"Report on the adsorption and/or catalytic performances of porous solids derived from biomasses valorization and non-recyclable plastic wastes [GRIP - D2.7]

1 NODES – Nord Ovest Digitale e Sostenibile FLAGSHIP PROJECT GRIP SPOKE 2 –GREEN TECHNOLOGIES AND SUSTAINABLE INDUSTRIES DELIVERABLE D2.7 “Report on the adsorption and/or catalytic performances of porous solids derived from biomasses valorization and non-recyclable plastic wastes” REPORTING PERIOD Period covered: from M8 to M 32 Periodic report date and version: 26-09-2025 Deliverable # Responsible Bisio-Marchese RM2 Responsible Arlorio This report is part of the project NODES which has received funding from the MUR – M4C2 1.5 of PNRR funded by the European Union - NextGenerationEU (Grant agreement no. ECS00000036) 2 Glossary Definition Hub Coordinator (HC) The Hub Coordinator represents the single point of contact for the implementation of the innovation ecosystem towards the MUR. It carries out the management and coordination activities of the innovation ecosystem, receives the fundings, verifies, and transmits to the MUR the reporting of the activities carried out by the Spoke and their affiliates. National Recovery and Resilience Plan (NRRP) This document uses the Italian acronym for the NRRP, which is PNRR (Piano Nazionale della Ripresa e Resilienza) Research Program Manager The person who will be the responsible for the overall scientific contents of the NODES project. The NODES will appoint the Research Program Manager. It refers to “Responsabile del Programma di Ricerca” in the MUR’s Call of proposal for “Ecosistemi di Innovazione” NODES’ Research and innovation program NODES’ Research and Innovation program is articulated in specific programs for each Spoke, with the aim to promote and support applied research on topics consistent with the Intelligent Specialization Strategy, with the guidelines of the 2021-2027 partnership agreement scheme, with regional operational plans and regional and national research and innovation priorities. Although NODES’ Spokes are concentrated on different themes, they will organize their activities and actions within a common framework – NODES’ Booster Methodoloy Spoke Coordinator The University in charge of coordinating the Spoke’s ecosystem. It refers to “Spoke” in the MUR’s Call of proposal for “Ecosistemi di Innovazione” Spoke Data Manager The person who will be the responsible for the monitoring and management of data generated at the Spoke level. The Spoke Coordinator will appoint the Spoke Data Manager. Spoke Partner The entity associated to the Spoke Coordinator. It can be an Innovation Cluster, Competence Center, Research Center related to the Spoke’s ecosystem and contributes to achieve objectives and impact under the Spoke’ leadership and management. It refers to “soggetti affiliati” in the MUR’s Call of proposal for “Ecosistemi di Innovazione”. Spoke Project manager The person who will be the responsible for the management, coordination and progress of the project at the Spoke level. The Spoke Coordinator will appoint the Spoke Project Manager. Spoke research and innovation program NODES’ Research and Innovation program is articulated in specific programs for each Spokes. The spoke will leverage a consolidated collaboration with leading private and public companies and will focus the applied research activity on technological domains and applications that can favour the integration of SMEs into new value chains. Spoke Scientific and Technical Manager The person who will be the responsible for the overall scientific contents of the project at the Spoke level. The Spoke Coordinator will appoint the Spoke Scientific and Technical Manager. Spoke Stakeholders Committee (SC) Consultation structure formed by relevant stakeholders (Government, universities, companies, civil society, third sector, etc.) Spoke Thematic General target focus and domain of the Spoke research. Spoke Topics Specific areas/lines of development within the Spoke. Spoke Work Package Leader At the Spoke level, Work Packages (WPs) will be organized by WP leaders, who will be responsible for performance evaluation and reporting. Flagship Project Main research project at the Spoke level with the goal of prototyping, testing, demonstrating the research activities towards higher TRLs. 3 List of Deliverables D. No Name Type Dissemina tion Level Delivery Date (actual) [number] [name] [R — Document, report] [DEM — Demonstrator, pilot, prototype] [DEC — Websites, patent filings, videos, etc] [DATA — data sets, microdata, etc] [DMP — Data Management Plan] [ETHICS] [SECURITY] [OTHER] [PU — Public] [SEN — Sensitive] [R] [C] [S] [dd/mm/yyyy] D2.1 Data about chemical and nutritional profiling of raw wastes and by products R PU D2.2.1 On line lab-scale technical multidevice for waste processing* Other (material) PU D2.2.2 Delivery of protocols (lab-scale) ready to scale-up the production of new high-value material (in collaboration with Companies) R PU D2.3.1 New data about valorized matrices characterization and high value products R PU D2.3.2 New characterized ingredients/materials for food, nutraceuticals, pharma and cosmetic applications Other (material) PU D2.4.1 New data about sustainable production of new materials from biomasses R PU D2.4.2 New characterized materials from biomasses Other (material) PU D2.5.2 Porous sorbents from biomasses valorization Other (material) PU D2.6.1 New material produced at pilot scale ready to the formulation or co-formulation (in collaboration with Companies) Other (material) PU D2.6.2 New well characterized process and formulated pilot-products (in collaboration with Companies) R/Other (Material) PU D2.7 Report on the adsorption and/or catalytic performances of porous solids derived from biomasses valorization and nonrecyclable plastic wastes R PU 29/09/2025 4 A) INTRODUCTION The work and the outcomes reported in this Deliverable are related to the activity scheduled in Task 2.2 (focusing on Sub-Task 2.2.4). The main goal was the evaluation of the performances of the porous material (as described in D2.5.2), as well as the evaluation of their potential catalytic activity. B) ROLE OF PARTNERS The role of the Partners involved in this activity (DiSSTE-UPO) was primarily to assess the usefulness of the new porous materials produced, in terms of new tool for environmental applications. C) EXPLANATION OF THE WORK CARRIED OUT AND OVERVIEW OF THE PROGRESS The properties of the porous and layered solids prepared from the biogenic silica extracted from rice husks described in the D2.5.2 “Porous sorbents from biomasses valorisation” were thoroughly investigated using a multi-technique approach with the help of a variety of analytical instruments. In addition, each product derived from the conversion of the rice husk to the silicate solution was analysed to evaluate its properties. Particularly, X-ray powder diffraction (PXRD) and FT-Infrared spectra of rice husks before and after thermal & acidic treatments confirmed: i) the formation of the amorphous siliceous structure, mainly constituted by siloxane (Si-O-Si) bonds and lacking a long-range order; ii) the disappearance of the signals related with the organic moieties present in rice husk (lignin, cellulose, hemicellulose) and of the phases associated with metal oxide impurities (e.g. CaO, Na2O, K2O) generated during the calcination and removed upon the acid process. The acid treatment also acts as surface activator, increasing the content of reactive isolated silanol groups (Si-OH), as suggested by FT-Infrared spectroscopy. Morphological analyses using FE-SEM microscope further confirmed the transformation of rice husks into a solid enriched with silicon dioxide, with the formation of small round-shaped particles in aggregates typical of amorphous silica. 29Si HR NMR spectra of the sodium silicate solutions reveal the nature of the silicon species generated in water upon the alkaline dissolution of rice husk ashes. Si nuclei are mainly present in the form of highly reactive ortho silicic acid (i.e., Si(OH)4), and their distribution was found to be compatible with that those formed in the synthesis of porous silicas and layered clays when classical fumed silica or alkoxysilanes are used. In the case of the mesoporous MCM-41 and SBA-15 of biogenic origin (labelled RH-nanoMCM and RH-SBA-15, respectively), PXRD demonstrated the formation of their hexagonally long-range ordered mesoporous structure, with the presence in their diffractograms of the characteristic 5 reflections of (100), (110), (200) and (210) crystal planes of parent porous silicas. HR-TEM micrographs of MCM-41 showed particles having a mean diameter of 20-30 nm with hexagonally ordered mesopores , due to the effect of Pluronic F127 micelles on the suppression of the particle growth at nanoscale level. In water suspensions, these particles tend to form aggregates between 40-60 nm with a highly negative net surface charge (-35 mV at pH < 6) due to deprotonation of Si-OH groups, as observed from DLS and -potential analyses. The surface charge of the solid adsorbent is a crucial aspect in adsorption studies, as it strongly influences the nature of the noncovalent interactions with guest molecules (e.g. organic dyes), as well as the adsorption mechanism involved. SBA-15 showed micrometric particles (approx. 500-1000 m) with longrange mesopores arrange in a hexagonal pattern in the TEM micrographs, while in water the particles aggregate with sizes up to 1.5 m. To further evaluate their potential adsorption performance, which are closely linked to their textural properties, N2 adsorption-desorption isotherms at 77K and pore size distributions were measured, from which information on specific surface areas (SSABET), pore volumes and thickness of the silicate walls were calculated (Tab. 1). SSABET [m2·g-1] Pore volume [cc·g-1] Wall thickness [Å] V micro [<20 Å] V meso [20-500 Å] V macro [>500 Å] V tot RH-nanoMCM 1050 / 1.57 0.09 1.66 3.30 RH-SBA-15 670 / 1.14 / 1.14 28.90 Tab 1. SSABET, pore volumes and wall thicknesses of biogenic MCM41 and SBA-15 porous solids. The N2 physisorption isotherms of both biogenic MCM-41 and SBA-15 correspond to a IVa model of the IUPAC classifications, typical of mesoporous materials. MCM-41 displayed two hysteresis loops, H1 and H3 type, typical of samples with cylindrical mesopores with uniform size (approx. 42 Å) and with the presence of meso-/macropores. The H1 hysteresis loop was also observed in the isotherm of SBA-15, at higher relative pressure than MCM-41 which is indicative of larger mesopores (approx. 87 Å). The pore size distribution of SBA-15 also revealed the presence of other mesopore families, between 45-75 Å. MCM-41 is characterized by a SSABET of 1050 m2/g and a total pore volume of 1.66 cc/g, whereas SBA-15 shows a lower SSABET of 670 m2/g with a total pore volume of 1.14 cc/g. The thickness of the silicate walls of SBA-15 sample was found to be 28.90 Å, while in MCM-41 they are narrower (3.30 Å), which is consistent with literature studies on the structural features of parent samples. The saponite clay of biogenic origin showed the typical structural features of layered hydrous phyllosilicates in the PXRD diffractogram, characterized by reflections associated to (001)- 6 (020),(110)-(004)-(130),(201)-(311)-(060) crystal planes which are indicative of the 2:1 trioctahedral structure of smectite clays consisting of two tetrahedral sheets enclosing a central octahedral sheet (Fig. 1). This confirmed the formation of the desired lamellar material. FE-SEM and HR-TEM micrographs collected on the saponite showed the presence of structures with sheet-like or lamellar morphology, with formation of tactoids of different size, and with an average length of the 2D-lamellae of approx. >100 nm (Fig. 1). Due to the H2O/Si ratio used during the synthetic procedure (= 20) and the adoption of the sodium silicate solution as a source of silicon, sodium and almost all the total synthesis water, the cation-exchange capacity of the solid reached a very high value for this kind of clays (more than 100 meq/100 g). This parameter is extremely important in the field of removing metal cations from polluted water (e.g. heavy metals or precious metals such as rare earths): the higher the value, the greater the capacity to sequester these analytes from contaminated water and, therefore, to purify the water itself. Fig. 1. Graphical representation of the layered structure of biogenic saponite clay (left) and FE-SEM micrograph of the clay under high magnification (right), showing the lamellar morphology of the particles. Subsequently, the material was submitted to a thoroughly investigation of its acidity features through a combination of FT-Infrared and solid-state NMR spectroscopies, in order to evaluate its potential catalytic properties. Indeed, Brønsted acid sites are often used in the heterogeneous catalytic field, for example in the decomposition of hazardous organic substances into non-toxic products or in the conversion of specific molecules into other useful compounds. In this sense, clay materials possess Brønsted acid sites generated from the isomorphic replacement of silicon centres with aluminium during the synthesis step of the material itself. The saponite solid prepared from rice husk exhibited a significant Brønsted acidity (up to 0.30 mmol/g H+) due to 7 the high isomorphic substitution of Si(IV) by Al(III) in its tetrahedral structural layers, with a AlIV (T) / AlVI (O) ratio of approx. 20 (parent saponites normally have values between 2-6), as observed from FT-Infrared spectroscopy using NH3(g) as a probe to estimate the amount of Brønsted acid sites and from solid-state NMR measurements on 29Si and 27Al nuclei (Fig. 2). To accomplish this, in particular, FTIR analysis of adsorbed NH3(g) were carried out on the pristine saponite and two postsynthesis derivative samples, one with Na+ and one with H+ ions “inserted” in the clay’s interlayer gallery through cation-exchange procedures, to evaluate the effect of intercalated cations on the acidity of the material produced. By analysing the spectra of NH3(g) adsorbed and then evacuated for each sample and integrating the band centred around 1450 cm-1, associated with the asymmetric bending modes of NH4+ formed by interaction of gaseous NH3 with the Si-O(H+)-Al sites, acid sites density values of 0.14, 0.06 and 0.30 mmol/g H+ were calculated for saponite, Na+- saponite and H+-saponite clay, respectively. The high acidity value of this last sample, in particular, is among the highest found amid parent H+-exchanged smectite clays studied in the literature. The high surface acidity of a solid, as demonstrated by our samples, is generally a very important parameter in the field of catalysis, since acidity can play a significant role in the breakdown of certain contaminants (such as pesticides, highly toxic organic pollutants, etc.) in water through hydrolytic reactions or in more controlled environments (e.g., in anhydrous solvents such as ethyl acetate...), often in combination with oxidizing agents such as hydrogen peroxide to promote oxidative degradation processes into harmless by-products. 8 Fig. 2. A) FTIR spectra of NH3 (50 mbar) adsorbed and then evacuated at IR beam temperature for 90 min on biogenic saponite (SAP-R) and on derived solids exchanged with Na+ (Na-SAP-R) and H+ (H-SAP-R) ions. Samples were outgassed at 623 K for 3 h prior the analyses; spectra are reported after subtraction of the bare samples. A graphical representation of a Brønsted acid site Si-O(H+)-Al is shown below the graph. B) Quantitative 27Al HPDEC solid-state NMR spectrum of SAP-R, displaying the resonance peaks of tetrahedral (T) and octahedral (O) aluminium species. Finally, from a textural point-of-view, saponite presented a IV(a) model isotherm with a H4 hysteresis loop indicative of mesoporous samples containing aggregates of lamellae (that generate such mesoporosity). The clay showed a SSABET of 158 m2/g, a total pore volume of 0.144 cc/g and an unordered pore size distribution with families of mesopores from 15-210 Å. These values are consistent with those found for classical synthetic saponites studied in the literature. The biogenic materials prepared and characterised as described above were tested in a variety of environmental applications, from the removal of organic dyes and precious/heavy metals from real and simulated contaminated water (supplied by water companies in the Piedmont region, Italy) to use in the catalytic degradation of pesticides in aqueous and anhydrous environments. Furthermore, in collaboration with other NODES partners from the Universities of Turin and Pavia, experiments were conducted on the adsorption and exchange capacities of a series of organic (IPA, PCB, dyes, etc.) and inorganic (metal cations) contaminants from simulated and real contaminated water by biogenic solids. Most of these studies have been and are currently being conducted within the framework of RM4 “Wastewater Treatment Platform”, Task 4.2 “Testing of materials produced for the removal of metal ions and for the adsorption/decomposition of target molecules used as models of environmental pollutants”, in whose reports more detailed information can be found. In addition, mesoporous silica monoliths functionalised with organic chelates (e.g., DTPA, EDTA, citrate), prepared using optimised synthesis procedures in the laboratories of the DiSIT Department of the UPO in Alessandria (Italy), were tested for the removal of various paramagnetic metal ions (Gd³⁺, Co²⁺, Cu²⁺, Ni²⁺) from simulated contaminated water matrices. These experiments were also conducted to evaluate the procedures later adopted with biogenic solids for similar purposes, such as the use of non-traditional techniques like 1H NMR relaxometry (at 10 MHz, 25 °C, pH 5) to evaluate the removal of metal ions in real time without any pretreatment of the samples. The silica monoliths were able to remove high amounts of divalent and trivalent metal ions from water after 24 hours of contact testing, up to approximately 18.5 mg/g 9 in the case of Cu2+ ions. Regeneration experiments were conducted under slightly acidic conditions to evaluate the reusability of these solids and the possibility of recovering the precious metals for various applications, in anticipation of possible future commercial uses. The interplays between RM2 and RM4 (as previously described) activities confirm the significant degree of interdisciplinarity of the work within the GRIP Project, as expected.