Hierarchical porous biochar from kelp: Insight into self-template effect and highly efficient removal of methylene blue from water

Preparation of high-performance adsorption carbon materials via hydrothermal carbonization of agricultural solid waste-grapevines

This study uses grapevine agricultural waste to prepare grapevine-derived biobased activated carbon (AGV) through chemical activation with NaOH after hydrothermal carbonization. A comprehensive analysis of the adsorption performance and mechanisms of AGV for methylene blue (MB) was conducted. The results demonstrated that AGV possesses a highly developed reticular pore structure, with a specific surface area of 3230.57 m2 g-1 and is rich in oxygen functional groups (OFGs). At pH 7.0, AGV achieved a removal rate of 90 % within 30 min, with a maximum adsorption capacity of 661.7 mg g-1, surpassing that of most previously reported activated carbons. Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, with thermodynamics confirming endothermic and spontaneous MB adsorption. The adsorption mechanism primarily involves chemical adsorption, including electrostatic interactions, pore filling, hydrogen bonding, acid-base interactions, and π-π stacking. The AGV maintained 86.7 % adsorption efficiency after 5 cycles, demonstrating excellent recyclability. This study provides a novel approach for preparing high-performance adsorption materials from waste biomass.

A pyridinium-functionalized chitosan derivative as ecofriendly carrier for efficient adsorption and controlled release of 2,4-dichlorophenoxyacetic acid sodium

Herbicides with wide use and low efficiency in agriculture severely threaten the environment. However, employing adsorbents and controlled-release formulations (CRFs) can alleviate these environmental risks. Herein, a pyridinium-functionalized chitosan derivative (PFCS) was prepared successfully and characterized by various techniques. The abundant cationic pyridinium groups enable PFCS to strongly adsorb a typical anionic herbicide, 2,4-dichlorophenoxyacetic acid sodium (2,4-D Na), across a broad pH range of 4 to 10. The adsorption kinetics follow the pseudo-second-order model, and the adsorption isotherms align with the Langmuir equation. The adsorption capacity can exceed 618.03 mg·g-1. Batch assays and further characterization reveal the mechanism of PFCS adsorbing 2,4-D Na anions mainly involves electrostatic attraction, anion exchange and other forces (e.g., π-π stacking and H bonding). Notably, PFCS loaded with 2,4-D Na (2,4-D@PFCS) demonstrates a significant sustained-release behavior, responding to changes in environmental pH and ion strength. The release rate was more influenced by ion strength than pH, and the release process adhered to a first-order kinetic model, primarily driven by ion exchange. Additionally, the 2,4-D@PFCS CRF has shown high biological efficacy on rapeseed. This work demonstrates the PFCS can effectively adsorb and control the release of anionic herbicides, minimizing their adverse impact on aquatic ecosystems.

Preparation and electromagnetic waves absorption performance of novel peanut shell/CoFe2O4/(RGO)x/PVA nanocomposites

Novel functional materials possessing the capability to attenuate electromagnetic energy are being increasingly incorporated into home decor as concerns over excessive electromagnetic radiation pollution continue to grow. The properties of magnetism and dielectricity in the flexible peanut shell/CoFe2O4/reduced graphene oxide/polyvinyl alcohol (PS/CF/(RGO)x/PVA) nanocomposites can be finely tuned by adjusting the amount of RGO in the mixture. An examination of the composite's absorption capabilities revealed a direct link between higher RGO content and enhanced absorption. Due to the presence of multiple pathways for electromagnetic wave transmission through the three-dimensional porous structure, as well as the synergistic effects of dielectric-magnetic properties and various defects in the carbon derived from peanut shells, the PS/CF/(RGO)x/PVA nanocomposites exhibit remarkable impedance matching and exceptional attenuation capabilities to -20.98404 dB for a thickness of 1 mm. Additionally, the PS/CF/(RGO)x/PVA nanocomposites have shown great promise in the production of flexible electronic devices like light-dependent resistors. Their lightweight and flexible nature play a crucial role in their success in this application. It is worth mentioning, however, that these nanocomposites bear a resemblance to traditional absorber equipment used in the industry.

Efficient removal of high concentration dyes from water by functionalized in-situ N-doped porous biochar derived from waste antibiotic fermentation residue

Using biochar for dye wastewater treatment is attracting interest due to its excellent adsorption properties and low costs. In this work, a novel biochar derived from oxytetracycline fermentation residue (functionalized OFR biochar, FOBC) was investigated as a efficient adsorbent for typical dyes removal. At 25 °C, the maximum adsorption capacity calculated by Langmuir model of FOBC-3-600 for methylene blue (MB), malachite green (MG), and methyl orange (MO) reached 643.97, 617.89, and 521.03 mg/g, respectively. The kinetics and isotherm model fitting showed that the chemisorption and physisorption both occurred during the adsorption process. Dyes were efficiently adsorbed through pore filling, electrostatic attraction, π-π interactions, and surface complexation. And the cycling experiment and environmental risk assessment indicated that the FOBC-3-600 had excellent recyclability and utilization safety. Overall, this study provides a practical method to simultaneously treat the dyeing wastewater and utilize the antibiotic fermentation residue.

One stone two birds: Recycling of an agri-waste to synthesize laccase-immobilized hierarchically porous magnetic biochar for efficient degradation of aflatoxin B1 in aqueous solutions and corn oil

Aflatoxin B1 (AFB1) contamination of oils is a serious concern for the safety of edible oil consumers. Enzyme-assisted detoxification of AFB1 is an efficient and safe method for decontaminating oils, but pristine enzymes are unstable in oils and require modifications before use. Therefore, we designed a novel and magnetically separable laccase-carrying biocatalyst containing spent-mushroom-substrate (SMS)-derived biochar (BF). Laccase was immobilized on NH2-activated magnetic biochar (BF-NH2) through covalent crosslinking, which provided physicochemical stability to the immobilized enzyme. After 30 days of storage at 4 °C, the immobilized laccase (product named "BF-NH2-Lac") retained ~95 % of its initial activity, while after five repeated cycles of ABTS oxidation, ~85 % activity retention was observed. BF-NH2-Lac was investigated for the oxidative degradation of AFB1, which exhibited superior performance compared to free laccase. Among many tested natural compounds as mediators, p-coumaric acid proved the most efficient in activating laccase for AFB1 degradation. BF-NH2-Lac demonstrated >90 % removal of AFB1 within 5.0 h, while the observed degradation efficiency in corn oil and buffer was comparable. An insight into the adsorptive and degradative removal of AFB1 revealed that AFB1 removal was governed mainly by degradation. The coexistence of multi-mycotoxins did not significantly affect the AFB1 degradation capability of BF-NH2-Lac. Investigation of the degradation products revealed the transformation of AFB1 into non-toxic AFQ1, while corn oil quality remained unaffected after BF-NH2-Lac treatment. Hence, this study holds practical importance for the research, knowledge-base and industrial application of newly proposed immobilized enzyme products.

Preparation of mesoporous biogas residue biochar via a self-template strategy for efficient removal of ciprofloxacin: Effect of pyrolysis temperature

Biochar preparation and application is an anticipated pathway for the resource utilization of biogas residue. In this study, biochars were prepared by the pyrolysis of biogas residue from food waste anaerobic digestion (named as BRBCs) under various pyrolysis temperatures (300, 500, 700, and 900 °C), and the effect of pyrolysis temperatures on the physicochemical characteristics of BRBCs was examined. The adsorption performance toward ciprofloxacin (CIP), a typical antibiotic in waterbodies, was also investigated. The results showed that pyrolysis temperature significantly changed the physicochemical properties of BRBCs. In addition, the minerals in the biogas residue, especially SiO2, were rearranged to form a mesoporous structure in biochar through a self-template strategy (without activator). BRBC prepared at 900 °C exhibited a high specific surface area and pore volume, well-developed mesopore structure, and more carbon structure defects, and exhibited the largest CIP adsorption capacity with 70.29 mg g-1, which was ascribed to the combined interaction of pore diffusion, π-π interactions, hydrogen bonding, complexation, and electrostatic forces. Furthermore, the adsorption of CIP by BRBC900 was well described by two-compartment kinetic and Langmuir isotherm models. BRBC900 showed good adsorption performance toward CIP at pH 7-9. The adsorption of CIP by BRBC is a spontaneous, exothermic, entropy-increasing process. Moreover, BRBC also presented a good recycling potential. Therefore, the preparation of mesoporous biochar based on a self-template strategy not only provides an option for the resource utilization of biogas residue but also offers a new option for the treatment of antibiotic wastewater.

Exploring the Potential of Biochar Derived from Chinese Herbal Medicine Residue for Efficient Removal of Norfloxacin

One-step carbonization was explored to prepare biochar using the residue of a traditional Chinese herbal medicine, Atropa belladonna L. (ABL), as the raw material. The resulting biochar, known as ABLB4, was evaluated for its potential as a sustainable material for norfloxacin (NOR) adsorption in water. Subsequently, a comprehensive analysis of adsorption isotherms, kinetics, and thermodynamics was conducted through batch adsorption experiments. The maximum calculated NOR adsorption capacity was 252.0 mg/g at 298 K, and the spontaneous and exothermic adsorption of NOR on ABLB4 could be better suited to a pseudo-first-order kinetic model and Langmuir model. The adsorption process observed is influenced by pore diffusion, π-π interaction, electrostatic interaction, and hydrogen bonding between ABLB4 and NOR molecules. Moreover, the utilization of response surface modeling (RSM) facilitated the optimization of the removal efficiency of NOR, yielding a maximum removal rate of 97.4% at a temperature of 304.8 K, an initial concentration of 67.1 mg/L, and a pH of 7.4. Furthermore, the biochar demonstrated favorable economic advantages, with a payback of 852.5 USD/t. More importantly, even after undergoing five cycles, ABLB4 exhibited a consistently high NOR removal rate, indicating its significant potential for application in NOR adsorption.

Norfloxacin adsorption by urban green waste biochar: characterization, kinetics, and mechanisms

Biochar, as a potential adsorbent, has been widely employed to remove pollutants from sewage. In this study, a lignin-based biochar (CB-800) was prepared by a simple high-temperature pyrolysis using urban green waste (Cinnamomum camphora leaves) as a feedstock to remove norfloxacin (NOR) from water. Batch adsorption test results indicated that CB-800 had a strong removal capacity for NOR at a wide range of pH values. The maximum adsorption achieved in the study was 50.90 ± 0.64 mg/g at 298 K. The pseudo-first and second-order kinetic models and the Dubinin-Radushkevich isotherm fitted the experimental data well, indicating that NOR adsorption by CB-800 was a complex process involving both physi-sorption and chemi-sorption. The physical properties of CB-800 were characterized by SEM and BET. The mesoporous structures were formed hierarchically on the surface of CB-800 (with an average pore size of 2.760 nm), and the spatial structure of NOR molecules was more easily adsorbed by mesoporous structures. Combined with Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis, it was showed that the main NOR adsorption mechanisms by CB-800 included ion exchange, π-electron coordination, hydrogen bonding, and electrostatic adsorption. Meanwhile, the reduction of C = O and pyridine nitrogen, and the presence of C-F2, also indicated the occurrence of substitution, addition, and redox. This study not only determined the reaction mechanism between biochar and NOR, but also provides guidance to waste managers for the removal of NOR from water by biochar. It is envisaged that the results will broaden the utilization of urban green waste.

Effects of cation types in persulfate on physicochemical and adsorptive properties of biochar prepared from persulfate-pretreated bamboo

The adsorption behaviors of biochar are largely impacted by biomassfeedstock. In this study, two biochars were prepared from torrefaction of ammonium persulfate- and potassium persulfate-pretreated bamboo and then activated by cold alkali, which are named as ASBC and KSBC, respectively. The two biochars were characterized by different instruments, and their adsorption properties over cationic methylene blue (MB) were compared. The type of persulfates little affected the specific surface areas, but significantly impacted O (29.54 % vs. 35.113 %) and N (12.13 % vs. 3.74 %) contents, functional groups, and zeta potentials of biochars. MB adsorption onto ASBC/KSBC is a single-layer chemical endothermic process and ASBC/KSBC exhibit high adsorption capacity over MB (475/881 mg·g-1) at 303 K. Obviously, the sorption capacity of MB onto KSBC much surpasses that of MB onto ASBC. These results indicate biomass pre-treatment is a cheap and convenient method to prepare biochars with unique physicochemical and adsorptive properties.

Efficient synthesis and investigation of waste-derived adsorbent for water purification. Exploring the impact of surface functionalization on methylene blue dye removal

In pursuit of sustainable water management, the preparation of adsorbent materials via waste upcycling for water purification practices plays a decisive role. The sulphonated biochar, PiNe-SO3H, employed to target the methylene blue dye adsorption, was successfully synthesized via a mild, step-economical chemical carbonization-functionalization reaction. The presence of SO3H groups on the PiNe-SO3H surface played a critical role in significantly enhancing the adsorption capacity. The observed MB dye uptake was predominantly attributed to chemisorption processes as evidenced by the results from kinetics, thermodynamics, and isotherms. To further confirm the role of -SO3H in the adsorption mechanism, a comparison was made with other PiNe materials lacking sulphonic groups, highlighting the superior adsorption capacity of PiNe-SO3H. Additionally, a fast and efficient regeneration process was proposed to develop a truly waste minimized protocol, enabling the recovery of up to 94 % of the ethanolic mixture used during this step.

Comprehensive review on recent production trends and applications of biochar for greener environment

The suitability of biochar as a supplement for environmental restoration varies significantly based on the type of feedstocks used and the parameters of the pyrolysis process. This study comprehensively examines several aspects of biochar's potential benefits, its capacity to enhance crop yields, improve nutrient availability, support the co-composting, water restoration and enhance overall usage efficiency. The supporting mechanistic evidence for these claims is also evaluated. Additionally, the analysis identifies various gaps in research and proposes potential directions for further exploration to enhance the understanding of biochar application. As a mutually advantageous approach, the integration of biochar into agricultural contexts not only contributes to environmental restoration but also advances ecological sustainability. The in-depth review underscores the diverse suitability of biochar as a supplement for environmental restoration, contingent upon the specific feedstock sources and pyrolysis conditions used. However, concerns have been raised regarding potential impacts on human health within agricultural sectors.

In Situ N, O-Dually Doped Nanoporous Biochar Derived from Waste Eutrophic Spirulina for High-Performance Supercapacitors

Sustainable and high-performance energy storage materials are crucial to address global energy and environmental challenges. In this study, Spirulina platensis was used as the carbon and nitrogen source, and Spirulina-based nanoporous biochar (SNPB) was synthesized through chemical activation using KOH as the activating agent in N2 atmosphere. SNPB-800-4 was characterized by N2 adsorption-desorption and XPS, showing a high specific surface area (2923.7 m2 g-1) and abundant heteroatomic oxygen (13.78%) and nitrogen (2.55%). SNPB-800-4 demonstrated an exceptional capacitance of 348 F g-1 at a current density of 1 A g-1 and a remarkable capacitance retention of 94.14% after 10,000 cycles at a current density of 10 A g-1 in 6 M KOH. Notably, symmetric supercapacitors SNPB-800-4//SNPB-800-4 achieved the maximum energy and power densities of 17.99 Wh kg-1 and 162.48 W kg-1, respectively, at a current density of 0.5 A g-1, and still maintained 2.66 Wh kg-1 when the power density was increased to 9685.08 W kg-1 at a current density of 30 A g-1. This work provides an easily scalable and straightforward way to convert waste algae biomass into in situ N, O-dually doped biochar for ultra-high-power supercapacitors.