Search Results (79)

The activation of persulfate (PS) to oxidize and degrade 2,4-dichlorophenol (2,4-DCP) in aqueous solution represents a prevalent advanced oxidation technology. This study established a PS activation system using sulfide-modified nanoscale zero-valent iron supported on biochar (S-nZVI@BC). The optimal conditions included a PS:2,4-DCP mass ratio of 70:1 and S-nZVI@BC:PS of 1.5:1. The activator had excellent stability after being reused five times, which lead to high cost-effectiveness and sustainable usability. This system exhibited broad pH adaptability (3–11), with enhanced efficiency under acidic/neutral conditions. Chloride ion, nitrate, and carbonate had effects during the degradation. During the initial degradation phase, S-nZVI@BC played a primary role, with a greater contribution rate of adsorption than reduction. Fe⁰ played a dominant role in the PS activation process; reactive species—including HO•, SO₄•⁻, and O₂•⁻—were identified as key agents in subsequent degradation stages. The overall degradation processes comprised three distinct stages: dechlorination, ring-opening, and mineralization. Full article

With the frequent occurrence of global droughts, modified biochar has demonstrated the potential to be an efficient soil amendment, which could affect carbon and nitrogen sequestration in arid soil. Therefore, this study investigated the co-application of pristine biochar (BC), Fe-modified biochar (FB) and H₂O₂-modified biochar (HB) with green manure during a 70-day laboratory incubation under drought conditions and normal moisture conditions. The emissions were quantified using gas chromatography, while microbial necromass carbon and nitrogen were measured by quantifying the amino sugar content by gas chromatography–mass spectrometry, and other soil carbon and nitrogen fractions were determined through chemical analysis. The results revealed that under drought conditions, compared to BC co-application with green manure, the total carbon loss of FB and HB co-application with green manure was reduced from 24.38% to 13.14% and 14.27%, respectively, and the total nitrogen loss was also reduced from 14.61% to 7.23% and 7.27%, respectively. This reduction occurred because FB and HB protected soil organic matter through iron oxide binding and micropore adsorption, thereby increasing the content of soil total humus acid (>5%) and microbial necromass nitrogen (>16%). In addition, under normal moisture conditions, BC, FB and HB co-application with green manure enhanced microbial activity and promoted the formation of stable total humus acid, thereby enhancing carbon and nitrogen sequestration. In conclusion, this study provides crucial theoretical support for the optimization of the green manure return via modified biochar co-application in arid environments. Full article

In this study, red mud (RM) was utilized as an iron and aluminum source, and reed biomass served as a carbon precursor to prepare red mud-modified biochar beads (RM/CSBC) via the gel-calcination method. Under a pyrolysis temperature of 900 °C and an RM/biomass dosage of 3 g each, RM/CSBC exhibited an optimal balance between adsorption performance and cost. Within typical pH range of 6–9 in wastewater, RM/CSBC maintained effective adsorption performance, while metal ion leaching (Fe ≤ 0.3 mg·L⁻¹, Al ≤ 0.2 mg·L⁻¹) complied with Class II surface water standards in China. Kinetic data were well fitted by the pseudo second-order model, supported by the Elovich model, indicating the involvement of both chemical and physical adsorption mechanisms. Isotherm results showed that the Langmuir model provided the best fit, indicating monolayer adsorption, with a maximum capacity of 85.16 mg·g⁻¹ at 25 °C. XPS analysis revealed the formation of AlPO₄ and FePO₄ precipitates, confirming chemical precipitation as a key mechanism, along with electrostatic attraction and physical sorption. This study highlights the feasibility of RM/CSBC as an efficient and low-cost phosphate adsorbent and provides a theoretical basis for phosphorus removal and recovery from wastewater using waste-derived materials. Full article

Cadmium {Cd (II)} poses a high risk to ecological security and human health due to its high toxicity, easy migration and difficult degradation. Using waste rubber seed shell biochar (RSSB) as the carrier material of nZVI may inhibit the caking oxidation of zero-valent iron and improve the removal efficiency of Cd (II) from water. Through a series of batch experiments, the adsorption mechanism of modified biochar on Cd (II) clarified that the removal effect of nano-zero-valent iron-rubber seed shell biochar (nZVI-RSSB) on heavy metals in water was better than that of RSSB. The results showed that when the dosage of complex biochar was 80 mg, the initial concentration of Cd (II) was 50 mg/L, and the solution pH was 6, the maximum adsorption capacity of nZVI-RSSB for Cd (II) reached 30.42 mg/g, compared with the RSSB of 13.32 mg/g. The adsorption kinetics model showed that chemisorption and physical adsorption existed simultaneously. The results of the in-particle diffusion model show that the adsorption process may be divided into two stages. The Langmuir competitive adsorption model was followed. Electrostatic adsorption and precipitation/co-precipitation could be the main ways for the removal of Cd (II) by composite materials. Meanwhile, the synergistic adsorption of nZVI-RSSB composites with multiple metals in actual water showed its application potential in water pollution control. Hence, the nZVI-RSSB not only successfully inhibits the caking oxidation of zero-valent iron, but also effectively improves the removal efficiency of heavy metals from water. Full article

Phytoremediation is widely acknowledged as a viable method for soil remediation; however, its efficacy remains limited in soils co-polluted with petroleum hydrocarbons and heavy metals. To overcome this constraint, the present study explored an innovative approach utilizing ferrate-modified biochar (FeBC) to augment phytoremediation efficiency. Experimental findings revealed that ferrate treatment markedly modified the physicochemical characteristics of biochar, yielding thinner, smoother-surfaced structures with pronounced iron enrichment. At a 5% application rate alongside ryegrass cultivation, FeBC exhibited superior remediation performance, achieving 52.0% degradation of petroleum hydrocarbons (notably within the meso-aggregate fraction) and a 19.2% decline in zinc bioavailability via immobilization, thereby reducing zinc uptake in ryegrass tissues. Furthermore, FeBC amendment induced significant shifts in rhizosphere soil biochemistry and microbial ecology, characterized by diminished catalase activity but elevated urease and alkaline phosphatase activities. Phospholipid fatty acid profiling indicated a substantial rise in bacterial biomass (encompassing both Gram-positive and Gram-negative groups), particularly in meso- and micro-aggregates, whereas soil bacterial α-diversity declined markedly, accompanied by distinct compositional changes across aggregate size fractions. These results offer mechanistic insights into the synergistic interaction between FeBC and ryegrass in co-contaminated soil rehabilitation, the aggregate-dependent distribution of remediation effects, and microbial community adaptations to FeBC treatment. Collectively, this study advances the understanding of ferrate-modified biochar’s role in phytoremediation enhancement and clarifies its operational mechanisms in petroleum-zinc co-contaminated soil systems. Full article

This study explores the enhancement of fluoride adsorption using biochar derived from the brown macroalga Sargassum polycystum, which was treated with iron oxide (Fe₃O₄). The macroalgal biomass underwent pyrolysis at 400 °C, followed by Fe₃O₄ impregnation, to improve surface functionality and create active sites for fluoride ion binding. Various factors affecting fluoride removal were systematically examined. A maximum fluoride removal effectiveness of 90.2% was attained under ideal circumstances (pH 2, 60 mg adsorbent dose, 30 mg/L fluoride concentration, and 150 min contact duration). Adsorption isotherm analysis showed that the Langmuir model provided a better fit (R² = 0.998) than the Freundlich model (R² = 0.941), with a maximum adsorption capacity (qₘ) of 3.41 mg/g, indicating monolayer adsorption on a homogeneous surface. Kinetic modeling revealed that the pseudo-second-order model best described the adsorption process (R² = 0.9943), suggesting chemisorption as the dominant mechanism, while the intraparticle diffusion model also showed a good fit (R² = 0.9524), implying its role in the rate-limiting step. Surface complexation, facilitated by the enhanced surface area and porosity of the iron-modified biochar, was identified as the primary mechanism of fluoride ion interaction. This study highlights the potential of Fe₃O₄-modified macroalgal biochar as an effective and sustainable solution for fluoride remediation in contaminated water sources. Full article

In the present work, six biochars were produced from the pyrolysis of poultry manure at 400 °C and 600 °C (PM-B-400 and PM-B-600), and their post-modification with, respectively, iron chloride (PM-B-400-Fe and PM-B-600-Fe) and potassium permanganate (PM-B-400-Mn and PM-B-600-Mn). First, these biochars were deeply characterized through the assessment of their particle size distribution, pH, electrical conductivity, pH at point-zero charge, mineral composition, morphological structure, and surface functionality and crystallinity, and then valorized as biofertilizer to grow spring barley at pot-scale for 40 days. Characterization results showed that Fe- and Mn-based nanoparticles were successfully loaded onto the surface of the post-modified biochars, which significantly enhanced their structural and surface chemical properties. Moreover, compared to the control treatment, both raw and post-modified biochars significantly improved the growth parameters of spring barley plants (shoot and root length, biomass weight, and nutrient content). The highest biomass production was obtained for the treatment with PM-B-400-Fe, owing to its enhanced physico-chemical properties and its higher ability in releasing nutrients and immobilizing heavy metals. These results highlight the potential use of Fe-modified poultry manure-derived biochar produced at low temperatures as a sustainable biofertilizer for soil enhancement and crop yield improvement, while addressing manure management issues. Full article

Biochar, a porous carbonaceous material derived from the pyrolysis of biomass under oxygen-limited conditions, offers several advantages for environmental remediation, including a high specific surface area, ease of preparation, and abundant raw material sources. However, the application of pristine biochar is limited by its inherent physicochemical shortcomings, such as a lack of active functional groups and limited elemental compositions. To overcome these limitations, metal-modified biochars have garnered increasing attention. In particular, iron-manganese (Fe-Mn) modification significantly enhances the adsorption capacity, redox potential, and microbial activity of biochar, owing to the synergistic interactions between Fe and Mn. Iron-manganese-modified biochar (FM-BC) has demonstrated effective removal of heavy metals, organic matter, phosphate, and nitrate through mechanisms including mesoporous adsorption, redox reactions, complexation, electrostatic interactions, and precipitation. Moreover, FM-BC can improve soil physicochemical properties and support plant growth, highlighting its promising potential for broader environmental application. This review summarizes the preparation methods, environmental remediation mechanisms, and practical applications of FM-BC and discusses future directions in mechanism elucidation, biomass selection, and engineering implementation. Overall, FM-BC, with its tunable properties and multifunctional capabilities, emerges as a promising and efficient material for addressing complex environmental pollution challenges. Full article

Waste and chemicals generated from industry have been a major source of pollution and a prominent threat to human health via the food chain; hence, an efficient and durable material that can be used to detoxify polluted soil and water bodies is necessary to attain ecosystem equity and security. This study hypothesized that biochar (BC) made from poultry manure (PM) through pyrolysis and fortification with iron (Fe–BC) can be used to remove methyl orange dye from aqueous solution. Furthermore, this study evaluated the effect of solution pH on the sorption of methyl orange through batch sorption studies. The similarity in the modeled data and experimental data was measured by the standard error of estimate, whereas sorption isotherms were examined using nonlinear forms of different sorption equations. With the use of Langmuir models, a maximum sorption capacity of 136.25 mg·g⁻¹ and 98.23 mg·g⁻¹ was recorded for Fe–BC and BC, respectively. Fe–BC possessed a higher adsorption ability in comparison to BC. The pseudo-second-order best described the sorption kinetics of both adsorbents at R² = 0.9973 and 0.9999, indicating a strong interaction between MO and Fe–BC. Furthermore, the efficiency with which MO was removed by the absorbent was highest at lower pH (pH = 4). It is therefore concluded that Fe–BC can be used as an effective and environmentally friendly material for detoxification of wastewater; however, further research on the application and usage of biochar modified techniques for enhancing adsorption efficacy on a large scale should be encouraged. Full article

Biochar is a solid product generated through the pyrolysis of biomass materials under anaerobic or hypoxic conditions, and it is characterized by its strong adsorption capacity. To investigate the phosphorus adsorption performance of biochar derived from wheat straw, bamboo, and water hyacinth in wastewater, iron modification treatments were applied to these biochars, and the most effective modified biochar was identified. The physicochemical properties of the modified biochars were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and scanning electron microscopy (SEM). The results showed that optimal modification was achieved with an iron–carbon mass ratio of 0.70 for wheat straw biochar (Fe-WBC) and 0.45 for both bamboo biochar (Fe-BBC) and water hyacinth biochar (Fe-HBC). The maximum phosphorus adsorption capacities of the three modified biochars were as follows: 31.76 mg g⁻¹ (Fe-WBC) > 27.14 mg g⁻¹ (Fe-HBC) > 25.31 mg g⁻¹ (Fe-BBC). It was demonstrated that the adsorption behavior of Fe-BBC was predominantly multi-molecular layer adsorption, whereas the adsorption behavior of Fe-WBC and Fe-HBC was primarily monolayer adsorption. All three types of modified biochars reached adsorption equilibrium within 30 min, with Fe-WBC exhibiting the best adsorption performance. Analysis revealed that the modified biochars contained a large number of unsaturated C bonds and aromatic rings, indicating relatively stable structures. The surfaces of the modified biochars were rich in hydroxyl and carbonyl groups, which contributed to their strong adsorption properties. Post-modification analysis indicated that iron in the biochars predominantly existed in forms such as goethite (FeOOH) and hematite (Fe₂O₃). The iron content in each type of modified biochar constituted approximately 3.08% for Fe-WBC, 5.94% for Fe-BBC, and 5.68% for Fe-HBC relative to their total elemental composition. Overall, the iron-modified biochars employed in this study significantly enhanced the adsorption capacity and efficiency for phosphorus removal in wastewater. Full article

Hexavalent chromium (Cr(VI)) is of significant interest in the environmental field due to its high toxicity. Biochar is commonly used as an adsorbent for Cr(VI) removal from wastewater. However, its lower removal efficiency remains a persistent challenge. This study develops an iron-modified rice straw biochar through a simple precipitation and pyrolysis method and applies it for Cr(VI) removal in wastewater, which could convert waste into treasure and improve the adsorption performance of adsorbent. In the adsorption experiments, the results revealed that the adsorption efficiency of Cr(VI) reached 95.54% within 480 min (conditions: adsorbent dosage 2.67 g/L, pH 2.5, temperature 25 ± 2 °C). The Langmuir isotherm model was more suitable to describe the adsorption behavior of Cr(VI) by Fe-BC, and the fitted adsorption capacity achieved 10.03 mg/g. The experimental process was better described by the pseudo-second-order kinetic model, indicating that the adsorption process chemical adsorption was the rate-limiting step. The thermodynamic experiments revealed that the adsorption process of Cr(VI) by Fe-BC was spontaneous and endothermic. Column experiments demonstrated that a lower flow speed was beneficial to adsorption performance. Mechanistic studies highlighted the synergistic roles of electrostatic attraction, ion exchange, and reduction in Cr(VI) removal. These findings provide novel perspectives and innovative approaches for the development and application of adsorbents. Full article

The contamination of paddy soils with arsenic (As) and cadmium (Cd), coupled with the depletion of soil organic carbon (SOC), poses significant threats to rice yields and quality. There is an urgent need to identify a suitable soil additive capable of achieving simultaneous heavy metal remediation and promotion of organic matter enrichment. The current study introduced two novel iron (Fe)/magnesium (Mg)-based bimetal-oxide-modified rice straw biochar (RSB), namely RSB-Fe/Mn and RSB-Fe/Mg. It evaluated their effectiveness in As/Cd immobilization and SOC preservation. An 8-week cultivation experiment was carried out in sequential drying–flooding moisture fluctuation conditions, with the soil pore water As/Cd (PWAs/Cd) and SOC fractions monitored. The mechanisms of As/Cd immobilization were investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) characterizations. Results revealed that PWAs and PWCd were reduced by up to 67.1% and 80.2% during the drying period and by 27.0% and 76.5% during the flooding period, respectively. Additionally, SOC content increased by 16.3% and 33.9% with RSB-Fe/Mn addition during the drying and flooding period, respectively, with an increase in the mineral-associated organic carbon (MAOC) fraction. The study proves that RSB-Fe/Mn and RSB-Fe/Mg are effective for soil As/Cd passivation and SOC stabilization, offering a promising solution to mitigate As and Cd pollution in paddy soils while maintaining soil quality. Full article

The transition from fossil resources to renewable raw materials derived from lignocellulosic waste is crucial for economic and environmental sustainability. Advancing toward a bio-based economy necessitates the development of innovative heterogeneous catalysts. This study explores the use of modified sugarcane bagasse biochar, embedded with ruthenium and iron particles, as a green catalyst for converting levulinic acid (LA) to γ-valerolactone (GVL). The efficiency of both raw and modified biochar in the LA to GVL conversion process, utilizing formic acid (FA) exclusively as the hydrogen source, was systematically assessed through characterization techniques, including XRD, TGA, XPS, and SEM/EDS. The gelification method using alginate enhanced the ruthenium and iron content on the surface of the biochar. The results demonstrate that the modified material has significant potential for efficient LA-to-GVL conversion, achieving a yield of 73.0 ± 9.2% under optimized conditions (0.5 g of BC₅₀₀Fe/3%Ru at 180 °C for 3 h, with 4 mmol LA, 8 mmol FA, and 10 mL of water). Iron on the biochar surface facilitated the formation of adsorption sites for LA, supporting the notion of this novel catalyst for LA conversion in an aqueous medium in the presence of FA. This research underscores the potential of this green catalyst in advancing sustainable biomass conversion and contributes to the ongoing shift towards a bio-based economy. Full article

Tetracycline (TC) contamination in wastewater presents a significant global environmental challenge, with conventional water treatment methods often proving ineffective at eliminating antibiotic pollutants. As a result, there is an urgent need for cost-effective and efficient remediation technologies. In this study, we utilized the abundant and low-cost Eichhornia crassipes as a precursor to prepare sulfuric acid-modified functional biochar (SC-Fe) through a two-step pyrolysis process. This SC-Fe was then employed to activate peroxydisulfate (PDS) for the removal of TC from wastewater. The structural and physicochemical properties of SC-Fe were extensively characterized, and its efficiency in activating PDS for TC degradation was evaluated. The results demonstrated that the SC-Fe/PDS system effectively removed 99.36% of TC within 60 min under optimal conditions (0.3 g/L SC-Fe, 5 mM PDS, initial pH 7.09, and 25 °C). The outstanding removal efficiency can be attributed to the high specific surface area, large porosity, and defect-rich structure of SC-Fe. Furthermore, during the TC removal process, the SC-Fe/PDS system generated SO₄^•−, •OH, and ¹O₂, with SO₄•⁻ and •OH acting as the primary reactive species. The high catalytic efficiency and low consumption of the SC-Fe/PDS system present a promising strategy for effective wastewater treatment. Full article

In this study, an effective composite material, manganese-modified magnetic dual-sludge biochar (Mn@MDSBC), was developed for the adsorption of ciprofloxacin hydrochloride (CIP). This composite was prepared by means of a simple one-pot method, which involved the pyrolysis of iron-based waterworks sludge (IBWS) and paper mill sludge (PMS) loaded with manganese (Mn) under controlled conditions in a nitrogen atmosphere. The synthesized Mn@MDSBC was subjected to a comprehensive suite of characterization approaches, which included N₂ adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Subsequently, static adsorption tests were conducted to investigate how different factors, including the initial solution pH, reaction time and temperature, CIP concentration, and ionic strength influence the adsorption of CIP by Mn@MDSBC. Mn@MDSBC had the maximum CIP adsorption capacity of 75.86 mg/g at pH 5, among the pH values ranging from 3 to 9. The pseudo-second order model provided the best description of the adsorption process, while the experimental data aligned more closely with the Langmuir equation than with the Freundlich model, indicating monolayer adsorption. The adsorption process was found to be non-spontaneous and exothermic according to thermodynamic analysis. The presence of Cl⁻ and SO₄²⁻ enhanced CIP adsorption, while PO₄³⁻ weakened it. After five cycles of reuse, Mn@MDSBC experienced a 17.17% loss in CIP adsorption capacity. The primary mechanisms for CIP removal by Mn@MDSBC were identified as physical and chemical adsorption, hydrogen bonding, and π-π stacking interactions. In summary, the study underscores the high efficiency of Mn@MDSBC as a composite material for CIP adsorption, highlighting its potential for application in wastewater treatment processes. Full article