Method for producing magnetic biocoal from pea shells using the hydrothermal method

Abstract

In traditional biochar production, most catalysts are difficult to recycle because they are in powder form. In this invention, biochar has been converted into magnetic biochar, which can be easily separated using a magnet, thereby increasing its recyclability. Magnetic biochar can be easily separated from the solution, which not only significantly improves its recyclability but also prevents secondary pollution in the water body. The purpose of this invention is to produce magnetic biochar from pea shells using the hydrothermal method and to present the method involved. This invention introduces the processing of biochar obtained from biomass sources in our country using the hydrothermal process to impart different physical and chemical properties. In this process, pea shells were processed under specific temperature and pressure conditions to obtain biochar. Its activation with peroxymonosulfate was demonstrated for use as a catalyst material in water purification.

Description

[0001] DESCRIPTION

[0002] METHOD FOR PRODUCING MAGNETIC BIOCOAL FROM PEA SHELLS USING THE HYDROTHERMAL METHOD TECHNICAL FIELD

[0003] The invention relates to the production of magnetic biochar from pea shells using the hydrothermal method and is related to the field of environmentally friendly and green technology materials.

[0004] PRIOR ART

[0005] Today, major environmental issues such as pollution and global warming are in focus, and climate change and the energy crisis have emerged as globally concerning problems.

[0006] Research groups and governments are working to develop ecological, simple, and cost-effective solutions to address these issues. In this context, the availability of renewable energy sources is becoming increasingly important in achieving sustainable development goals. However, inefficient biomass resource management leads to significant economic losses, and a large portion of biomass is either discarded or burned. This burning process causes air pollution and the spread of harmful substances into the environment. Furthermore, waste biomass storage areas pose problems such as pollution risks and groundwater contamination (Ghodake et al., 2021 ). The global amount of biomass is expected to continue increasing; therefore, the pyrolysis of waste biomass holds great potential for producing biochar or charcoalbased products and supporting renewable energy sources (Zhai et al., 2015).

[0007] Food loss and waste management have become a significant global issue due to greenhouse gas emissions and the wastage of resources. According to data from the Food and Agriculture Organization (FAO), approximately 1.3 billion tons of food are wasted each year, which accounts for one-third of total food production. A 2020 study showed that China, India, and Nigeria produced 91.65, 68.75, and 37.94 million metric tons of household food waste, respectively. Among other countries, Vietnam, Japan, Ethiopia, Bangladesh, Mexico, Brazil, Pakistan, the United States, and Indonesia contributed between 7.35 and 20.94 million metric tons to food waste production. Unprocessed food waste discarded in open areas contributes to greenhouse gas emissions, exacerbating climate change, environmental pollution, and biodiversity loss. Therefore, increasing the value of food waste is important for an environmentally friendly environment. Vegetable waste is a particular area of concern as it has a greater impact during transportation, storage, and processing. Peas (Pisum sativum L) are the second most important legume in many countries, with approximately 11.7 million tons of pea pod waste produced worldwide. India produces over 1 million tons of peapod husks in 5 years, and a significant portion of this is left as waste in open fields. Peapod shells contain 69% cellulose, 22% hemicellulose, 5% sugar, and 4% lignin. Given this lignocellulose composition, pea shells can be used as a valuable commercial waste material to improve soil quality and agricultural productivity (Pradhan et al., 2024). Research in the field of water treatment technologies has demonstrated that various carbon-based materials hold significant potential for their effectiveness in the physical, chemical, and biological treatment of wastewater. In particular, biochar, a carbon-rich material produced through biomass pyrolysis, has recently gained significant interest as a potential ameliorative material in wastewater treatment (Chon et al., 2024).

[0008] Biochar is a carbon-rich porous material obtained through the pyrolysis process of biomass feedstocks at slow heating rates and temperatures ranging from 400 to 700 °C. The International Biochar Initiative ( I B I) defines biochar as a carbon-resistant solid material formed by the thermochemical conversion of biomass feedstocks in the absence of oxygen (Pourhashem etal., 2019; Tomczyk et al., 2020). Biomass feedstock is a low-cost and sustainable material that includes various organic waste materials such as agricultural and forestry residues, wood chips, algae, sewage sludge, manure, and organic municipal solid waste (Xiang et al., 2020). The selection of biomass plays a critical role in determining the properties and application potential of the resulting biocarbon. Different biomass feedstocks possess unique compositions and properties, resulting in biochar with variable porosity, surface area, and chemical characteristics. These differences emerge as a significant factor affecting the effectiveness of biochar in wastewater treatment and its application areas (Xiang et al., 2020).

[0009] In a study using pea shells, they investigated the adsorption of Cr6+ions from water sources using biochar modified with amine groups (El-Nemr et al., 2023). In another study, after obtaining nano magnetic biochar from pea shells, the removal of wastewater containing methylene blue by adsorption was investigated (Rubangakene et al., 2023).

[0010] Adsorption is a widely preferred method due to its cost-effectiveness, high removal efficiency, and minimal secondary pollution advantages. Biochar offers an attractive alternative for adsorption applications thanks to its low-cost structure and high adsorption capacity. In a study conducted by Rubangakene and colleagues, the combustion of biochar at high temperatures is found to result in less ash formation. In contrast, the combustion of the material produced at lower temperatures yields more ash formation, thereby reducing costs. Therefore, it is important to optimize biochar in a way that increases both its adsorption efficiency and economic efficiency. However, the relatively low surface area and limited porosity properties of biochar in practical applications can limit its effectiveness in removing pollutants. This situation highlights the need for innovative studies to optimize biochar and improve its performance. DESCRIPTION OF THE INVENTION

[0011] In traditional biochar production, most catalysts are difficult to recycle because they are in powder form. In this invention, biochar has been converted into a magnetic form that can be easily separated using a magnet to increase its recyclability. Magnetic biochar can be separated from the solution very easily, which not only greatly increases its recyclability but also prevents secondary contamination in the solution.

[0012] The objective of this invention is to produce magnetic biochar from pea shells using the hydrothermal method and to present the method associated with it. This invention demonstrates the processing of biochar obtained from biomass sources in our country using a hydrothermal process to impart different physical and chemical properties. In this process, pea shells were processed under specific temperature and pressure conditions to obtain biochar. Its activation with peroxymonosulfate was demonstrated for use as a catalyst material in water purification.

[0013] Magnetic biochar (MBK) is defined as a modified composite in which magnetic materials are integrated into biochar; MBK exhibits an increase in specific surface area, porosity, and oxygen-containing functional groups, while also enhancing its magnetic separation capabilities. One advantage of the invention is that it enables the removal of stubborn contaminants (e.g., RM19 dye) with high efficiency. Another advantage of the invention is that the material can be separated from the system using magnetic methods and reused, offering a sustainable and economical solution by delaying waste generation.

[0014] Another advantage of the invention is that the magnetic biochar produced can be used as a catalyst, enabling applications in different fields. Another advantage of the invention is that the produced magnetic biochar causes less secondary pollution compared to adsorption processes. Another advantage of the invention is that the produced magnetic biochar allows for long-term use.

[0015] Figure Captions

[0016] Figure 1. Stages of magnetic biochar production using the hydrothermal method Figure 2. SEM images of magnetic biochar

[0017] Figure 3. XRD images of magnetic biochar

[0018] Figure 4. FTIR spectra of BK and Fe3O4-BK samples produced at 500°C

[0019] Figure 5. (a) VSM result of magnetic biochar

[0020] Figure 5. (b) Attraction with a magnet in an aqueous environment

[0021] Figure 6. Effect of combustion temperatures on RM19 removal efficiency with peroxymonosulfate activation in obtaining magnetic biochar

[0022] Figure 7. Effect of iron biomass ratios of magnetic biochar on RM19 removal efficiency with peroxymonosulfate activation

[0023] Figure 8. Effect of peroxymonosulfate activation of magnetic biochar at different initial pH values on RM 19 removal efficiency

[0024] Figure 9. Effect of different magnetic biochar dosages on RM 19 removal efficiency via peroxymonosulfate activation

[0025] Figure 10. Effect of magnetic biochar's four-time reusability on RM 19 removal efficiency via peroxymonosulfate activation DETAILED DESCRIPTION OF THE INVENTION

[0026] In this study, the surface properties and morphology of magnetic biochar (MBK) were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). SEM images show that FesO4 nanoparticles have a spherical morphology and are homogeneously distributed around smaller-sized biochar. XRD analysis determined the crystal structure and composition of the magnetic biochar, which was indexed to magnetite and maghemite nanoparticles. FTIR analysis indicated the presence of various functional groups and signaled that the iron loading was bound within the material.

[0027] VSM analysis revealed that magnetic biochar has superparamagnetic properties and a saturation magnetization value of -32.63 emu / g. Despite its low magnetization value, magnetic biochar can be easily separated using a magnet. BET analysis determined that MBK has a surface area of 64.62 m2 / g and an average pore diameter of 8.532 nm. During the preparation of magnetic biochar, the decision on the combustion temperature was made by examining the peroxymonosulfate activation of the produced magnetic biochar. In this process, the effect on Reactive Blue 19 removal was examined at different combustion temperatures (400, 500, 600°C). At 400, 500, and 600°C, the RM19 removal efficiencies after 60 minutes of reaction time were determined to be 19%, 36%, and 29%, respectively. As seen, at the end of the 60-minute reaction time, higher RM19 removal efficiencies were obtained at 500°C. The amount of ash formed at these combustion temperatures decreased as the temperature increased. Considering the removal efficiency, a combustion temperature of 500°C was chosen for the subsequent experiments.

[0028] During the production of magnetic biochar, after determining the combustion temperatures, decisions regarding different iron biomass ratios were made based on the peroxymonosulfate activation of the magnetic biochar. The effect of peroxymonosulfate activation of magnetic biochar on RM19 removal was investigated. After 60 minutes, the removal efficiency of RM19 was observed to be 36%, 43%, and 48% for iron biomass ratios of 1:1, 2:1, and 3:1 , respectively. Upon examination of the results, the iron biomass ratio of 3:1 for peroxymonosulfate activation demonstrated the highest performance in RM19 removal. Other parameters affecting RM19 removal were investigated by taking the combustion temperature of 500°C and the iron biomass ratio of 3 / 1 in magnetic biochar production.

[0029] In experiments investigating the effect of magnetic biochar in a polluted environment, it was found that the pH value of the solution has a significant effect on the activation of peroxymonosulfate (Wang et al., 2024). Therefore, the effect of pH on the magnetic BK / PMS system was investigated at pH 3, 5, 7, and 9, respectively. Below a pH value of 7, sulfate radicals are the dominant reactive species; however, hydroxyl and sulfate radicals participate equally in reactions at neutral pH values. Similarly, peroxymonosulfate (HSO5-) can be activated by forming sulfate radicals. The resulting radicals can then participate in other reactions (Matzek, 2016).

[0030] In Figure 8, the removal efficiency decreases as the initial pH of the reaction increases from 3 to 5, 7, and 9. The effect of initial pH on RM19 removal using a 25 mg / L RM19 solution at a 0.5 mM peroxymonosulfate concentration and a 0.02 g / L magnetic biochar dosage is shown in Figure 8. When the initial pH of the RM19 solution was 3, 5, 7, and 9, the RM19 removal efficiency obtained during the 60-minute reaction time was 86%, 44%, 40%, and 26%, respectively. Removal efficiencies decreased gradually at pH levels of 5, 7, and 9. The lowest removal efficiency was obtained at pH 9, at 26%. Under acidic conditions, peroxymonosulfate (PMS) stands out in the form of HSO5-, which has a stronger oxidation capacity compared to SO52-. Furthermore, functionalization may occur on the catalyst surface under alkaline solutions, which can lead to the deterioration of PMS's adsorption and catalytic oxidation capabilities at higher pH conditions due to the electrostatic repulsive force formed between PMS and catalysts.

[0031] At the same time, to determine whether the presence of magnetic biochar causes oxidation or adsorption, the removal efficiency of RM19 was observed to be 7% in a 60-minute reaction time using only magnetic biochar (MBK: 0.2 g / L and PMS: 0 mM) without peroxymonosulfate. As shown in Figure 9(b), in the presence of magnetic biochar and peroxymonosulfate, this removal efficiency increased to 87%.

[0032] In traditional biochar production, most catalysts are difficult to recycle because they are in powder form. In this study, biochar has been converted into magnetic biochar that can be easily separated using a magnet to increase its recyclability. Magnetic biochar can be separated very easily from the solution, which not only greatly increases its recyclability but also prevents secondary pollution in the water body. First, the separated magnetic biochar can be reused after being cleaned 4 times, as shown in Figure 10. The RM19 removal efficiency performance of the original magnetic biochar decreased to 87%, 84%, 80%, and 79% from the first to the fourth cycle, respectively. The removal rate of the magnetic biochar decreased slightly after each reuse and still maintained 79% after four uses. There may be two reasons for this slight decrease. First, the deactivation of some active sites may have led to a decrease in catalytic performance. Second, RM19 adsorbed onto the catalyst may have been oxidized by ROS and converted into intermediate products, which may still be adsorbed onto the catalyst (Sun et al., 2023).

[0033] As a method, pea shells obtained from local producers in Kastamonu were dried in an oven at 60°C for 3 days and reduced to a particle size of 250-500 pm. The pea shells were stirred in a 20% Na2CO3solution for 30 minutes and carbonized at 500°C for 2 hours in a nitrogen gas atmosphere. Subsequently, they were left to stand with 0.1 M HCI until no more gas bubbles formed, washed until a neutral pH was reached, and dried at 105°C. The resulting biochar was named pea shell biochar (PSBC). To impart magnetic properties, 3 g FeCI36H2O and 3 g FeSO47H2O were added to a solution containing 100 mL of distilled water and 50 mL of ethanol. 1 g of BCBK was heated in a hydrothermal reactor at 180°C for 12 hours and the pH was increased with 1 M NaOH to obtain a black precipitate. The precipitate obtained was washed with ethanol and pure water and dried at 105°C and named magnetic pea shell biochar (MPSBC).

Claims

CLAIMS1- The invention is a method for producing magnetic biochar from pea shells using a hydrothermal method, characterized by:• Collection of pea shells,• Drying them in an oven at 60°C for 3 days,• Reducing them to a particle size of 250-500 pm,• Mixing the particles in a 20% Na2COs (sodium carbonate) solution for 30 minutes and leaving them overnight,• Drying them,• Carbonizing at 400-600°C, preferably 500°C, for 2 hours in a nitrogen gas environment,• Leaving it in 0.1 M HCI (hydrochloric acid) until no gas bubbles form,• Washing it until it reaches a neutral pH and drying it at 105°C,• Adding 3 g FeCl3'6H2O (iron(lll) chloride hexahydrate) and 3 g FeSO4'7H2O (iron(ll) sulfate heptahydrate) to a solution containing 100 mL distilled water and 50 mL ethanol to impart magnetic properties to the resulting biochar,• Heating 1 gram of pea shell biochar in a hydrothermal reactor at 180°C for 12 hours,• The pH was raised to a fundamental value using 1 M NaOH (sodium hydroxide) until a black precipitate was obtained.• Washing the obtained precipitate with ethanol and distilled water.• Drying it at 105°C.these steps characterize the process.

Images