Rui M. Novais

University of Aveiro | UA · Department of Materials and Ceramics Engineering

Innovative and multifunctional building materials with low embodied energy and reduced CO2 emissions have attracted considerable attention. Herein, a comprehensive comparison between the use of cork and commercial synthetic aggregates (expanded vermiculite, expanded polystyrene (EPS), and lightweight expanded clay (Leca®)) in the production of geop...

Cork composites have shown excellent potential in impact mitigating systems. Their sustainability greatly surpasses the currently used solutions. In addition, recent advances in developing cork composites with shear thickening fluids (STFs) have demonstrated exciting results for impact mitigation. This study explores different STF formulations base...

Cork is a renewable and sustainable material, highly porous and lightweight. We valorised waste cork and recycled wine stoppers to make pyrolysed/carbonised solid cork, for use as economic and sustainable microwave (MW) absorbers at the microwave X-band (8-12 GHz), without binder or additives. Although cork is already a very lightweight material (0...

Spent fluid catalytic cracking (FCC) catalyst is a waste from oil industry generated in very high amounts globally, being a major environmental burden as it is mostly landfilled. The direct use of this waste in wastewater treatment applications is rare, and the present study aims to fill the existing research gap. This is the first systematic inves...

The synthesis and growth of carbon nanotubes (CNTs) on red mud containing alkali activated materials (AAMs) envisioned for wastewater treatment applications is reported for the first time. This novel avenue takes advantage of the iron present in the red mud (RM), a massively produced industrial waste, promoting the growth of CNTs and avoiding the n...

This review article discusses the potential of porous geopolymers as a promising approach for the removal of various contaminants, including heavy metals, dyes, drug residues, pharmaceuticals, and pesticides from aqueous solutions. Additionally, this review provides an overview of the recent preparation methods of geopolymers and their characterist...

Lightweight geopolymers have been researched and used in specific applications due to their differentiated properties and, particularly, due to the lower environmental impacts in their manufacture, mainly associated with the use of raw materials with a low environmental impact and the reduction in greenhouse gas emissions. In this study, light geop...

In this work, lightweight geopolymer composites were produced by varying the content of expanded perlite and geopolymer spheres, used as aggregates. Firstly, highly porous geopolymer spheres containing mostly red mud as the solid precursor were produced, which leads to the valorization of significant amounts of this metallurgical waste. Then, the i...

In this study, metakaolin and red mud were used as solid precursors to synthesize geopolymer monoliths coupling hierarchical porosity with suitable compressive strength (4.5 MPa) enabling their use as bulk-type (not powders) sorbents. Then, the lead removal ability of these novel materials was investigated under various conditions. The present work...

This work reports a novel management strategy for a hazardous waste derived from the alumina industry, known as bauxite residue or red mud (RM). Herein, and for the first time, RM-containing porous structures were prepared by direct ink writing (DIW) and then used directly to extract methylene blue (MB) from synthetic wastewater. The lattices were...

The chemical foaming technique is possibly the most common method of producing porous geopolymers. Despite this, to date, the role of the content and type of surfactant on the pore size distribution of porous geopolymers is not fully perceived, as constant surfactant dosages are usually employed. In addition, the comparison of literature studies is...

The demand for products derived from the pulp and paper industry has been increasing over the past years and is projected to further increase over the coming decades. Although being one of Portugal’s most relevant industrial activities, contributing to nearly 2.3% of the GDP, this sector is known to generate a variety of wastes including fly ashes,...

Alkali-activated materials are generally considered a more sustainable alternative to Portland cement binders. This derives not only from the use of solid wastes as precursors, but also from the low temperatures required for their synthesis. However, to increase the environmental advantages of these materials, alternative activators should be explo...

Environmentally conscious biomorphic ceramics (Ecoceramics) are a new class of material manufactured from renewable resources and wastes. Sustainable cork wastes were pyrolysed, and this activated carbon template infiltrated with a sol-gel precursor (from aqueous green-chemistry) to form TiO2 on heating in air, with the honeycomb microstructure of...

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The foams’ selectivity towards lead, cadmium, zinc, and copper ions was evaluated in single, binary, and multicompon...

Alkali-activated materials (AAMs) are an emerging alternative to the use of common adsorbents in wastewater treatment applications for both environmental and technical reasons. Herein, the most relevant and recent research focusing the use of AAMs as adsorbents to depollute aqueous solutions is summarized and critically discussed. This chapter will...

The immobilization of hazardous wastes in ordinary Portland cement (OPC)-based materials has been widely studied and implemented. OPC-based materials have a high carbon footprint associated with their production and geopolymer materials are a sustainable and eco-friendly alternative. Therefore, this work aimed to immobilize two hazardous industrial...

The extraction of raw materials in many productive sectors has become problematic for the environment because of the negative impacts of the process and the inappropriate destination of the generated waste. Stone waste (SW) from the dimension stone industry has physical and chemical characteristics with great potential for use as an alternative raw...

Energy demand in the construction sector has continued to grow over the past years, despite the European commitment to promote energy efficiency. The development of multifunctional materials to tackle the energy consumption and improve the thermal performance of buildings is in huge demand. Herein, we report for the first time the synthesis of a bi...

In anaerobic digestion processes, pH has a vital role due to the direct impacts on the microbial community. An eco-friendly approach has been applied to control pH in anaerobic bioreactors, using waste-containing fly ash geopolymer spheres (GS) instead of powdered chemical compounds, to promote continuous alkalis leaching. The influence of GS poros...

Ordinary Portland Cement is the most widely used binder in the construction sector; however, a very high carbon footprint is associated with its production process. Consequently, more sustainable alternative construction materials are being investigated, namely, one-part alkali activated materials (AAMs). In this work, waste-based one-part AAMs bin...

Future generation building materials produced using sustainable precursors and exhibiting multifunctional properties are in huge demand, as they might be a key tool to tackle the carbon dioxide emissions from the building sector. This study provides new insights regarding the impact of the cork particle size on the hardened-state properties of inor...

In this research, compositional and processing parameters were varied to obtain zeolites‐containing geopolymers using mainly biomass fly ash wastes. In addition to curing temperatures, another primary factor affecting the typologies of the resulting zeolites was composition. The mixture composition used in the synthesis crucially affects the nature...

Red mud-based inorganic polymer spheres were used as alternative pH regulators and process enhancers in sequencing batch anaerobic reactors treating cheese whey. This byproduct tends to quickly acidify under anaerobic conditions, and the common route to control pH and ensure suitable conditions for methane production involves the use of commercial...

This work reports a simple and safe, but powerful, route to depollute lead-containing aqueous solutions. Inorganic polymer foams (cm-size) were used as bulk-type adsorbents. The influence of the specimens’ porosity and activator molarity on the foams’ physical properties and on their lead extraction ability was studied. Then, the best performing sa...

Solar thermochemical conversion of H2O and captured CO2 is considered for the production of high-value solar fuels and CO2 valorization, using non-stoichiometric oxygen-exchange redox materials. This work aims to compare the thermochemical cycle performance of different ceria structures, including biomimetic cork-templated ceria (CTCe), ceria foam...

The use of calcium-rich materials in geopolymerization has been reported in the literature and generally induces an increase in mechanical properties. In this work, stone cutting waste (SW) was used in new geopolymers formulations and the interaction of the components was evaluated. In addition to the filler effect, SW affected the compositional sy...

Reduction of the energy consumption and CO2 emissions by the building sector might be a huge driver to mitigate climate change. One promising approach to mitigate energy consumption is the use of lightweight and low thermal-conductivity materials that could reduce the energy losses inside buildings and at the same time the use of heating and coolin...

Water splitting by solar energy-driven two-step thermochemical cycles is a promising approach for large-scale production of renewable fuels (e.g. hydrogen). The key challenge is developing materials capable of withstanding the harsh environmental conditions and to ensure high reliability in use, particularly in terms of redox kinetics and better ac...

DOWNLOAD FREE FOR 1 MONTH AT: https://authors.elsevier.com/c/1aRxwI6yu4ckf Geopolymer foams (highly porous materials) have emerged as one of the most exciting materials over the past few years due to their remarkable properties, low cost and green synthesis protocol, enabling their use in various high added-value applications. Review papers on poro...

DOWNLOAD FREE FOR 50 DAYS AT https://authors.elsevier.com/c/1aWWQ~2-EzKM- . Hexagonal ferrites can be employed in a multitude of applications, the most common hexaferrites are the M ferrites such as BaFe12O19 (barium hexaferrite, BaM). It is known that if Fe3+ is substituted with a combination of Ti4+/Co2+ the coercivity of BaM can be reduced to pr...

In this study, the possibility of using glass fibre wastes as reinforcement agent of waste-based and low thermal conductivity geopolymer mortars was evaluated to expand on previous work performed on dense geopolymers. The individual and combined influence of the glass fibre and the blowing agent amount on the fresh- and hardened-state properties of...

This work evaluates, for the first time, the possibility of producing multifunctional alkali-activated composites combining ultra-low density, low thermal conductivity, high acoustic absorption, and good moisture buffering capacity. The composites were prepared using cork as a lightweight aggregate. This novel material might promote energy savings...

Alkali-activated materials, also known as geopolymers, are a class of binders that have emerged as an excellent alternative to the use of Portland cement. However, the geopolymers full potential has yet to be fully exploited. A key driver to foster the use of geopolymers is by extending their application range beyond those where Portland cement can...

FREE TO DOWNLOAD FOR 50 DAYS AT: https://authors.elsevier.com/c/1ZkEC3O1E1GMLC In this investigation, and for the first time, pyrolysed sustainable cork was used to produce waste-based geopolymer-cork composites with enhanced electromagnetic interference (EMI) shielding properties. The influence of the pyrolysed cork amount and the geopolymer poro...

This review explores the advances in the synthesis of ceria materials with specific morphologies or porous macro- and microstructures for the solar-driven production of carbon monoxide (CO) from carbon dioxide (CO2). As the demand for renewable energy and fuels continues to grow, there is a great deal of interest in solar thermochemical fuel produc...

This study seeks the valorization of industrial residues (fly ash and construction and demolition waste (CDW)) through the production of geopolymer mortars. The effect of the sand substitution by CDW and the influence of the particle size range of CDW fine aggregates on the fresh and hardened properties of the mortars were evaluated. Geopolymer mor...

In this study, and for the first time, the possibility of using bulk type waste-based granulated alkali-activated materials (AAM) for inducing heavy metals extraction by precipitation and adsorption was evaluated. Waste metakaolin and aluminium scrap recycling waste proved to be suitable precursors to create AAM. Results indicate that both methods...

FREE DOWNLOAD FOR 50 DAYS at: https://authors.elsevier.com/c/1Ydn43QCo9UqBU Green liquor dregs are the most challenging waste stream coming from the pulp and paper industry. Despite tremendous efforts, there are not currently any viable recycling alternatives for this massively produced waste (2 Mt/year), which inevitably ends up in landfills. Urge...

FREE DOWNLOAD FOR 50 DAYS AT: https://authors.elsevier.com/c/1YZ-u7tGO~9vto For the first time, highly porous ZnO-based biomorphic materials were synthesised using cork as a natural sustainable template. In the first step, waste cork powder was pyrolysed and converted into inorganic carbon. This template was then infiltrated using a novel approach...

Porous inorganic polymer (IP) monoliths were synthesised using a modified bauxite residue (BR) as the reactive fraction with the objective of using them as adsorbents for methylene blue (MB) from synthetic wastewater. First, unreactive, as-produced BR was transformed into a suitable glassy precursor material for IPs by blending BR with minor quanti...

Cover of Materials Today 23, March 2019, showing an SEM image of our geopolymer spheres ( a few mm in diameter) made from valorised / recylced industrial wastes.

Uncovered article

FREE DOWNLOAD FOR 50 DAYS at: https://authors.elsevier.com/c/1YRYU3PCJl7rDJ Cork templates were used to produce lightweight bulk biomimetic ecoceramic (environmentally conscious ceramic) monoliths. Bulk/monolithic ceramics are vital for many applications, i.e. energy materials and fuel cells. Using simple and flexible, aqueous green-chemistry proce...

FREE DOWNLOAD FOR 50 DAYS at https://authors.elsevier.com/a/1YKca3Q2WYbH-2 In this investigation cork was used as a low density aggregate in the production of ultra-lightweight and low thermal conductivity inorganic polymer (geopolymer) composites. This novel and highly sustainable material, synthesised at room temperature (23 ºC), may decrease t...

Microstructure tailoring of metallurgical slags allows the production of alternative construction binders with customized properties. In this study, the variations of rheology and strength of alkali-activated basic-oxygen-furnace (BOF) slags are quantified. Two modifications of BOF slag were created adding amounts of alumina and silica at high temp...

This study aims to evaluate the in-situ synthesis of zeolites through geopolymerization of biomass fly ash wastes at low temperature in a hermetic container. The raw materials were activated using a mixture of sodium silicate and sodium hydroxide, and then the specimens cured at 60 �C to obtain zeolitecontaining geopolymers. Hydrogen peroxide (H2O2...

In this study, lightweight waste-based geopolymeric mortars were evaluated for the first time regarding their potential to passively adjust indoor relative humidity (RH) levels. Geopolymer mortars were prepared using a mixture of fly ash (FA) and metakaolin (MK) as a binder, in a proportion of 75:25 wt% (FA:MK), construction and demolition waste as...

The perception of industrial waste has changed, in the last decades, from an economic and environmental problem to a potential raw material. In this work, the synthesis of a stable pigment was prepared by combining two hazardous and unexplored wastes: red mud (RM, rich in Fe) and electroplating sludge (ES, rich in Ni/Cr). The wastes were mixed in d...

In this work, and for the first time, fly ash (FA)-based geopolymer (d = 2.6 mm) spheres were used to extract methylene blue from synthetic wastewaters. The influence of sorption time, dye initial concentration and adsorbent amount on the dye removal efficiency and uptake by the porous spheres was evaluated. The adsorbents’ recyclability and their...

In this investigation, an innovative and sustainable solution for glass fibre off-cuts is proposed. For the first time, glass fibre fabrics (non-woven mat) produced during wind turbine blade manufacture were used to produce reinforced inorganic polymer composites. The influence of fabric amount on the composites’ microstructure, water absorption, s...

This work investigates the production a green geopolymer-based concrete for a sustainable construction material using biomass wastes from a kraft pulp industry: fly ash (as main alumina-silicate source) and grits (as aggregate). Moreover, a simple, reproducible, ambient temperature, and low-cost manufacture is followed. Mix design aims to maximize...

Green liquor dregs wastes coming from pulp and paper production are currently disposed in landfills at a huge cost for industry and the environment. In this work, a novel and more sustainable waste manage�ment strategy is proposed. Dregs were used for the first time as fine filler in the production of biomass fly ash-based geopolymeric mortars. The...

Synthetic dyes, essentially due to their toxic nature, are considered one of the most serious wastewater pollutants and, once deposited in the water lines, become a problem to be removed. 1,2 Adsorption is considered the most effective and simple method for water decontamination. Activated carbons present singular properties, such as their high spe...

This work addresses the solar-driven thermochemical production of CO and O2 from two-step CO2-splitting cycles, using both ceria granules prepared from cork templates (CG) and ceria foams from polyurethane templates (CF). These materials were cycled in a high-temperature indirectly-irradiated solar tubular reactor using a temperature-swing process....

For the first time the feasibility of using an alkaline wastewater coming from the pulp and paper industry as an activator, partially (50 vol.%) replacing commercial sodium hydroxide, in the production of cork-based activated carbons was evaluated. The activated carbons showed the highest value of specific surface area ever reported for cork-based...

In this study, and for the first time, red mud (RM)-based geopolymer spheres were synthesised, with varying porosity and RM content, and then their use as pH regulators was evaluated. The aluminosilicate sources of these inorganic polymers were 100 % waste-based, consisting of a mixture of RM and fly ash wastes. Geopolymer spheres containing up to...

The application of phase change materials (PCM) in building materials is an emerging field, aiming to improve the energy efficiency of buildings. This article presents part of the work of developing methods for the incorporation of PCMs in ceramic materials for application in the construction. The tests performed show the variability in the incorpo...

The production of low thermal conductivity geopolymers has attracted increasing attention over the past years due to their low cost and green processing technology. In this work, light and porous geopolymers were produced by the proper association of aluminium content and solid-to-liquid ratio. This allowed the production of very low thermal conduc...

Red mud (RM), a highly alkaline iron oxide rich sludge obtained during the production of alumina, was treated to work as a coloring agent for ceramic glazes. The approach aims the valorization of this residue, adding environmental and economic value. RM was sintered at different temperatures (1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C and 1350 °C)...

Anaerobic digestion (AD) is a well-known technology for organic waste treatment with recognised environmental benefits including the generation of renewable energy (methane) and other added-value products. However, when applied to very easily biodegradable substrates, there is a need to mitigate the sudden pH drop, in order to improve the stability...

Sustainability in construction is a major concern worldwide, due to the huge volume of materials and energy consumed by this sector. Associated supplementing industries (e.g. Portland cement production) constitute a significant source of CO2 emissions and global warming. Valorisation and reuse of industrial wastes and by-products make geopolymers a...

For the first time biomass fly ash geopolymer monoliths were used as adsorbents for the removal of methylene blue from synthetic wastewaters. Highly porous and lightweight fly ash-based geopolymers were produced and then evaluated as methylene blue adsorbents. The geopolymers’ porosity strongly affects the dye extraction, a threefold increase (from...

The industrial wastes, FA and c-CDW, show suitable properties for the development of geopolymeric mortars; c-CDW containing mortars show lower spread on table values than the ones prepared with sand, since clay particles are finer in size and tend to adsorb water. Thickening affects are then observed; On the hardened condition, mortars prepared wit...