A direct carbon solid oxide fuel cell fueled with char from wheat straw

Direct carbon solid oxide fuel cell (DC‐SOFC) is a promising technology for electricity generation from biomass with high conversion efficiency and low pollution. Biochar derived from wheat straw is utilized as the fuel of a DC‐SOFC, with cermet of silver and gadolinium‐doped ceria as the material of both cathode and anode and yttrium stabilized zirconia as electrolyte. The output performance of a DC‐SOFC operated on pure wheat straw is 197 mW cm^?2 at 800°C and increases to 258 mW cm^?2 when 5% of Ca, as a catalyst of the Boudouard reaction, is loaded on the wheat straw char. Higher power and fuel conversion utilization are achieved by using Ca as the Boudouard reaction catalyst. X‐ray diffraction, scanning electron microscopy, energy‐dispersive spectrometer, and programmed‐temperature gravimetric experiment are applied to characterize the leaf char. It turns out that the wheat straw char is with porous structure and composed of C, K, Mg, Cl, Fe, and Ca elements. The effects of the Ca catalyst on the Boudouard reaction, the performance of the DC‐SOFCs operated on the wheat straw char, and the economic advantages of the wheat straw char are demonstrated and analyzed in detail.     

Air-breathing bio-cathodes based on electro-active biochar from pyrolysis of Giant Cane stalks

An innovative low-tech solution to fabricate electro-active biochar (e-biochar) electrodes for bio-electrochemical systems (BES) is proposed. Ligno-cellulosic stalks of Giant Cane (Arundo Donax L.) were subjected to pyrolysis treatment at 900 °C for 1 h. The material kept its original hollow cylindrical shape, rigid morphology and porous texture, as confirmed by 3DX-ray micro-computed tomography. These characteristics are suitable for its use at the air-water interface in BES, as air-breathing bio-cathodes. BET (Brunauer-Emmett-Teller) specific surface area was equal to 114 ± 4 m² g⁻¹, with more than 95% of pores in the microporosity range (pore diameter < 1 nm). Surface electrocatalytic activity was sufficient to sustain oxygen reduction reaction at pH 7, in terms of both onset potential (−0.02 V vs Ag/AgCl) and reduction limiting current density (1 A m⁻²). Electrical resistivity measurements confirmed sufficient conductivity (8.9 × 10⁻³ ± 1 × 10⁻⁴ Ω m) of the material and Raman spectroscopy allowed to estimate a graphitization degree in relation to the I_D/I_G, equal to 2.26. In parallel, the e-biochar were tested as air-exposed bio-cathodes in BES, coupled to carbon cloth bio-anodes. After inoculation with wastewater from swine-farming, current densities were generated in the range of 100–150 mA m⁻², along more than 2 months of operation, under sodium acetate feeding. Confocal laser scanning imaging revealed consistent biofilm formation on the water-side surface of the cathodes, while a nearly-complete absence of it at the air-side.These e-biochar electrodes might open innovative perspectives to scale-up BES for different applications. Here, consistent salts depositions on the material after 70 days of exposure to the wastewater, suggest that e-biochar biocathodes might serve to recycle nutrients to agricultural soils, through minerals-enriched biochar.     

Production and characterization of carbon-based adsorbents from waste lignocellulosic biomass: their effectiveness in heavy metal removal

Abstract

In this study, hazelnut shell and walnut shell which are the agricultural wastes existent abundantly in many countries were pyrolyzed at different temperatures in the temperature range of 400–700?°C in order to optimize the physicochemical properties of biochars. The biochars with large surface area were used to removal of lead (Pb²⁺) ions, one of the most important heavy metal pollutant, from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, BET, SEM, partial and elemental analysis techniques. In order to determine the adsorption characteristics of both biochars, batch adsorption experiments were carried out under different experimental conditions. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of Pb²⁺ ions from aqueous solution. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion model, and the model constants were investigated.     

The production of hydrogen gas from modified water hyacinth (Eichhornia Crassipes) biomass through pyrolysis process

In this study, the generation of hydrogen from synthesis gas through the pyrolysis of modified Water Hyacinth (Eichhornia Crassipes) biomass was investigated. The modified Water Hyacinth feedstocks were prepared by immersing its dried samples into Iron Chlorides (III) solution under different concentrations (0.5, 1, 1.5, and 2 M). After a 60 min pyrolysis at 540 °C, each created biochar sample also generates a different volume of synthesis gas depending on the properties of the feedstock that were applied to the system. In that manner, it is clear that the value of ferric chloride concentration plays an important role in the generating of synthesis gas. The study indicates that the increase of ferric chloride concentration may also raise the production of synthesis gas, and the amount of hydrogen as well. The result indicates that the 2WH sample (with 2 M of ferric chloride catalyst) exhibited the highest conversion for Water Hyacinth pyrolysis volatiles, with 280 mL of total gas production (42% of hydrogen included, 23% of carbon dioxide, 22% of carbon monoxide and 7% of methane). Therefore, the main objective of the work is achieved by revealing the influence of the metal catalyst over the production of gases via the pyrolysis. On the other hand, the fact that the Water Hyacinth can be utilized effectively also contributes greatly to the matter of environmental betterment.     

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Biomasses are very important natural products. Transferring biomass into catalysts for the advanced oxidation process (AOP) via heat treatment has attracted extensive attention. This review systematically introduces and summarizes two kinds of innovative biomass-based catalysts according to the treating temperature. At low temperature ( < 300  ° C), biomasses are converted into hydrothermal carbonation carbon (HTCC) with semiconductive properties for photocatalysis application. At high temperature ( > 300  ° C), by contrast, the products lose their semiconductive nature and become a conductive carbon-based conductor (biochar). They usually work as AOP catalysts by activating oxidant of O₂, H₂O₂, and peroxysulfate for environmental treatment. This review summarizes and compares HTCC and biochar according to their formation process, structure, catalytic mechanism, and key points for the activity enhancement. The active units in HTCC are the sp²-hybridized polyfuran unit while those in biochar are the persistent free radicals, nitrogen-containing unit, or defects. HTCC converts water into OH radicals by using the photoexcited electron/hole pairs induced by solar illumination, while biochar activates oxidants via the active unit on its surface. More importantly, this review summarizes and demonstrates the key points to obtain high-efficiency HTCC and biochar catalysts. Finally, conclusions are drawn and the future aspects for biomass-based catalysis are given.     

老化生物炭表面性质的变化及其对土壤吸附Cu(II)的影响

为研究生物炭进入土壤环境后表面性质的变化及其对土壤吸附Cu(Ⅱ)的影响，在土壤环境中对两种不同温度制备稻壳生物炭模拟老化培养，运用元素分析、扫描电镜漫反射红外光谱、X射线光电子能谱等手段比较老化前后生物炭表面性质的变化，并将生物炭以3%、5%的比例添加到土壤中老化，通过等温吸附试验研究老化生物炭对土壤吸附重金属铜离子的影响。结果表明：在土壤中经过240 d老化后，两种不同温度制备稻壳生物炭所含C元素含量减少，O元素增加，羧基、羰基、脂肪族羟基等含氧官能团增多，生物炭极性增强。老化后的稻壳生物炭对铜离子的最大吸附量增加，生物炭的添加及其老化作用促进土壤对Cu(Ⅱ)的吸附固定作用，并且具有一定的长期稳定性。     

A combined effect of adsorption and reduction potential of biochar derived from Mentha plant waste on removal of methylene blue dye from aqueous solution

ABSTRACT

Plant biochars were prepared by slow pyrolysis of Mentha plant waste to remove cationic dye methylene blue (MB) from aqueous solution. The biochars were characterized by X-Ray diffraction, IR-spectroscopy, thermogravimetric analysis, scanning electron microscope, cyclic voltammetry (CV), Brunauer-Emmett-Teller analysis, and zeta potential analyzer. Adsorption isotherms and kinetics applied on the MB dye removal by biochars showed monolayer chemisorption of MB dye. Present investigation revealed that removal of MB dye was due to synergistic action of chemisorption coupled with reductive electron transfer mechanisms. CV test showed a reversible, coupled redox reaction at interface of MB dye and biochar particles.     

Biochar as a filler in mixed matrix materials: Synthesis,characterization, and applications

The use of mixed-matrix materials (MMM) has become a major topic of research in recent years, due to unique properties achieved in these composites. In this work, biochar from sunflower seed hull pyrolysis and biochar/polysulfone (PSF) MMMs were produced and characterized. The optimal pyrolysis temperature for biochar production was determined to be 500 °C. The resulting biochar properties were an iodine number of 203 mg/g and a pore volume of 0.595 mL/g. In MMM fabrication, the use 4% ethanol as nonsolvent in the wet phase inversion process increased the glass transition temperature by 8 °C, indicating improved biochar/PSF interaction. The presence of biochar was shown to create pores in otherwise dense surfaces. The critical surface energy was also increased by the addition of biochar from 28.6 mN/m in pristine PSF to 35.7 mN/m in biochar/PSF MMMs. We identified and discussed several potential applications based on the determined properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48027.     

生物炭及其复合材料吸附重金属离子的研究进展

生物炭作为废弃生物质在缺氧条件下热解得到的固态产物,由于其表面具有丰富的官能团及较强的吸附性能等优点而被广泛应用到重金属废水处理。近年来,众多学者将生物炭与其他材料通过物理、化学方法结合,制备出对重金属离子具有优良吸附性能的生物炭复合材料。首先介绍了生物炭及其复合材料的制备方法和基本特性,其次考察了生物炭及其复合材料对重金属离子的吸附效果及影响因素,最后阐述了生物炭及其复合材料吸附重金属离子的机制,并对生物炭及其复合材料处理重金属离子的发展方向进行了展望。     

温度和CO2对热解成型生物质炭孔隙结构和表面分形维数的影响

通过SEM分析和氮气等温吸附实验,对不同热解温度和CO_2浓度下热解成型炭样进行孔隙结构特性分析,同时根据FHH方程计算了炭样的孔隙表面分形维数D_S,研究了孔隙结构与表面分形维数的关系以及温度和CO_2浓度对两者关系的影响。结果表明:表面分形维数可以较好地表征孔隙结构的复杂性和炭样表面不规则性,但是与BET比表面积(S_(BET))、总孔积和平均孔径没有直接联系,而是与微孔面积和微孔容积含量占比较为一致。在氮气热解情况下,600℃时炭样孔隙结构最为发达,S_(BET)和D_S都达到最大值。在CO_2和N_2混合气氛下,S_(BET)随着CO_2浓度的增加而变大,而D_S则是先减小后变大,当CO_2浓度大于10%后才会随着CO_2浓度的增加而变大。