Rice husk biochar activation and its effects on

Rice husk biochar activation and its effects on the characteristics of the final products to be used as sorbents or catalysts support Nikolaos Mourgkogiannis, Ioannis Nikolopoulos, Eleana Kordouli, Christos Kordulis, Alexis Lycourghiotis, Hrissi K. Karapanagioti * Department of Chemistry, University of Patras, 26504, Patras, Greece * Corresponding author: E-mail: karapanagioti@upatras. gr, Tel +30 2610996728 The problem Due to climate change, it is necessary to search and implement green and sustainable technologies to reduce or eliminate its effects. Over the last years, the idea of a circular economy has been adopted. Based on this, waste biomass materials have been used for the production of biochars obtained with environmentally friendly processes such as pyrolysis. The present study aims to characterize the physicochemical properties of biochars obtained from rice husk for the determination of their characteristics related to their use as catalysts support and sorbent materials. 1/5 Objectives Biochar Pyrolysis

Rice husk biochar activation and its effects on the characteristics of the final products to be used as sorbents or catalysts support Nikolaos Mourgkogiannis, Ioannis Nikolopoulos, Eleana Kordouli, Christos Kordulis, Alexis Lycourghiotis, Hrissi K. Karapanagioti * Department of Chemistry, University of Patras, 26504, Patras, Greece * Corresponding author: E-mail: karapanagioti@upatras. gr, Tel +30 2610996728 The Samples/Methods Annually, large amounts of rice husk (> 80 tonnes) are produced around the world and high quantities of them are produced by developing countries. Determination of chemical and physical properties of new materials produced from the activation of rice husk biochars such as ash, surface area, surface topography, surface elemental analysis, surface functional groups and suspension p. H could affect sorption capacity and catalyst properties. In this study, biochars (RH), produced from raw rice husk (Raw-RH) at 850 o. C through pyrolysis process, were activated with H 2 O (W-RH), H 2 SO 4 (RH-S), H 3 PO 4 (RH-P), and Na. OH (RH-ALK) and their physicochemical parameters were analysed. RH RH-ALK 2/5 RH-P W-RH RH-S Surface area and porosity Suspension p. H FTIR analysis Ash Content SEM/EDS

Rice husk biochar activation and its effects on the characteristics of the final products to be used as sorbents or catalysts support Nikolaos Mourgkogiannis, Ioannis Nikolopoulos, Eleana Kordouli, Christos Kordulis, Alexis Lycourghiotis, Hrissi K. Karapanagioti * Department of Chemistry, University of Patras, 26504, Patras, Greece *Corresponding author: E-mail: karapanagioti@upatras. gr, Tel +30 2610996728 Results RH produced at 850 o. C have high specific surface and micropore area and at the same time, low external surface area. The tplot for the RHs disclosed that the activation with Na. OH leads to high specific surface (938 m 2/g) and micropore area (588 m 2/g) compared to other RH samples (367 - 386 m 2/g). Simultaneously, the activation of RH increases the pore size of biochar and the highest pore size was observed for the RH-ALK (51 Å) compared to activated RH-S and RH-P (48 Å). This can be attribute to the silica removal from RAW-RH by alkaline solution which is attained to create a mesoporous material that is more suitable as a catalyst support for balky reactants. RAW-RH presents various peaks on its surface corresponding to different functional groups. For the activated RH, RH-P (p. H 6. 2) is slightly more acidic than the RH-S (p. H 6. 1) and RH-ALK (p. H 8. 5) is also slightly alkaline than W-RH (p. H 8. 4). 3/5 Surface area and porosity Suspension p. H Ash Content Pore size distribution

Rice husk biochar activation and its effects on the characteristics of the final products to be used as sorbents or catalysts support Nikolaos Mourgkogiannis, Ioannis Nikolopoulos, Eleana Kordouli, Christos Kordulis, Alexis Lycourghiotis, Hrissi K. Karapanagioti * Department of Chemistry, University of Patras, 26504, Patras, Greece *Corresponding author: E-mail: karapanagioti@upatras. gr, Tel +30 2610996728 Results During the high pyrolysis temperature (850 o. C) most of functional groups appeared on the surface of raw RH either disappeared or began to diminish on the produced and activated biochars. Only few new peaks formed on RH-ALK spectrum. 4/5 FTIR SEM Elemental Analysis

Rice husk biochar activation and its effects on the characteristics of the final products to be used as sorbents or catalysts support Nikolaos Mourgkogiannis, Ioannis Nikolopoulos, Eleana Kordouli, Christos Kordulis, Alexis Lycourghiotis, Hrissi K. Karapanagioti * Department of Chemistry, University of Patras, 26504, Patras, Greece *Corresponding author: E-mail: karapanagioti@upatras. gr, Tel +30 2610996728 Conclusion Biochar activation with Na. OH solution (RH-ALK) led to a great increase of specific surface area by � 600 m 2 /g due to the increase of micropore area. In RH-ALK micropores were reduced; 18% of the pore volume of the activated biochar was attributed to micropore area compared to the microporosity of the unactivated RH biochar. For the five biochar samples, the characterization results indicated that the RH-ALK is more favourable to be further investigated for the removal of organic pollutants from water and to be tested as catalysts support for renewable diesel production. 5/5 Conclusions Acknowlegment

Objectives The present study aims to: Ø Investigate biochars development and properties at high pyrolysis temperature. Ø Develop new effective sorbents with desired physicochemical characteristics for their potential use in wastewater treatment. Ø Characterize raw and produced materials: a) b) c) d) the surface area and the porosity of RH. the suspension p. H and ash content of RH. the functional groups observed on the surface of RH. the SEM micrographs of raw RH, biochar and activated biochars RH. X

Biochar • Biochar is a rich in carbon by product produced from agro-industrial wastes when biomass is heated under various pyrolytic conditions. • Raw rice husk obtained from Agrino Company, Agrinio, Greece, was used for the production of biochar RH. • Biochar RH was activated with distilled H 2 O (W-RH), H 2 SO 4 (RH-S), H 3 PO 4 (RH-P), and Na. OH (RH-ALK). X

RH • RH – Biosorbents – raw 850 o. C – Biochars – pyrolyzed X

W-RH • Flushing with distilled water (3 D) • at 70 o. C • Into Vacuum Flask • p. H neutral • Washed biochar heated over night at 110 o. C X

RH-ALK • • Standard solution (Na. OH) Concentration 2 M Into Round Bottom Flask Double Neck m biochar / V solution: 1 g / 20 m. L at 80 o. C 4 h Activated biochar heated over night at 110 o. C X

FTIR • 0. 5 mg of dried sample turned into a pellet. • 50 mg of dried KBr. • Wavenumber measurement range was 4000 -400 cm-1 • Performed with a Perkin. Elmer FTIR spectrometer. • Analysed by IRSearch. Master 6. 0 software. X

Suspension p. H • • Electrolyte solution (Na. NO 3) p. H 7 Concentration 0. 1 M Into vials m sample / V solution: 0. 32 g / 20 m. L 24 h Analysed by a portable multi-parameter analyser with p. H electrode X

Ash Content • Materials were placed in a Memmet oven at 50 ± 5 o. C for several hours to remove the moisture. • 1 g of drying raw RH was heated at 750 o. C for the determination of the ash content. • 1 g of biochar RH was heated at 750 o. C for the determination of the ash content. X

Surface area and porosity • Raw RH was degassed at 60 o. C under mild nitrogen flow for 1 h. • Biochar RH was degassed at 300 o. C under mild nitrogen flow for 1 h. • Performed by gas (N 2) adsorption−desorption with the Micromeritics Tri. Star 3000 Analyzer system using the Brunauer, Emmett, and Teller (BET) equation. • Analysed by Micromeritics Tri. Star 3000 software. X

Pore size distribution RH W-RH RH-P RH-S RH-ALK X

Suspension p. H 10 9 8 7 6 5 4 3 2 1 0 Raw RH RH RH-P RH-S RH-ALK W-RH X

Ash Content Raw RH RH 18% 60% X

Surface area and Porosity SSA (m 2/g) Micro. SA (m 2/g) External SA (m 2/g) Pore volume (cm 3/g) Micropore volume (cm 3/g) Pore size (Å) Raw RH 0. 53 0. 31 0. 22 0. 0011 0. 00014 -- Biochar RH 367 230 137 0. 23 0. 11 43 W-RH 378 231 147 0. 25 0. 11 47 RH-P 386 235 151 0. 25 0. 11 48 RH-S 382 231 151 0. 25 0. 11 48 RH-ALK 938 588 350 0. 67 0. 27 51 Samples X

RH-P • • Standard solution (H 3 PO 4) Concentration 2 M Into Round Bottom Flask Double Neck m biochar / V solution: 1 g / 20 m. L at 80 o. C 4 h Activated biochar heated over night at 110 o. C X

SEM Gold sputtering JEOL, JFC-1100. SEM, JEOL 6300 SEM parts X

SEM Raw RH Biochar RH obtained at 850 o. C 1/3

SEM Biochar RH activated with H 2 SO 4 (RH-S) Biochar RH activated with H 3 PO 4 (RH-P) 2/3

SEM Biochar RH activated with Na. OH (RH-ALK) Biochar RH activated with H 2 O (W-RH) 3/3 X

FTIR X

SEM Surface Elemental Analysis • Surface Elemental Analyses of raw RH (left) and biochar RH (right), respectively. X

RH-S • • Standard solution (H 2 SO 4) Concentration 2 M Into Round Bottom Flask Double Neck m biochar / V solution: 1 g / 20 m. L at 80 o. C 4 h Activated biochar heated over night at 110 o. C X

Pyrolysis a) A fireproof ceramic vessel of 265 cm 3 was used. b) Samples were: Ø Heated at 850 o. C under limited oxygen conditions. Ø Placed in an oven with operating range 30 -1100 o. C. X

Conclusions • Biochars RH are mainly microporous materials with high specific surface area. • The activation of RH biochar either with distilled H 2 O or aqueous acidic solutions, do not significantly affect the specific surface area and micropore area. • The activated RH-ALK shows a significant increase of specific surface area and decrease of microporosity compared to the initial biochar. • Micrographs of materials showed obvious differences in morphology between raw RH and biochar RH. • Many pores formed (macropores) were formed on the surface of activated biochar with aqueous solution of NAOH than the initial RH biochar. • Biochar RH obtained at 850 o. C is alkaline in nature. • Formation of some new peaks were more distinct in RH-ALK spectra than the initial and activated biochar RH. 1/2

General Conclusions • Among the raw rice husk, resulted biochar and activated samples, statistically, there was a significant difference of the physicochemical properties of the biochar activated with the aqueous solution of Na. OH. • The results of the present study can be used by industries who deal with these by-products. The RH-ALK can be used as an ideal sorbent for water purification by the same industries. X 2/2

Acknowlegment We acknowledge support of this work by the project “Research Infrastructure on Food Bioprocessing Development and Innovation Exploitation – Food Innovation RI” (MIS 5027222), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014 -2020) and cofinanced by Greece and the European Union (European Regional Development Fund). X