Biochar Composites Research Articles

Study on the decarbonization mechanism of composite adsorbent by Mg-MOF-74-based modified biochar

In this paper, the composite adsorbent by MOFs-based modified biochar was prepared by in-situ growth method based on the structural design of modified biochar and Mg-MOF-74, both of which contained unsaturated metal centers and oxygen-containing functional groups. The coupling mechanism between MOFs and biochar was investigated by CO2 adsorption properties and various characterizations. Based on the density functional theory (DFT), the three-dimensional model of composite adsorbent was constructed by combining the characterization of various microscopic properties to reveal CO2 adsorption mechanism of the composite adsorbent. Finally, the correctness of the microscopic mechanism of the composite adsorbent was verified by using surface element analysis. The results reveal that biochar causes lattice defects in MOFs, improving the pore structure, and the composite of biochar and MOFs increases the CO2 adsorption performance. Biochar is connected with Mg-MOF-74 through oxygen-containing functional groups and unsaturated metal centers to form a composite adsorbent. The four adsorption sites constructed with electron-bearing oxygen vacancies, metal ions, lattice oxygen, and chemisorbed oxygen are coupled to act on CO2 adsorption, chemisorption properties of the composite adsorbent are enhanced. MOFs are affected by the spatial site resistance effect brought by the biochar to produce oxygen defects, which couples with the unsaturated metal adsorption sites to realize the composite adsorption of metals. There is electron transfer during CO2 adsorption by the composite adsorbent and the stable carbonate is generated.

Evaluation of the content and degradation rates of PAHs in biochars, in terms of assessing the environmental risks of their application for soil remediation

The growing worldwide practice of biochar application as soil ameliorants, as well as adsorbents for remediation of soil contaminated with oil products and heavy metals, can lead to an increase the risk of environmental pollution by pyrolysis by-products. One of the most dangerous components of biochars is polycyclic aromatic hydrocarbons (PAHs), which are inevitably formed during the production of pyrogenic material. In this work, biochars obtained from various plant materials (millet, corn, willow, linden) under different pyrolysis temperatures were tested for the content of polycyclic aromatic hydrocarbons. The total content of PAHs in the studied samples ranged from 8.49 to 221.21 µg/kg, which does not exceed the limit concentrations established by the International Biochar Initiative. At the same time, polynuclear hydrocarbons with high carcinogenic and immunotoxic properties are found in the composition of biochars. A natural question arises about the effect of the final pyrolysis temperature on the total content and composition of PAHs in pyrolysis by-products. To study the degradation of polycyclic aromatic hydrocarbons in soil, linden biochar obtained by pyrolysis at 250 °C was used, from which the contaminants were extracted and applied to the soil so that the concentration of the marker was 20 and 40 µg/kg. The determination of the residual amount of polycyclic aromatic hydrocarbons was carried out after 1, 2, 6, and 11 months of incubation. Complete degradation of some 3–5-membered polycyclic aromatic hydrocarbons was found after 1–2 months of incubation. The most persistent pollutants were benzo(a)pyrene, benzo(b)fluoranthene, and pyrene, the concentration of which decreased to 31–71% on after 11 months of incubation. The slower degradation was found in the variant of the experiment with the high concentration level of polycyclic aromatic hydrocarbons. It was concluded that in soils selective accumulation of polynuclear PAHs, that most resistant to biodegradation, can occur.

Enhanced removal capacities and mechanisms of Mn/Fe-loaded biochar composites functionalized with chitosan Schiff-base or hydroxyl toward Pb(II) and Cd(II) from aqueous solutions

The efficient capture of heavy metal ions from actual wastewater is a global challenge. To enhance Pb(II) and Cd(II) removal, novel biochar composites (MF@CBC, MF-S@CBC and MF-OH@CBC) were successfully fabricated by loading magnetic Mn-Fe binary oxides and functionalizing chitosan Schiff-base or hydroxyl on biochar in the study. The maximum adsorption capacities of MF-OH@CBC and MF-S@CBC toward Pb(II)/Cd(II) were 196.69/187.29 mg/g and 161.61/153.69 mg/g (pH = 5.0, adsorbent dosage = 0.5 g/L), which were 2.09/3.05 and 1.54/2.33 times higher than corn cob biochar (CBC), respectively. The adsorption processes were conformed to Langmuir isothermal model and pseudo second order model. The numerous functional groups presented on MF-OH@CBC resulting from loading Mn-Fe nanoparticle and hydroxylation might be the main reason for dominating adsorption of Pb(II)/Cd(II) by complex interaction (contribution rate (CR) = 45.66%/43.12%). And also, the negative charge on MF-OH@CBC might be another reason for enhancing adsorption of Pb(II)/Cd(II) by electrostatic interaction (CR = 23.11%/22.45%). Besides, ion exchange (CR = 17.95%/19.33%) and physical adsorption (CR = 13.28%/15.10%) could also contributed to Pb(II)/Cd(II) removal. In addition, MF-OH@CBC displayed favorable recycling ability and its adsorption capacity retained over 80% after five cycles. It also exhibited anti-interfering ability, the adsorption capacity for Pb(II)/Cd(II) in actual sewage was 85.27%/80.47%, respectively. The results indicated that MF-OH@CBC possessed good potential for eliminating Pb(II) and Cd(II) from the complex aqueous environment.

Enhanced complexation and electrostatic attraction through fabrication of amino- or hydroxyl-functionalized Fe/Ni-biochar composite for the adsorption of Pb(II) and Cd(II)

To enhance Pb(II) and Cd(II) elimination, new composites (FeNi-RSN-(OH)(NH2) and FeNi-RSN-OH) were fabricated by loading biochar with Fe-Ni nanoparticles and functionalizing biochar by amination/hydroxylation in the study. The maximum sorption capacities of both adsorbents toward Pb(II)/Cd(II) were 217.09/209.36 mg/g and 242.15/229.52 mg/g, respectively, which were 4.30–4.79 times higher than those of the raw biochar. The significantly enhanced adsorption capacity could be attributed to the increased O/N-containing groups and Fe-Ni nanoparticles on the adsorbent surface. The introduction of Fe-Ni nanoparticles and O/N-containing groups promoted the complexation and electrostatic interactions and made them playing major roles in the adsorption. Besides, ions exchange and physical adsorption played non-negligible roles in the adsorption process. Additionally, the both adsorbents exhibited favorable anti-interference ability and cycling stability. Taken together, the study revealed that the new biochar composites of FeNi-RSN-(OH)(NH2) and FeNi-RSN-OH could be used as a reusable magnetic adsorbents with promising prospect in current practice for the effective remediation of heavy metals-bearing wastewater. The study not only provided a feasible design, synthesis and optimization strategy of biochar for heavy metals contaminants removal, but also realized the sustainable utilization of waste.

Management of a contaminated mine soil: Effect of soil water content on antimony and arsenic immobilisation by iron‐based amendments and biochar composites

AbstractAlteration of wet and dry periods affects soil geochemical properties that drive contaminant availability and mobility. Consequently, the efficiency of soil remediation may vary, and thus soil management needs to consider these variations. This study reveals the effect of soil moisture manipulation on the behaviour of the toxic metalloids antimony (Sb) and arsenic (As) and the immobilisation efficiency of nanoscale zero‐valent iron (nZVI), biochar (BC) and BC modified by iron or iron/ferrous sulphide (nZVI‐BC and Fe/FeS‐BC). Soil samples from an abandoned Sb mining site were tested under laboratory conditions. Two distinct (organic and mineral) soil layers were incubated with each of the amendments (2% w/w application rate) at 50% and 100% water holding capacity (WHC) of the soils for 10 weeks, and subsequently extracted with demineralised water and rainwater. The immobilisation efficiency of the tested amendments was significantly influenced by the different soil moisture regimes and type of contaminant. Sorption onto secondary Fe minerals was the dominant Sb/As immobilizing mechanism. The iron‐based amendments showed up to 97% efficiency for Sb and up to 96% for As. However, Sb/As release was generally higher at 100% WHC and in the rainwater extracts compared to the other conditions, indicating that heavy rainfall and flooding of soils in‐situ may increase contaminant availability and mobility. In the organic layer, enhanced formation and leaching of metalloid‐DOC complexes and sorption competition of the negatively charged Sb/As species and DOC can be expected. Also, reductive dissolution of Sb or As‐bearing metal oxides could lead to the observed higher Sb/As release under flooded conditions, resulting in exacerbated environmental and health risks. Therefore, it is crucial to (1) improve the sorption characteristics of the tested amendments and/or develop other effective amendments for Sb/As immobilisation in different water regimes in soil; (2) test the amendments under real field conditions to evaluate the long term wet/dry exposure; and (3) develop proper risk assessment and soil remediation strategy for the study area and similar sites.

Oxalic acid enhanced removal of heavy metal and pesticide by peroxymonosulphate activation with a green biochar iron composite: Reactivity and mechanism

Nowadays, clean-up of heavy metals and pesticides from environment has received great attention. A green biochar iron composite (PC-ZVI) was successfully synthesized using pomelo peel residues and FeCl3 solution. Peroxymonosulfate (PMS) was introduced into the PC-ZVI system for Cr(VI) and atrazine (AE) removal, and results showed that PMS greatly promoted Cr(VI) and AE removal. The presence of oxalic acid (OA) could maintain a relatively high dissolved Fe2+ species for Cr(VI) reduction and AE oxidation in the PC-ZVI/PMS process. The contribution order of reactive oxygen species followed as HO• > SO4•- greater than1O2 > O2•− in both Cr(VI) and AE removal by PC-ZVI/PMS/OA process. A total of six intermediates products of AE degradation were detected, and AE molecular was effectively degraded into CO2, H2O, inorganic N and Cl through hydroxylation, substitution and de-alkylation processes. The underlying mechanism of Cr(VI) and AE removal by PC-ZVI/PMS/OA process was also proposed. Most Cr(VI) species were transformed into Cr2O3 and Cr(OH)3 through reduction and precipitation processes. PC-ZVI has a relatively high recyclability toward both Cr(VI) and AE removal from solutions. The potential toxicity of PC-ZVI solution was small at three PC-ZVI dosages levels, and the corresponding toxicity of AE reaction solution by PC-ZVI/PMS/OA process decreased as reaction time increased. The order of both Cr(VI) and AE removal in different water systems was tap water > river water > lake water > wastewater, and this PC-ZVI/PMS/OA process exhibited the better adaptability in application for several actual water environments.

Moringa Growth Response in Treatment of Bokashi Composition and Dosage of Moringa Leaf (Moringa oleifera) Using Subsoil

Subsoil soil which is at a depth of more than 30 cm below the topsoil is a marginal soil for agricultural cultivation but has great potential for utilization. Improvement of subsoil soil with the use of organic fertilizers alone has been widely carried out. However, the use of moringa leaf bokashi fertilizer is thought to be able to improve the subsoil physically and chemically. The aim of the research was to find out the composition of the best moringa leaf bokashi fertilizer and the right dosage for the growth of moringa. Research using Completely Randomized Design. The first factor was the composition of moringa leaf bokashi, biochar and cow manure (K), namely K1 ratio of moringa leaves: biochar: cow manure (1:1:1); K2: (2:1:1); K3 (3:1:1). The second factor is the dose of moringa leaf bokashi fertilizer. Bo: control 5; B1:10; B2: 20; B3: 30; B4: 40 tons per hectare. The results showed that the K1 composition showed the highest plant height, number of primary roots, and canopy wet weight. A dose of 10 tons per hectare (B1) showed the best growth of Moringa seedlings with the highest dry weight of canopy. Keywords: Bokashi, Composition, Dosage, Moringa leaves, Moringa seedling

Efficient removal of per- and polyfluoroalkyl substances from biochar composites: Cyclic adsorption and spent regenerant degradation

In order to solve the problem of efficient desorption of per- and polyfluoroalkyl substances (PFAS) and regeneration of adsorbents, a novel biochar composite was prepared based on the quaternary ammonium groups and hydrophobicity of sulfobetaine polymer, which can be used for the efficient removal of various PFASs and has great regeneration ability. Through adsorption, regeneration and degradation experiment, the comprehensive effect of the novel biochar composite on the whole process of removal of PFAS was systematically investigated. The results showed that the maximum adsorption capacity of PFOS, PFOA, PFBS, and PFBA reached 634 mg/g, 536 mg/g, 301 mg/g and 264 mg/g, respectively. The adsorption process involved hydrophobicity, electrostatic, pore diffusion and complexation. The NaI + NaOH solution was used at 50 °C to achieve efficient regeneration of the adsorbent, which can be recycled more than 4 times. When the vacuum-ultraviolet (VUV)/sulfite reduction system was used for deep degradation of the regenerated solution, the effect of hydrated electrons on PFAS was enhanced due to the inclusion of NaI and NaOH in the regeneration reagent, resulting in an increase in the degradation efficiency (89.1%–99.9%) and defluorination efficiency (63.3%–84.1%). Based on the performance of BC-P(SB-co-AM) and the treatment efficiency of PFAS, the design idea of the whole process treatment technology of PFAS proposed in this work is expected to hold great promise in environmental applications. This work provides a novel idea and system for the efficient adsorption removal and desorption of PFAS, and subsequent deep degradation.

Fabrication of CeO2/municipal sludge-based biochar composites with outstanding photocatalytic degradation properties

CeO2/sludge-based biochar composites were prepared by a combination of carbonization and oxidation and applied to photocatalytic degradation of humic acid reactions. The effects of the preparation process sequence on the products were investigated from the perspectives of microscopic morphology and phase composition. The results showed that when the carbonization temperature was selected as 700 °C and the oxidation temperature was selected as 650 °C, accompanied by a certain holding time, structurally stable composites were obtained. In the composites, the biochar increased the adsorption property of the system, as well as facilitated the improvement of CeO2 photocatalytic activity. The adsorption degradation rates of SICO and SCIO on humic acid after 3 h of illumination were 57.92% and 82.88%, respectively, which were much better than those of pristine CeO2 and pure sludge-based biochar. This study provided new path for the practical application of municipal sludge disposal products.

Aromaticity, polarity, and longevity of biochar derived from disposable bamboo chopsticks waste for environmental application

Transforming disposable bamboo chopstick (DBC) wastes into biochar is an effective way to achieve waste-to-resource conversion. This research focused on the elemental and chemical composition of biochar and revealed how these properties affect biochar performance in real-world applications, particularly with respect to climate change mitigation. This research is aimed at examining the effect of pyrolysis temperature on the aromaticity, polarity, and longevity of DBC biochar. The DBC feedstock was pyrolyzed at different temperatures of 400 °C, 450 °C, 500 °C, and 550 °C with a holding time of 20 min at a constant heating rate of 20 °C min−1. The chemical composition, including carbon (C), hydrogen (H), nitrogen (N), oxygen (O), volatile matter (VM), ash, and fixed carbon (FC) contents, were analyzed. The aromaticity, polarity, and longevity of biochar are presented by the atomic ratios of H/C, O/C, (O + N)/C, and C/N, and these ratios are used to determine the potential of biochar for use in climate change mitigation applications. The findings demonstrated that DBC biochar produced at various pyrolysis temperatures contained C contents ranging from 77.54% to 88.06%, ash contents ranging from 2.62% to 2.99%, and a half-life of over 1000 years (O/C < 0.2). Pyrolysis temperature significantly affected biochar properties, as supported by the results for the FC/ash ratio (>10); the ash, FC, C, and N contents increased with increasing temperature; in contrast, the VM, H, and O contents decreased. The results revealed that DBC wastes are the potential feedstock to produce good-quality biochar that could be applied for environmental purposes. Furthermore, the research demonstrated that the best-performing DBC biochar was produced at 500 °C, which had the highest C content, aromaticity, and longevity and the lowest polarity as represented by the values of O/C, H/C, and (O + N)/C, and this biochar could be applied for climate change mitigation purposes.

Analysis of the elemental composition of biochar using ICP OES spectrometry and chemometric methods

W pracy wykonano oznaczenia 20 pierwiastków w próbkach karbonizatów otrzymanych w wyniku pirolizy biomasy stałej pochodzenia roślinnego oraz próbki osadów ściekowych – biomasy stanowiącej uboczny produkt procesu oczyszczania ścieków. Najniższe stężenia pierwiastków oznaczono w karbonizatach biomasy roślinnej otrzymanych z trocin sosnowych, natomiast najwyższe w próbkach karbonizatów osadów ściekowych. Ten ostatni rodzaj odpadów z procesu oczyszczania ścieków zawierał największe stężenia takich składników mineralnych jak: wapień, magnez, żelazo, siarka i fosfor, lecz także metali ciężkich: chromu, miedzi, niklu, molibdenu, ołowiu, wanadu i cynku. W karbonizatach otrzymanych z materiału roślinnego w najwyższych stężeniach oznaczono: potas, wapń, magnez i fosfor – makroelementy niezbędne do prawidłowego zachowania funkcji życiowych roślin. W celu określenia prawidłowości oraz relacji występujących pomiędzy danymi pomiarowymi zastosowano metody chemometryczne. W badaniach wykorzystano analizę wiązkową (ang. cluster analysis), tzn. metodę grupowania badanych próbek w taki sposób, aby obiekty podobne znajdowały się w tej samej grupie. W wyniku przeprowadzenia obliczeń otrzymano cztery skupienia. Dla każdego skupienia obliczono średnie stężenia pierwiastków wchodzących w jego skład oraz sumaryczne stężenie oznaczanych pierwiastków. Skupienia te to dwa składające się z próbek jednego rodzaju i pozostałe dwa, z których każde zawierało dwie różnego rodzaju próbki. Zaobserwowano, że w przypadku próbek biomasy roślinnej (skorupy orzechów włoskich), dla których zastosowano dwa odmienne sposoby ogrzewania, próbki tego samego rodzaju zostały zaklasyfikowane do różnych skupień: pierwszego – po ogrzewaniu tradycyjnym i drugiego – po ogrzewaniu mikrofalowym. W warunkach prowadzenia procesu pirolizy z wykorzystaniem ogrzewania mikrofalowego oznaczono badane pierwiastki w stężeniach 2–4 razy wyższych, niż gdy proces był prowadzony w tej samej temperaturze, ale z użyciem ogrzewania tradycyjnego.

Impact of Biochar on Fusarium Wilt of Cotton and the Dynamics of Soil Microbial Community

The effects of biochar on leaf and soil-borne diseases of plants can be seen in addition to its ability to sequester carbon, improve soil quality, and enhance plant performance. However, the mechanisms by which soil-borne pathogens are suppressed and plant performance is enhanced are not well understood. The present work aims to comprehensively establish the links between biochar-induced changes in the richness of the rhizosphere microbial population, in association with the reduction of soil-borne Fusarium wilt disease (Fusarium oxysporum f. sp. vasinfectum), in cotton (Gossypium hirsutum), with improved plant performance. Biochar made from organic waste significantly decreased the colonization and survival of Fusarium in soil, raised the culture-able counts of numerous microbes with biocontrol potential (microorganisms that boost plant growth and development), and inhibited Fusarium wilt of cotton. The biochar amendment significantly enhanced the cotton plant development and physiological parameters such as chlorophyll content, etc. Overall, 9% organic waste biochar had shown a significant impact on cotton growth as compared to other treatments with or without biochar. Compared to the soil-only control, the disease index was considerably reduced in all biochar-amended treatments. In terms of the plant’s resistance to Fusarium wilt, biochar-induced increases in the level of overall chlorophyll content and biochemicals such as phenolics, flavonoids, etc. Additionally, cotton plants grown with a 9% biochar composition had considerably greater NPK levels than other treatments with or without biochar. The biochar addition resulted in increased counts of Pseudomonas spp., Actinomycetes spp., and Trichoderma spp., while Acidobacteriales, Rhodospirillales, and Frankiales were less when compared with an un-amended (without biochar) soil control. Thus, the composition of rhizosphere bacteria in the treatments with and without modified biochar was found to differ significantly.

Adsorption Removal of Phosphate from Rural Domestic Sewage by Ca-Modified Biochar Derived from Waste Eggshell and Sawdust

In recent years, in order to improve the rural living environment, rural domestic sewage treatment has received more and more attention in China. However, the standard compliance rate of total phosphorus (TP) in rural domestic sewage after treatment is very low, and TP has become the main pollutant that prevents rural domestic sewage treatment facilities from meeting water pollutants discharge standards. In this study, to prepare calcium-modified biochar composites (E-BC) by one-step pyrolysis, waste eggshell (E) was employed as a calcium source and waste pine sawdust (BC) was employed as a carbon source. The E-BC composites produced were effective in adsorbing phosphate (P) from aqueous solutions in a broad pH range of 3–11, with good adsorption selectivity. E-BC’s adsorption capacity for P increased as the pyrolysis temperature increased from 700 °C to 900 °C, which was attributed to the higher specific surface area and calcium oxide content at higher pyrolysis temperatures. The E-BC sample, which was made from eggshell (filtered through 100 mesh sieves) and pine sawdust (filtered through 100 mesh sieves) with a mass ratio of 2:1 and a pyrolysis temperature of 900 °C, had a maximum adsorption capacity of 301 mg/g. The Langmuir model and pseudo second-order model were the best at describing the adsorption process, and the predominant sorption mechanism for P is the chemisorption reaction of calcium oxide or calcium hydroxide with phosphate to create hydroxyapatite. E-BC can effectively remove P from rural domestic sewage. The total phosphorus (TP) removal rate in rural domestic sewage ranges from 95.3 to 99.5%. After adsorption treatment, the discharge of TP in rural sewage meets the second-grade (TP &lt; 3 mg/L) or even the first-grade (TP &lt; 2 mg/L). This study provides an experimental basis for efficient P removal using E-BC adsorbent materials and suggests possible applications in rural domestic sewage.

Application of magnesium and biosurfactant functionalized biochar composite in treating cyanobacteria in phosphorus and crude oil contaminated water

Various human activities have led to multiple contamination of natural water systems. The present study investigated the effect of a novel multifunctional biochar to treat nutrients, oil, and harmful algae in water. Specifically, magnesium (Mg) and biosurfactant rhamnolipid (RL) were incorporated into biochar, including Mg-biochar, RL-biochar, and Mg-RL-biochar. Their adsorption efficiency on phosphate and total petroleum hydrocarbons (TPH) was evaluated in separate batch studies. Also, the inhibition effect of RL-modified biochars on cyanobacteria was investigated. The results showed that Mg-impregnated biochar showed high adsorption capacity on phosphate (118 mg g−1), while RL-modified biochar significantly reduced TPH (especially aromatic and light aliphatic fraction) with adsorption capacity of 44.4 mg g−1. The inhibition effects of biochar composites on algae in water without contaminants were in order of Mg-RL-biochar > RL-biochar > biochar with biomass reduction ranging 61–64%. Overall, Mg-RL-biochar was suggested based on this study due to its ability to remove PO43− and TPH, and inhibit the growth of toxic algae.Graphical abstract

Efficient Adsorption and Photocatalytic Degradation of Organic Pollutant by Ag3PO4/ZnO/Chitosan–Biochar Composites

Efficient Adsorption and Photocatalytic Degradation of Organic Pollutant by Ag3PO4/ZnO/Chitosan–Biochar Composites

Adsorption and photocatalytic degradation of quinolone antibiotics from wastewater using functionalized biochar

Quinolone antibiotics are emerging environmental contaminants, which cause serious harm to the ecological environment and human health. How to effectively remove these emerging pollutants from water remains a major challenge worldwide. In this study, a novel Fe/Ti biochar composite (Fe/Ti-MBC) was prepared by facile one-step co-pyrolysis of wood chips with hematite and titanium dioxide (TiO2) for adsorption and photocatalytic degradation of ciprofloxacin (CIP) and norfloxacin (NOR) in water. The results showed that the degradation efficiencies of Fe/Ti-MBC to CIP and NOR were 88.4% and 88.0%, respectively. The π-π interactions and polar interactions are the main adsorption mechanisms for CIP and NOR. In the photocatalytic process, h+ and ·OH are the main active substances for the oxidative degradation of CIP and NOR. This study shows that Fe/Ti-MBC is an effective and recyclable composite, providing a novel alternative way for antibiotics degradation.

A novel Corchorus olitorius-derived biochar/Bi12O17Cl2 photocatalyst for decontamination of antibiotic wastewater containing tetracycline under natural visible light

Herein, a novel composite of Corchorus olitorius-derived biochar and Bi12O17Cl2 was fabricated and utilized for the degradation of tetracycline (TC) in a solar photo-oxidation reactor. The morphology, chemical composition, and interaction between the composite components were studied using various analyses. The biochar showed a TC removal of 52.7% and COD mineralization of 59.6% using 150 mg/L of the biochar at a pH of 4.7 ± 0.5, initial TC concentration of 163 mg/L, and initial COD of 1244 mg/L. The degradation efficiency of TC increased to 63% and the mineralization ratio to 64.7% using 150 mg/L of bare Bi12O17Cl2 at a pH of 4.7 ± 0.5, initial TC concentration of 178 mg/L, and COD of 1034 mg/L. In the case of biochar/Bi12O17Cl2 composite, the degradation efficiency of TC and COD mineralization ratio improved to 85.8% and 77.7% due to the potential of biochar to accept electrons which retarded the recombination of electrons and holes. The synthesized composite exhibited high stability over four succeeding cycles. According to the generated intermediates, TC could be degraded to caprylic acid and pentanedioic acid via the frequent attack by the reactive species. The prepared composite is a promising photocatalyst and can be applied in large-scale systems due to its high degradation and mineralization performance in a short time besides its low cost and stability.

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water.

In this study, a composite of pond mud and lanthanum- and nano-zero valent iron-modified-biochar was investigated for its ability to adsorb methylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgite and nano-zero valent iron (surface area enhanced by 43.7% via Brunauer-Emmett-Teller analysis) were successfully loaded onto the straw-sediment biochar (BC) surface. With the increase in pyrolysis temperature, the biocompatibility yield, the H, O, and N content, and the ratio of carbon elements decreased, while the pH value, surficial micropores, C element, and ash content increased. The biocarbon small molecules were gradually and tightly ordered, and the organic groups such as hydroxyl, carboxyl groups, and carbon oxygen double bonds were gradually lost or disappeared. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than others with a higher adsorption capacity possibly through the Schiff base reaction. The effect of various pH (2-9), temperature (15-35 °C), and initial concentration (1-25 mg L-1) on adsorption was investigated. pH and temperature were the main factors governing the adsorption process. The maximum adsorption capacity was observed at pH 4. The adsorption performances for MB followed the order Fe-BC > La-BC > BC, and the maximum removal rate was over 98.45% with pH = 7. The three types of BC dosages between 0.2 (6.67 g L-1) and 0.4 g showed a removal rate of 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC for MB was 2.201, 1.905, and 2.401 mg L-1 with pH = 4, while 4.79, 4.58, and 5.55 mg g-1 were observed with BC dosage at 0.025 g. For SMZ, the higher the temperature, the better the adsorption effect, and it reaches saturation at approximately 25 °C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkin models were tested and the adsorption capacities were evaluated on the surface of the BC composite. The three modified materials were physisorbed to SMZ, while MB was chemisorbed. For MB, the adsorption performance of BC is the best < 0.2 g (6.67 g L-1) at pH 7.0 at 35 °C. The Elovich model was more suitable for MB, while the Freundlich and Temkin models could better fit the adsorption process of MB. The preparatory secondary dynamics equation and Langmuir equation were more compliant for SMZ, and the saturated adsorption capacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088, and 5.678 mg L-1, respectively.

In situ self-sacrificial synthesis of polypyrrole/biochar composites for efficiently removing short- and long-chain perfluoroalkyl acid from contaminated water

Efficient removal of perfluoroalkyl acids (PFAAs), especially short-chain ones, from contaminated water is of great challenge and is urgently called for so as to safeguard the ecosystem and human health. Herein, polypyrrole (PPy) functionalized biochar (BC) composites were innovatively synthesized by an in situ self-sacrificial approach to allow efficient capture of PFAAs with different chain lengths. Compared with conventional PPy-based composites synthesized by direct polymerization using FeCl3 as an oxidizing agent, PPy/BC composites were fabricated utilizing freshly generated Fe3+ as an oxidizing agent from self-sacrificial Fe3O4 for pyrrole monomers in situ polymerizing on BC. As a result, with the support of BC and gradual release of Fe3+, PPy overcame its tendency to aggregate and became uniformly dispersed on BC, and meanwhile, PPy could well tailor the surface chemistry of BC to endow its positively charged surface. Consequently, the composites exhibited strong sorption capacities of 3.89 and 1.53 mmol/g for short-chain perfluorobutanoic acid (PFBA) and perfluorobutane sulfonic acid (PFBS), 2.55 and 1.22 mmol/g for long-chain perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), respectively, which were superior to those of pristine BC, commercial activated carbon, and anion exchange resins reported. Additionally, they could effectively remove 17 different classes of per- and polyfluoroalkyl substances (PFAS) (removal >95%) from actual PFAS-contaminated water, and the spent sorbent could be well regenerated and reused at least 5 times. An integrated analysis indicated that such an outstanding PFAA sorption performance on PPy/BC composites could be mainly attributed to surface adsorption enhanced by electrostatic attractions (anion exchange interaction) with the traditional hydrophobic interaction and pore filling of less contribution, particularly for short-chain analogues. These results are expected to inform the design of BC with greater ability to remove PFAS from water and the new sorbent could help water facilities comply with PFAS regulations.

Biochar loaded with CoFe2O4 enhances the formation of high-valent Fe(IV) and Co(IV) and oxygen vacancy in the peracetic acid activation system for enhanced antibiotic degradation

Corn straw and sludge-derived biochar composite (BC) loaded with CoFe2O4 was successfully prepared to activate peracetic acid (PAA) for efficient degradation of tetracycline hydrochloride (TCH). Within 60 s, 96 % TCH removal efficiency was achieved through a non-free radical degradation pathway, primarily driven by singlet oxygen (1O2). The mechanism involves the electron-rich groups on the biochar surface, which facilitate the cleavage of the PAA OO bond to generate •O2−/1O2 and provide electrons to induce the formation of high-valent Fe(IV) and Co(IV). The oxygen vacancies on the surface of the CoFe2O4-loaded biochar composite (CFB-2) contribute partially to 1O2 production through their transformation into a metastable intermediate with dissolved oxygen. Moreover, elevated temperatures further enhance PAA activation by CFB-2, leading to increased reactive oxygen species (ROS) production through PAA decomposition, thereby promoting TCH removal. This study offers new insights into the catalysis of metal-loaded biochar for efficient TCH degradation via non-free radical generation.