Surface Area Of Biochar Research Articles

Fuel, thermal and surface properties of microwave-pyrolyzed biochars depend on feedstock type and pyrolysis temperature

We evaluated the fuel, thermal and surface properties of twelve biochars produced from three lignocellulosic (canola straw, sawdust, wheat straw) and one non-lignocellulosic feedstock (manure pellet) pyrolyzed at three temperatures using a microwave. Regardless of feedstock type, increasing pyrolysis temperature progressively reduced the abundance of -OH functional group and yield, but increased pH and thermal stability of biochar. Gross calorific values (GCV), carbon stability, and degree of aromaticity of biochars derived from lignocellulosic feedstocks increased with increasing temperature due to decreased elemental oxygen content. However, high ash content in the non-lignocellulosic feedstock retarded its thermal degradation, producing biochars with low GCV. The specific surface area of biochars was low, with the highest value of 43 m2 g−1 achieved for sawdust biochar produced at 500 °C. We conclude that the fuel, thermal, and surface properties of the biochars were dependent on the feedstock type and pyrolysis temperature.

Double-layer magnetized/functionalized biochar composite: Role of microporous structure for heavy metal removals

Magnetization facilitates the separation and reuse of adsorbents, but significantly reduces the adsorption capacity. In this study, a double layer magnetized/functionalized biochar composite was synthesized through a hybrid post-pyrolysis magnetization which sustained and even significantly increased the adsorption capacity of microporous carbonaceous biochar (BC). The developed process included i) structural modification of biochar under ultrasound waves, ii) magnetization with magnetite (Fe3O4) nanoparticles, and iii) functionalization with 3-aminopropyltriethoxysilane (TES). Ultrasound irradiation exfoliates and breaks apart the irregular graphite layers of biochar, and creates new, or opens blocked, micropores, thus enhancing the BC’s porosity. For its part, TES stabilizes the magnetic nanoparticles on the biochar surface, while it participates in water decontamination through the strong chelation ability of its amino groups toward metal ions. Scanning electron microscopy demonstrated the stable and uniform distribution of Fe3O4 nanoparticles on the surface of microporous biochar, and Fourier-transform infrared spectroscopy indicated effective surface functionalization. In addition, although magnetization usually reduces the porosity of carbonaceous adsorbents, the ultraviolet–visible spectroscopic analysis showed that double layer magnetic biochar composite exhibited a much greater ability to remove Ni(II) and Pb(II), with 139 % and 38 % higher adsorptions than raw biochar. Almost complete removal of Pb (91 %) was observed by magnetic-BC and the adsorbent could easily be separated using a neodymium magnet. This high performance can be attributed to the synergistic effect of ultrasound activation on increasing the porosity and surface area of biochar along with enhanced chelation imparted by amine functionalization. The developed technique can be used for synthesizing advanced adsorbents for removal of nuclear waste-related metal ions from aqueous environments.

Bioformulation of biochar as a potential inoculant carrier for sustainable agriculture

The dependence on chemical fertilizers and pesticides to increase agricultural outputs owing to the demands of a growing human population creates the need for a sustainable fertilizer. Biochar is presently a promising candidate as an inoculant carrier, given its highly porous structure, with nutrients naturally derived from the biomass, high water, and nutrient retention properties, which favor microbial growth. Biochar can be produced through pyrolysis, hydrothermal carbonization, gasification, and torrefaction. The porosity and adsorption ability of biochar allows it to be effectively used as a carrier to immobilize plant growth-promoting rhizobacteria (PGPR) for enhanced crop growth. Furthermore, the physicochemical properties of biochar like surface area, pore properties, and surface functional groups can be further modified via several activation methods, such as chemical oxidation and reduction, and physical activation to optimize the PGPR immobilization. The understanding of the agronomic impacts of biochar and the possible scaling up of cell immobilization will provide insights on the mechanism of biochar as an efficient inoculant carrier. This will contribute to fewer environmental hazards with the utilization of biochar for promoting plant growth. The complex interplay of physicochemical properties of biochar as a carrier to immobilize PGPR and the potential mechanisms of biochar-based inoculants are significant to achieve agricultural sustainability.

Oxidised Biochar from Palm Kernel Shell for Eco-friendly Pollution Management

Oil palm plantations produce palm kernel shell (PKS) that can be converted into biochar for environment-friendly soil remediation and water treatment. Oxidation with hydrogen peroxide (H2O2) may enhance surface characteristics and the quality of low-rank PKS biochar as a sorbent for environmental decontamination. This study aims to determine the effect of oxidation on the surface characteristics (i.e., specific surface area, surface charge, and chemical properties) of PKS biochar, and compared with that of PKS activated carbon. The surface area for the oxidised PKS biochar was similar to that of PKS biochar, indicating that oxidation did not remove the pore blocking material from the surface area of the PKS biochar. However, oxidation has increased the amount of negatively charged oxygen functional groups in PKS biochar, as indicated by the analyses of the Fourier transform infrared spectroscopy (FTIR) and cation exchange capacity (CEC). The CEC value of raw and activated PKS biochar were similar and 4.6 and 2.6 times lower for PKS biochar and oxidised PKS biochar, respectively. Oxidation caused enlargement of pores on PKS biochar and caused a reduction of specific surface area. More research is required to establish the process conditions to create a greater surface area and sorption capacity.

Investigation the isotherm and kinetics of adsorption mechanism of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on corn cob biochar

The aim of this work was to study the isotherm and kinetics of adsorption mechanism of the herbicide 2,4-D on corn cob biochar in aqueous solution. Corn cob biochar was synthesized at 600 °C for 4 h, then, it was washed by HF acid modification. The characteristics of the biochar were considered including the point of zero charge, surface morphology, surface area, and functional groups. The specific surface area of biochar was 298.01 m2.g−1. Solution pH at 2.0 had the greatest removal efficiency for 2,4-D. The experimental adsorption data fitted with the Pseudo-second-order and Langmuir isotherm models. The chemical adsorption and pore-filling are the main interactions of 2,4-D and corn cob biochar. However, H-bonding is the most important interaction of chemical adsorption. Corn cob biochar is a very useful material for 2,4-D removal and pesticide pollutants, they can be further applied in the wastewater treatment plants as well as the water supply units.

A new insight into chemical reactions between biomass and alkaline additives during pyrolysis process

Understanding the chemical reactions during biomass and alkaline additives during pyrolysis process is critical to better utilization of biomass resource. In this study, the influence of seven alkaline additives (KOH, K2CO3, KHCO3, CH3COOK, NaOH, Ca(OH)2, and Mg(OH)2) on biomass pyrolysis was investigated in fixed-bed system, as well as the reaction mechanism through combining the evolution properties of biochar, bio-oil, gas products, and alkaline additives. Results showed that alkaline additives promoted the formation of biochar and gas products, while inhibited the generation of bio-oil. The content of phenols (reaching 80% for NaOH, mainly non‑methoxy phenols) and hydrocarbons (reaching 38% for Ca(OH)2, mainly aromatics) increased greatly at the cost of acetic acid and O-species. Carbon content of biochar decreased largely, while oxygen content increased greatly, and the main O-containing species were –OH, -O–CO and -COOH groups. The surface area of biochar also increased greatly (reaching 764 m2/g for KOH). During pyrolysis process, alkaline additives could react with high active O-containing species and carbon fragments to generate lots of vacancies, then some anions of alkaline additive quickly occupied these vacancies to form new O-containing groups in biochar. Alkaline additives also converted into more stable structure (K2CO3, Na2CO3, CaO, and MgO). The possible reaction pathway between biomass and alkaline additives was first proposed.

Characterization and Artificial Neural Networks Modelling of methylene blue adsorption of biochar derived from agricultural residues: Effect of biomass type, pyrolysis temperature, particle size

Biochar has been explored as a sorbent for contaminants, soil amendment and climate change mitigation tool through carbon sequestration. Through the optimization of the pyrolysis process, biochar can be designed with qualities to suit the intended uses. Biochar samples were prepared from four particle sizes (100–2000 µm) of three different feedstocks (oak acorn shells, jift and deseeded carob pods) at different pyrolysis temperatures (300–600 °C). The effect of these combinations on the properties of the produced biochar was studied. Biochar yield decreased with increasing pyrolysis temperature for all particle sizes of the three feedstocks. Ash content, fixed carbon, thermal stability, pH, electrical conductivity (EC), specific surface area (SSA) of biochar increased with increasing pyrolysis temperature. Volatile matter and pH value at the point of zero charge (pHpzc) of biochar decreased with increasing pyrolysis temperature. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the surface of the biochar was rich with hydroxyl, phenolic, carbonyl and aliphatic groups. Methylene blue (MB) adsorption capacity was used as an indicator of the quality of the biochar. Artificial neural networks (ANN) model was developed to predict the quality of the biochar based on operational conditions of biochar production (parent biomass type, particle size, pyrolysis temperature). The model successfully predicted the MB adsorption capacity of the biochar. The model is a very useful tool to predict the performance of biochar for water treatment purposes or assessing the general quality of a design biochar for specific application.

Resource utilization conditions as biochar of an invasive plant Spartina alterniflora in coastal wetlands of China

AbstractConverting feedstocks of invasive plants into biochar is a new and cost‐effective measure for their control, and benefits for the sustainable development of native ecosystems. Spartina alterniflora, an invasive plant widely distributed in coastal wetlands of China, was used to produce biochar. We aimed to analyze how S. alterniflora biochar properties changed with desalination of feedstocks, pyrolysis temperature, and residence time. Results showed that desalting feedstocks increased biochar pH, stability, porosity, and surface area, but diminished biochar yield and polarity. Pyrolysis temperature positively affected biochar pH, surface area, and pore volume, while it had negative effects on biochar yield, oxygen and hydrogen contents, hydrogen/carbon and oxygen/carbon ratios, pore size, and function groups. However, residence time of pyrolysis had slight effects on biochar properties. The results are valuable for optimizing pyrolysis temperature and pretreatment measure of feedstocks, to tune S. alterniflora biochar properties for specific environmental usage.

Coupling adsorption and degradation in p-nitrophenol removal by biochars

Biochar is an attractive class of materials because of its various feedstock and wide application potential in agricultural and environmental remediation activities. Recent studies have suggested that biochar may both adsorb and degrade organic contaminants; however, the properties of biochar that control its apparent interactions with organic contaminants are still unknown. In this study, p-nitrophenol was chosen as a model organic pollutant. Its adsorption and degradation by biochar were investigated with a special focus on correlations with the biochar properties. The apparent removal of p-nitrophenol by biochars increased with the increase of pyrolysis temperature. After acetonitrile extraction of the biochars, p-nitrophenol adsorption increased while degradation decreased. Thus, there was no significant change in the apparent removal of p-nitrophenol across eight reaction cycles. An analysis of the physicochemical properties of biochar showed that p-nitrophenol adsorption was determined by the biochar surface area, while the degradation may be because of the varying compositions of biochars, including free radicals, functional groups determining its redox activities, and transition metals. The relative importance of these compositions varied with the pyrolysis temperature. More extensive study is warranted on the relationship between biochar properties and reactivity for targeted biochar production and application. The results of this study provide fundamental information on biochar preparation and its application in organic pollutant removal.

Adsorption of potentially toxic elements in water by modified biochar: A review

Biochar, as a adsorbent, can remove potentially toxic elements (PTE) in water by physical adsorption, as well as chemical interactions such as ion exchange, electrostatic attraction, surface and inner sphere complexation, precipitation, and redox. However, unsatisfactory adsorption effects and difficult recovery of adsorbents limit the application of biochar as PTE adsorbent in water. Therefore, several methods of modifying biochar have been used to improve the removal efficiency of PTE (mainly includes heavy metals and metalloids), such as physical activation with steam, chemical modification with acids, bases, metals, metal oxides, organic compounds and carbon base materials. This review explains how these methods above change the adsorption mechanism, and which method is more suitable for adsorbing a certain target pollutant than others. Physical activation contributes to an increase in specific surface area of biochar, while chemical treatments enhance the proportion of oxygen-containing functional groups and introduce new particles as adsorption sites. We focus on the removal of Pb(II), Cd(II), Cu(II), Cr(VI), Cr(VI), and As(V), evaluate the effectiveness of different modification methods in removing these heavy metals and metalloids in water. The research direction of modified biochar is prospected.

Influence of Aged Biochar Modified by Cd2+ on Soil Properties and Microbial Community

Biochar is a promising addition for cadmium-contaminated soil in-situ remediation, but its surface properties change after aging, cadmium adsorption is not well-documented, and subsequent environmental effects are still unknown. In this study, wood-derived (Eucalyptus saligna Sm.) biochar was pre-treated to simulate aging and the cadmium sorption process. We then analyzed the resulting physicochemical characteristics. We conducted comparative incubation studies on three age stages of biochar under cadmium adsorption or no cadmium adsorption and then measured soil properties and microbial communities after incubation. Biochar addition raised soil organic carbon (SOC), and aging significantly increased C/N ratios. Aged biochar promoted higher microbial abundance. Aged biochar treatments possessed different microflora with more gram-positive bacteria, significantly altering gram-positive/gram-negative bacteria ratios. Aging significantly increased the oxygen-containing functional groups (OCFGs) and surface area (SA) of biochar. Thus, aged biochar adsorbed more cadmium. Cadmium-binding biochar increased the proportion of gram-negative bacteria and decreased the proportions of gram-positive bacteria and fungi. Similar patterns in phospholipid fatty acids (PLFAs) across adsorption treatments indicated that changes in microbial communities due to the effects of cadmium were confined. The results reveal that biochar aging altered microbial community structure and function more than cadmium binding.

Properties Analysis and Preparation of Biochar–Graphene Composites Under a One-Step Dip Coating Method in Water Treatment

In order to improve the adsorption efficiency of biochar in water treatment, biochar–graphene (BG) composites were prepared by the one-step dip coating method and applied to remove phthalates from water. Firstly, the materials and equipment needed for the experiment are introduced. The steps of preparing graphene oxide (GO) by the improved Hummers method and BG composites by one-step dip coating are discussed. Then, the morphology characterization, adsorption performance measurement, and isothermal model of BG composites are introduced. Finally, the structure characterization, adsorption kinetics, and adsorption isotherms of BG composites are analyzed. The results show that the properties of biochar could be changed by one-step dip coating, and the biochar could form composites with graphene. Compared with biochar, biochar–graphene composites have greater surface area and porosity. When the pyrolysis temperature was 600 °C, the specific surface area of biochar was 8.4 m2g−1, and the specific surface area of the biochar–graphene composite was 221.3 m2g−1. When the temperature was 300 °C, the specific surface area of biochar was 11.01 m2g−1, and the specific surface area of biochar–graphene composite was 251.82 m2g−1. The formation of graphene on the surface of biochar can increase the stability of the composite and acts as a very high potential active site. The porous structure and surface properties of biochar–graphene composites regulate the adsorption rate of pollutant molecules, thereby improving the adsorption performance. When the adsorption equilibrium was reached, the adsorption effect of phthalate esters on the biochar/graphene composite at the pyrolysis temperature of 600 °C was the best, and the adsorption capacity of Dimethyl phthalate (DMP)was 35.2 mg/g, that of Diethyl phthalate (DEP) was 26.4 mg/g, and that of Dibutyl phthalate (DBP) was 25.1 mg/g. The adsorption effect of DMP was the best. The results of the isotherm study indicate that the adsorption of phthalates by BG composites has great potential, which provides a good theoretical basis for the application of BG composites in environmental protection in China.

Process Intensification: Activated Carbon Production from Biochar Produced by Gasification

The recent increase in the number of policies to protect the environment has led to a rise in the worldwide demand for activated carbon, which is the most extensively utilised adsorbent in numerous industries and has a high probability to be used in the energy and agriculture sectors as electrodes in supercapacitors and for fertiliser production. This paper is about the production of activated biochar from oak woodchips char generated by an updraft fixed bed gasifier reactor. Following this, using steam as activating agent and thermal energy from produced synthesis gas (syngas), the resulting highly microporous carbonaceous biomaterial was subjected to physical activation at 750ºC. The properties of activated biochar include adsorption or desorption of nitrogen to identify the physical adsorption and surface area measurement, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The biochar surface area, generated as a result of the gasification process, showed substantial improvement after steam activation. Also, significant discrepancies were obtained from the surface volume and areas of biochar byproducts from the gasifier and activated biochar obtained by steam activation after the gasification treatment (total pore volume 0.022 cm3g−1and 0.231 cm3g−1, Brunauer–Emmett–Teller (BET) surface area 21.35 m2g−1and 458.28 m2g−1, respectively). The two samples also yielded noteworthy differences in performance. As a consequence, it may be concluded that the kinetics of steam gasification is quicker and more efficient for the conversion of biochar to activated carbon. The pore sizes of the carbon produced by steam activation were distributed over a wide spectrum of values, and both micro- and mesoporous structures were developed.

Mechanism of catalytic tar reforming over biochar: Description of volatile-H2O-char interaction

The two-stage fluidized bed/fixed bed reaction system was used to study the evolution characteristics of catalytic tar reforming process over biochar. The effect of different interaction time (feeding time varies within 10–50 min) between volatiles and char on the characteristics of char/tar is considered. InVia-Reflex Raman spectrometer (Raman), Fourier transform infrared spectrometer (FTIR), automatic specific surface and porosity analyzer, X-ray photoelectron spectrometer (XPS), inductively coupled plasma optical emission spectrometer (ICP-OES) were used to characterize the structural characteristics and alkali metal and alkaline earth metal species (AAEMs) content of biochar. The tar components were analyzed by gas chromatography-mass spectrometry (GC–MS) and the gas components were monitored by MCA 100 SYN synthetic gas analyzer. The results indicate that the tar removal efficiency of gasification char is over 70% when the interaction time is within 30 min. When corn straw is fed for 40 min, the carbon deposition on the surface of biochar reaches saturation. The size of coke particles is mainly in the range of 2–5 nm, and the structure is mainly small aromatic ring within five rings. During catalytic tar reforming over biochar, the content number of O-containing functional groups and surface K element decrease rapidly. The main removal path of toluene, styrene, phenol and indene in tar is heterogeneous reforming on biochar surface. Carbon deposition results in the increase of biochar external surface area (73.8 m2/g to 158.1 m2/g). The homogeneous reforming of styrene and toluene on biochar surface is enhanced. Under the catalysis of biochar surface, the self-gasification of biochar, water–gas shift reaction and methane steam reforming reaction are all promoted. This results in the increase of CO, CO2 and H2 yield (9.68%, 52.38% and 69.63%), as well as the decrease of CH4 yield (25.23%) in the syngas of corn straw gasification.

Preparation of TiO2-modified Biochar and its Characteristics of Photo-catalysis Degradation for Enrofloxacin

In order to solve the problem that the traditional biochar(BC) has insufficient removal ability of enrofloxacin and TiO2 is difficult to recycle. In this study, TiO2-modified biochar composites were prepared by impregnation method. Through characterization analysis, The BET specific surface area results indicated that after loading TiO2, the specific surface area of TiO2-biochar(Ti-BC), TiO2-ironized biochar(Ti-FBC) and TiO2-alkaline biochar(Ti-KBC) increased by 4.34, 10.43 and 11.52 times, respectively. The analysis results of SEM, EDS, FT-IR, XRD and XPS showed that TiO2 was supported on biochar in the anatase state. The UV-vis DRS measurement showed that the band width of Ti-KBC was the smallest and the best catalytic activity. Under 15 W UV lamp (254 nm) irradiation, the photocatalytic degradation process of enrofloxacin by different biochar accords with the first-order kinetic equation. Ti-KBC showed best degradation effect under different initial concentrations of enrofloxacin. When the pH of the solution was 5.0 and the dosage of Ti-KBC was at 2.5 g·L−1, the enrofloxacin degradation rate of 100 mg·L−1 reached 85.25%. The quenching test confirmed that the active substance O2•— played a major role in the photocatalytic degradation process. After five cycles of the test, the degradation rate of Ti-KBC for enrofloxacin was 77.14%, which was still better than that of BC, Ti-BC and Ti-FBC.

Adsorption of Perfluorooctane sulfonate (PFOS) onto metal oxides modified biochar

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant (POP), which poses potential toxicity to biotic and abiotic ecosystem. Adsorption of PFOS from soil and water has emerged as promising remediation practice due to low cost, high removal performance, low environmental impact, and recalcitrant to induce secondary contamination. In this study, red mud modified sawdust (RMSDN600) and unmodified sawdust (SDN600) were prepared for sorption of PFOS from aqueous solution. The presence of magnetites (Fe 3 O 4 ), ferrihydrites, and desilicated minerals are identified in the RMSDN600 using XRD (X-ray diffraction) and XANES (X-ray absorption near-edge structure). Sorption isotherm for RMSD600 and SDN600 showed close-fitting with Langmuir and Freundlich model demonstrated monolayer and multilayer sorption of PFOS over the active sites of the adsorbents. The potential formation of micelles and hemi-micelles can occur in interparticle porous biochars as the concentration of PFOS exceeds critical hemi-micelle concentration (4.57–45.7 mg/L). The kinetic study followed Pseudo-second-order model for both adsorbents, demonstrated both physisorption and chemisorption of PFOS. The results revealed the adsorption of PFOS was governed by both hydrophobic and electrostatic interaction, with hydrophobic interaction as the dominant sorption mechanism. The higher adsorption capacity for RMSDN600 (194.6 mg/g) was recorded than that for SDN600 (178.6 mg/g) at pH 3.1 due to the abundance of protonated metal-based functional groups, and more ordered graphitic carbon structure resulting from catalytic degradation and transformation of cellulose and hemicellulose. Aromatic structure can potentially enhance PFOS sorption by non-ionic interaction. In contrast, metal-based and other oxygen-containing functional groups of adsorbents enhance adsorption capacity through electrostatic interaction and ion exchange reactions. Lower solution pH and smaller particle size of the adsorbents could also enhance sorption of PFOS from aqueous phase. • Carbon content, surface area, and porosity of biochar reduced after modification with metal oxides. • Iron minerals in red mud transformed to magnetites, and ferrihydrites in RMSDN600. • Highly pyrolyzed (600 °C) hydrophobic biosorbents favor PFOS adsorption. • Metal oxide modified biochar has more ordered aromatic structure than the raw biochar. • The adsorption capacity was 178.1 and 194.6 mg/g for SDN600 and RMSDN600.

A high-performance biochar produced from bamboo pyrolysis with in-situ nitrogen doping and activation for adsorption of phenol and methylene blue

Nitrogen doping is a promising method for the preparation of functional carbon materials. In this study, a nitrogen-doped porous coral biochar was prepared by using bamboo as raw material, urea as nitrogen source, and KHCO 3 as green activator through in-situ pyrolysis. The structure of the obtained biochar was characterized by various techniques including nitrogen adsorption and desorption, Raman spectroscopy, X-ray photoelectron spectrometer, and etc. The adsorption properties of nitrogen-doped biochar were evaluated with phenol and methylene blue probes. The results showed that the nitrogen source ratio had a significant effect on the evolution of pore structure of biochar. Low urea addition ratio was beneficial to the development of pore structures. The optimum specific surface area of nitrogen-doped biochar could be up to 1693 m 2 ·g −1 . Nitrogen doping can effectively improve the adsorption capacity of biochar to phenol and methylene blue. Biochar prepared at 973.15 K with low urea addition ratio exhibited the highest adsorption capacity for phenol and methylene blue, and the equilibrium adsorption capacity was 169.0 mg·g −1 and 499.3 mg·g −1 , respectively. By comparing the adsorption capacity of various adsorbents in related fields, it is proved that the nitrogen-doped biochar prepared in this study has a good adsorption effect.

Widespread tropical agrowastes as novel feedstocks for biochar production: characterization and priority environmental uses

Biochar, a carbon-rich pyrolytic product, has demonstrated positive results as a soil improver and carbon sequestration agent. Its production could be an appropriate and innovative practice for agricultural waste management in the context of environmentally smart agriculture. However, considering the relevant effect of the production conditions on the final biochar properties, its characterization is a necessary step, moreover, if an unknown feedstock is being used. Coffee hulls (CH), pineapple stubble (PS), and palm oil fiber (PF) are typical tropical agro-industrial wastes, and biochar from the first two are not reported before. In this work, biochars from them were obtained after 1 h of pyrolysis at 600 °C. Surface area and pH of biochars were close to 60 m2g−1 and 9, respectively (except for PF which was 29 m2g−1), while torrefied biomass (charred material prepared at 300 °C) presented a surface area close to 1 m2g−1 and neutral pH. Fixed C was approximately 80% (PF and CH) and 59% (PS) for biochars and close to 40% in torrefied biomass. It was concluded that key properties of biochars were mostly determined by the feedstock’s origin. Due to its high ash content and surface area, PS biochar was identified as a suitable soil amendment, while PF and CH biochars showed a higher potential for carbon sequestration in soil due to their high fixed carbon content, demonstrating that the production of biochars from widespread tropical wastes tailored for specific environmental uses is possible.

Hyper sorption capacity of raw and oxidized biochars from various feedstocks for U(VI)

• Increased surface area and sorption capacity of biochars pyrolysed above 700 °C. • U(VI) to U(IV) reduction by non-oxidized biochars. • Oxidation of biochars eliminates reductive surface moieties. • Sorption of U(VI) on oxidized biochars by surface carboxylic moieties. The removal of uranium from aqueous solutions by biochars produced from different feedstocks at increased temperatures (850 °C), such as malt spent rootlets, coffee espresso residue, and olive kernels has been investigated by means of batch-type experiments. The sorption experiments were performed prior and after oxidation of the biochars to compare their removal capacities and the materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy and X-ray diffraction (XRD) measurements to identify surface species and solid phases, respectively. In addition, surface oxidation increases further the sorption capacity due to the formation of carboxylic moieties presenting increased affinity for the U(VI) cations. However, due to oxidation the reducing moieties on the biochar surface are eliminated and the reduction of U(VI) to U(IV), which precipitates, decreases resulting in an apparent decreased sorption capacity.

High-yield and high-performance porous biochar produced from pyrolysis of peanut shell with low-dose ammonium polyphosphate for chloramphenicol adsorption

Adsorptive removal by porous carbon materials has been considered an attractive technique to treat wastewater polluted by antibiotics. To produce porous biochar with high-yield and high-performance for chloramphenicol adsorption, this study prepared biochar from peanut shells using ammonium polyphosphate via pyrolysis. The combined effects of the main process parameters on biochar production were studied to determine the optimum operating conditions by response surface methodology based on Box-Behnken design. Low-dose ammonium polyphosphate has a significant positive effect on the yield, surface functional groups, pore volume, and surface area of biochar. This is caused by the richness of nitrogen and phosphorus in ammonium polyphosphate and its flame retardant property. The high-yield biochar with a surface area of 979 ± 25 m2/g was obtained at a mass ratio of ammonium polyphosphate/peanut shell of 0.55, at 650 °C with a retention time of 60 min. The as-prepared biochar exhibited excellent adsorption performance with a monolayer chloramphenicol adsorption capacity of 423.7 mg/g. This was due to the high surface area, micropores formed by nano-sized particles, and richness of N- and P-containing functional groups. The characterization before and after chloramphenicol adsorption indicated micro-pore-filling, Van der Waals force, π-π interaction, and hydrogen-bonding interaction are the main adsorption mechanisms of chloramphenicol adsorption on as-prepared biochar. This study offered new insights on the preparation of biochar from waste biomass for application in wastewater treatment.