A novel role of various hydrogen bonds in adsorption, desorption and co-adsorption of PPCPs on corn straw-derived biochars

Deposition behaviors and interfacial interaction mechanism between carboxyl-modified polystyrene nanoplastics and magnetite in aquatic environment

In aquatic environments, the deposition behaviors of nanoplastics (NPs) are closely associated with interfacial interaction between NPs and iron (hydr)oxides minerals, which are typically coupled with solution chemistry and organic matter. However, the roles of solution chemistry and organic matter in the deposition behavior of NPs with iron (hydr)oxides minerals and related interfacial interaction mechanism are still poorly understood. In this study, the deposition behaviors of carboxyl-modified polystyrene nanoparticles (COOH-PSNPs) with magnetite were systematically investigated. The results showed that electrostatic attraction, hydrogen bond, and charge-assisted hydrogen bond (CAHB) were the main forces for the deposition and interfacial interaction mechanism between COOH-PSNPs and magnetite. Increasing pH could significantly inhibit the deposition of COOH-PSNPs with magnetite. At pH 6.5, phosphate and dichromate significantly inhibited the deposition of COOH-PSNPs since their competitive adsorption for the surface sites on magnetite led to a potential reversal of magnetite, resulting in the strong electrostatic repulsion between COOH-PSNPs and magnetite. Moreover, when the concentration of phosphate exceeded 0.01 mM, the deposition of COOH-PSNPs was completely hindered. Organic macromolecules (OMs) markedly inhibited the interfacial interaction and deposition of COOH-PSNPs with magnetite by enhancing the electrostatic repulsion and steric hindrance between COOH-PSNPs and magnetite due to the formation of magnetite-OM associations. The inhibition abilities followed the order sodium alginate (0.1 mM) > humic acid (0.2 mM) > bovine serum albumin (5 mM). This study may provide insights for better understanding of environmental behaviors of COOH-PSNPs associated with magnetite and organic matter in natural environments at the molecular level.

Should releasing risk of sulfamethoxazole in bound-residual fraction of biochar-soil systems be neglected?

Bound residual (BR) fraction typically represents the "endpoint" of soil pollution risk assessment and remediation. However, it remains unclear whether the BR fraction of sulfamethoxazole (SMX) still presents a release risk after immobilized by biochar. Therefore, the SMX migration rate in different fractions were quantified. Results revealed that there are three extractable fractions of SMX in biochar-soil systems, allowing the migration of SMX among these various fractions. 1.0 % biochar could increase 8.5 %∼14.1 % BR fraction and 17.9 %∼36.9 % non-extractable fraction, respectively. Model simulations and Sobol Global Sensitivity Analysis results revealed that migration of SMX from BR fraction to labile fraction or stably-adsorbed fraction significantly affects overall fraction migration, suggesting BR fraction still poses a potential release risk. When considering the BR fraction, the half-life of SMX extended to 93.8 ∼ 132.0 days. Thus, the potential release risk of SMX in the BR fraction should not be overlooked when applying biochar for soil remediation.

Desorption hysteresis of antibiotics on biochar produced at high temperature: The role of amine groups and amidation reaction

Knowledge of antibiotic desorption from high-temperature biochar is essential for assessing their environmental risks, and for the successful application of biochar to remove antibiotics. In previous studies, irreversible pore deformation, formation of charge-assisted hydrogen bonds or amide bonds were individually proposed to explain the desorption hysteresis of antibiotics on biochars, leading to a debate on hysteresis mechanism. In this study, desorption of sulfamethoxazole (SMX), ciprofloxacin (CFX) and tetracycline (TET) on a wood chip biochar produced at 700 °C (WBC700) and its oxidized product (O-WBC700) was investigated to explore the underlying hysteresis mechanism. Significant desorption hysteresis was observed for SMX, CFX and TET on WBC700 and O-WBC700. Hysteresis index (HI) of each antibiotic was higher on O-WBC700 with more oxygen-containing groups than WBC700, and was higher at lower equilibrium concentration. HI of antibiotics on WBC700 (or O-WBC700) increased in the order of SMX < CFX < TET. The calculated adsorption enthalpy of each antibiotic on WBC700 was positive, indicating an endothermic process. These phenomena together with FTIR, XPS spectra confirmed that the desorption hysteresis mechanism of antibiotics on high-temperature biochar is the formation of amide bonds by amidation reaction, but not the pore deformation or the hydrogen bond. Moreover, antibiotic can form amide bonds with WBC700 only if the amine group with pKa > 4.0, and the HI values were positively correlated with their pKa values. Amine group of antibiotics with higher pKa value show more nucleophilicity and could form stronger amide bonds with carboxyl group of biochar. The obtained results could help to solve the debate on desorption hysteresis mechanism of antibiotics on high-temperature biochars, and provide a new insight into the role of amine groups and amidation reaction on the hysteresis.

Amended biochar in constructed wetlands: Roles, challenges, and future directions removing pharmaceuticals and personal care products

Pharmaceuticals and personal care products (PPCPs) in wastewater pose significant threats to both human health and aquatic ecosystems. Wastewater discharge from various sources is the primary cause of these contaminants, and proper treatment is essential for protecting the environment. Traditional treatment technologies are often too expensive and ineffective in removing PPCPs. Constructed wetlands (CWs) offer a sustainable, cost-efficient alternative for wastewater treatment, though their capability to eliminate PPCPs can vary based on multiple aspects. Recent studies highlight biochar-a carbon-rich material resultant from biomass pyrolysis-as a promising amendment to improve CW performance. However, there is a deficiency of proper literature reviews on using biochar in CWs specifically for PPCP removal. This review focuses on biochar's role in CWs and its effectiveness in removing PPCPs and enhancing microbial activity and nutrient cycling. A bibliometric analysis using Vosviewer software was used to assess the current research trends in the biochar-amended CWs to attenuate PPCPs. While biochar shows potential in eliminating PPCPs, challenges, such as optimizing its application and addressing long-term operational concerns for treating emerging pollutants like PPCPs. Future research should enhance biochar production and low-cost techniques for diverse groups of PPCPs and perform field trials to validate laboratory results under actual conditions exploring microbial-biochar and plant-biochar interactions. Addressing these challenges is crucial to advancing biochar-amended CWs and enhancing wastewater treatment on a global scale.

Size effect of ZIF-8 based nanocarrier pesticide delivery system on targeted release and insecticidal activity

BACKGROUND

Traditional chemical pesticides are easily lost by surface runoff and only small quantities reach the target, thus causing serious environmental pollution. In this work, dinotefuran@zeolitic imidazolate framework-8@polydopamine@zein (DNF@ZIF-8@PDA@zein), was constructed to deliver DNF with pH and enzyme double response of release, thereby achieving targeted release and efficient long-term pest control.

RESULTS

DNF@ZIF-8@PDA@zein was synthesized with three hydrated diameters (249.73 ± 9.99 nm, 142.94 ± 5.63 nm and 75.16 ± 4.66 nm, respectively). The release of DNF from DNF@ZIF-8@PDA@zein after 28 h was significantly higher at pH 5.0 (89.22 ± 7.18%) compared to that at pH 8 (81.8 ± 6.11%). Protease-assisted release of DNF was notably higher than that without protease (pH 5: 89.22 ± 5.55% versus 27.19 ± 3.22%; pH 8: 81.8 ± 6.11% versus 25.39 ± 3.87%). The stimuli-responsive release of DNF from DNF@ZIF-8@PDA@zein increased with decreased particle size due to increased pore size, reduced binding forces (i.e., weaker π-π stacking, hydrogen bonding, and Zn-N covalent bonding), and the shortening of diffusion path, leading to faster disintegration and drug release. Additionally, the anti-photolysis ability of DNF@ZIF-8@PDA@zein was 3.2 times that of pure DNF. The insecticidal activity improved with smaller nanoparticles due to higher drug release rate and greater inhibition of detoxification enzyme activity by more zinc ion (Zn2+) dissolution.

CONCLUSION

The pH and enzyme dual-responsive release as well as insecticidal activity of DNF@ZIF-8@PDA@zein increase with decreased nanoparticle size, showing effective pest management in long-term and potential application prospects in sustainable agriculture. © 2024 Society of Chemical Industry.

Co-transport of citrate-modified biochar nanoparticles and released plant-available silicon in saturated porous media: Effect of LMWOAs and solution chemistry

Citrate-modified biochar nanoparticles (CBCNPs) represent a promising amendment with plant-available silicon (PASi) releasing capacity. However, the co-transport behavior with released PASi remain poorly understood. This study investigated their co-transport in saturated porous media under various solution chemistry and low molecular weight organic acids (LMWOAs). Experimental and two-site kinetic model results revealed that higher ionic strength caused favorable aggregation and size-selective, hindering CBCNPs transport. Divalent Ca2+ ions retained CBCNPs more effectively than K+ due to stronger charge screening and cation bridging. The pH buffering capacity of CBCNPs resulted in consistent transport behavior across a broad pH range (4-8). XDLVO calculation clarified the impact mechanisms of IS, ion types and pH on CBCNPs transport. Furthermore, LMWOAs exhibited a time-dependent blocking effect on CBCNPs transport. Oxalic acid (OA) and citric acid (CA) facilitated CBCNPs transport though mechanisms beyond XDLVO, including steric hindrance, competitive adsorption, and surface hydrophilicity. The presence of LMWOAs significantly hindered PASi co-transport, with the inhibitory effect ranked as acetic acid (AA) ≈ CA > OA > absence of organic acids. The inhibition is attributed to the blocking effect and formation of Si-organic acid complexes, as evidenced by breakthrough curves and density functional theory calculations. This study provides novel insights into the co-transport of CBCNPs with released PASi through mutual mechanisms, indicating both potential environmental benefits and risks.

The boom era of emerging contaminants: A review of remediating agricultural soils by biochar

Emerging contaminants (ECs) are widely sourced persistent pollutants that pose a significant threat to the environment and human health. Their footprint spans global ecosystems, making their remediation highly challenging. In recent years, a significant amount of literature has focused on the use of biochar for remediation of heavy metals and organic pollutants in soil and water environments. However, the use of biochar for the remediation of ECs in agricultural soils has not received as much attention, and as a result, there are limited reviews available on this topic. Thus, this review aims to provide an overview of the primary types, sources, and hazards of ECs in farmland, as well as the structure, functions, and preparation types of biochar. Furthermore, this paper emphasizes the importance and prospects of three remediation strategies for ECs in cropland: (i) employing activated, modified, and composite biochar for remediation, which exhibit superior pollutant removal compared to pure biochar; (ii) exploring the potential synergistic efficiency between biochar and compost, enhancing their effectiveness in soil improvement and pollution remediation; (iii) utilizing biochar as a shelter and nutrient source for microorganisms in biochar-mediated microbial remediation, positively impacting soil properties and microbial community structure. Given the increasing global prevalence of ECs, the remediation strategies provided in this paper aim to serve as a valuable reference for future remediation of ECs-contaminated agricultural lands.

Biochar derivation at low temperature: A novel strategy for harmful resource usage of antibiotic mycelial dreg

Antibiotic mycelial dreg (AMD) has been categorized as hazardous waste due to the high residual hazardous contaminants. Inappropriate management and disposal of AMD can cause potential environmental and ecological risks. In this study, the potential of pleuromutilin mycelial dreg (PMD) as a novel feedstock for preparing tetracycline hydrochloride (TC) adsorbent was explored to achieve safe management of PMD. The results suggested that residual hazardous contaminants were completely eliminated after pyrolysis. With the increase of pyrolysis temperature, the yields, H/C, O/C, (O + N)/C, and pore size in PMD-derived biochars (PMD-BCs) decreased, while BET surface area and pore volume increased, resulting in the higher stability of the PMD-BCs prepared from higher temperatures. The TC adsorption of the PMD-BCs increased from 27.3 to 46.9 mg/g with the increase of the pyrolysis temperature. Surprisingly, pH value had a strong impact on the TC adsorption, the adsorption capacity of BC-450 increased from 6.5 to 71.1 mg/g when the solution pH value increased from 2 to 10. Lewis acid-base interaction, pore filling, π-π interaction, hydrophobic interaction, and charge-assisted hydrogen bond (CAHB) are considered to drive the adsorption. This work provides a novel pathway for the concurrent detoxification and reutilization of AMD.

Recovery of Ag(I) from Wastewater by Adsorption: Status and Challenges

Untreated or inadequately treated silver-containing wastewater may pose adverse effects on hu-man health and the ecological environment. Currently, significant progress has been made in the treatment of Ag(I) in wastewater using adsorption methods, with adsorbents playing a pivotal role in this process. This paper provides a systematic review of various adsorbents for the recovery and treatment of Ag(I) in wastewater, including MOFs, COFs, transition metal sulfides, metal oxides, biomass materials, and other polymeric materials. The adsorption mechanisms of these materials for Ag(I) are elaborated upon, along with the challenges currently faced. Furthermore, insights into optimizing adsorbents and developing novel adsorbents are proposed in this study.

Enhanced adsorption of dye wastewater by low-temperature combined NaOH/urea pretreated hydrochar: Fabrication, performance, and mechanism

The highly stable biomass structure formed by cellulose, hemicellulose, and lignin results in incomplete conversion and carbonization under hydrothermal conditions. In this study, pretreated corn straw hydrochar (PCS-HC) was prepared using a low-temperature alkali/urea combination pretreatment method. The Mass loss rate of cellulose, hemicellulose, and lignin from pretreated biomass, as well as the effects of the pretreatment method on the physicochemical properties of PCS-HC and the adsorption performance of PCS-HC for alkaline dyes (rhodamine B and methylene blue), were investigated. The results showed that the low-temperature NaOH/urea pretreatment effectively disrupted the stable structure formed by cellulose, hemicellulose, and lignin. NaOH played a dominant role in solubilizing cellulose and the combination of low temperature and urea enhanced the ability of NaOH to remove cellulose, hemicellulose, and lignin. Compared to the untreated hydrochar, PCS-HC exhibited a rougher surface, a more abundant pore structure, and a larger specific surface area. The unpretreated hydrochar exhibited an adsorption capacity of 64.8% for rhodamine B and 66.32% for methylene blue. However, the removal of rhodamine B and methylene blue by PCS-BC increased to 89.12% and 90.71%, respectively, under the optimal pretreatment conditions. The PCS-HC exhibited a favorable adsorption capacity within the pH range of 6-9. However, the presence of co-existing anions such as Cl-, SO42-, CO32-, and NO3- hindered the adsorption capacity of PCS-HC. Among these anions, CO32- exhibited the highest level of inhibition. Chemisorption, including complexation, electrostatic attraction, and hydrogen bonding, were the primary mechanism for dye adsorption by PCS-HC. This study provides an efficient method for utilizing agricultural waste and treating dye wastewater.

Effects of charge-assisted hydrogen bond on sorption and co-sorption of pharmaceutical contaminants on carbonaceous materials: Spectroscopic and theoretical studies

Charge-assisted hydrogen bond (CAHB) is a key mechanism that affects the environmental behavior of pharmaceutical pollutants (PCs). However, the strength and stability of various CAHBs, and their effects on the co-sorption behavior of PCs are still unclear. Herein, DFT calculation with different solvent models including two implicit solvent model (PCM and SMD), and one explicit solvent model (ESM) were applied in this study, to investigate the effects of different CAHBs on the sorption and co-sorption behavior of four PCs (e.g., clofibric acid, p-aminobenzoic acid, acetaminophen, and sulfamerazine) on three model carbonaceous materials. First, the appearance of new peaks in the very low field of 1H NMR, and the blue shift of OH and NH2 peaks in FTIR indicated that CAHBs were indeed formed between PCs and carbonaceous materials. Next, according to the principal component analysis and correlation analysis of parameters (e.g., ΔEads, bond length, bond angle, Egap, and ΔG) of these CAHBs calculated by the DFT with different solvent models, the results showed that SMD is the optimal model for calculating the strength and stability of CAHBs by DFT, and the strength and stability of CAHBs formed between PCs and carbonaceous materials in this study were in the order of homonuclear [O⋯H⋯O]- CAHB > heteronuclear [O⋯HN]-/[N⋯HO]+ type of CAHB > homonuclear [N⋯H⋯N]+. Also, the co-sorption behavior of different PCs co-existing in binary systems further confirmed that, all above types of CAHBs formed between PCs and carbonaceous materials can produce obvious competition effect on the co-existing PCs that only OHB formed between them. This study not only reveals the environmental behavior of co-existing PCs, but also provides a theoretical basis for the design of obligate sorption materials for PCs in the natural environment.

The Impact of Surface Chemistry and Synthesis Conditions on the Adsorption of Antibiotics onto MXene Membranes

MXene, a two-dimensional (2D) nanomaterial with diverse applications, has gained significant attention due to its 2D lamellar structure, abundance of surface groups, and conductivity. Despite various established synthesis methods since its discovery in 2011, MXenes produced through different approaches exhibit variations in structural and physicochemical characteristics, impacting their suitability for environmental application. This study delves into the effect of synthesis conditions on MXene properties and its adsorption capabilities for four commonly prescribed antibiotics. We utilized material characterization techniques to differentiate MXenes synthesized using three prevalent etchants: hydrofluoric acid (HF), mixed acids (HCl/HF), and fluoride salts (LiF/HCl). Our investigation of adsorption performance included isotherm and kinetic analysis, complemented by density functional theory calculations. The results of this research pinpointed LiF/HCl as an efficient etchant, yielding MXene with favorable morphology and surface chemistry. Electrostatic interactions and hydrogen bonding between MXene surface terminations and ionizable moieties of the antibiotic molecules emerge as pivotal factors in adsorption. Specifically, a higher presence of oxygen terminations increases the binding affinities. These findings provide valuable guidance for etchant selection in environmental applications and underscore the potential to tailor MXenes through synthesis conditions to design membranes capable of selectively removing antibiotics and other targeted substances.

Straw-derived biochar for the removal of antibiotics from water: Adsorption and degradation mechanisms, recent advancements and challenges

Antibiotics, a kind of containments with the properties of widely distributed and difficult to degrade, has aroused extensive attention in the world. As a prevalent agricultural waste, straws can be utilized to prepare biochar (straw-derived biochar, SBC) to remove antibiotics from aquatic environment. To date, although a number of review papers have summarized and discussed research on biochar application in wastewater treatment and soil remediation, there are few reviews on SBC for antibiotic removal. Due to the limitations of poor adsorption and degradation performance of the pristine SBC, it is necessary to modify SBC to improve its applications for antibiotics removal. The maximum antibiotic removal capacity of modified SBC could reach 1346.55 mg/g. Moreover, the adsorption mechanisms between modified SBC and antibiotics mainly involve π-π interactions, electrostatic interactions, hydrophobic interactions, and charge dipole interactions. In addition, the modified SBC could completely degrade antibiotics within 6 min by activating oxidants, such as PS, PDS, H2O2, and O3. The mechanisms of antibiotic degradation by SBC activated oxidants mainly include free radicals (including SO4•-, •OH, and O2•-) and non-free radical pathway (such as, 1O2, electrons transfer, and surface-confined reaction). Although SBC and modified SBC have demonstrated excellent performance in removing antibiotics, they still face some challenges in practical applications, such as poor stability, high cost, and difficulties in recycling. Therefore, the further research directions and trends for the development of SBC and biochar-based materials should be taken into consideration.

Emerging applications of biochar: A review on techno-environmental-economic aspects

Biomass fast pyrolysis produces bio-oil and biochar achieving circular economy. This review explored the emerging applications of biochar. Biochar possesses the unique properties for removing emerging contaminants and for mine remediation, owing to its negative charge surface, high specific surface area, large pore size distribution and surface functional groups. Additionally, biochar could adsorb impurities such as CO2, moisture, and H2S to upgrade the biogas. Customizing pyrolysis treatments, optimizing the feedstock and pyrolysis operating conditions enhance biochar production and improve its surface properties for the emerging applications. Life cycle assessment and techno-economic assessment indicated the benefits of replacing conventional activated carbon with biochar.

The Removal of Pollutants from Wastewater Using Magnetic Biochar: A Scientometric and Visualization Analysis

In recent years, the use of magnetic biochar in wastewater treatment has shown significant effects and attracted scholars' attention. However, due to the relatively short research time and the lack of systematic summaries, it is difficult to provide a more in-depth analysis. This study utilizes RStudio and CiteSpace software to comprehensively analyze the research trends and progress of magnetic biochar in wastewater treatment. The analysis of bibliometrics is performed on 551 relevant papers retrieved from the Web of Science, spanning the period between 2011 and 2022. The most influential countries, institutions, journals, disciplinary distribution, and top 10 authors and papers in this field have been identified. The latest dataset has been used for keyword clustering and burst analysis. The results indicated that: (1) Bin Gao is the most influential author in this field, and high-level journals such as Bioresource Technology are more inclined to publish articles in the field of magnetic biochar. (2) Research in this field has predominantly focused on the removal of heavy metals and organic compounds. Keyword burst analysis shows a shift in research direction towards the removal of complex organic pollutants recently. (3) For the future development of magnetic biochar, an environment-friendly approach, economic viability, and joint technology are the directions that need more exploration. Finally, this paper provides a summary of the various adsorption mechanisms of magnetic biochar and several common modification methods, aiming to assist scholars in their research endeavors.