxicity, and durability. Moreover, the few proposals for their recycling are clearly insufficient, and new ones are welcome. For a new proposal regarding the reuse of used cigarette butts as acoustical absorbers in building construction, previous conditioning of the used butts is performed. This conditioning includes the elimination of moisture and toxic products accumulated in the filter of the cigarettes. Thus, in this work, the moisture content effect in acoustical absorption was analyzed, and a proposal for elimination is made. Moreover, a chemical cleaning procedure is proposed, and its influence on the acoustical behavior of the samples was also analyzed. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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15 pages, 3750 KiB

Open AccessArticle

A Novel Dry Treatment for Municipal Solid Waste Incineration Bottom Ash for the Reduction of Salts and Potential Toxic Elements

by Marco Abis, Martina Bruno, Franz-Georg Simon, Raul Grönholm, Michel Hoppe, Kerstin Kuchta and Silvia Fiore

Materials 2021, 14(11), 3133; https://doi.org/10.3390/ma14113133 - 07 Jun 2021

Cited by 3 | Viewed by 2389

Abstract

The main obstacle to bottom ash (BA) being used as a recycling aggregate is the content of salts and potential toxic elements (PTEs), concentrated in a layer that coats BA particles. This work presents a dry treatment for the removal of salts and PTEs from BA particles. Two pilot-scale abrasion units (with/without the removal of the fine particles) were fed with different BA samples. The performance of the abrasion tests was assessed through the analyses of particle size and moisture, and that of the column leaching tests at solid-to-liquid ratios between 0.3 and 4. The results were: the particle-size distribution of the treated materials was homogeneous (25 wt % had dimensions <6.3 mm) and their moisture halved, as well as the electrical conductivity of the leachates. A significant decrease was observed in the leachates of the treated BA for sulphates (44%), chlorides (26%), and PTEs (53% Cr, 60% Cu and 8% Mo). The statistical analysis revealed good correlations between chloride and sulphate concentrations in the leachates with Ba, Cu, Mo, and Sr, illustrating the consistent behavior of the major and minor components of the layer surrounding BA particles. In conclusion, the tested process could be considered as promising for the improvement of BA valorization. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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19 pages, 5239 KiB

Open AccessArticle

Effect of Metal Lathe Waste Addition on the Mechanical and Thermal Properties of Concrete

by Marcin Małek, Marta Kadela, Michał Terpiłowski, Tomasz Szewczyk, Waldemar Łasica and Paweł Muzolf

Materials 2021, 14(11), 2760; https://doi.org/10.3390/ma14112760 - 23 May 2021

Cited by 19 | Viewed by 3008

Abstract

The amount of steel chips generated by lathes and CNC machines is 1200 million tons per year, and they are difficult to recycle. The effect of adding steel chips without pre-cleaning (covered with production lubricants and cooling oils) on the properties of concrete was investigated. Steel waste was added as a replacement for fine aggregate in the amounts of 5%, 10% and 15% of the cement weight, which correspond with 1.1%, 2.2% and 3.3% mass of all ingredients and 0.33%, 0.66% and 0.99% volume of concrete mix, respectively. The slump cone, air content, pH value, density, compressive strength, tensile strength, tensile splitting strength, elastic modulus, Poisson’s ratio and thermal parameters were tested. It was observed that with the addition of lathe waste, the density decreased, but mechanical properties increased. With the addition of 5%, 10% and 15% metal chips, compressive strength increased by 13.9%, 20.8% and 36.3% respectively compared to plain concrete; flexural strength by 7.1%, 12.7% and 18.2%; and tensile splitting strength by 4.2%, 33.2% and 38.4%. Moreover, it was determined that with addition of steel chips, thermal diffusivity was reduced and specific heat capacity increased. With the addition of 15% metal chips, thermal diffusivity was 25.2% lower than in the reference sample, while specific heat was 23.0% higher. No effect was observed on thermal conductivity. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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11 pages, 5559 KiB

Open AccessEditor’s ChoiceArticle

Neutralization of Acidic Wastewater from a Steel Plant by Using CaO-Containing Waste Materials from Pulp and Paper Industries

by Tova Jarnerud, Andrey V. Karasev and Pär G. Jönsson

Materials 2021, 14(10), 2653; https://doi.org/10.3390/ma14102653 - 18 May 2021

Cited by 7 | Viewed by 2598

Abstract

In this study, CaO-containing wastes from pulp and paper industries such as fly ash (FA) and calcined lime mud (LM) were utilized to neutralize and purify acidic wastewaters from the pickling processes in steel mills. The investigations were conducted by laboratory scale trials using four different batches of wastewaters and additions of two types of CaO-containing waste materials. Primary lime (PL), which is usually used for the neutralization, was also tested in the same experimental set up in the sake of comparison. The results show that these secondary lime sources can effectively increase the pH of the acidic wastewaters as good as the commonly used primary lime. Therefore, these secondary lime sources could be potential candidates for application in neutralization processes of industrial acidic wastewater treatment. Moreover, concentrations of metals (such as Cr, Fe, Ni, Mo and Zn) can decrease dramatically after neutralization by using secondary lime. The LM has a purification effect from the given metals, similar to the PL. Application of fly ash and calcined lime mud as neutralizing agents can reduce the amount of waste from pulp and paper mills sent to landfill and decrease the need for nature lime materials in the steel industry. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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15 pages, 1659 KiB

Open AccessArticle

Effect of Acid Leaching Pre-Treatment on Gold Extraction from Printed Circuit Boards of Spent Mobile Phones

by Nicolò Maria Ippolito, Franco Medici, Loris Pietrelli and Luigi Piga

Materials 2021, 14(2), 362; https://doi.org/10.3390/ma14020362 - 13 Jan 2021

Cited by 24 | Viewed by 2321

Abstract

The effect of a preliminary acid leaching for the recovery of gold by thiourea from printed circuit boards (PCBs) of spent mobile phones, was investigated. Preliminary leaching is aimed to recover copper in the leachate that would compete with gold in the successive leaching of the residue with thiourea, thus preventing the formation of the gold-thiourea complex. Two hydrometallurgical routes were tested for the recovery of copper first, and gold after. The first one was based on a two-step leaching that utilizes sulfuric acid and hydrogen peroxide in the preliminary leaching and then thiourea for the recovery of gold in the successive leaching: A copper and gold recovery of 81% and 79% were obtained, respectively. In the second route, nitric acid was used: 100% of copper was recovered in the leachate and 85% of gold in the thiourea successive leaching. The main operative parameters, namely thiourea and ferric sulphate concentrations, leach time, liquid-solid ratio, and temperature were studied according to a factorial plan strategy. A flowsheet of the processes was proposed, and a mass balance of both routes was obtained. Finally, qualitative considerations on the technical and economic feasibility of the different routes were made. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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13 pages, 1420 KiB

Open AccessArticle

Biochars from Post-Production Biomass and Waste from Wood Management: Analysis of Carbonization Products

by Wojciech Kosakowski, Malgorzata Anita Bryszewska and Piotr Dziugan

Materials 2020, 13(21), 4971; https://doi.org/10.3390/ma13214971 - 04 Nov 2020

Cited by 13 | Viewed by 2288

Abstract

Waste biomass can be used as an alternative source of energy. However, such use requires prior treatment of the material. This paper describes the physicochemical characteristics of biochar obtained by the thermochemical decomposition of six types of agricultural waste biomass: residues from the production of flavored spirits (a pulp of lime, grapefruit and lemon), beetroot pulp, apple pomace, brewer’s spent grain, bark and municipal solid waste (bark, sawdust, off-cuts and wood chips). The biomass conversion process was studied under conditions of limited oxygen access in a reactor. The temperature was raised from 450 to 850 °C over 30 min, followed by a residence time of 60 min. The solid products were characterized in terms of their elemental compositions, mass, energy yield and ash content. The gaseous products from pyrolysis of the biomass were also analyzed and their compositions were characterized by GCMS (Gas Chromatography–Mass Spectrometry). The carbonization process increased the carbon content by, on average, 1.7 times, from an average percentage of 46.09% ± 3.65% for biomass to an average percentage of 74.72% ± 5.36% for biochars. After carbonization, the biochars were found to have a net calorific value of between 27 and 32 MJ/kg, which is comparable or even higher than good-quality coal (eco pea coal 24–26 MJ/kg). The net calorific values show that the volatile products can also be considered as a valuable source of energy. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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Review

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29 pages, 5659 KiB

Open AccessReview

Extraction of Value-Added Minerals from Various Agricultural, Industrial and Domestic Wastes

by Virendra Kumar Yadav, Krishna Kumar Yadav, Vineet Tirth, Govindhan Gnanamoorthy, Nitin Gupta, Ali Algahtani, Saiful Islam, Nisha Choudhary, Shreya Modi and Byong-Hun Jeon

Materials 2021, 14(21), 6333; https://doi.org/10.3390/ma14216333 - 23 Oct 2021

Cited by 17 | Viewed by 4204

Abstract

Environmental pollution is one of the major concerns throughout the world. The rise of industrialization has increased the generation of waste materials, causing environmental degradation and threat to the health of living beings. To overcome this problem and effectively handle waste materials, proper management skills are required. Waste as a whole is not only waste, but it also holds various valuable materials that can be used again. Such useful materials or elements need to be segregated and recovered using sustainable recovery methods. Agricultural waste, industrial waste, and household waste have the potential to generate different value-added products. More specifically, the industrial waste like fly ash, gypsum waste, and red mud can be used for the recovery of alumina, silica, and zeolites. While agricultural waste like rice husks, sugarcane bagasse, and coconut shells can be used for recovery of silica, calcium, and carbon materials. In addition, domestic waste like incense stick ash and eggshell waste that is rich in calcium can be used for the recovery of calcium-related products. In agricultural, industrial, and domestic sectors, several raw materials are used; therefore, it is of high economic interest to recover valuable minerals and to process them and convert them into merchandisable products. This will not only decrease environmental pollution, it will also provide an environmentally friendly and cost-effective approach for materials synthesis. These value-added materials can be used for medicine, cosmetics, electronics, catalysis, and environmental cleanup. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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16 pages, 950 KiB

Open AccessReview

Pyrolytic Conversion of Plastic Waste to Value-Added Products and Fuels: A Review

by Sadegh Papari, Hanieh Bamdad and Franco Berruti

Materials 2021, 14(10), 2586; https://doi.org/10.3390/ma14102586 - 16 May 2021

Cited by 103 | Viewed by 9646

Abstract

Plastic production has been rapidly growing across the world and, at the end of their use, many of the plastic products become waste disposed of in landfills or dispersed, causing serious environmental and health issues. From a sustainability point of view, the conversion of plastic waste to fuels or, better yet, to individual monomers, leads to a much greener waste management compared to landfill disposal. In this paper, we systematically review the potential of pyrolysis as an effective thermochemical conversion method for the valorization of plastic waste. Different pyrolysis types, along with the influence of operating conditions, e.g., catalyst types, temperature, vapor residence time, and plastic waste types, on yields, quality, and applications of the cracking plastic products are discussed. The quality of pyrolysis plastic oil, before and after upgrading, is compared to conventional diesel fuel. Plastic oil yields as high as 95 wt.% can be achieved through slow pyrolysis. Plastic oil has a heating value approximately equivalent to that of diesel fuel, i.e., 45 MJ/kg, no sulfur, a very low water and ash content, and an almost neutral pH, making it a promising alternative to conventional petroleum-based fuels. This oil, as-is or after minor modifications, can be readily used in conventional diesel engines. Fast pyrolysis mainly produces wax rather than oil. However, in the presence of a suitable catalyst, waxy products further crack into oil. Wax is an intermediate feedstock and can be used in fluid catalytic cracking (FCC) units to produce fuel or other valuable petrochemical products. Flash pyrolysis of plastic waste, performed at high temperatures, i.e., near 1000 °C, and with very short vapor residence times, i.e., less than 250 ms, can recover up to 50 wt.% ethylene monomers from polyethylene waste. Alternatively, pyrolytic conversion of plastic waste to olefins can be performed in two stages, with the conversion of plastic waste to plastic oil, followed by thermal cracking of oil to monomers in a second stage. The conversion of plastic waste to carbon nanotubes, representing a higher-value product than fuel, is also discussed in detail. The results indicate that up to 25 wt.% of waste plastic can be converted into carbon nanotubes. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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24 pages, 3328 KiB

Open AccessEditor’s ChoiceReview

Influence of Design Parameters on Fresh Properties of Self-Compacting Concrete with Recycled Aggregate—A Review

by Rebeca Martínez-García, P. Jagadesh, Fernando J. Fraile-Fernández, Julia M. Morán-del Pozo and Andrés Juan-Valdés

Materials 2020, 13(24), 5749; https://doi.org/10.3390/ma13245749 - 16 Dec 2020

Cited by 17 | Viewed by 2647

Abstract

This article presents an overview of the bibliographic picture of the design parameter’s influence on the mix proportion of self-compacting concrete with recycled aggregate. Design parameters like water-cement ratio, water to paste ratio, and percentage of superplasticizers are considered in this review. Standardization and recent research on the usage of recycled aggregates in self-compacting concrete (SCC) exploit its significance in the construction sector. The usage of recycled aggregate not only resolves the negative impacts on the environment but also prevents the usage of natural resources. Furthermore, it is necessary to understand the recycled aggregate property’s role in a mixed design and SCC properties. Design parameters are not only influenced by a mix design but also play a key role in SCC’s fresh properties. Hence, in this overview, properties of SCC ingredients, calculation of design parameters in mix design, the effect of design parameters on fresh concrete properties, and the evolution of fresh concrete properties are studied. Full article

(This article belongs to the Special Issue Recovery of Waste Materials: Technological Research and Industrial Scale-Up)

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