New, biobased carbon foams

Abstract The use of biomass has grown tremendously among energy-producing factories recently. In addition to burning biomass to produce heat and electricity, new and environment friendly products are being developed in order to utilize biomass more efficiently. Due to the variety of rich carbon sources in biomass, this thesis focuses on the use of such carbon sources in producing activated carbon foams. The first part of this thesis consists of two sections. First, it notes that carbon foams are produced using sugar as a source of carbon. It further notes that the sugar-based carbon foams that have been produced were too brittle and, therefore, require further adjustment in order to produce mechanically stronger foams. In the second section of the first part, this thesis addresses how hydrolysable tannin, as well as hydrolysable tannin in combination with different lignin types, is used to produce carbon foams and activated carbon foams. This section also studies the physical properties of these foams. The results indicate that changing the catalyst during foaming, or using the right lignin-to-tannin ratio (25 w%) and a four-hour thermal treatment at 1073 K, obtains the highest influence on these foams’ mechanical strength. Up to 10 times stronger foams, can be achieved with this method. The second part of this thesis focuses on studying the properties and performance of activated carbon foams based on hydrolysable tannin, pine bark, and spruce bark extracts as catalyst supports in the conversion of furfural to 2-methylfuran and as adsorbents for the removal of methylene blue. Based on the results, chemically activated carbon foams from spruce bark work better than physically activated carbon foams in removing methylene blue from solutions due to their more developed pore size distribution and higher specific surface area. The performance of activated carbon foam derived from pine bark extracts in the conversion of furfural to 2-methylfuran was similar to commercial reference materials’ 58%.Tiivistelmä Biomassan hyödyntäminen energiaa tuottavissa laitoksissa on kasvanut hurjasti viime aikoina. Vaikka biomassaa poltetaankin lämmön ja energian tuotannon takia, uusia ja ympäristöystävällisiä tuotteita pyritään kuitenkin tuottamaan biomassasta, jotta sen hyödyntäminen olisi mahdollisimman tehokasta. Tässä opinnäytetyössä käytetään biomassan sisältäviä hiilirikkaita yhdisteitä kuten tanniineja, sokereita ja ligniiniä aktivoitujen hiilivaahtojen valmistamiseen. Väitöstutkimuksen ensimmäinen osa koostuu kahdesta osasta: Ensiksi, hiilivaahtoja ja aktiivihiilivaahtoja tuotetaan käyttämällä sokeria hiilen lähteenä. Tutkimuksissa huomattiin, että hiilivaahdot olivat mekaanisesti liian hauraita. Vahvempien vaahtojen tuottamiseksi, käytetään tutkimuksen toisessa osassa hydrolysoituvaa tanniinia ja hydrolysoituvaa tanniinia yhdessä eri ligniinityyppien kanssa hiilivaahtojen ja aktiivihiilivaahtojen tuottamiseksi sekä tutkittiin niiden fysikaalisia ominaisuuksia. Tulokset osoittivat, että mekaaniseen lujuuteen voidaan vaikuttaa käyttämällä eri katalyyttiä vaahdotuksessa tai käyttämällä oikeaa ligniini / tanniinisuhdetta (25 paino-%) ja 4 tunnin lämpökäsittelyä lämpötilassa 1073 K. Jopa 10 kertaa vahvempia vaahtoja voidaan saavuttaa tällä tavoin. Väitöstutkimuksen toisessa osassa tutkitaan puhtaista hydrolysoituvista tanniini-, mänty- ja kuusenkuoriuutteista valmistettuja aktiivihiilivaahtoja furfuraalin konversiossa 2-metyylifuraaniksi ja adsorbentteina metyleenisinisen poistossa. Tulosten perusteella kuusen kuoriuutteesta tehdyt kemiallisesti aktivoidut hiilivaahdot toimivat metyleenisinisen poistossa kehittyneemmän huokoskokojakaumansa ja suuremman ominaispinta-alansa vuoksi paremmin kuin fysikaalisesti aktivoidut hiilivaahdot. Männyn kuoriuutteesta valmistettu aktiivihiilivaahto toimi furfuraalin konversiossa 2-metyylifuraaniksi lähes kaupallisten vertailukatalyyttien 58 %:n tavoin

Catalytic effect of transition metals (copper, iron, and nickel) on the foaming and properties of sugar-based carbon foams

Abstract Recently, bio-based carbon foams have gained much interest in many chemical industry fields because of their unique structure and properties. This study provides new information on the effects of catalytic metals (iron, nickel, and copper) on the foaming process. Specifically, the effects of these catalysts on the density, foam growth, and cell size and then further on the pore size distribution and specific surface areas after the physical activation are considered. Furthermore, some of the activated sugar foams were used in adsorption tests using methylene blue as adsorbent. Results showed that the highest effect on foam density was obtained using the iron catalyst in the foaming process. In addition, increasing the iron amount, the development of micro-pores decreased from 95.2 to 60.3% after cabonization and activation of the foams. Nickel and iron had the highest and lowest effect on foam rise at 1375 and 500%, respectively. Interestingly, when the nickel catalyst was used, cell sizes and surface areas two times larger than those when the foams were prepared with the iron and copper catalysts was obtained. The specific surface area of activated sugar-based carbon foams changed significantly with the increased copper amount inside the foaming solution in compared with iron or nickel catalyst. Methylene blue adsorption capacity of additional series of activated sugar foams decreased from 28 to 9% when meso-pore amount decreased

Physical activation and characterization of tannin-based foams enforced with boric acid and zinc chloride

Abstract In this study, tannin-furanic-based foams enforced with H3BO3 and ZnCl2 are investigated, as well as their properties such as mechanical strength, specific surface area, and pore size distribution. From an industrial point of view, the aforementioned properties of these foams play a key role when used as catalyst, adsorbent, or gas storing materials. Therefore, this study aims to prove that such enforced tannin-furanic foams are promising materials for these types of applications. According to the results, materials that are up to five times stronger can be achieved by carbonizing the foams in comparison to maturing them. With physical activation, it was possible to obtain a specific surface area as high as 845 m2/g with a pore volume of up to 0.35 cm3/g. Chemical activation, using ZnCl2as the activating agent, produced a specific surface area and pore volume of 737 m2/g and 0.31 cm3/g. However,the pore sizes were mostly microporous, independently of activation procedure used

Activated carbon from hydrolysis lignin:effect of activation method on carbon properties

Abstract This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO₃, and H₃PO₄), different steam rates for physical activation, and different chemical activating agents (ZnCl₂, Na₂CO₃, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) surface areas as high as 616 m²/g could be achieved with physical activation and 2054 m²/g with chemical activation. Different steam rates in the selected interval (0.5–2 cm³/min) did not change the pore size distribution but had small positive effect on the specific surface area, while chemical activation with ZnCl₂ increased the mesoporosity, and activation with KOH increased the microporosity and oxygen groups in the form of ether and alcohol bonds

Comparison of the properties of activated carbons produced in one-stage and two-stage processes

Abstract Activated carbons (ACs) can be produced from biomass in a thermal process either in a direct carbonization-activation process or by first carbonizing the biomass and later activating the bio-chars into activated carbons. The properties of the ACs are dependent on the type of process used for production. In this study, the properties of activated carbons produced in one-stage and two-stage processes are considered. Activated carbons were produced by physical activation of two types of starting materials: bio chars produced from spruce and birch chips in a commercial carbonization plant and from the corresponding raw chips. The activated carbons produced were characterized regarding specific surfaces, pore volumes, and pore size distributions. The un-activated bio chars had varying surface areas, 190 and 140 m² g⁻¹ for birch and spruce, respectively, and pore volumes of 0.092 and 0.067 cm³ g⁻¹, respectively. On the other hand, 530–617 and 647–679 m² g⁻¹ for activated bio chars from birch and spruce, respectively, and pore volumes 0.366–0.509 and 0.545–0.555 cm³ g⁻¹, respectively, were obtained. According to the results obtained, two slightly different types of activated carbons are produced depending on whether a one-stage or a two-stage carbonization and activation process is used. The ACs produced in the one-stage process had higher specific surface areas (SSA), according to the BET-model (Brunauer–Emmett–Teller), compared to the ones produced in a two-stage process (761–940 m² g⁻¹ vs. 540–650 m² g⁻¹, respectively). In addition, total pore volumes were higher in ACs from the one-stage process, but development of micro-pores was greater compared to those of the two-stage process. This indicates that the process can have an influence on the ACs’ porosity. There was no significant difference in total carbon content in general between the one-stage and two-stage processes for spruce and birch samples, but some differences were seen between the starting materials. Especially in the one-stage procedure with 2 and 4 h steam activation, there was nearly a 10% difference in carbon content between the spruce and birch samples

Characterization of lignin enforced tannin/furanic foams

Abstract Worldwide, tons of lignin is produced annually in pulping plants and it is mainly considered as a waste material. Usually lignin is burned to produce energy for the pulping reactors. The production of value-added materials from renewable materials like lignin, has proved to be challenging. In this study, the effects of addition of three different types of lignin in the production of tannin/furanic foams is investigated. The foams were matured, first at 373 K and finally carbonized at 1073 K and the properties of them including mechanical strength, specific surface area and pore development are investigated before and after thermal treatment. According to the results, higher mechanical strength is obtained if samples are carbonized at 1073K compared to matured ones at 373K. Up to 10 times stronger materials are achieved this way, which makes them promising as insulating or constructive materials. With physical activation, it is possible to obtain specific surface areas and pore volumes close to 1200 m2/g and 0,55 cm3/g respectively. Mainly micropores are developed during the steam activation which makes these foams more suitable and selective to be used as catalyst support materials in the catalytic conversion of small molecules or in adsorption or gas storage application

Activated carbon production from peat using ZnCl₂:characterization and applications

Abstract The process for producing activated carbon from peat was optimized. The peat was impregnated with different ratios of ZnCl₂, and the impregnated biomass was activated at different temperatures. The specific surface area, pore size distribution, total carbon content, and yield of the activated carbon were investigated. The best results for the specific surface area and mesoporosity of the activated peat were obtained by using a high impregnation ratio (2) and high activation temperature (1073 K). Highly porous activated carbon was produced that had a specific surface area of approximately 1000 m²/g and total pore volume that was higher than 0.5 cm³/g for most samples. The activated carbon had a high degree of mesoporosity. The adsorptive properties of the activated carbon were determined with methylene blue and orange II dyes

Applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon

Abstract Hybrid aspens have long attracted scientific interest, but the research on their use as feedstocks for chemical applications are still very limited. The bark biomass of the poplar species contains many valuable extractives that can be utilized as value-added products. This paper examines the applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon. To explore this, the study considers 1) the basic chemical composition of the bark in terms of added value potential, 2) the basic chemical composition of the bark extract and the effect of its pretreatment on the extract composition, 3) the production of rigid carbon foam, and 4) the chemical activation of carbon foam with different impregnating agents. The study determines that the bark extract of the hybrid aspen can be used as a precursor for rigid carbon foam and further processed into an activated carbon product. Therefore, the bark extract of Populus tremula L. × P. tremuloides Michx. can be assessed as a potential value-added product that increases the use value of the hybrid aspen biomass

Alkali-activated adsorbents from slags:column adsorption and regeneration study for nickel(II) removal

Abstract Alkali-activated adsorbents were synthesized by mixing three different slags from the steel industry: blast furnace slag (BFS), ladle slag (LS), and Lintz–Donawitz converter slag (LD). These powdered slag-based geopolymers (GP) were used to remove nickel(II) from aqueous solutions in fixed-bed column studies. The experiments were conducted in pH 6 using a phosphate buffer with initial nickel(II) concentration of 50 mg/L. Samples were taken at time intervals of between 5 and 90 min. Three adsorption–desorption cycles were implemented with a flow rate of 5 mL/min. The geopolymers were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), X-ray fluorescence (XRF), specific surface area measurements, and a leaching test. The data were found to describe the Thomas, Adams–Bohart, and Yoon–Nelson models well. For GP (BFS, LS), experimental adsorption capacity was 2.92 mg/g, and for GP (LD, BFS, LS), it was 1.34 mg/g. The results indicated that the produced adsorbents have the potential to be used as adsorbents for the removal of nickel(II)

Ibuprofen degradation using a Co-doped carbon matrix derived from peat as a peroxymonosulphate activator

Abstract The wider presence of pharmaceuticals and personal care products in nature is a major cause for concern in society. Among pharmaceuticals, the anti-inflammatory drug ibuprofen has commonly been found in aquatic and soil environments. We produced a Co-doped carbon matrix (Co–P 850) through the carbonization of Co²⁺ saturated peat and used it as a peroxymonosulphate activator to aid ibuprofen degradation. The properties of Co–P 850 were analysed using field emission scanning electron microscopy, energy filtered transmission electron microscopy and X-ray photoelectron spectroscopy. The characterization results showed that Co/Fe oxides were generated and tightly embedded into the carbon matrix after carbonization. The degradation results indicated that high temperature and slightly acidic to neutral conditions (pH = 5 to 7.5) promoted ibuprofen degradation efficiency in the Co–P 850/peroxymonosulphate system. Analysis showed that approx. 52% and 75% of the dissolved organic carbon was removed after 2 h and 5 h of reaction time, respectively. Furthermore, the existence of chloride and bicarbonate had adverse effects on the degradation of ibuprofen. Quenching experiments and electron paramagnetic resonance analysis confirmed that SO4·-, ·OH and O2·− radicals together contributed to the high ibuprofen degradation efficiency. In addition, we identified 13 degradation intermediate compounds and an ibuprofen degradation pathway by mass spectrometry analysis and quantum computing. Based on the results and methods presented in this study, we propose a novel way for the synthesis of a Co-doped catalyst from spent NaOH-treated peat and the efficient catalytic degradation of ibuprofen from contaminated water