Post-consumer Plastic Waste Research Articles

Upcycling polynorbornene derivatives into chemically recyclable multiblock linear and thermoset plastics.

Synthetic polymers have found widespread use with functional lifetimes from seconds to decades. However, the lack of end-of-life treatment for these plastics is causing a significant environmental and human health crisis due to their persistence and bioaccumulation. Upcycling post-consumer plastic waste to products with inherent recyclability is an attractive strategy to tackle this problem, as it can broaden the range of accessible materials and uncover unprecedented features while dealing with current plastic waste. Here, we demonstrate the upcycling of polynorbornene derivatives (pNBEs) including polydicyclopentadiene (pDCPD) thermosets through their transformation into distinct oligomeric buildings blocks which can be repolymerized into chemically recyclable pNBEs-like multiblock linear and crosslinked plastics. These materials exhibit a diverse set of mechanical properties, while integrate a high melting transition temperature with a broad range of glass transition temperature, controlled by the feed ratio of building blocks. After use, upcycled plastics could be effectively deconstructed back to the oligomers for recovery and repolymerization. Overall, this work establishes an approach that can be utilized to upcycle pNBEs and pDCPD into previously inaccessible multiblock thermoset and thermoplastics with full recyclability, and may be generalizable to a range of polymers to shift their end-of-life waste disposal toward sustainable recovery and reuse.

Numerical and experimental analysis and verification of plastics derived from post-consumer plastic wastes

The present study aims at replacing virgin polypropylene with a percentage of recycled plastics to assess the impact of this substitution on the mechanical properties of the original material. Homogenization is employed to predict the mechanical properties of the mixtures and verification is performed by considering tensile tests for each blend and mechanical properties are compared. Homogenized material properties achieved from numerical analysis and properties achieved from experiments are comparable with an error between 10 and 20%; such uncertainties might be connected with the unknown perfect mix present in the blend between the virgin and the recycled parts.

Combined valorization of industrial and post-consumer plastic waste. An industrial symbiosis approach

The aim of this work is to analyze two different strategies based on industrial symbiosis (IS) approaches, for the combined valorization of plastic waste from rubber polymerization process (WSBR) and plastic from Waste Electrical and Electronic Equipment (WEEE). The proposed strategies are: (a) WSBR as compatibilizer for HIPS/ABS mixtures from WEEE; and (b) WSBR as a component in mixtures with plastics from WEEE (HIPS or ABS). In the first strategy, two different proportions of HIPS/ABS mixtures are studied using three different concentrations of WSBR onto each one. In the second one, mixtures of each plastic WEEE, ABS and HIPS, with two different amounts of WSBR are analyzed. Tensile strength and ductility of ABS with 20 wt% of WSBR, increased around 8% and 40% respectively, with respect to the ABS. Regarding tensile behavior of HIPS and HIPS with 20 wt% of WSBR, both matches up to the break of the last one at a strain of 1.5 %, approximately. Obtained results indicate that the second strategy, is the best one for the combined valorization of both plastic wastes. This conclusion is based on the fact that properties are not deteriorated in successive melt-mixing. It is completely aligned with IS approaches, combining two plastic waste, an industrial one (WSBR) and a postconsumer one (WEEE), for the obtention of new materials with appropriate properties for their use.

Chemical recycling of polymer contaminated poly(ethylene terephthalate) by neutral hydrolysis

Plastic recycling is gaining traction to reduce the demand for fossil resources for plastic production. Poly(ethylene terephthalate) (PET), mainly used in the packaging and textile sectors, is often isolated in the sinking fraction during the density-based separation of mixed plastic waste streams. The heterogeneity of the sinking fraction makes direct mechanical recycling of PET impossible. Therefore, neutral hydrolysis of PET was investigated in the presence of other polymer contaminants to study their impact on the neutral hydrolysis of PET. PA6, PC, POM, and PVC were found to decompose during hydrolysis, whereas ABS, PMMA and a mixture of PE, PP and PS was chemically inert during the hydrolysis treatment. The subsequent BHET synthesis with excess ethylene glycol was performed directly on a mix of the polymer contaminated hydrolysis products or a hydrolyzed post-consumer plastic waste fraction. BHET was successfully formed in the plethora of decomposition products in the synthesis, and a subsequent recrystallization recovered the BHET in high purity with only water being used as solvent. This demonstrated a robust method to handle PET fractions in mixed plastic waste that can be applied without purification prior to BHET synthesis – enabling chemical recycling of PET.Abbreviations: ABS, Poly(acetonitrile-butadiene-styrene); ATR-FTIR, Attenuated Total Reflectance Fourier Transformed Infrared Spectroscopy; BC, Bis(2-Hydroxyethyl) terephthalate crystals; BHET, Bis(2-Hydroxyethyl) terephthalate; DMSO, Deuterated dimethyl sulfoxide; DSC, Differential Scanning Calorimetry; EG, Ethylene glycol; 1H NMR, Proton Nuclear Magnetic Resonance; Hm, Melting enthalpy; Oligo, Oligomers; PA6, Polyamide 6; PC, Polycarbonate; PE, Polyethylene; PET, Poly(ethylene terephthalate); PMMA, Poly(methyl methacrylate); POM, Polyoxymethylene; PP, Polypropylene; PS, Polystyrene; P, Purity; PVC, Poly(vinyl chloride); rpm, Revolutions per minute; SPHP, Solid Phase Hydrolysis Product; Ti(IV)OBu, Titanium(IV) butoxide; Tm, Melting temperature; TPA, Terephthalic acid; Wt, Weight; Y, Solid Phase Hydrolysis Product yield; Yt, Bis(2-Hydroxyethyl) terephthalate yield; ν, IR stretching mode; δ, IR bending mode; ω, IR wagging mode.

Anodic Commodity Polymer Recycling: The Merger of Iron-Electrocatalysis with Scalable Hydrogen Evolution Reaction.

Plastics are omnipresent in our everyday life, and accumulation of post-consumer plastic waste in our environment represents a major societal challenge. Hence, methods for plastic waste recycling are in high demand for a future circular economy. Specifically, the degradation of post-consumer polymers towards value-added small molecules constitutes a sustainable strategy for a carbon circular economy. Despite of recent advances, chemical polymer degradation continues to be largely limited to chemical redox agents or low energy efficiency in photochemical processes. We herein report a powerful iron-catalyzed degradation of high molecular weight polystyrenes through electrochemistry to efficiently deliver monomeric benzoyl products. The robustness of the ferraelectrocatalysis was mirrored by the degradation of various real-life post-consumer plastics, also on gram scale. The cathodic half reaction was largely represented by the hydrogen evolution reaction (HER). The scalable electro-polymer degradation could be solely fueled by solar energy through a commercially available solar panel, indicating an outstanding potential for a decentralized green hydrogen economy.

Assessing the Impact of Shredded Polyethylene Terephthalate (PET) Post-Consumer Plastic as a Partial Replacement for Coarse Aggregates in Unreinforced Concrete.

This study investigates the feasibility of incorporating shredded polyethylene terephthalate (PET) post-consumer plastic waste as a partial replacement for coarse aggregates in unreinforced concrete such as masonry blocks. Standard concrete blocks were produced with varying PET content (0%, 5%, 25%, 35%, 50%) and tested for workability, air content, density, compressive strength, flexural strength, and thermal conductivity. Results indicated that replacing up to 25% of traditional aggregates with PET maintains adequate compressive strength for non-load-bearing applications and enhances thermal insulation by reducing the thermal conductivity from 0.7 W/m·°K to 0.27 W/m·°K at 25% replacement level, representing a significant improvement of approximately 61%. Higher PET content (35-50%) resulted in reduced structural integrity but improved insulation, suggesting its suitability for non-structural applications. This research highlights the potential of using PET plastic waste in unreinforced concrete, promoting sustainable construction practices by reducing plastic waste and conserving natural resources.

Compositional Analysis and Mechanical Recycling of Polymer Fractions Recovered via the Industrial Sorting of Post-Consumer Plastic Waste: A Case Study toward the Implementation of Artificial Intelligence Databases.

Nowadays, society is oriented toward reducing the production of plastics, which have a significant impact on the environment. In this context, the recycling of existing plastic objects is currently a fundamental step in the mitigation of pollution. Very recently, the outstanding development of artificial intelligence (AI) has concerned and continues to involve a large part of the industrial and informatics sectors. The opportunity to implement big data in the frame of recycling processes is oriented toward the improvement and the optimization of the reproduction of plastic objects, possibly with enhanced properties and durability. Here, a deep cataloguing, characterization and recycling of plastic wastes provided by an industrial sorting plant was performed. The potential improvement of the mechanical properties of the recycled polymers was assessed by the addition of coupling agents. On these bases, a classification system based on the collected results of the recycled materials' properties was developed, with the aim of laying the groundwork for the improvement of AI databases and helpfully supporting industrial recycling processes.

Impacts of washing and deodorization treatment on packaging-sourced post-consumer polypropylene

AbstractEmerging legal requirements will likely considerably heighten demand for high-quality recycled raw materials for e.g., packaging and automotive applications; key EU legislation mandates recycling as the future end-of-life option for municipal solid plastic waste. Yet recycled plastic use remains low due to safety concerns, undesirable aesthetic, olfactory, and mechanical properties, mainly attributable to contaminants present in recyclates. Advanced treatment options for recovered polypropylene (PP) packaging and the impact of such treatments on the polymer are currently poorly documented. We investigated the effectiveness of hot/cold washing and hot air devolatilization treatments in removing volatile substances from residential post-consumer PP plastic waste to improve its scope of application and value and to assess possible side effects on mechanical and processing parameters. Cold- and hot-washed recyclates exhibited similar contaminant levels and most substances were removed within 7 h. The recycling procedure had no adverse effects on mechanical or processing parameters although reprocessing caused polymer degradation, indicated by decreasing viscosity, elongation at break, and tensile strength. Washing and hot air devolatilization treatment of plastic wastes improve their scope of application and value by enhancing mechanical properties and considerably reducing the amounts of odorous substances, but is often not suited to high-quality applications, such as packaging. The dominance of packaging waste and strict legislation on food-grade recyclate applications will make widespread recyclate use challenging since it represents the primary use of plastic. Recyclate must consequently be extensively utilized in non-food contact applications until advances in waste sorting, washing, and devolatilization yield less contaminated recyclates with improved properties.

Integrating thermodynamic and kinetic approaches for the design of effective and sustainable PET chemical upcycling systems

Understanding and optimizing the individual contributions of recycling process components are critical in the development of effective and sustainable upcycling systems. Herein, each process component, i.e., alcohol, co-solvent, Lewis acid, and reaction conditions, is newly and holistically assessed for the alcohol-based conversion of postconsumer polyethylene terephthalate (PET) to terephthalic acid (TPA) and its precursors by integrating thermodynamic and kinetic considerations. First, an analysis based on the Flory-Huggins interaction parameter (χ1,2) establishes the importance of co-solvents in the depolymerization process due to reduction of thermodynamic potential. Second, a kinetic analysis of the catalyst component proves the vitality of the solubility of the Lewis acid source for efficient PET deconstruction. In addition, further validation experiments determine methanol as the most effective option in tandem alcoholysis given its reduced steric hindrance and relatively higher nucleophilicity, whereas process optimization tests suggest the existence of an optimum methanol molar ratio (XMetOH) of 0.16 and operation at 50 °C to realize TPA yields that exceed 90 % within 15 min across various pure and mixed PET feedstocks. Selection and implementation of greener solvents in the process is also found to reduce co-solvent based emissions by 96.3 % whilst retaining comparable monomer production efficiency. Overall, the implementation of thermodynamic considerations and kinetics-based understanding of roles played by each component is found to boost the overall depolymerization process, and the integration of these thermodynamic and kinetic approaches provides a unified avenue for optimizing and developing sustainable recycling processes for post-consumer plastic waste.

Standoff Identification of Plastic Waste Using a Low-Cost Compact Laser-Induced Breakdown Spectroscopy (LIBS) Detection System.

We report the standoff/remote identification of post-consumer plastic waste by utilizing a low-cost and compact standoff laser-induced breakdown spectroscopy (ST-LIBS) detection system. A single plano-convex lens is used for collecting the optical emissions from the plasma at a standoff distance of 6.5 m. A compact non-gated Czerny-Turner charge-coupled device (CCD) spectrometer (CT-CCD) is utilized to analyze the optical response. The single lens and CT-CCD combination not only reduces the cost of the detection system by tenfold, but also decreases the collection system size and weight compared to heavy telescopic-based intensified CCD systems. All the samples investigated in this study were collected from a local recycling plant. All the measurements were performed with only a single laser shot which enables rapid identification while probing a large number of samples in real time. Furthermore, principal component analysis has shown excellent separation among the samples and an artificial neural network analysis has revealed that plastic waste can be identified within ∼10 ms only (testing time) with accuracies up to ∼99%. Finally, these results have the potential to build a compact and low-cost ST-LIBS detection system for the rapid identification of plastic waste for real-time waste management applications.

Chemical Recycling of Mixed Polyolefin Post-Consumer Plastic Waste Sorting Residues (MPO323)-Auto-Catalytic Reforming and Decontamination with Pyrolysis Char as an Active Material.

Mixed plastic packaging waste sorting residue (MPO323) was treated by thermal pyrolysis to utilize pyrolysis oil and char. The pyrolysis oil was found to contain aromatic and aliphatic hydrocarbons. The chlorine and bromine contents were as high as 40,000 mg/kg and 200 mg/kg, respectively. Additionally, other elements like sulfur, phosphorous, iron, aluminum, and lead were detected, which can be interpreted as impurities relating to the utilization of oils for chemical recycling. The pyrolysis char showed high contents of potentially active species like silicon, calcium, aluminum, iron, and others. To enhance the content of aromatic hydrocarbons and to reduce the level of contaminants, pyrolysis oil was reformed with the corresponding pyrolysis char to act as an active material in a fixed bed. The temperature of the reactor and the flow rate of the pyrolysis oil feed were varied to gain insights on the cracking and reforming reactions, as well as on performance with regard to decontamination.

Decomposition and fragmentation of conventional and biobased plastic wastes in simulated and real aquatic systems

AbstractPlastics play a crucial role in our daily lives. The challenge, however, is that they become waste and contribute to a global environmental problem, increasing concerns about pollution and the urgent need to protect the environment. The accumulation and fragmentation of plastic waste, especially micro- and nanoplastics in aquatic systems, poses a significant threat to ecosystems and human health. In this study, the decomposition and fragmentation processes of conventional and biobased plastic waste in simulated water bodies (waters with different pH values) and in real water systems (tap water and seawater) are investigated over a period of one and six months. Three types of plastic were examined: thermoplastic polyethylene terephthalate and thermoset melamine etherified resin in the form of nonwovens and biobased polylactic acid (PLA) in the form of foils. Such a comprehensive study involving these three types of plastics and the methodology for tracking degradation in water bodies has not been conducted before, which underlines the novelty of the present work. After aging of the plastics, both the solid fraction and the leachate in the liquid phase were carefully examined. The parameters studied include mass loss, structural changes and alterations in functional groups observed in the aged plastics. Post-exposure assessment of the fragmented pieces includes quantification of the microplastic, microscopic observations and confirmation of composition by in situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. The leachate analysis includes pH, conductivity, turbidity, total carbon and microplastic size distribution. The results highlight the importance of plastic waste morphology and the minor degradation of biobased PLA and show that microfibers contribute to increased fragmentation in all aquatic systems and leave a significant ecological footprint. This study underlines the crucial importance of post-consumer plastic waste management and provides valuable insights into strategies for environmental protection. It also addresses the pressing issue of plastic pollution and provides evidence-based measures to mitigate its environmental impact. Graphical abstract

A Highly Sustainable Supramolecular Bioplastic Film with Superior Hydroplasticity and Biodegradability.

Massive accumulation of postconsumer plastic waste in eco-system has raised growing environmental concerns. Sustainable end-of-life managements of the indispensable plastic are highly demanding and challenging in modern society. To relieve the plastic menace, herein we present a full life cycle sustainable supramolecular bioplastic made from biomass-derived polyelectrolyte (chitosan quaternary ammonium salt, QCS) and natural sodium fatty acid (sodium laurate, SL) through solid-phase molecular self-assembly (SPMSA), by which the QCS-SL complexes, precipitated from mixing the aqueous solutions, self-assemble to form bioplastic film by mildly pressing at room temperature. The QCS-SL bioplastic films display superior hydroplasticity owing to the water-activated molecular rearrangement and electrostatic bond reconstruction, which allows facile self-healing and reprocessing at room temperature to significantly extend the service lifetime of both products and raw materials. With higher water content, the dynamic electrostatic interactions and precipitation-dissolution equilibrium endow the QCS-SL bioplastic films with considerable solubility in water, which is promising to mitigate the plastic accumulation in aquatic environment. Because both QCS and SL are biocompatible and biodegradable, the dissolved QCS-SL films are nontoxic and environmentally friendly. Thus, this novel supramolecular bioplastic is highly sustainable throughout the whole life cycle, which is expected to open a new vista in sustainable plastic materials.

Industrial and Laboratory Technologies for the Chemical Recycling of Plastic Waste.

Synthetic polymers play an indispensable role in modern society, finding applications across various sectors ranging from packaging, textiles, and consumer products to construction, electronics, and industrial machinery. Commodity plastics are cheap to produce, widely available, and versatile to meet diverse application needs. As a result, millions of metric tons of plastics are manufactured annually. However, current approaches for the chemical recycling of postconsumer plastic waste, primarily based on pyrolysis, lag in efficiency compared to their production methods. In recent years, significant research has focused on developing milder, economically viable methods for the chemical recycling of commodity plastics, which involves converting plastic waste back into monomers or transforming it into other valuable chemicals. This Perspective examines both industrial and cutting-edge laboratory-scale methods contributing to recent advancements in the field of chemical recycling.

Aplicações da nanotecnologia em embalagens inteligentes para alimentos

The growing demand for food has contributed to the increase in plastic waste, mainly from packaging. In 2020, only 23.1% of post-consumer plastic waste was recycled in Brazil, resulting in a significant amount of non-biodegradable waste that remains in the environment for long periods, affecting human health and the environment. Most of this waste comes from traditional petroleum-based food packaging, such as polyethylene, polypropylene, and polystyrene. It is estimated that annually, 31.9 million tons of plastic waste enter the environment, with a considerable portion contaminating the oceans. Despite these environmental challenges, the demand for plastics is expected to continue to grow to meet society's resource-efficient needs (FERREIRA et al., 2022).

Transforming a mixture of real post-consumer plastic waste into activated carbon for biogas upgrading

Plastic waste management is a current environmental issue that demands potential solutions since complete mechanical recycling is limited to the complexity and feasibility regarding the quality and purity of plastic waste. Pyrolysis has emerged as a reasonable solution for the recycling of those fractions that are not further suitable for recycling. Although the implementation of this technology is mature, the generated solid fraction or char has not been completely inserted in the closed loop of plastic recycling. This work explores the possibility of using the carbonaceous char as a precursor for the preparation of porous activated carbons for environmental application as CO2 adsorbent and biogas upgrading. The effect of the pyrolysis temperature (450 or 500 ºC) on the obtained chars has been assessed for the benefits in the second stage of chemical activation, exploring the possibility of the use of diverse chemical agents. The composition, textural, and surface properties of the porous materials were characterized. N2 isotherms showed that the char prepared at 500 ºC provided the best textural properties with a performance of K2CO3 ∼ KOH > Na2CO3 > NaOH > ZnCl2 > FeCl3. Isotherms of CO2 adsorption showed that the activation with K2CO3 displayed the best uptake (130.2 mg g−1 at 273 K), closely followed by KOH (125.0 mg g−1 at 273 K), also confirmed by dynamic tests in a fixed bed column configuration. The uptake was well correlated with the ultramicropore volume and the oxygenated functional groups. The CO2 and CH4 adsorption were studied either in static or dynamic assays. The behavior of the sample activated with K2CO3 was studied in detail in column tests, suggesting that the activated material exhibits promising behavior for biogas upgrading.

Evaluating the economic and environmental benefits of deploying a national-scale, thermo-chemical plastic waste upcycling infrastructure in the United States

Emerging chemical technologies can upcycle plastic waste by producing high-value polymers and other products. In this work, we study the economic and environmental benefits of deploying an upcycling infrastructure in the continental United States for producing low-density polyethylene (LDPE) and polypropylene (PP) from post-consumer plastic waste. Our analysis is based on a computational framework that integrates techno-economic analysis, life-cycle assessment, and value chain optimization. Our results demonstrate that the infrastructure could generate a market of nearly 20 billion USD per year and that this market is robust to various externalities. Our analysis also indicates that the infrastructure can achieve a plastic-to-plastic degree of circularity of 34% relative to residential plastic waste production, and leads to significant environmental benefits over alternative waste disposal methods, including 69%–75% lower greenhouse gas emissions than waste-to-energy systems and 38 million tonnes of avoided landfill waste per year.

Microwave-assisted catalytic gasification of mixed plastics and corn stover for low tar, hydrogen-rich syngas production

The challenge for efficient management of post-consumer plastic and biomass waste has grown over the past few decades due to their dramatic increases. In comparison to conventional gasification, microwave-assisted co-gasification of plastics and corn stover offers many benefits, including increased H2 yield and gas components compared to unfavorable char/tar. Nonetheless, for future commercialization of the process and ease of product separation, further reduction of the undesirable tar is necessary, which can be achieved over the catalytic route. In this work, we studied the catalytic effect of magnetite for microwave-assisted co-gasification of corn stover and plastic to make syngas with higher H2 and lower tar selectivity over non-catalytic conditions. A 1:1:1 ratio of plastic-corn stover-magnetite was used to evaluate the reaction parameters such as temperature, space velocity, heating media, and catalytic cycles under gasification conditions. In comparison with the microwave non-catalytic route, a 100% increase in the total H2 yield with 76% higher H2 production efficiency (mmol/kWh) was achieved in the presence of the magnetite catalyst, while reducing the overall tar formation from 9% to 2%. When magnetite was reduced in situ during the reaction, it coupled with microwave and delivered oxygen radicals that cracked down plastic and corn stover intermediates generated from the synergistic effect under microwave heating. Soon after the oxygen transfer process initiated, magnetite reached its final oxidation state consisting of microwave-active Fe and Fe3C phases that continued coupling with microwaves along with the generated graphitic carbon to maintain the heat necessary to further reduce the generated tar and make additional gaseous products, as confirmed by XRD, Raman, and TGA analyses.

Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

The valorization of post-consumer mixed plastics in pyrolysis processes represents an abundant reservoir of carbon that can be effectively converted into useful chars. This process not only holds appeal in terms of improving plastic waste concerns but also contributes to the reduction of greenhouse gas emissions, thus aligning with the principles of a circular economy paradigm. In this study, the char produced from the pyrolysis of post-consumer mixed plastic waste has been activated with Na2CO3, KOH, NaOH, and K2CO3 to improve the textural, structural, and composition characteristics, leading to improved adsorption capability. These characteristics were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, elemental and immediate analysis, and X-ray photoelectron spectroscopy. The developed surface area (SBET) was 573, 939, 704 and 592 m2 g−1 for Na2CO3, KOH, NaOH and K2CO3 activated carbons, respectively. These activated chars (ACs) were tested for the adsorption of heavy metals in both synthetic waters containing Pb, Cd, and Cu and industrial wastewater collected at an agrochemical production plant. Na2CO3-AC was the best performing material. The metal uptake in synthetic waters using a batch set-up was 40, 13 and 12 mg g−1 for Pb, Cd and Cu. Experiments in a column set-up using Na2CO3-AC resulted in a saturation time of 290, 16, and 80 min for Pb, Cd, and Cu synthetic waters, respectively, and metal uptakes of 26.8, 4.1, and 7.9 mg g−1, respectively.The agrochemical effluents, containing mainly Cr, Cu, Mn, and Zn were tested in a plug-flow column. The metal uptake notably decreased compared to synthetic water due to a competition effect for active sites.

Impact of Metal Impregnation of Commercial Zeolites in the Catalytic Pyrolysis of Real Mixture of Post-Consumer Plastic Waste

This work reports the study of the catalytic pyrolysis of rejected plastic fractions collected from municipal solid waste whose mechanical recovery is not plausible due to technical or poor conservation issues. The chemical recycling using catalytic pyrolysis was carried out over commercial zeolites formulas, i.e., HY and HZSM-5, in which Ni or Co metals were deposited at two different loadings (1 and 5%, wt.). The presence of these transition metals on the zeolitic supports impacted the total production of compounds existing in the liquid oil. The samples were characterized in terms of structural, chemical, and morphologic properties, and the production of different fuel fractions (gasoline, light cycle oil, and heavy cycle oil) was correlated with a combined parameter defined as a ratio of Acidity/BET area.