Preparation of biochar adsorption material from walnut shell by supercritical CO₂ pretreatment

Abstract

In order to treat dyes in the wastewater of the printing industry and to reutilize walnut shell (WS) waste generate economic benefits, supercritical carbon dioxide (SC-CO₂) pretreatment technology was developed to prepare porous biochar as a precursor for adsorption material. Orthogonal experiments were conducted at the temperatures of 200, 300, and 400 ℃ with durations of 20, 40, and 60 min, and a control group was set up using N₂ pretreatment. Then, KOH activation was employed to prepare biochar adsorption material. The biochars were analyzed and characterized using TGA, BET, SEM, FT-IR, and XRD, and the liquid and gas phase products of the pretreatment process were analyzed semi-quantitatively and quantitatively using GC–MS and gas chromatography. Methylene blue (MB) dye was selected as an indicator to measure the adsorption capacity of biochar, and adsorption kinetics were analyzed based on the data. The results indicate that pretreatment with SC-CO₂ effectively enhanced the performance and yield of the activated carbon. The highest specific surface area increased by 18%, and the maximum adsorption of MB increased by 23% compared to the N₂ control group. The yield increased by 8–262% and the specific surface area increased by 50–192% compared to the direct activation of walnut shell (WS). During the pretreatment processes for the preparation of biochar adsorption material with the best specific surface area, phenol-enriched bio-oil was produced as a by-product which has economic value.

Highlights

1.	The poly-generation of biochar precursor and bio-oil could be realized by supercritical CO2.
2.	Prepared activated carbon had great physical performance and excellent dye adsorption capacity.
3.	The pretreatment process produced high-value organic liquid by-products.
4.	Mild pretreatment conditions were more advantageous.

Keywords

Supercritical carbon dioxide / Walnut shell / Biochar / Methylene blue adsorption

References

[1] Albarelli JQ, Rabelo RB, Santos DT, Beppu MM, Meireles MAA. Effects of supercritical carbon dioxide on waste banana peels for heavy metal removal. J Supercrit Fluids, 2011, 58(3): 343-351,

[2] Badgujar KC, Dange R, Bhanage BM. Recent advances of use of the supercritical carbon dioxide for the biomass pre-treatment and extraction: a mini-review. J Indian Chem Soc, 2021, 98(1),

[3] Balahmar N, Mokaya R. Pre-mixed precursors for modulating the porosity of carbons for enhanced hydrogen storage: towards predicting the activation behaviour of carbonaceous matter. J Mater Chem A, 2019, 7(29): 17466-17479,

[4] Butterman HC, Castaldi MJ. Biomass to fuels: impact of reaction medium and heating rate. Environ Eng Sci, 2010, 27(7): 539-555,

[5] Egbosiuba TC, Abdulkareem AS, Kovo AS, Afolabi EA, Tijani JO, Auta M, Roos WD. Ultrasonic enhanced adsorption of methylene blue onto the optimized surface area of activated carbon: adsorption isotherm, kinetics and thermodynamics. Chem Eng Res Des, 2020, 153: 315-336,

[6] El-Bery HM, Saleh M, El-Gendy RA, Saleh MR, Thabet SM. High adsorption capacity of phenol and methylene blue using activated carbon derived from lignocellulosic agriculture wastes. Sci Rep, 2022, 12(1): 5499,

[7] Farrow TS, Sun C, Snape CE. Impact of CO₂ on biomass pyrolysis, nitrogen partitioning, and char combustion in a drop tube furnace. J Anal Appl Pyrol, 2015, 113: 323-331,

[8] Gao M, Xu F, Li S, Ji X, Chen S, Zhang D. Effect of SC-CO₂ pretreatment in increasing rice straw biomass conversion. Biosys Eng, 2010, 106(4): 470-475,

[9] García ER, Medina RL, Lozano MM, Hernández Pérez I, Valero MJ, Franco AMM. Adsorption of azo-dye orange II from aqueous solutions using a metal-organic framework material: iron-benzenetricarboxylate. Materials, 2014, 7(12): 8037-8057,

[10] González-García P. Activated carbon from lignocellulosics precursors: a review of the synthesis methods, characterization techniques and applications. Renew Sustain Energy Rev, 2018, 82: 1393-1414,

[11] Hanaoka T, Sakanishi K, Okumura Y. The effect of N₂/CO₂/O₂ content and pressure on characteristics and CO₂ gasification behavior of biomass-derived char. Fuel Process Technol, 2012, 104: 287-294,

[12] Jiang J, Yang W, Cheng Y, Liu Z, Zhang Q, Zhao K. Molecular structure characterization of middle-high rank coal via XRD, Raman and FTIR spectroscopy: implications for coalification. Fuel, 2019, 239: 559-572,

[13] Jiang F, Cao D, Hu S, Wang Y, Zhang Y, Huang X, Zhao H, Wu C, Li J, Ding Y, Liu K. High-pressure carbon dioxide-hydrothermal enhance yield and methylene blue adsorption performance of banana pseudo-stem activated carbon. Biores Technol, 2022, 354,

[14] Jiang K, Zhang B, Wang W, Jin H (2022) Effect of the variable physical properties on sub- and supercritical CO₂ flowing over a stationary spherical particle. Phys Fluids 34(10).

[15] Kawamoto H. Lignin pyrolysis reactions. J Wood Sci, 2017, 63(2): 117-132,

[16] Keiluweit M, Nico PS, Johnson MG, Kleber M. Dynamic molecular structure of plant biomass-derived black carbon (Biochar). Environ Sci Technol, 2010, 44(4): 1247-1253,

[17] Kumar A, Jena HM. Removal of methylene blue and phenol onto prepared activated carbon from Fox nutshell by chemical activation in batch and fixed-bed column. J Clean Prod, 2016, 137: 1246-1259,

[18] Liu G, Zhang L. Preparation and process optimization of polyaminated walnut shell adsorbent. Petrochem Technol, 2023, 52(5): 645-651

[19] Liu Q, Wang S, Zheng Y, Luo Z, Cen K. Mechanism study of wood lignin pyrolysis by using TG–FTIR analysis. J Anal Appl Pyrol, 2008, 82(1): 170-177,

[20] Liu Z, Zhang F, Liu H, Ba F, Yan S, Hu J. Pyrolysis/gasification of pine sawdust biomass briquettes under carbon dioxide atmosphere: study on carbon dioxide reduction (utilization) and biochar briquettes physicochemical properties. Biores Technol, 2018, 249: 983-991,

[21] Mashkoor F, Nasar A. Magsorbents: potential candidates in wastewater treatment technology—a review on the removal of methylene blue dye. J Magn Magn Mater, 2020, 500,

[22] Mohammed N, Grishkewich N, Berry RM, Tam KC. Cellulose nanocrystal–alginate hydrogel beads as novel adsorbents for organic dyes in aqueous solutions. Cellulose, 2015, 22(6): 3725-3738,

[24] Naik SN, Goud VV, Rout PK, Dalai AK. Production of first and second generation biofuels: a comprehensive review. Renew Sustain Energy Rev, 2010, 14(2): 578-597,

[25] Om Prakash M, Raghavendra G, Panchal M, Ojha S (2020) Thermogravimetric analysis of biochar from Arhar fiber powder prepared at different pyrolysis temperatures, Singapore, Springer Singapore

[26] Pusceddu E, Montanaro A, Fioravanti G, Santilli S, Foscolo P, Criscuoli I, Raschi A, Miglietta F. Comparison between ancient and fresh biochar samples, a study on the recalcitrance of carbonaceous structures during soil incubation. Int J New Technol Res, 2017, 3: 39-46

[27] Rafatullah M, Sulaiman O, Hashim R, Ahmad A. Adsorption of methylene blue on low-cost adsorbents: a review. J Hazard Mater, 2010, 177(1): 70-80,

[28] Santoso E, Ediati R, Kusumawati Y, Bahruji H, Sulistiono DO, Prasetyoko D. Review on recent advances of carbon based adsorbent for methylene blue removal from waste water. Mater Today Chem, 2020, 16,

[29] Shafizadeh F. Introduction to pyrolysis of biomass. J Anal Appl Pyrol, 1982, 3(4): 283-305,

[30] Shi Q, Wang W, Zhang H, Bai H, Liu K, Zhang J, Li Z, Zhu W. Porous biochar derived from walnut shell as an efficient adsorbent for tetracycline removal. Biores Technol, 2023, 383,

[31] Tan F, Cheng J, Zhang Y, Jiang X, Liu Y. Genomics analysis and degradation characteristics of lignin by Streptomyces thermocarboxydus strain DF3-3. Biotechnol Biofuels Bioprod, 2022, 15(1): 78,

[32] Wang C, Zhang S, Wu S, Sun M, Lyu J. Multi-purpose production with valorization of wood vinegar and briquette fuels from wood sawdust by hydrothermal process. Fuel, 2020, 282,

[33] Wang C, Zhang S, Huang S, Cao Z, Xu J, Lyu J. Effect of hydrothermal treatment on biomass structure with evaluation of post-pyrolysis process for wood vinegar preparation. Fuel, 2021, 305,

[23] Wang W, Zhao Q, Lu B, Shi J, Jin H. Pure hydrogen gas production in a coal supercritical water gasification system with CO2 as transporting medium. Applied Thermal Engineering, 2024, 237: 121529,

[34] Xiao K, Liu H, Li Y, Yi L, Zhang X, Hu H, Yao H. Correlations between hydrochar properties and chemical constitution of orange peel waste during hydrothermal carbonization. Biores Technol, 2018, 265: 432-436,

[35] Yahya MA, Al-Qodah Z, Ngah CWZ. Agricultural bio-waste materials as potential sustainable precursors used for activated carbon production: a review. Renew Sustain Energy Rev, 2015, 46: 218-235,

[36] Yan X, Wang D, Zhang S, Dong X, Yang J, Liu R. Adsorption performance of modified walnut shell adsorbent to Pb²⁺. J Qingdao Agric Univ (Nat Sci), 2022, 39(4): 298-303

[37] Yang L, Wang N, Li X. Adsorption of acid fuchsin by walnut shell activate carbon in light and microwave. N Chem Mater, 2022, 50(11): 212-215

[38] Yao X, Ji L, Guo J, Ge S, Lu W, Cai L, Wang Y, Song W, Zhang H. Magnetic activated biochar nanocomposites derived from wakame and its application in methylene blue adsorption. Biores Technol, 2020, 302,

[39] Yi Z, Li C, Li Q, Zhang L, Zhang S, Wang S, Qin L, Hu X. Influence of CO₂ atmosphere on property of biochar from pyrolysis of cellulose. J Environ Chem Eng, 2022, 10(3),

[40] Zhang H, Wu S. Enhanced enzymatic cellulose hydrolysis by subcritical carbon dioxide pretreatment of sugarcane bagasse. Biores Technol, 2014, 158: 161-165,

[41] Zhao C, Jiang E, Chen A. Volatile production from pyrolysis of cellulose, hemicellulose and lignin. J Energy Inst, 2017, 90(6): 902-913,

[42] Zhou C, Ge Z, Wang Y, Shang F, Guo L. Experimental study on supercritical carbon dioxide gasification of biomass. Carbon Neutral, 2023, 2(1): 2,

[43] Zhu S, Bai Y, Luo K, Hao C, Bao W, Li F. Impacts of CO₂ on char structure and the gasification reactivity. J Anal Appl Pyrol, 2017, 128: 13-17,

Funding

National Natural Science Foundation of China(52242609)