Hierarchical porous biochars with controlled pore structures derived from co-pyrolysis of potassium/calcium carbonate with cotton straw for efficient sorption of diethyl phthalate from aqueous solution

Exploring adsorption capacity and mechanisms involved in cadmium removal from aqueous solutions by biochar derived from euhalophyte

Biochar has shown potential as a sorbent for reducing Cd levels in water. Euhalophytes, which thrive in saline-alkali soils containing high concentrations of metal ions and anions, present an intriguing opportunity for producing biochar with inherent metal adsorption properties. This study focused on biochar derived from the euhalophyte Salicornia europaea and aimed to investigate its Cd adsorption capacity through adsorption kinetics and isotherm experiments. The results demonstrated that S. europaea biochar exhibited a high specific surface area, substantial base cation content, and a low negative surface charge, making it a highly effective adsorbent for Cd. The adsorption data fit well with the Langmuir isotherm model, revealing a maximum adsorption capacity of 108.54 mg g-1 at 25 °C. The adsorption process involved both surface adsorption and intraparticle diffusion. The Cd adsorption mechanism on the biochar encompassed precipitation, ion exchange, functional group complexation, and cation-π interactions. Notably, the precipitation of Cd2+ with CO32- in the biochar played a dominant role, accounting for 73.7% of the overall removal mechanism. These findings underscore the potential of euhalophytes such as S. europaea as a promising solution for remediating Cd contamination in aquatic environments.

Recent insights into mechanism of modified bio-adsorbents for the remediation of environmental pollutants

Rapid industrialization has exacerbated the hazard to health and the environment. Wide spectrums of contaminants pose numerous risks, necessitating their disposal and treatment. There is a need for further remediation methods since pollutant residues cannot be entirely eradicated by traditional treatment techniques. Bio-adsorbents are gaining popularity due to their eco-friendly approach, broad applicability, and improved functional and surface characteristics. Adsorbents that have been modified have improved qualities that aid in their adsorptive nature. Adsorption, ion exchange, chelation, surface precipitation, microbial uptake, physical entrapment, biodegradation, redox reactions, and electrostatic interactions are some of the processes that participate in the removal mechanism of biosorbents. These processes can vary depending on the particular biosorbent and the type of pollutants being targeted. The systematic review focuses on the many modification approaches used to remove environmental contaminants. Different modification or activation strategies can be used depending on the type of bio-adsorbent and pollutant to be remediated. Physical activation procedures such as ultrasonication and pyrolysis are more commonly used to modify bio-adsorbents. Ultrasonication process improves the adsorption efficiency by 15-25%. Acid and alkali modified procedures are the most effective chemical activation strategies for adsorbent modification for pollution removal. Chemical modification increases the removal to around 95-99%. The biological technique involving microbial culture is an emerging field that needs to be investigated further for pollutant removal. A short evaluation of modified adsorbents with multi-pollutant adsorption capability that have been better eliminated throughout the adsorption process has been provided.

Improvement of the specific surface area of biochar by calcium-precipitated nanoparticles synthesized by microbial induction as a template skeleton: Removal mechanism of tetracycline in water

The template method is an effective means to improve the specific surface area and porosity of biochar, but the synthesis of template agents and the way they are integrated with biomass materials still need further development. Therefore, the free Pseudomonas sp. Y1 was used to synthesize calcium-precipitated nanoparticles (CPN) on sludge as a fused template skeleton to enlarge the surface area of sludge biochar facilitating the adsorption of tetracycline (TC) in this work. The modified biochar (FBC) showed excellent specific surface area (448.55 m2 g-1) and porosity (0.0053 cm³ g-1), stable morphological structure, abundant active functional groups, and appreciable adsorption capacity (65.43 mg g-1) based on several characterization and adsorption experiments. Moreover, the adsorption model postulated that the removal of TC is mainly a chemisorption-based heat-trapping, disordered multilayer interaction. In detail, this process involved the joint contribution from electrostatic interactions, ligand exchange, hydrogen bonding, π-π bonding, complexation, and pore filling. Meanwhile, the adaptability and stability of FBC were examined by pH and coexisting substances. This template skeleton induced by microorganisms can provide new insight into the modification of biochar with the template method.

Removal performance and mechanisms of aqueous Cr (VI) by biochar derived from waste hazelnut shell

Cr (VI) is still of great concern due to its high toxicity, solubility, and mobility. The transformation of waste biomass to biochar is favorable for sustainable development. Hazelnut shell, an agriculture waste, was utilized as precursor to prepare biochar at 700 °C and firstly conducted for Cr (VI) removal. Nearly all 50 mg L-1 of Cr (VI) was removed from aqueous media in 180 min under the optimal conditions. The best compliance with pseudo-second-order kinetic model (R2 = 0.999) and Langmuir isotherm model (R2 = 0.999) indicated Cr (VI) removal was a monolayer chemisorption process. The hazelnut shell biochar exhibited superior performance on Cr (VI) removal at low pH (2.0) and Cr (VI) concentrations (≤ 50 mg L-1). Various techniques illustrated that the predominant mechanism of Cr (VI) removal by hazelnut shell biochar involved electrostatic attraction, reduction, and complexation. This study provides a promising low-cost alternative for Cr (VI) elimination from acidic wastewater and groundwater after extraction following by pH adjustment to 2.0.

Hierarchically porous graphene-like biochar for efficient removal of aromatic pollutants and their structure-performance relationship: A combined experimental, MD and DFT study

Development of high-efficiency adsorbents and exploration of the structure-performance relationship holds exciting implications for removal of aromatic pollutants (APs) from water. Herein, hierarchically porous graphene-like biochars (HGBs) were successfully prepared by K₂CO₃ simultaneous graphitization and activation of Physalis pubescens husk. The HGBs possess high specific surface area (1406-2369.7 m²/g), hierarchically meso-/microporous structure and high graphitization degree. The optimized HGB-2-9 sample exhibits rapid adsorption equilibrium time (t_e) and high adsorption capacities (Q_e) for seven widely-used persistent APs with different molecular structures (e.g., phenol: t_e = 7 min, Q_e = 191.06 mg/g; methylparaben: t_e = 12 min Q_e = 482.15 mg/g). HGB-2-9 also shows a wide pH (3-10) suitability and good ionic strength (0.01-0.5 M NaCl) resistance properties. The effects of the physicochemical properties of HGBs and APs on the adsorption performance were deeply investigated by the adsorption experiments, molecular dynamics (MD) and density functional theory (DFT) simulation. The results demonstrate that the large specific surface area, high graphitization degree and hierarchically porous structure of HGB-2-9 can supply more active sites on accessible surface and facilitate the transport of APs. And the aromaticity and hydrophobicity of APs play the more crucial roles during the adsorption process. Besides, the HGB-2-9 presents good recyclability and high removal efficiency for APs in various real water, which further confirms its potential for practical applications.

Preparation of biochar derived from waste cotton woven by low-dosage Fe(NO3)3 activation: characterization, pore development, and adsorption

Currently, researchers are looking for efficient and sustainable methods to synthesize biochar for the adsorption of pollutants. In this study, biochar with high specific surface area, tunable pore structure, and abundant functional groups were prepared from waste cotton woven (WCW) using low-dosage Fe(NO₃)₃ activation at 400-900 °C. The biochar obtained at 800 °C possessed the excellent specific surface area of 1167.37 m²/g with a unique micro-mesoporous structure. XRD analysis showed that the Fe species changed from Fe₂O₃ to Fe₃O₄ and then Fe⁰ with the increase of pyrolysis temperature. TEM images further confirmed the template effect of iron oxides for mesoporous formation. The effect of Fe(NO₃)₃ on the pyrolysis pathway of waste cotton woven was systematically investigated by TG and XPS analyses to explore the pore development of biochar. The results indicated that Fe(NO₃)₃ could enhance the dehydration, decarbonylation and dehydroxylation of WCW components, thereby reducing the temperature required for WCW pyrolysis. Moreover, the synergistic effect of Fe and N species improved the development of microporous and mesoporous structure through carbon structure corrosion and reorganization, and volatile release. Additionally, satisfactory adsorption capacity for Eriochrome Black T (456.01 mg/g) of the prepared biochar was obtained at 25 °C. This study demonstrated that low-dosage Fe(NO₃)₃ activation of waste cotton woven could be used as a facile method to prepare promising inexpensive biochar for contaminants removal.

Comparative analysis of the sorption behaviors and mechanisms of amide herbicides on biodegradable and nondegradable microplastics derived from agricultural plastic products

Coexisting of microplastics (MPs) and residual herbicides has received substantial attention due to concerns about the pollutant vector effect. Here, the widely used amide herbicides were examined for their sorption behaviors on the priority biodegradable and nondegradable MPs identified in intensive agriculture. The fitting results indicated that the interactions between napropamide (Nap)/acetochlor (Ace) and the MPs, i.e., poly (butyleneadipate-co-terephthalate) microplastic (PBATM), polyethylene microplastic (PEM), and polypropylene microplastic (PPM), may be dominated by hydrophobic absorptive partitioning on the heterogeneous surfaces. Additionally, chemisorption cannot be ignored for the sorption of Nap/Ace on the biodegradable MPs. The sorption capacities of Nap/Ace on the MPs followed the order of PBATM > PEM > PPM. The differences in sorption capacity which varied by the MP colors were not significant. The hydrophobicity of the herbicides and the MPs, the rubber regions, surface O-functional groups, benzene ring structures and large specific surface area of the biodegradable MPs played key roles in the better performance in sorbing amide herbicides. Moreover, MPs, especially biodegradable MPs, might lead to a higher vector effect for residual amide herbicides than some other common environmental media. This study may provide baseline insights into the great potential of biodegradable MPs to serve as carriers of residual amide herbicides in intensive agrosystems.

Coassisted carbonization with HCOOK/(HCOO)2Ca for the fabrication of bamboo-derived oxygen-doped porous carbons exhibiting high-performance sorption of diethyl phthalate from aqueous solutions

Porous carbons are excellent sorbents for removing organic pollutants. Green conversion of biowaste into advanced porous carbons is crucial for industrialized production and practical applications, which, however, have rarely been investigated. This study develops a coassisted carbonization method for the preparation of porous carbons with the environmentally friendly agents HCOOK and (HCOO)₂Ca for the first time. The bamboo waste-derived hydrochar was transformed into oxygen-doped porous carbons, which displayed a large surface area and pore volume, abundant oxygen content, graphene structure and many surface functional groups. These properties contributed to the extremely high sorption of large quantities of diethyl phthalate, which reached 761 mg g^-1. Surface adsorption, including pore filling, hydrogen bonding, and π-π stacking, rather than partitioning, was the main sorption process. Therefore, this study provides a sustainable and promising route for the preparation of porous carbons that can be applied in the efficient removal of organic pollutants.

N-Doped Biochar from Lignocellulosic Biomass for Preparation of Adsorbent: Characterization, Kinetics and Application

Medulla tetrapanacis is composed of a lignocellulosic biopolymer and has a regular porous structure, which makes it a potential biomass material for preparing porous N-doped biochar. Herewith, N-doped Medulla tetrapanacis biochar (UBC) was successfully prepared by modification with urea and NaHCO₃ under pyrolysis at 700 °C. The nitrogen-containing groups were efficiently introduced into biochar, and the micro-pore structures of the UBC were developed with sizeable specific surface area, which was loaded with massive adsorption sites. The adsorption kinetics and isotherms of the UBC conformed to pseudo-second-order and Langmuir model. The superior adsorption capacities of the UBC for methylene blue (MB) and congo red (CR) were 923.0 mg/g and 728.0 mg/g, and the capacities for Cu²⁺ and Pb²⁺ were 468.5 mg/g and 1466.5 mg/g, respectively. Moreover, the UBC had a stronger affinity for Cr³⁺ and Fe³⁺ in multiple metal ions and retained at a preferable adsorption performance for dyes and heavy metals after five cycles. Precipitation, complexation, and physical adsorption were the main mechanisms of the UBC-adsorbing metal ions and dyes. Thus, lignocellulosic biochar has great potential for removing dyes and heavy metals in aqueous solutions.

Preparation of bamboo-derived magnetic biochar for solid-phase microextraction of fentanyls from urine

In this study, a biochar-based magnetic solid-phase microextraction method, coupled with liquid chromatography-mass spectrometry (LC/MS), was developed for analyzing fentanyl analogs from urine sample. Magnetic biochar was fabricated through an one-step pyrolysis carbonization and magnetization process, followed by an alkali treatment. In order to achieve desired extraction efficiency, feed stocks (wood and bamboo) and different pyrolysis temperatures (300-700 °C) were optimized. The magnetic bamboo biochar pyrolyzed at 400°C was found to have the greatest potential for extraction of fentanyls, with enrichment factors ranging from 58.9 to 93.7, presumably due to H-bonding and π- π interactions between biochar and fentanyls. Various extraction parameters, such as type and volume of desorption solvent, pH, extraction time were optimized, respectively, to achieve the highest extraction efficiency for the target fentanyls. Under optimized conditions, the developed method was found to have detection limits of 3.1-9.4 ng/L, a linear range of 0.05-10 μg/L, good precisions (1.9-9.4% for intra-batch, 2.9-9.9% for inter-batch), and satisfactory recoveries (82.0-111.3%). The developed method by using magnetic bamboo biochar as adsorbent exhibited to be an efficient and promising pretreatment procedure and could potentially be applied for drug analysis in biological samples. This article is protected by copyright. All rights reserved.