Pretreatment of Plastic Waste: Removal of Colorants from HDPE Using Biosolvents

Plastics recycling remains a challenge due to the relatively low quality of the recycled material, since most of the developed recycling processes cannot deal with the additives present in the plastic matrix, so the recycled products end up in lower-grade applications. The application of volatile organic solvents for additives removal is the preferred choice. In this study, pretreatment of plastic packaging waste to remove additives using biosolvents was investigated. The plastic waste used was high-density polyethylene (HDPE) with blue and orange colorants (pigment and/or dye). The first step was to identify the type of colorants present in the HDPE, and we found that both plastics presented only one colorant that was actually a pigment. Then, limonene, a renewable solvent, was used to solubilize HDPE. After HDPE dissolution, a wide range of alcohols (mono-, di-, and tri-alcohols) was evaluated as antisolvents in order to selectively precipitate the polymer and maximize its purity. The use of limonene as solvent for plastic dissolution, in combination with poly-alcohols with an intermediate alkyl chain length and a large number of hydroxyl (OH) groups, was found to work best as an antisolvent (1,2,3-propanetriol and 1,2,4-butanetriol), leading to a removal of up to 94% and 100% of the blue and orange pigments, respectively. Finally, three cycles of extraction were carried out, proving the capability of the solvent and antisolvent to be recovered and reused, ensuring the economic viability and sustainability of the process. This pretreatment provides a secondary source of raw materials and revenue for the recycling process, which may lead to an increase in the quality of recycled polymers, contributing to the development of an economical and sustainable recycling process.

The use of construction and rubber recycled material for the production of cement composites with thermal insulation function

This article presents the results of the possible use of construction waste and rubber granulate as a filler substitute for the production of cement composites with thermal insulation properties. It describes the individual components of the materials necessary for the designing of recipes and their properties. The article presents the thermal insulation properties and strength characteristics of the designed recipes of non-traditional cement composite after 7, 14, 28 and 90 days.

Recycled Polyester Geosynthetic Influence on Improvement of Road and Railway Subgrade Bearing Capacity— Laboratory Investigations

After years of using geosynthetics in civil engineering and infrastructure construction, it has recently become necessary to consider the possibility of recycling and reusing these materials. This paper presents the results of laboratory tests of the effect of recycled geogrid on the bearing capacity of soils using a CBR test. A polyester geosynthetic was selected for testing due to its high resistance to biodegradation and wide application. In a series of laboratory tests, two types of road and railway subgrade were used, mixed with geosynthetic cuttings in two different weight concentrations. The aim of the research was to demonstrate whether old demolition geosynthetics could be used to strengthen road and rail subgrade as recycled material. The influence of the geosynthetic cutting shape was also considered. The obtained results confirm the possibility of using recycled geogrid to improve the bearing capacity of the pavement subgrade, at least under these laboratory conditions. In the case of sand, the use of 2.0% additive causes that the poorly compacted soil obtains sufficient bearing capacity for the layer of road improved subgrade. As expected, the level of this improvement depends on the type of soil and the shape of geogrid cuttings.

Surface treatments of recycled brick aggregate and their influence on selected properties of concrete

The paper is devoted to surface treatment of recycled brick aggregate with various impregnating substances in order to reduce its absorbency and verify the use of such treated recycled material as a partial replacement of natural aggregate (fraction 4/8) in concrete. Selected properties of the tested samples were monitored after 28 and 60 days of curing. The results show that the treatment of recycled bricks with water glass appears to be a less suitable alternative compared to the use of a hydrophobic solution of silanes and siloxanes.

Consumer Attitudes Towards New Circular Models in the Fashion Industry

The fashion industry ranks among the most resource-intensive and environment-polluting industries. Circularity has been discussed as a solution to these problems. However, the transition towards a circular economy (CE) requires fundamental changes in the behavior and actions of all market entities. Consumer interest in sustainability and circularity can stimulate businesses to become more responsible and to offer circular solutions, and thus create a significant competitive advantage for these firms in a globalized market. This paper examines consumer attitudes towards the new circular models in the fashion industry (e.g. slow fashion, swapping, clothes rent, etc.). Consumer knowledge of these models, consumer willingness to support them as well as a correlation to selected demographic characteristics will be described along with consumer attitudes towards textile products made of waste and recycled material. Results will be introduced from a questionnaire survey carried out in October and November 2019 using the sample of 468 respondents in Slovakia. The obtained data were evaluated using statistical methods (Pearson Chi-Square, Wilcoxon test, Spearman’s correlation coefficient). While generally a low awareness of Slovak consumers of new models in the fashion industry was confirmed, the willingness of consumers to engage and support circular solutions was shown, especially among the younger generations. These results show that businesses that react to consumer expectations regarding circularity by offering products and services with environmental benefits may increase their competitiveness.

Innovative Biochar-Based Composite Fibres from Recycled Material

Carbon materials are becoming crucial in several industrial sectors. The drawbacks of these materials include their high cost and oil-based essence. In recent years, recycled materials have become possible alternative sources of carbon with several advantages. Firstly, the production of this alternative source of carbon may help to reduce biomass disposal, and secondly, it contributes to CO2 sequestration. The use of carbon derived from recycled materials by a pyrolysis treatment is called biochar. Here, we present composite materials based on different biochar filler contents dispersed in several thermoplastic polymer matrixes. Electrical conductivity and tensile break strength were investigated together with the material characterisation by DTA/TGA, XRD, and scanning electron microscopy (SEM) imaging. Materials with good flexibility and electrical conductivity were obtained. The local ordering in composites resembles both biochar and polymer ordering. The similarity between biochar and carbon nanotubes’ (CNTs) XRD patterns may be observed. As biochar is highly cost-effective, the proposed composites could become a valid substitute for CNT composites in various applications.

Generalized Interface Shear Strength Equation for Recycled Materials Reinforced with Geogrids

In this research, large direct shear tests were conducted to evaluate the interface shear strength between reclaimed asphalt pavement (RAP) and kenaf geogrid (RAP–geogrid) and to also assess their viability as an environmentally friendly base course material. The influence of factors such as the gradation of RAP particles and aperture sizes of geogrid (D) on interface shear strength of the RAP–geogrid interface was evaluated under different normal stresses. A critical analysis was conducted on the present and previous test data on geogrids reinforced recycled materials. The D/FD, in which FD is the recycled materials’ particle content finer than the aperture of geogrid, was proposed as a prime parameter governing the interface shear strength. A generalized equation was proposed for predicting the interface shear strength of the form: α = a(D/FD) + b, where α is the interface shear strength coefficient, which is the ratio of the interface shear strength to the shear strength of recycled material, and a and b are constants. The constant values of a and b were found to be dependent upon types of recycled material, irrespective of types of geogrids. A stepwise procedure to determine variable a, which is required for analysis and design of geogrids reinforced recycled materials in roads with various gradations was also suggested.

Polypropylene Contamination in Post-Consumer Polyolefin Waste: Characterisation, Consequences and Compatibilisation

Plastic recycling strikes a balance between functional, mass producible products and environmental sustainability and is pegged by governments for rapid expansion. However, ambitious targets on recycled material adoption across new markets are at odds with the often heterogenous properties of contaminated regranulates. This study investigated polypropylene (PP) contamination in post-consumer low-density polyethylene (PE-LD) and mixed polyolefin (PO) regranulates. Calibration curves were constructed and PP content, its effect on mechanical properties and property recovery in compatibilised material assessed. FT-IR band ratios provided more reliable estimations of PP content than DSC melt enthalpy, which suffered considerable error for PP copolymers. PE-LD regranulates contained up to 7 wt.% PP contamination and were considerably more brittle than virgin PE-LD. Most mixed PO regranulates contained 45–95 wt.% PP and grew more brittle with increasing PP content. Compatibilisation with 5 wt.% ethylene-based olefin block copolymer resulted in PE-LD blends resembling virgin PE-LD and considerable improvements in the properties of mixed PO blends. These results illustrate the prevalence of PP in recycled PE, challenges associated with its quantification, effect on mechanical properties, and compatibilisation viability, thereby representing an important step towards higher quality regranulates to meet the recycling demands of tomorrow.