Preparation and characterization of boron-doped corn straw biochar: Fe (Ⅱ) removal equilibrium and kinetics

The adsorption behavior and mechanism of Cu(Ⅱ), Fe(Ⅱ) and Co(Ⅱ) on straw biochar and their Fenton-like performance for ciprofloxacin decontamination

In this study, the adsorption of aqueous Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) on biochars at diverse synthesized temperatures was evaluated. The optimal sample BC-800 achieved superior adsorption performance of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) at 10-50 mg L-1 initial concentration. Due to the larger surface area (349.6 m2/g), total pore volume (0.24 cm3/g), average pore diameter (6.4 nm), higher degree of graphitization (IG/ID = 1.00) and stable aromatic carbon structure, BC-800 achieved excellent adsorption of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) through multilayer chemical adsorption, corresponding to the pseudo-2nd-order and Freundlich model (Qm Cu(Ⅱ) = 433.4 mg g-1, Qm Fe(Ⅱ) = 472.0 mg g-1 and Qm Co(Ⅱ) = 301.0 mg g-1). After then, the adsorbed biochars with Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) were directly used as heterogeneous catalysts in Fenton-like reaction for ciprofloxacin (CIP) degradation. Compared with Co-BC-800/peroxymonosulfate (PMS) system, Co-BC-800/H2O2 system exhibited the 56.6% decontamination of CIP with lower ions leaching (0.53 mg/L) within 70 min. The 97.9% of CIP was finally removed by Co-BC-800/H2O2 under optimized conditions: initial pH = 6.94, catalyst dosage = 1.0 g L-1, H2O2 concentration = 0.44 g L-1. Furthermore, Co-BC-800 exhibited superior acid-base adaptability (2.94-10.94) and anti-anion interference ability. The removal of CIP was achieved by the synergistic effect of adsorption and oxidative degradation. This study proposes some insights into the behavior and mechanism of metal ions adsorption on biochar and hazardous waste treatment.

The synergistic interaction effect between biochar and plant growth-promoting rhizobacteria on beneficial microbial communities in soil

Excessive use of chemical fertilizers and extensive farming can degrade soil properties so that leading to decline in crop yields. Combining plant growth-promoting rhizobacteria (PGPR) with biochar (BC) may be an alternative way to mitigate this situation. However, the proportion of PGPR and BC at which crop yield can be improved, as well as the improvement effect extent on different eco-geographic region and crops, remain unclear. This research used cabbage [Brassica pekinensis (Lour.) Rupr.] as the target crop and established as treatment conventional fertilization as a control and a 50% reduction in nitrogen fertilizer at the Yunnan-Guizhou Plateau of China, adding BC or PGPR to evaluate the effects of different treatments on cabbage yield and the soil physicochemical properties. Specifically, high-throughput sequencing probed beneficial soil microbial communities and investigated the impact of BC and PGPR on cabbage yield and soil properties. The results revealed that the soil alkaline hydrolyzable nitrogen (AH-N), available phosphorus (AP), and available potassium (AK) contents were higher in the BC application than in control. The BC application or mixed with PGPR significantly increased the soil organic matter (OM) content (P<0.05), with a maximum of 42.59 g/kg. Further, applying BC or PGPR significantly increased the abundance of beneficial soil microorganisms in the whole growth period of cabbage (P<0.05), such as Streptomyces, Lysobacter, and Bacillus. Meanwhile, the co-application of BC and PGPR increased the abundance of Pseudomonas, and also significantly enhanced the Shannon index and Simpson index of bacterial community (P<0.05). Combined or not with PGPR, the BC application significantly enhanced cabbage yield (P<0.05), with the highest yield reached 1.41 fold of the control. Our research indicated that BC is an suitable and promising carrier of PGPR for soil improvement, combining BC and PGPR can effectively ameliorate the diversity of bacterial community even in acid red soil rhizosphere, and the most direct reflection is to improve soil fertility and cabbage yield.

High-performance electrode materials of heteroatom-doped lignin-based carbon materials for supercapacitor applications

Supercapacitors are the preferred option for supporting renewable energy sources owing to many benefits, including fast charging, long life, high energy and power density, and saving energy. While electrode materials with environmentally friendly preparation, high performance, and low cost are important research directions of supercapacitors. At present, the growing global population and the increasingly pressing issue of environmental pollution have drawn the focus of numerous researchers worldwide to the development and utilization of renewable biomass resources. Lignin, a renewable aromatic polymer, has reserves second only to cellulose in nature. Ten million tonnes of industrial lignin are produced in pulp and paper mills annually, most of which are disposed of as waste or burned for fuel, seriously depleting natural resources and polluting the environment. One practical strategy to accomplish sustainable development is to employ lignin resources to create high-value materials. Based on the high carbon content and rich functional groups of lignin, the lignin-based carbon materials generated after carbonization treatment display specific electrochemical properties as electrode materials. Nevertheless, low electrochemical activity of untreated lignin precludes it from achieving its full potential for application in energy storage. Heteroatom doping is a common modification method that aims to improve the electrochemical performance of the electrode materials by optimizing the structure of the lignin, improving its pore structure and increasing the number of active sites on its surface. This paper aims to establish theoretical foundations for design, preparation, and optimizing the performance of heteroatom-doped lignin-based carbon materials, as well as for developing high-value-added lignin materials. The most reported the mechanism of supercapacitors, the doping process involving various types of heteroatoms, and the analysis of how heteroatoms affect the performance of lignin-based carbon materials are also detailed in this review.

Utilization of biochar for remediation of heavy metals in aqueous environments: A review and bibliometric analysis

Biochar usage for removing heavy metals from aqueous environments has emerged as a promising research area with significant environmental and economic benefits. Using the PICO approach, the research question aimed to explore using biochar to remove heavy metals from aqueous media. We merged the data from Scopus and the Web of Science Core Collection databases to acquire a comprehensive perspective of the subject. The PRISMA guidelines were applied to establish the search parameters, identify the appropriate articles, and collect the bibliographic information from the publications between 2010 and 2022. The bibliometric analysis showed that biochar-based heavy metal remediation is a research field with increasing scholarly attention. The removal of Cr(VI), Pb(II), Cd(II), and Cu(II) was the most studied among the heavy metals. We identified five main clusters centered on adsorption, water treatment, adsorption models, analytical techniques, and hydrothermal carbonization by performing keyword co-occurrence analysis. Trending topics include biochar reusability, modification, acid mine drainage (AMD), wastewater treatment, and hydrochar. The reutilization of heavy metal-loaded spent biochar includes transforming it into electrodes for supercapacitors or stable catalyst materials. This study provides a comprehensive overview of biochar-based heavy metal remediation in aquatic environments and highlights knowledge gaps and future research directions.

Recent trends and economic significance of modified/functionalized biochars for remediation of environmental pollutants

The pollution of soil and aquatic systems by inorganic and organic chemicals has become a global concern. Economical, eco-friendly, and sustainable solutions are direly required to alleviate the deleterious effects of these chemicals to ensure human well-being and environmental sustainability. In recent decades, biochar has emerged as an efficient material encompassing huge potential to decontaminate a wide range of pollutants from soil and aquatic systems. However, the application of raw biochars for pollutant remediation is confronting a major challenge of not getting the desired decontamination results due to its specific properties. Thus, multiple functionalizing/modification techniques have been introduced to alter the physicochemical and molecular attributes of biochars to increase their efficacy in environmental remediation. This review provides a comprehensive overview of the latest advancements in developing multiple functionalized/modified biochars via biological and other physiochemical techniques. Related mechanisms and further applications of multiple modified biochar in soil and water systems remediation have been discussed and summarized. Furthermore, existing research gaps and challenges are discussed, as well as further study needs are suggested. This work epitomizes the scientific prospects for a complete understanding of employing modified biochar as an efficient candidate for the decontamination of polluted soil and water systems for regenerative development.

Qualitative and quantitative analysis for Cd2+ removal mechanisms by biochar composites from co-pyrolysis of corn straw and fly ash

Removal of heavy metals (e.g., Cd) from contaminated water using waste-converted adsorbents is promising, but the efficiency still needs to be improved. Here, we prepared a functional biochar composite as novel Cd adsorbents by co-pyrolysis of two typical solid wastes, i.e., agricultural corn straw and industrial fly ash. The adsorption behavior and mechanism were investigated using batch and column adsorption experiments and modern characterization techniques. Results showed that alkali-modified fly ash (AMFA) was loaded onto the surface of the corn straw biochar as some fine particle forms, with quartz (SiO₂) and silicate being the main mineral phases on the surface. The maximum sorption capacity fitted by Langmuir model for functionalized biochar composite (FBC700) was up to 137.1 mg g^-1, which was 7.7 times higher than that of the original corn straw biochar (BC700). Spectroscopic analysis revealed that adsorption mechanisms of Cd onto the FBC700 included mainly precipitation and ion exchange, with complexation and Cd-π interaction also contributing. The AMFA could effectively improve the mineral precipitation with Cd. The adsorption columns filled with FBC700 exhibited a longer breakthrough time than that filled with BC700. The adsorption capacity calculated by Thomas model for FBC700 was also approximately 6.0 times higher than that for BC700, showing that FBC700 was more suited to practical applications. This study provided a novel perspective for recycling solid wastes and treating Cd-contaminated water.

Algae-derived metal-free boron-doped biochar acts as a catalyst for the activation of peroxymonosulfate toward the degradation of diclofenac

In this study, plain seaweed biochar (SW) and boron-doped seaweed biochar (BSW) were prepared through a simple pyrolysis process using Undaria pinnatifida (algae biomass) and boric acid. The BSW catalyst was utilized to degrade organic pollutants in aqueous environments by activating peroxymonosulfate (PMS). Surface characterization of the BSW demonstrated successful doping of boron into the biochar materials. BSW₆₀₀ exhibited greater catalytic activity than SW₆₀₀, as evidenced by the former's maximum adsorption capacity of diclofenac (DCF) onto BSW₆₀₀ (q_max = 30.01 mg g^-1) and the activation of PMS. Complete degradation of DCF was achieved in 30 min using 100 mg L^-1 BSW₆₀₀, 0.5 mM PMS, and 6.5 initial solution pH as critical parameters. The pseudo-first-order kinetic model accurately described the DCF degradation kinetics. The scavenger experiment displayed that radical and non-radical reactive oxygen species (ROS) formed in the BSW₆₀₀/PMS system. Furthermore, the generation of ROS in the BSW₆₀₀/PMS system was confirmed by electron spin resonance spectroscopy (ESR). The percentage contribution of ROS was assessed to be 10, 65, and 25% for HO^•, SO₄^•-, and ¹O₂, respectively. Additionally, the electron transfer pathway was also confirmed by electrochemical analysis. Moreover, the influence of water matrics on the BSW₆₀₀/PMS system was demonstrated. The co-existence of anions and humic acid (HA) did not affect the catalytic activity of the BSW₆₀₀/PMS system. The recyclability of BSW₆₀₀ was assessed by DCF removal (86.3%) after three cycles. Ecological structure-activity relationships software was used to assess by-product toxicity. This study demonstrates the efficacy of non-metallic heteroatom-doped biochar materials as eco-friendly catalysts in groundwater applications.

Enhanced adsorption performance of bensulfuron methyl with B doping biochar: Mechanism and density functional theory calculations

It is an urgent task to develop suitable adsorbents for the control of herbicide-bensulfuron methyl (BSM) in the paddy rice fields at cold regions. Herein, B doping biochar was synthesized via one-step method. Results showed that the adsorption capacity for BSM on 1.0BBC was significantly superior to BC at 15 °C. Besides, low temperature resistance, wide pH adaptability, stable adsorption performance and reusability test suggested that 1.0BBC have potential practical application. The mechanisms of BSM removal by 1.0BBC were mainly attributed to pore filling and π-π electron donor-acceptor (EDA) interaction. Theoretical calculations revealed that BCO₂ could enhance the adsorption capacity by π-π EDA between BSM and adsorbent. Meanwhile, hydroponic experiment demonstrated that the toxicity to soybean after adsorption of BSM by 1.0BBC was within the safe range. This study proves that 1.0BBC is an easy-to-prepare adsorbent with promising application in BSM removal in the rice paddy fields at lower temperature.

A Novel Adsorbent of Attapulgite & Carbon Composites Derived from Spent Bleaching Earth for Synergistic Removal of Copper and Tetracycline in Water

Simultaneously eliminating tetracycline (TC) and copper (Cu-II) from wastewater was investigated by applying a novel adsorbent fabricated by transforming spent bleaching earth (SBE) into attapulgite & carbon composites (A&Cs). Pyrolysis temperature for A&Cs preparation exhibited a positive effect on Cu(II) adsorption, while the AC500 possessed the greatest performance for TC remediation. Interestingly, a synergistic effect instead of competitive adsorption occurred between Cu(II) and TC under the combined binary system, as both TC and Cu(II) adsorption amount on A&C500 increased more than that in the single system, which could be mainly attributed to the bridge actions between the TC and Cu(II). In addition, hydrogen bonding, ᴨ-ᴨ EDA interaction, pore-filling and complexation exerted significant roles in the adsorption process of TC and Cu(II). In general, this study offered a new perspective on the regeneration of livestock and poultry industry wastewater polluted with antibiotics and heavy metals.

Biochar addition regulates soil phosphorus fractions and improves release of available phosphorus under freezing-thawing cycles

Currently, the shortage of phosphorus resources is becoming more and more serious. In general, phosphorus fertilizer is poorly utilized in soil and tends to gradually accumulate. Freezing-thawing cycles (FT) are seasonal phenomenon occurring in high latitudes and altitudes regions, which have obvious influence on the form of phosphorus in soil. This study investigates the effect of biochar on soil physicochemical properties, phosphorus form and availability under FT and thermostatic incubation (TH) condition. Compared with treatment without biochar, 4 % biochar addition increased the soil pH value, electrical conductivity, organic matter and Olsen-P of soil by a maximum of 0.76, 285.55 μS/cm, 28.60 g/kg and 139.27 mg/kg, respectively. Moreover, according to Hedley-P classification results, under FT condition, the content of labile phosphorus pool is always higher than those under TH. FT may promote the conversion of phosphorus from other fractions to labile phosphorus pool. Redundancy analysis results show that biochar addition and FT can not only directly change the soil phosphorus pool, but also alter the soil physicochemical properties and microbial community, which further affect the adsorption and mineralization of phosphorus in soil. The results of this study will be devoted to understanding the changes in soil phosphorus fractions under the effects of biochar addition and FT, providing references for agricultural production in areas where FT occur.

Screening the functions of modified rice straw biochar for adsorbing manganese from drinking water

The seasonal out-of-limit of manganese ions (Mn²⁺) in the drinking water reservoirs is an intractable problem to water supply, which can pose a threat to the human health. In this study, the removal of Mn²⁺ by using pristine (BC), pre-alkali (Pre-BC) and post-alkali (Post-BC) modified biochar originating from rice straw was investigated. The maximum adsorption capacities obtained for BC, Pre-BC, and Post-BC were 20.59, 28.37, and 8.06 mg g⁻¹, respectively. The Langmuir isotherm model and the pseudo-second-order kinetic model were suitable fitting models to describe the adsorption process. The investigation of adsorption functions was carried out that revealed that the predominant forces were precipitation and cation exchange with the proportions of 43.38–69.15% and 38.05–55.79%, respectively. With regard to precipitation, Mn(ii) particles (Al–Si–O–Mn and MnCO₃) and insignificantly oxidized insoluble Mn(iv) particles (MnO₂) were formed on the biochar surface. Alkali and alkaline earth metals facilitated the behavior of cation exchange, where the primary contributing ions for cation exchange were Na⁺, Mg²⁺ and Ca²⁺ during the adsorption process. These outcomes suggest that alkali pre-treated modification of biochar is practical for the application of manganese pollution control in lakes and reservoirs.

Modified biochar was used to remove Mn²⁺ from water with principal adsorption functions of precipitation and cation exchange. The MnCO₃ and Al–Si–O–Mn mainly driven precipitation and Na⁺, Mg²⁺ and Ca²⁺ primarily contributed to the cation exchange.