Structure Of Biochar Research Articles

Achieving up to 95% removal efficiency of chlorpyrifos pesticide using sugarcane bagasse-based biochar alginate beads in a continuous fixed-bed adsorption column.

Pesticide contamination in wastewater poses a significant environmental challenge, driven by extensive agricultural use. This study evaluates the removal of chlorpyrifos (CPS) using sugarcane bagasse-based biochar alginate beads in a continuous fixed-bed adsorption column, achieving a remarkable 95-98% removal efficiency. Compared to conventional adsorbents like activated carbon, which typically show CPS adsorption capacities ranging from 50-70 mg g⁻1 under similar conditions, the biochar alginate beads demonstrate better performance with a sorption capacity of 91.93 mg g⁻1. Fixed-bed column (FBC) experiments demonstrated optimal CPS removal at 10 ppm concentration, 5 cm bed height and a flow rate of 25 mL min⁻1. The Yoon-Nelson Model exhibited the best fit, with high correlation coefficients (R2 = 0.80 to 0.98), low Akaike's Information Criterion (AIC) and Sum of Square Error (SSE) values, confirming its predictive accuracy. The model predicted a CPS removal efficiency of 95-98% and a sorption capacity of 91.93 mg g⁻1. The immobilization process using sodium alginate not only provided structural integrity to the biochar alginate beads but also improved their surface area and functional groups, significantly enhancing the adsorption dynamics. An inverse relationship between breakthrough time (τcal) and flow rate was observed, indicating improved adsorption dynamics at higher flow rates. SEM analysis revealed a porous biochar structure with significant surface area (131.09 m2/g) and pore volume (0.165 cm³/g), contributing to its high adsorption efficiency. XRD analysis indicated the partial crystalline nature of the biochar alginate beads, influenced by the presence of alginate. Additionally, breakthrough curves suggested a rapid initial uptake followed by a plateau, highlighting the material's fast adsorption kinetics. Biochar alginate beads for pesticide adsorption demonstrated good results in the scale-up investigation. This research demonstrates the potential of biochar-based adsorbents for efficient and scalable pesticide remediation in contaminated water systems, underscoring the unique contributions of alginate-immobilized biochar in enhancing performance.

Controlled Synthesis of Biochar with Flower-like Morphology for CO2 Adsorption: Enrichment and Efficient Accessibility of N-Containing Sites.

The N-doped biochar is recognized as a promising, cost-effective, and efficient material for CO2 adsorption. However, achieving efficient enrichment of N-containing adsorption sites and improving their accessibility remains a bottleneck problem that restricts the adsorption performance of N-doped biochar. Herein, a synthesis strategy for nitrogen-doped biochar by one-pot ionothermal treatment of biomass and zeolitic imidazolate framework (ZIF) precursors accompanied by pyrolysis is demonstrated. Through ion thermal ZIF modification, biochar exhibits a controllable flower-like morphology with effective enrichment of nitrogen elements (nitrogen retention rates ranging from 62% to 88%). After pyrolysis, this regular morphology is retained, and a developed hierarchical pore structure is formed. Compared with pristine biochar and ZIF-derived carbon, ZIF-modified biochar has superior CO2 adsorption capacity (up to 3.5 mmol/g) and excellent CO2/N2 adsorption selectivity (up to 38.6). The CO2 adsorption capacities of ZIF-modified biochars have a good linear relationship with both bulk and surface N content, with correlative coefficients of around 0.998 and 0.950, respectively. This positional indifference reflects the effective accessibility of N-containing sites, which can be attributed to the ordered flower-like morphology and hierarchical pore structure of ZIF-modified biochar. The DFT results confirmed the importance of the number and accessibility of such N-containing sites for CO2 adsorption.

Effects of By-products of Co-pyrolysis on Biochar for Benzene Vapor Adsorption Performance

To explore the effects of the components in the raw materials and by-products of co-pyrolysis on the physicochemical properties of biochar, rice husk （RH, which has a high percentage of lignin and a low content of N） and sawdust （SD, which has a high percentage of both cellulose and N） were used as typical raw materials to prepare co-pyrolysis biochar. The benzene vapor adsorption performance of the obtained biochar was then tested on a fixed-bed device. At the same time, the by-product components generated during pyrolysis were analyzed using thermogravimetric （TG）, scanning electron microscopy （SEM）, and gas chromatography-mass spectrometry （GC-MS）. Several characteristic methods such as X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, and Raman spectroscopy were used for the structural analysis of biochar. The effect mechanism of the by-products of co-pyrolysis on the structure of biochar and the adsorption efficiency of biochar for benzene vapor was discussed. The results showed that the crystal structures of the prepared samples were not significantly different. The specific surface area of SD with a high cellulose content was 1.6 times higher than that of RH with a high lignin content after pyrolysis. The oleic acid in the raw material had a synergistic effect with the intermediate product, ammonia, from the decomposition of N-containing amino acids during co-pyrolysis. The by-product oleic amide was generated and aggregated to block the pores. The specific surface areas of RC1 was 134.28 m2·g-1. The benzene vapor adsorption capacity of co-pyrolysis biochar （RCn） was worse than that of pyrolysis biochar （RC and SC） and mixing pyrolysis biochar （RC-mSC）. Furthermore, the generation of oleic acid amides decreased with an increase in the amount of sawdust during pyrolysis. Thus, the adsorption capacity and specific surface area of RC4 increased to 238.78 mg·g-1 and 367.37 m2·g-1, respectively. The fitting k value from the Yoon Nelson kinetic equation of RCn was 0.060-0.084 min-1, which was higher than the value of 0.039 min-1 of SC. Thus, the co-pyrolysis improved the adsorption rate. In summary, the by-products of co-pyrolysis had an inhibitory effect on the benzene vapor adsorption capacity of the biochar. As the sawdust ratio increased, the inhibitory effect decreased. Furthermore, the adsorption process was fitted to a pseudo-first-order kinetic model, which mainly consisted of physical adsorption. The regeneration efficiency of RC3 exceeded 85% after five cycles, indicating its potential for industrial applications. The results revealed the key factor in the benzene adsorption performance of co-pyrolysis biochar from the composition of raw materials and by-products and provided a reference for the reduction, resource utilization, and harmless utilization of biomass.

Thermal treatment and densification of manure and biomass blends to produce stabilized soil amendments.

Land application of dairy manure is the most common practice for disposal of this waste. Agricultural fields surrounding concentrated animal feeding operations (CAFOs) often have high levels of N and P because of manure over-application. However, its low bulk density limits the amount of manure that can be profitably transported for use as fuel or fertilizer. As an alternative, selective carbonization can be used to create densified-stabilized N-containing products that can be delivered to regions with low soil N and P contents. This research reports developing a biomass (Douglas fir)/manure thermally treated product containing a maximum fraction of N integrated into the biochar structure. Response Surface Methodology (RSM) was used to identify processing conditions resulting in high C and N conversion efficiencies. Experimental results show maximum N conversion efficiencies were achieved at Douglas fir contents higher than 50wt % and temperatures close to 260°C. H3PO4 levels at 2wt % seems to be sufficient to catalyze the desired reactions. The KOH treatment did not significantly affect product yield and the efficiency of C and N conversion. The structural strength of densified char was evaluated using dynamic rheometric (amplitude sweep test).

Dynamic formation mechanism of persistent free radicals driven by water-phase oxidation-dependent heterogeneity of the carbon−silicon coupling structure in biochar

The formation of persistent free radicals (PFRs) in biochar (BC) is closely related to the structural characteristics and reactivity of BC, which have toxic effects on the environment. However, the mechanisms driving PFRs formation through structural evolution during oxidative aging of BC remain unclear. Herein, we propose a novel dynamic mechanism for BC-PFRs formation driven by oxidation-dependent heterogeneity in carbon−silicon coupling structures by evaluating their heterogeneous correlations, sequential responses, and synergistic relations. The sequential destruction of the “outer carbon−middle silicon−inner carbon” spatial layer and the transformation of molecular components caused by continuous oxidation of BC contributed to the formation of BC-PFRs with two concentration peaks. Moreover, two-dimensional correlation spectroscopy combined with infrared spectroscopy and high-resolution mass spectrometry revealed the sequential responses of carbon−silicon functional groups in BC (Si−O−Si groups → silicon enclosed structures → carbon groups) and BC-derived dissolved organic molecules (lipid-/aliphatic-/carbohydrate-like molecules → lignin-/tannin-like molecules → condensed aromatic molecules), leading to the staged formation of BC-PFRs. High molecular-weight lignin-/tannin-like and condensed aromatic molecules in the carbon layer contributed to BC-PFRs formation, whereas crystalline silicon components hindered the oxidative degradation of inner aromatic carbon and subsequent PFRs formation. Our findings help elucidate potential environmental behaviors and risks associated with BC-PFRs.

Study on adsorption characteristics of biochars and their modified biochars for removal of organic dyes from aqueous solution

Abstract To address organic dye pollution and agricultural waste comprehensive utilization, the biochar (ZB) was prepared using Rosa roxburghii residue as the material for preparation. Three modified biochars (ZBO, ZBS, and ZBH) were created using NaOH, Na2S, and H3PO4 as modifying agents. The morphology, structure, pore size, and elemental composition of biochars were characterized and analyzed by a combination of FTIR, SEM-EDS, and N2 adsorption–desorption techniques. Furthermore, the adsorption performance of the as-prepared biochars was investigated in the adsorption of RhB and MB dye process. The experimental findings showed that adsorption equilibrium for these dyes was achieved in 180 min. Moreover, the dye adsorption on biochars followed a pseudo-second-order kinetic equation. For the biochar (ZB), the Langmuir equation proved to be more appropriate than the Freundlich equation. In contrast, the Freundlich equation was more apt for the modified biochars. More importantly, Pearson's correlation analysis revealed that the adsorption rate and capacity of RhB positively correlated with the specific pore volume, t-plot micropore area, and BET surface area, but a negative one with the pore size. The MB adsorption showed the opposite correlations. This study reveals a novel biochar for adsorbing organic dyes, which provides a strategy for the treatment of Rosa roxburghii residue.

Removal of Cr(VI) from water using microalgae-based modified biochar: Adsorption performance, mechanisms, and life cycle assessment

Two types of biochar adsorbents, ZnCl₂-modified biochar (ZABC-5 and ZLBC) and H₃PO₄-modified biochar (HABC-5), were synthesized using algae powder and lake bloom algae. ZnCl2 as activator can change the surface structure of algal biochar and increase the adsorption site. ZABC-5 exhibited superior adsorption efficiency, achieving a maximum removal rate of 98.68 % for Cr(VI), featuring a defined surface area of 34.58 m2·g−1. Furthermore, it demonstrated excellent regeneration performance, maintaining over 98 % removal rate for Cr(VI) after three cycles using HCl as the desorbing agent. The multifaceted adsorption mechanism of Cr(VI) removal by ZABC-5 encompassed pore filling, electrostatic interaction, redox reactions, surface complexation, and ion exchange. Response surface optimization determined the optimal adsorption conditions for ZLBC, yielding an actual removal rate of 76 ± 4 %. Life cycle assessment revealed that the production of 1kg ZLBC and its utilization significantly reduce environmental impact, and the global warming potential is 12.70 kg CO2-Eq, while remaining cost-effective. Overall, this work provides a precedent by using lake bloom algae to create biochar adsorbents, showcasing the effectiveness and sustainability of algal biochar for removing Cr(VI) from water bodies and aiding environmental remediation.

Synergistic removal of ammonia nitrogen and hexavalent chromium by the hybrid-system of Acinetobacter baumannii AL-6 and original walnut shell biochar in solution: Mechanism and application

A novel hybrid-system was developed with the Acinetobacter baumannii AL-6 and original walnut shell biochar. Compared with strain AL-6 and biochar, hybrid-system exhibited an excellent synergistic removal ability for ammonia nitrogen (NH4+-N) and hexavalent chromium (Cr(VI)). And the maximum NH4+-N and Cr(VI) removal efficiency of hybrid-system were 93.30 % and 99.63 %, higher than 82.01 % and 56.49 % of strain AL-6, 5.35 % and 14.97 % of biochar, respectively. Strain AL-6 grew well in the presence of biochar and the ammonia oxygenase (AMO) activity of strain AL-6 was improved by adsorption of NH4+-N and Cr(VI) and release of beneficial elements (Ca, K and Mg) on biochar, which enhanced the biodegradation of NH4+-N. Environment persistent free radicals (EPFRs) and oxygen-containing functional groups of biochar could weaken the electron-competition between Cr(VI) and bacteria, biochar, which increased the removal performance of Cr(VI). The hydrophilic functional groups and mesoporous structure of biochar promoted the immobilization capacity of bacteria, which reduced the loose of bacteria from suspended bioreactor. Approximately 84.58 % - 87.97 % of NH4+-N and 1.18 mg·L−1-1.91 mg·L−1 of Cr(VI) were removed by the hybrid-system in sequencing batch reactor (SBR). Particularly, the removal performance of Cr(VI) was significantly improved as the per NH4+-N was degraded with increasing the operational time in SBR.

Understanding the physicochemical structure of biochar affected by feedstock, pyrolysis conditions, and post-pyrolysis modification methods – A meta-analysis

The impact of feedstock type, pyrolysis conditions, and post-pyrolysis modifications on the physicochemical properties of biochar has not been systematically evaluated. To this, a comprehensive meta-analysis was conducted to assess the impact of 17 effective variables including three groups of modification techniques (acidic, alkalic, H2O2, metal oxides, microbial, organic acids, physical, soil mineral), pyrolysis temperature (<400, 400–550, >550 °C), and feedstocks (herbaceous, hull, manure, nut, straw, wood). Also, 26 properties of the biochar were identified as being impacted; some of the most important among them are pH, cation exchange capacity (CEC), ash content (AC), specific surface area (SSA), carbonization (H/C), and surface functional groups (SFGs). The CEC of biochar modified by acidic, and soil mineral treatment significantly increased by 44.8 % and 48.5 %. The H/C ratio of biochar decreased in alkalic modification with a negative effect size of 7.2 %. Soil minerals, metal oxides, and alkalic modifications resulted in a positive change in AC with a 20.9 %, 15.7 %, and 13.6 % increase. Also, the highest SSA of modified biochar was observed when acidic and H2O2 modification methods were applied, with 57.1 % and 53.4 % effect sizes. Further, high pyrolysis temperature (>550 °C) aided in significantly increasing SSA and SFGs on modified biochar. Overall, the strong association of acidic modifiers, high pyrolysis temperature, and high lignin-based feedstock could contribute to high SSA, SFGs, and absorption efficiency of biochar. This meta-analysis establishes a robust comparative framework, advancing the precision of biochar modification strategies to maximize physicochemical properties for improved environmental remediation.

Green Power: The Role of Plant-Based Biochar in Advanced Energy Storage.

This comprehensive review aims to provide an overview of recent progress in utilizing plant-based biochar for supercapacitors. It specifically focuses on biochar derived from plant biomass such as agricultural residues, weeds and aquatic plants, examining their potential in energy storage applications. It explores various synthesis methods like pyrolysis and hydrothermal carbonization and evaluates their impact on biochar's structure and electrochemical properties. Additionally, it examines the electrochemical performance of biochar-based supercapacitors, focusing on parameters such as capacitance, cycling stability, and rate capability. Strategies to enhance biochar's electrochemical performance, such as surface modification and composite fabrication, are also discussed. Furthermore, it addresses existing challenges and prospects in harnessing plant-based biochar for supercapacitor applications, highlighting its potential as a sustainable and efficient electrode material for next-generation energy storage devices.

Removal of Pb2+ in aqueous solution by diatom-derived biochar: Role of inherent Ca/Mg minerals

Mineral components can significantly enhance the adsorption capacity of contaminants on biochar, yet research on the changes in mineral crystal structure within biochar and their effects on adsorption performance remains limited. In this study, biochar was prepared from diatom, an abundant and eco-friendly biomass, at various pyrolysis temperatures. Adsorption experiments were conducted to evaluate the removal of Pb²⁺ using diatom-derived biochar under different conditions. The results indicated that the primary mechanism of Pb²⁺ removal involved ion exchange between the inherent Ca/Mg minerals and Pb²⁺, followed by the formation of PbCO₃ and Pb₂(CO₃)₂(OH)₂ on biochar surface. Inherent Ca/Mg minerals contributed 93.1 % to Pb2+ adsorption capacity. Additionally, adsorption capacity of Pb²⁺ were found enhanced with increased pyrolysis temperature, which was due to the change of inherent Ca-minerals crystal structure in diatom-derived biochar. Furthermore, diatom-derived biochar demonstrated excellent adsorption capacity for Pb²⁺ up to 1027.0 mg·g⁻¹. The adsorption kinetics fitted well with pseudo-second-order model, and the adsorption isotherm was well-described by the Langmuir model. An increase in pH favored the adsorption process. These findings suggest that diatom-derived biochar could serve as a promising adsorbent for heavy metals in water.

The effect of biochar in a specialty adsorbent on enhanced PFAS removal from surface water

An enhanced specialty adsorbent, referred to as biochar-based iron and perlite-integrated green environmental media (BIPGEM), was designed to simultaneously remove both long-chain PFAS mainly including perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS) from surface water matrices. Batch-scale experiments using BIPGEM revealed that the removal efficiencies for PFOA and PFOS exceeded 98 % when treating a mixture of 3 short-chain PFAS, including perfluorobutanoic acid (PFBA), perfluorobutane sulfonic acid (PFBS), and hexafluoropropylene oxide dimer acid (GenX Chemicals). Additionally, a fixed-bed column study using BIPGEM revealed that the removal efficiencies of PFOA and PFOS were over 85 % within the first 12 h whereas the removal efficiency of PFBA was over 40 % at the fortieth hour. It was confirmed that the critical role of biochar in the removal of long-chain PFAS, particularly PFOA, can be attributed to the following factors: (1) the morphological structure and pore size of biochar restrict PFAS mobility, (2) the extensive specific surface area of biochar, with a positive charge (point of zero charge = 10.7) at the experimental condition, enhances the adsorption likelihood with the negatively charged hydrophilic heads of PFOA and PFOS, and (3) the presence of non-polar aromatic rings with high hydrophobicity in biochar facilitates the removal of PFAS through hydrophobic interactions with the functional groups of PFAS.

Enhanced sludge dewaterability and confined antibiotics degradation in biochar-mediated chemical conditioning through modulating Fe oxidative states distribution and reaction sites in multiphase

For antibiotic-enriched waste activated sludge, classical iron-based chemical conditioning significantly enhanced sludge dewaterability. Nevertheless, the intricate constituents within sludge rapidly depleted reactive oxygen species (ROS), leading to challenges such as excessive production of iron sludge and inadequate elimination of antibiotics from sludge. Herein, we proposed an innovative strategy integrating biochar with Fe(II) for peroxymonosulfate (PMS) activation, aiming to enhance both sludge dewaterability and antibiotics elimination simultaneously. Compared to classical chemical conditioning of Fe(II)/PMS, the presence of biochar not only reduced bound water content of sludge from 1.36 g/g DS to 0.97 g/g DS, but also enhanced sulfamethoxazole (SMX) degradation rate constant from 0.015 min-1 to 0.042 min-1. Mechanism studies disclosed the essential roles of biochar in modulating Fe oxidative states distribution and reaction sites in multiphase. Initially, biochar elevated Fe(II)/Fe(III) ratio from 0.38 to 0.78 by abundant carbon defects, which significantly promoted the cumulative concentration of predominant ROS, hydroxyl radicals (•OH), from 4.6 mM to 8.1 mM. Subsequently, EPS underwent destruction by •OH, leading to the liberation of antibiotics and negatively charged polysaccharides (PS), proteins (PN). Secondly, biochar enriched hydrophobic PN with an elevated ratio of PN/PS from 0.92 to 1.50, while the charge neutralization occurred between Fe(II)/Fe(III) and PN, PS, leading to sludge particles granulation. Finally, the mesoporous structure of biochar not only achieved SMX enrichment, but also enhanced the mass transfer of Fe(II)/Fe(III) from sludge aqueous phase to its surface, ensuring that the in-situ generated •OH efficiently targets the locally concentrated SMX. Overall, this work provides a new guidance for developing biochar-mediated chemical conditioning, aiming to enhance the generation and utilization of •OH for antibiotics elimination from sludge.

Magnetically separable sorbent based on activated carbon derived from a new precursor Rhizoclonium hookeri for facile oil spill clean-up

A huge quantity of synthetic toxic materials ends-up in water bodies causing long-lasting environmental and economic impacts due to catastrophic oil spill. Exploring marine algae as sorbent materials for oil spill remediation is a relatively new area and holds great potential. Herein, macroalgae Rhizoclonium hookeri (RH) derived magnetically recoverable activated carbon (RHAC@Fe3O4) composite has been proposed as an innovative and robust strategy for oil spill clean-up. The oil uptake efficiency of RHAC@Fe3O4 was probed using unused and used motor oil in synthetic seawater matrices by conducting batch wise experiments. Optimal conditions for the designed sorption system were met by varying time (10–60 min), dosage (0.2–1 g) and temperature (20, 30, 40 °C). Characterization studies showed that KOH-based activation played a vital role in developing pore structure and surface functionalities in the algal biochar. Batch experiments demonstrated over 90 % oil removal efficiency of RHAC@Fe3O4 from simulated oil spill after 30 min using 0.8 g of composite. Moreover, Fe3O4 loading onto carbon material allowed magnetic separation as a convenient alternative to filtration for the recovery of oil laden composite. Apart from superior oil removal ability, synthesized composite demonstrated robust performance up to five cycles in synthetic sea water matrices. Additionally, comparative study revealed better oil sequestration efficiency of the fabricated RHAC@Fe3O4 composite (93 %) as compared to its precursors, i.e. algal biochar (71 %) and AC (88 %). Based on these findings, it is advocated that designed RHAC@Fe3O4 composite being eco-friendly, economical and readily recoverable with enhanced oil uptake ability could potentially be an innovative platform for oil spill clean-up applications.

Hydrogen bonds between the oxygen-containing functional groups of biochar and organic contaminants significantly enhance sorption affinity

Sorption affinity is an essential parameter to immobilize contaminants, but the controlling structures of biochar with strong sorption affinity to organic compounds are unidentified, hindering targeted biochar modification. In the face of multiple types and structures of organic contaminants in the aquatic environment, it is urgent to prepare biochar which can remove a large number of contaminants by targeted biochar modification. This study compared the sorption and desorption of five different type organic contaminants on biochar and graphite to understand sorption affinity and to inform the structural regulation of biochar. The sorption capacity of organics on biochar was 3–7 times higher than graphite, and the desorption ratios of organics on biochar were approximately one-fourth of those on graphite. Hydrophobic areas and aromatic rings were confirmed to be low-energy sorption sites, and most pores were inaccessible. The stronger sorption affinity was thus attributed to the hydrogen bonds between biochar surface functional groups and organics. Furthermore, sorption capacity and desorption ratios correlated positively with calculated sorption thermodynamics and binding energies, aligning with theoretical models based on oxygen- and nitrogen-containing groups. Further verification experiments revealed that functionalized graphite with hydroxyl and carboxyl groups showed the most significantly increased sorption capacity and rate, and decreased desorption ratios, enhancing sorption affinity through hydrogen bonds. These findings offer valuable insights into biochar sorption affinity to organics and guide its structural regulation for organic pollution control in the aquatic environment.

Online in-situ modification of biochar for the efficient removal of elemental mercury and co-benefit of SO2/NO removal

In this study, non-thermal plasma discharge was proposed for online in-situ modification of biochar injected into coal-biomass co-combustion flue gas, aiming to achieve the combined removal of elemental mercury (Hg0), NO, and SO2 from flue gas. After plasma discharge, the pore structure of biochar was slightly improved whereas the surface morphology of biochar was almost unchanged. After plasma discharge under O2, SO2, and HCl atmospheres, the oxygen, sulfur, and chlorine contents of biochar were obviously increased. More exactly, additional functional groups were formed on the modified biochar surface, such as CO, C(O)OC, CS, and CCl. Compared with raw biochar, the biochar modified under HCl, SO2, O2, H2O and CO2 atmospheres exhibited higher Hg0 removal efficiency, and longer modification time resulted in better Hg0 removal performance. The optimal modification atmosphere and reaction temperature were the simulated flue gas (SO2 + HCl + CO2 + O2 + H2O + NO + N2) and 20 ℃-100 ℃, respectively. The modified biochar exhibited excellent resistance to SO2 and H2O. The addition of HCl, CO2, NO, and O2 contributed to Hg0 removal. The removal efficiency of NO and SO2 attained a maximum of 100 %. The Hg0 removal mechanism was further revealed, where CO, C(O)OC, CS, and CCl served as active components.

Nanoconfinement of MgO in nitrogen pre-doped biochar for enhanced phosphate adsorption: Performance and mechanism

Advanced metal-doped biochar with superior phosphate (P) adsorption capacity plays a crucial role in combating eutrophication, depending on the rational design of the biochar structure for uniform and nanoscale dispersion of metal oxides. Herein, the nanoconfinement of magnesium oxide (MgO) was successfully attained in nitrogen pre-doped biochar (Mg/N-BC). The well-dispersed MgO was confined within nanoscale structure of Mg/N-BC, delivering P adsorption capacity of 108.41 mg g−1 and adsorption rate of 18.01 mg g-1h−1. More importantly, its adsorption performance at equilibrium 0.5 mg P/L was 17.70 times higher. Results suggested the decrease in pore size was positively correlated with the increase of N, confirming the role of N pre-doping in structure shaping and MgO confinement. The enhanced P adsorption was attributed to the well-dispersed MgO nanoparticles within the biochar. This study introduced a facile synthesis approach for biochar-incorporated nanoscale MgO, offering a new strategy for enhanced P removal.

Hydrothermal preparation of pharmaceuticals adsorbents from chitin and chitosan: Optimization and mechanism

Hydrothermal treatment of fishery waste-derived chitin (CT) and chitosan (CS) was performed to prepare hydrochar adsorbents for the removal of pharmaceuticals of environmental concern. By systematically studying the effect of treatment conditions on the biochar structure, the correlation between hydrochar properties and the adsorption capacities was clarified to optimize the adsorption performance. CS hydrochars obtained by lower-temperature treatment showed high adsorption capacities for the pharmaceuticals having carboxyl groups attributed to the electrostatic binding. A decrease in the density of available amines in CS hydrochars prepared at higher temperatures resulted in lower adsorption capacities and the manifestation of different adsorption mechanisms based on hydrophobic and π-π interactions. CT hydrochars showed lower adsorption capacities than CS hydrochars due to inefficient carbonization and lack of adsorption sites. The hydrochar adsorbents prepared in this study address simultaneously the problems of marine waste bioresource utilization and environmental cleaning from the emergent pollutants.

Highly Efficient and Selective Hydrodeoxygenation of Guaiacol Using Ni-Supported Honeycomb-Structured Biochar and Phosphomolybdic Acid.

The sustainable development of energy has always been a concern. Upgrading biomass catalysis into hydrocarbon liquid fuels is one of the effective methods. In order to upgrade biomass derivative guaiacol by Hydrodeoxygenation (HDO) catalysis, this article report a three-dimensional honeycomb structure biochar loaded with Ni nanoparticles and phosphomolybdic acid demonstrating excellent catalytic performance in a short period of time. This is due to the porous structure of biochar, which allows Ni metal nanoparticles to be highly uniformly dispersed on the support, which enhances the catalytic hydrogenation of guaiacol in terms of both rate and efficiency. Furthermore, it was observed that the added phosphomolybdic acid dissolved within the temperature range of 78-90 °C, functioning as a homogeneous catalyst in the process. This proves advantageous, as the phosphomolybdic acid becomes accessible at any location within the porous Ni/C catalyst. The detailed characterization data revealed that the carbon support prepared in this study has a high specific surface area of up to 1375.61 m2/g. Additionally, the phosphomolybdic acid exhibited rich acidity, with Brønsted and Lewis acid contents of 2.55 μmol/g and 21.45 μmol/g, respectively. Reaction data demonstrated that at 240 °C for 180 min, 100 % conversion and 97.9 % cyclohexane selectivity were achieved. This study introduces a bifunctional catalyst with an unique catalyst's structure, facilitating a heterogeneous-homogeneous catalytic reaction and delivering an efficient catalytic effect.

Biochar captures ammonium and nitrate in easily extractable and strongly retained form without stimulating greenhouse gas emissions during composting.

During composting of organic waste, nitrogen is lost through gaseous forms and ion leaching. Biochar has been shown to capture mineral nitrogen (Nmin: NH4 + and NO3 -) from compost, which we hypothesize reduces N2O formation. However, associating Nmin captured by biochar with the dynamics of N2O and other greenhouse gas (GHG) emissions during composting remains unstudied and was the aim of this work. We composted (outdoor for 148 days) together kitchen scraps (43.3% dw, where dw is dry weight), horse manure (40.9% dw), and wheat (Triticum aestivum L) straw (15.8% dw) without (Control) or with biochar (Bc, 15% compost dw). The biochar consisted of hardwood and softwood pieces pyrolyzed at 680°C and exhibited 60% of particles with 4-8mm. We monitored compost GHG (CO2, CH4, N2O) emissions, Nmin content in compost and biochar particles (sequential extractions), and biochar surface transformations (SEM-EDX and 13C-NMR spectroscopy) along composting. Biochar did not significantly reduce or increase GHG emissions and Nmin content (mg kg-1) in compost. However, the final NO3 - amount (g compost pile-1) in the Bc treatment was significantly higher (54%) compared to the Control, indicating lower NO3 - losses. Despite the high aromaticity and minimal contribution of carboxyl C to the biochar structure, biochar retained NH4 +, mainly in easily extractable form (55%), in the first 2 weeks of composting and mainly in strongly retained form (75%) in the final compost. The NO3 - content in biochar increased continuously during composting. In the final compost, the NO3 - content extracted from biochar was 164 (37%, easily extractable), 80 (19%, moderately extractable), and 194mg NO3 --N kg-1 (44%, strongly retained). Although Nmin retention in biochar was not accompanied by lower N2O emissions, contradicting our hypothesis, we demonstrated the efficacy of biochar to recover Nmin from organic waste without stimulating GHG emissions.