Nitrogen-doped Biochar Research Articles

Conversion of N-doped biochar from carotenoid-extracted Tetraselmis suecica and its application to produce supercapacitors

Microalgae are one of the promising feedstocks for biorefinery, contributing significantly to net-zero emissions through carbon capture and utilization. However, the disposal of microalgal byproducts from the manufacturing process causes additional environmental pollution, thus, a new application strategy is required. In this study, the Tetraselmis suecica byproduct from the carotenoid extraction process was carbonized and converted into biochar. The converted biochar was proved to be nitrogen-doped biochar (NDB), up to 4.69%, with a specific surface area of 206.59 m2/g and was used as an electrode for a supercapacitor. The NDB electrode (NDB-E) in half-cell showed a maximum specific capacitance of 191 F/g. In a full-cell test, the NDB-E exhibited a high energy density of 7.396 Wh/kg and a high-power density of 18,100 W/kg, and maintained specific capacity of 95.5% after charge and discharge of 10,000 cycles. In conclusion, our study demonstrated that the carotenoid-extracted microalgal byproducts are a useful resource for the supercapacitor production. This approach is the first to convert T. suecica into active materials for supercapacitors.

Highly-efficient persulfate activation by nitrogen-doped biochar derived from dewatered sewage sludge for 2,4-dichlorophenol removal: Process and mechanism

Sewage sludge represents a promising substrate, meriting investigation for its nutrient content and potential for repurposing. Nitrogen-doped biochar (NSC) was synthesized from dewatered sludge over a range of pyrolysis temperatures, spanning 400–800 ℃. This study explores the efficacy of NSC in enhancing the removal of 2,4-dichlorophenol (2,4-DCP) through the integrated processes of adsorption and persulfate (PS) activation, marking its inaugural investigation in this work. The adsorption behavior was best described by both the pseudo-second-order kinetic model and the Freundlich isotherm model. Under conditions with an unadjusted pH value, [PS] at 2 mM, [NSC] at 5 g/L, and [2,4-DCP] at 100 mg/L, the NSC800 (pyrolyzed at 800 ℃)/PS system achieved a complete removal of 2,4-DCP within 120 minutes. The results from radical quenching tests, electron paramagnetic resonance (EPR), and electrochemical analysis indicated that 2,4-DCP degradation occurred via both radical and non-radical mechanisms. Among the nitrogen species, graphitic N was identified as the predominant PS activation site. The NSC800/PS system demonstrated notable catalytic efficiency and stability in the removal of 2,4-DCP, maintaining its efficacy in the presence of Cl-, NO3-, H2PO4-, and CO32-. Significantly, the optimal reaction stoichiometric efficiency (RSE = 72.059%) was observed at the minimal PS concentration. This research introduces a novel methodology for municipal sludge valorization, proposing an economical biochar designed for the combined adsorption and catalytic degradation of organic pollutants.

Unveiling the activation mechanism: The role of nitrogen-doped biochar in enhancing Fe(VI) catalysis

Despite the widespread use of biochar as a heterogeneous catalyst in AOPs, there is still a need to clarify the activation mechanism of nitrogen-doped biochar on ferrate (Fe(VI)). The Fe(VI) activation was significantly enhanced by the nitrogen-doped biochar synthesized at 800 °C (BCN-800) in this research, resulting in improved degradation of carbamazepine. Characterizations showed that a honeycomb-like pore and channel structure was formed on the inner layer of modified biochar and the SSA and pore volume were increased five and two times respectively as the temperature raised to 800 °C. Numerous indications indicated that the main active oxidizers in the BCN-800/Fe(VI) system were the high Fe species, and subsequent examination unveiled that the incorporation of nitrogen resulted in decreased resistance to charge transfer and enhanced efficiency of electron transfer for the production of high Fe species. DFT calculation illustrated that the SET path in the BCN-800/Fe(VI) system was spontaneous and single-electron oxygen atom transfer was the primary path for generating more highly reactive Fe(V) species. Notably, the BCN-800 remains stable after the organic degradation reaction and the toxicity of the intermediates produced during degradation decreases. This research will not only establish a theoretical foundation for designing eco-friendly catalysts based on biochar but also boost the investigation of biochar's ecological impacts.

Green synthesis of highly pyrrolic nitrogen-doped biochar for enhanced tetracycline degradation: New insights from endogenous mineral components and organic nitrogen synergy

The synthesis of efficient and environmentally friendly persulfate (PS) catalysts is currently a prominent research focus. This study employs single-step carbonization to investigate the interactions between endogenous mineral components (EMCs) and N-doping of nitrogen-rich biomass, aiming to design efficient biochar-based catalysts for enhanced tetracycline (TC) degradation. Biochars (PBC and SBC) derived from peanut hulls (PH) and soybean curd residue (SCR) with similar EMCs (ash ratio 16:19) but varying nitrogen content (1 % vs 1.53 %) were achieved, along with melamine-N-doped PBC (PBCN) for comparison under identical conditions. Physicochemical and quantum-chemistry analyses were conducted to investigate the synergistic effects between EMCs and organic-nitrogen in terms of morphological structures, active sites, and catalytic persulfate (PS)-mediated degradation of TC. The findings revealed that the optimal synthesis temperature for the efficient biochar-based catalyst was 800 °C. In contrast to exogenous N-doping with higher N-content (7.81 %), organic-N accelerated lattice disruption, leading to enhanced interactions with EMCs and resulting in the formation of hierarchical structures and pyrrole-N (organic-N 43.44 % > exogenous-N 17.67 %). The SBC/PS system exhibited superior degradation capability, with rapid removal of 95 % in 100 mg·L-1 TC. Density functional theory (DFT) confirmed that the non-radical pathways including 1O2 and electron transfer, facilitated by the presence of CO and pyrrole-N, were responsible for binding PS and forming biochar-PS*. This study furnishes both experimental data and theoretical insights, supporting the targeted control and efficient advancement of eco-friendly, high-value biochar-based catalysts.

Novel magnetic nitrogen-doped biochar (NBC) as an activator for peroxymonosulfate to degrade naphthalene: Emphasizing the synergistic effect between NBC and MnFe2O4

The conversion of agricultural biomass waste to value-added biochar (BC)-based catalysts receives tremendous interest because it falls under the resource recycle concept. In this work, a magnetic iron–manganese bimetallic catalyst (MnFe2O4@NBC) with nitrogen-doped BC as the carrier was prepared through the solvothermal method using agricultural waste walnut shells as the precursor. Moreover, the structure, morphology, and magnetic separation properties of the catalyst were comprehensively analyzed by various characterization methods. The prepared MnFe2O4@NBC catalyst was coupled with peroxymonosulfate (PMS) for oxidative degradation of naphthalene (NAP). Results showed that MnFe2O4@NBC could effectively activate PMS, and the removal rate of NAP could reach 80.17 % in 120 min. The degradation of NAP through the synergistic action of the free radical pathway (SO4− and OH) and the nonradical pathway (1O2), but the free radical pathway was dominant. XPS, electrochemical profiles, and DFT calculations confirmed that the catalyst surfaces of Fe2+, Mn2+, CO, and pyridine nitrogen and the defective structures are important reaction sites for PMS activation; the synergistic effect of Fe and Mn bimetals promotes the rapid cycling of metal redox pairs, whereas NBC promotes the dispersion of MnFe2O4, the direct activation of PMS, the enhancement of electron transfer, and the formation of a built-in electric field to facilitate the activation process. The catalysts showed a decrease in the removal of NAP after three times of reuse, but their activity could be restored by simple heat treatment, thus showing great potential for application. In brief, this work provides an efficient MnFe2O4@NBC heterogeneous catalyst and a new insight into PMS activation, which extends the potential application of BC-based catalysts for environmental remediation.

Single-atom iron cocatalyst for highly enhancing TiO2 photocatalytic degradation of antibiotics and antibiotic-resistant genes

The efficient and sustainable utilization of solar energy and biomass resources through photocatalysis is important for achieving a carbon–neutral energy cycle. Here, we report an efficient photocatalyst SA-Fe@TiO2, where single-atom Fe sites are anchored to nitrogen-doped biochar and coupled with anatase TiO2. This innovative biochar-supported single-atom catalyst serves as a novel cocatalyst that can facilitate charge carrier separation and transfer. SA-Fe@TiO2 achieves an increase of 4.3 times in apparent rate constant for the degradation of the antibiotic sulfamethoxazole (SMX) and exhibits superior capacity for inactivating antibiotic-resistant genes compared with pure TiO2. Experimental evidence reveals the remarkable resistance of SA-Fe@TiO2 against environmental interferences, unveiling the involvement of three primary reactive species (h+, •OH, and •O2−) in SMX photodegradation. In addition, we fabricate immobilized SA-Fe@TiO2 films that effectively degrade five distinct antibiotics within 20 min. This study presents a new method for developing single-atom photocatalysts for highly efficient environmental remediation in the context of carbon neutrality.

Synergistically enhancing nitrate reduction into N2 in water by N-doped Pd–Cu biochar bimetallic single-atom electrocatalysis

Noble metal materials have been identified as high efficiency catalysts for electrocatalytic reduction of nitrate, and the synthesis and manufacture of high catalytic activity and environmentally friendly catalysts of activating hydrogen for water purification applications is extremely attractive. In this work, the Pd–Cu single-atom catalysts (Pd–Cu-N-BC) were first prepared by direct growth of Pd–Cu single-atom on bamboo biochar by regulating the concentration of precursors and doping method, and then enhanced electrocatalytic reduction nitrate performance and N2 generation. The results showed that Pd–Cu-N-BC displayed excellent catalytic activity and reusability in electrocatalytic reduction nitrate with a low potential of 0.47 V vs. RHE (@10 mA cm−2). The maximum nitrate removal efficiency and N2 generation could reach about 100% and 72.32% within 180 min, respectively. The density functional theory (DFT) calculations confirmed that Cu atoms could catalyze the electrochemical reduction of nitrate to nitrite, and Pd atoms anchored in the nitrogen-doped biochar (N-BC) lattice could catalyze electrochemical reduction of nitrite to N2 involving the formation of hydrogen radical (H*). The characterization results of XANES showed that electronic synergistic effect between Pd and Cu single atoms significantly promotes the N2 production through hydrogenation while inhibiting the generation of byproducts, leading to significantly enhanced electrocatalytic reduction of nitrate to N2. Finally, Pd–Cu-N-BC was designed as a 3D particle electrode for enhanced electrocatalytic reduction of nitrate, exhibiting excellent stability and reusability, which could be considered as a suitable candidate for applications in the remediation of nitrate contamination.Graphical

Nitrogen-doped porous carbon through K2CO3-activated bamboo shoot shell for an efficient CO2 adsorption

In this paper, a two-stage approach was employed to produce nitrogen-doped porous carbons from bamboo shoot shells. These shells were utilized as a cost-effective biomass resource for the production of activated carbon in gas adsorption. The initial step involved co-carbonization of the bamboo shoot shells with urea, followed by activation using potassium carbonate. A series of nitrogen-doped biochar was prepared by varying the activation temperature and activator ratio. This approach allowed for the investigation of their potential in capturing CO2. Surface analyses were conducted using BET, SEM, and TEM techniques to examine the structural evolution of nitrogen-doped biochar. The results revealed that the fibrous structure of the bamboo shoot shells was well-preserved after carbonization and nitrogen doping, while activation resulted in the formation of a distinct worm-like microporous structure. Among them, the sample BNC-800-2 possessed the largest specific surface area of 1985 m2/g. Notably, the nitrogen-doped biochar activated at 800 °C exhibited remarkable capacity for adsorbing carbon dioxide, with values of 7.52 mmol/g and 3.60 mmol/g at 1 bar and temperatures of 0 °C and 25 °C, respectively. The adsorbent also demonstrated excellent cyclic stability and selectivity for gas mixture (CO2 and N2), attributed to its large specific surface area and narrow pore size, which synergistically contributed to its performance. Furthermore, the adsorption equilibrium was analyzed using the Langmuir and Freundlich isotherm models, with the experimental data showing significant agreement with the Freundlich isotherm model. Additionally, thermodynamic calculations confirmed that the adsorption process of CO2 on nitrogen-doped biochar was spontaneous and exothermic, indicating physical adsorption. This further validates the efficacy of the adsorbent in capturing CO2. This study demonstrates the potential of bamboo shoot shells as a low-cost biomass resource for producing effective adsorbents for CO2 capture.

Microporous Nitrogen-Doped Activated Biochars Derived from Corn: Use of Husk Waste and Urea for CO2 Capture

The increase in anthropogenic activity over time has led to an exponential increase in greenhouse gas emissions, especially CO2. Profitable technologies for CO2 capture and separation are conspicuous, and porous biochars derived from biomass waste can be a useful solution. Herein, we produced activated nitrogen-doped biochars for CO2 capture from corn husk waste, urea and K2CO3, named N-Bio-X (X = 600, 700, and 800 °C). N-Bio-X exhibited microporosity and different nitrogen contents and thus played an important role in the adsorption of CO2. N-Bio-700 exhibited the highest CO2 adsorption capacity, fastest adsorption kinetics and excellent stability after multiple adsorption-desorption cycles. N-Bio-600 showed excellent CO2/N2 selectivity, induced by nitrogen sites, particularly pyridinic and graphitic nitrogen. The cost-effectiveness of the raw material, coupled with its high adsorption capacity, rapid kinetics, and stable properties, provided highly promising N-doped biochars for practical implementation in CO2 capture and separations in postcombustion processes.

Fabrication of modified-N-doped porous biochar and its enhanced adsorption of bisphenol-A: Critical contribution to π–π interactions by nitrogen doping

A novel nitrogen-doped porous biochar (NS@LBC800) was prepared for bisphenol A (BPA) removal using waste loofah as raw materials, NaHCO3 as the activator, and urea as a nitrogen source. Pre-experiments confirmed the optimal preparation conditions. At 318 K, the adsorbed amount was 308.42 mg g−1. Higher temperatures and adsorbent dosage promoted adsorption. The pseudo-second-order model and Langmuir, respectively, described kinetic and isothermal processes well. Characterization and theory calculation showed that the efficient adsorption was attributed to its superb pore structure and N-atom doping. Among the numerous adsorption driving forces, the most important were the pore-filling effect and π-π interactions. Also, the contribution of hydrogen bonding and hydrophobic interactions was unable to be ignored. NS@LBC800 had good universality and recyclability. The results may provide theoretical guidance for nitrogen-doped biochar preparation and BPA removal.

Significant Differences in the Effects of Nitrogen Doping on Pristine Biochar and Graphene-like Biochar for the Adsorption of Tetracycline.

To improve the adsorption efficiency of pollutants by biochar, preparing graphene-like biochar (GBC) or nitrogen-doped biochar are two commonly used methods. However, the difference in the nitrogen doping (N-doping) effects upon the adsorption of pollutants by pristine biochar (PBC) and GBC, as well as the underlying mechanisms, are still unclear. Take the tetracycline (TC) as an example, the present study analyzed the characteristics of the adsorption of TCs on biochars (PBC, GBC, N-PBC, N-GBC), and significant differences in the effects of N-doping on the adsorption of TCs by PBC and GBC were consistently observed at different solution properties. Specifically, N-doping had varied effects on the adsorption performance of PBC, whereas it uniformly improved the adsorption performance of GBC. To interpret the phenomenon, the N-doping upon the adsorption was revealed by the QSAR model, which indicated that the pore filling (VM) and the interactions between TCs with biochars (Ead-v) were found to be the most important two factors. Furthermore, the density functional theory (DFT) results demonstrated that N-doping slightly affects biochar's chemical reactivity. The van der Waals (vdWs) and electrostatic interactions are the main forces for TCs-biochars interactions. Moreover, N-doping mostly strengthened the electrostatic interactions of TCs-biochars, but the vdWs interactions of most samples remained largely unaffected. Overall, the revealed mechanism of N-doping on TCs adsorption by biochars will enhance our knowledge of antibiotic pollution remediation.

Effect of CO2-rich atmosphere on nitrogen configuration of char and bio-oil during nitrogen-rich pyrolysis of cellulose

Different volume ratios of carbon dioxide and nitrogen were mixed into the nitrogen-rich pyrolysis of cellulose, resulting in the production of nitrogen-doped biochar and nitrogen-containing bio-oil. When the urea mixture ratio was greater than 50%, the added CO2 promoted the production of nitrogen-containing bio-oil, reaching a maximum of 26.03% (M = 50%) at 10 vol% CO2 + 90 vol% N2. Pyridine, pyrrole, and amines were the main nitrogen-containing compounds produced when using atmospheres of pure nitrogen and carbon dioxide. Upon increasing the volume ratio of CO2, the nitrile content increased significantly, becoming one of the main nitrogen-containing compounds. In addition, due to chemical stability, the thermal conversion of CO2 demands a significant input of energy, so the required activation energy also increased. Adding CO2 to simulate high-temperature anoxic flue gas is a promising method for biomass pyrolysis to obtain nitrogen containing chemicals with high added value and high nitrogen doped Biochar.

Incorporation of N-doped biochar into zero-valent iron for efficient reductive degradation of neonicotinoids: mechanism and performance

The extensive use of neonicotinoids on food crops for pest management has resulted in substantial environmental contamination. It is imperative to develop an effective remediation material and technique as well as to determine the evolution pathways of products. Here, novel ball-milled nitrogen-doped biochar (NBC)-modified zero-valent iron (ZVI) composites (named MNBC-ZVI) were fabricated and applied to degrading neonicotinoids. Based on the characterization results, NBC incorporation introduced N-doped sites and new allying heterojunctions and achieved surface charge redistribution, rapid electron transfer, and higher hydrophobicity of ZVI particles. As a result, the interaction between ZVI particles and thiamethoxam (a typical neonicotinoid) was improved, and the adsorption–desorption and reductive degradation of thiamethoxam and ·H generation steps were optimized. MNBC-ZVI could rapidly degrade 100% of 10 mg·L−1 thiamethoxam within 360 min, its reduction rate constant was 12.1-fold greater than that of pristine ZVI, and the electron efficiency increased from 29.7% to 57.8%. This improved reactivity and selectivity resulted from increased electron transfer, enhanced hydrophobicity, and reduced accumulation of iron mud. Moreover, the degradation of neonicotinoids occurred mainly via nitrate reduction and dichlorination, and toxicity tests with degradation intermediates revealed that neonicotinoids undergo rapid detoxification. Remarkably, MNBC-ZVI also presented favorable tolerance to various anions, humic acid, wastewater and contaminated soil, as well as high reusability. This work offers an efficient and economic biochar-ZVI remediation technology for the rapid degradation and detoxification of neonicotinoids, significantly contributes to knowledge on the relevant removal mechanism and further advances the synthesis of highly reactive and environmentally friendly materials.Graphical

Porous pie-like nitrogen-doped biochar as a metal-free peroxymonosulfate activator for sulfamethoxazole degradation: Performance, DFT calculation and mechanism

Design and development of low-cost, high-efficient, metal-free persulfate heterogeneous catalysts was a hot research topic. Herein, porous pie-like nitrogen-doped biochar (NBC) was prepared by one step high temperature pyrolysis of rape straw, urea and ZnCl2 mixture, and applied for peroxymonosulfate (PMS) activation toward sulfamethoxazole (SMX) degradation. Among these as-prepared catalysts, the NBC2.0 sample presented the best catalytic activity, with the 99.8 % SMX degradation efficiency in 5 mins and the 81.7 % total organic carbon (TOC) removal rate in 30 mins. Additionally, it could realize an excellent SMX degradation in the wide pH range of 3.0 to 9.0, and possessed the high degradation efficiency in presence of various organic pollutants or in real water environments, indicating its good pH adaptability, universality and practicality. Mechanistic investigations disclosed that the NBC2.0/PMS/SMX system involved both radical and non-radical degradation pathways, with singlet oxygen (1O2) and the direct electron transfer mechanism being the main contributors. The main active reaction sites of NBC were graphitic N, pyridinic N and C = O group, as corroborated by density functional theory (DFT) calculation and X-ray photoelectron spectroscopy (XPS) measurement. The possible SMX breakdown routes were determined by intermediate identification. This work provides a promising metal-free persulfate catalyst for environment remediation.

Shiitake spent mushroom substrate as a sustainable feedstock for developing highly efficient nitrogen-doped biochars for treatment of dye-contaminated water

Edible white-rot mushrooms are organisms that are cultivated at an industrial scale using wood-based substrates. The mushroom industry has an estimated annual production of 34 Mt of edible mushrooms, and approximately 70 wt% of the substrate is left as waste known as spent mushroom substrate (SMS). The huge volumes of SMS generated by mushroom farms hinder proper recycling, meaning that combustion or open-field burning are common disposal practices. This paper shows a concept that could help reduce the environmental impact of the mushroom industry. SMS from the cultivation of shiitake mushroom was used as a carbon precursor for the production of nitrogen-doped activated biochar that was used to remove reactive orange-16 (RO-16) azo dye from water, as well as contaminants from two synthetic effluents and real sewage water. Melamine was used as a nitrogen dopant and phosphoric acid as an activating agent. Samples without the addition of melamine were used for comparison. The doping/impregnation process was carried out in one-step, followed by pyrolysis at 700 and 900 °C for 1 h. BET, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used for the characterization of the biochars. The specific surface area of the doped samples was slightly lower, i.e., 1011 m2/g (SMS-700 °C), 810 m2/g (SMS-700 °C + N), 1095 m2/g (SMS-900 °C), and 943 m2/g (SMS-900 °C + N). Raman spectroscopic analysis showed that the N-doped biochars had more defective carbon structures than the non-doped ones. XPS analysis showed that doping with melamine led to the formation of N-functionalities on the surface of the biochar particles. The kinetics of adsorption were well represented by the Avrami model. The adsorption isotherms were well-fitted by the Liu model. The maximum adsorption capacities (qmax) of RO-16 were much higher for the N-doped biochars, i.e., 120 mg/g (SMS-700 °C), 216 mg/g (SMS-700 °C + N), 168 mg/g (SMS-900 °C), and 393 mg/g (SMS-900 °C + N). N-doped biochar samples were more effective for the removal of contaminants from synthetic effluents and sewage water. N-doped biochar produced at 900 °C showed good recyclability. This work concludes that SMS is a valuable waste that could be used for the production of activated carbon and that N-doping helped to improve the adsorption performance to a great extent.

Combined microbe-plant remediation of cadmium in saline-alkali soil assisted by fungal mycelium-derived biochar

Cadmium contamination in saline-alkali soil is becoming a great concern. Combined microbe-plant remediation is an economic way to treat this contamination, but is compromised by its low cadmium-removing capacity. In this study, the novel fungus-derived biochar was prepared to enhance the salt-tolerant bacterium-plant remediation of cadmium-contaminated saline-alkali soil. This biochar was prepared by pre-incubation of living Trichoderma atroviride hyphae with imidazole and further heating at 500 °C for 1 h. The obtained fungus-derived nitrogen-doped biochar (FBioCN) exhibited the high affinity to bacterial cells, leading to efficient colonization of exogenous salt-tolerant bacteria (e.g., Rhizobacter sp. and Sphingomonas sp.) on Amaranthus hypochondriacus roots. During culturing of the plants in the cadmium-contaminated saline-alkali soil, FBioCN drastically remodeled the rhizosphere microbiome, leading to enhance colonization of the exogeneous salt-tolerant bacteria, and increase bacterial diversity. The combination of FBioCN and the exogeneous bacteria further improved the activity of rhizosphere functional enzymes, protected the plants from the multiple stress, and promoted cadmium transport from the soil to the plants. Consequently, FBioCN together with the salt-tolerant bacteria drastically improved cadmium removal from the saline-alkali soil, with the percent of cadmium removal at the rhizosphere region increasing from 35.1% to 95.1%. This study sheds a light on the application of fungus-derived biochar in combined microbe-plant remediation in saline-alkali soil.

Nitrogen-doped biochar from algal biomass: preparation, modification, and application

Nitrogen-doped biochar from algal biomass: preparation, modification, and application

Production of bio-oil and biochar by the nitrogen-rich pyrolysis of cellulose with urea: Pathway of nitrile in bio-oil and evolution of nitrogen in biochar

The production of nitrogen-containing chemicals from renewable biomass under nitrogen-rich conditions represents a promising technological pathway. Urea, as a nitrogen carrier, offers advantages over gaseous ammonia due to its easier storage and transportation. In this study, cellulose and two of its model compounds (cellobiose and glucose) were used as raw materials. The effects of different urea concentrations on the types and relative contents of bio-oil components and the properties of nitrogen-doped biochar were analyzed using GC-MS, FT-IR, and elemental analysis. We further clarified the evolution of exogenous nitrogen in nitrogen-rich pyrolyzed bio-oil and biochar with different urea concentrations. Cellobiose was found to be a more suitable feedstock for the production of nitrogen-containing compounds from nitrile than cellulose or glucose. A significant increase in the relative content of nitrile compounds (44.45%) was observed at a ratio of 40% cellulose to nitrogen carrier. Analysis of the bio-oil fraction led to the conclusion that there may be two main pathways for the production of the two nitrile compounds, acetonitrile and propionitrile. This research provides a better understanding of the N transfer pathways during the nitrogen-rich pyrolysis of cellulose and its model compounds (cellobiose and glucose) when using urea as the nitrogen carrier. This will facilitate further improvements in the yield of nitrogen-containing compounds in bio-oil.

Effect of Nitrogen-doped − Palm Oil Mill Effluent Sludge-biochar as Peroxydisulfate Activator on the Removal of Methylene Blue Dye as an Environmental-friendly Approach

Introduction: Water pollution caused by dyes is a major problem as it is a toxic chemical that can cause chronic diseases when exposed to humans and aquatic habitats. Sulfate-based advanced oxidation process based on peroxydisulfate (PDS) has received a lot of attention recently for achieving color degradation in wastewater. Transition metal-based homogeneous/heterogeneous catalysts have shown to be a good alternative for the activation of persulfate. Nonetheless, this leads to significant secondary contamination due to metal leaching. Alternatively, nitrogen-doped biochar is a promising non-metal persulfate activator due to its lower cost and more environmentally friendly. Methods: Biochar from Palm Oil Mill Effluent (POME) sludge doped with nitrogen source of urea, ammonium chloride, and melamine was synthesized at a 700°C pyrolysis process and used to activate PDS. The nitrogen content of synthesized POME biochar was altered to ratios of 25:75, 50:50, and 75:25 respectively. Batch degradation experiments were then conducted to determine the feasibility of catalytic removal of methylene blue (MB) dye. Results: Based on experimental results, urea-doped biochar showed a greater MB removal compared to ammonium chloride and melamine-doped biochar. Besides that, higher nitrogen-to-biochar ratio increases the MB degradation significantly. A similar trend was demonstrated when a higher urea-doped biochar dosage was utilized. By utilizing 5.0 g of urea-doped biochar, a 100 ± 0.7% degradation of MB was achieved. Conclusion: This research provides an effective method to produce carbon-based catalysts from sludge recovery for activation of PDS, also enhancing the catalytic performance of biochar on MB dye removal by N-doping.

Enhanced SO2 adsorption performance on nitrogen-doped biochar: Insights from generalized two-dimensional correlation infrared spectroscopy

Nitrogen-doped biochar is considered as a renewable, cost-effective, and promising SO2 adsorbent. However, it is difficult to improve the physicochemical properties of biochar synergistically and clarify the adsorption mechanism. Therefore, in this study, a one-step high-temperature CO2-NH3 modification method was proposed for biochar to improve its SO2 adsorption, and the in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (in situ DRIFTS) was used to reveal the interface reaction mechanism between SO2 and nitrogen-doped biochar. The results showed that when the modification temperature exceeded 700 °C, CO2 and NH3 exhibited significant thermal activation and nitrogen doping on biochar simultaneously. Under a modification temperature of 800 °C (BCAN-800), the microporous surface area and nitrogen content of modified biochar reached the highest value of 563.83 m2/g and 6.63 wt%. The SO2 adsorption capacities of BCAN-800 were up to 201.89 mg/g and 145.68 mg/g at 30 °C and 120 °C, respectively. The results of in situ DRIFTS showed that dimeric and bridge hydrogen bonds were the main SO2 adsorption sites on nitrogen-doped biochar at 30 °C. With the increase of adsorption temperature, nitrogen-containing groups as the main adsorption site could combine with SO2 to form sulfamide (60 °C), which eventually existed in a more stable form of SO42−/R-O-SO2-OR′ (120 °C).