Electrical conductivity of wood biochar monoliths and its dependence on pyrolysis temperature

Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.

Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils

The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.

Effects of temperature on pyrolysis products of oil sludge

Temperature is the determining factor of pyro-lysis,which is one of the alternative technologies for oil sludge treatment.The effects of final operating temper-ature ranging from 350 to 550uC on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor.With an increase of temperature,the mass fraction of solid residues,liquids,and gases in the final product is 67.00%–56.00%,25.60%–32.35%,and 7.40%–11.65%,and their corresponding heat values are 34.4–13.8 MJ/kg,44.41–46.6 MJ/kg,and 23.94–48.23 MJ/Nm 3,respectively.The mass and energy tend to shift from solid to liquid and gas phase(especially to liquid phase)during the process,and the optimum temperature for oil sludge pyrolysis is 500uC.The liquid phase is mainly com-posed of alkane and alkene(C_(5)–C_(29)),and the gas phase is dominantly HC S and H 2.

Preparation of Kenaf Biochar and Its Adsorption Properties for Methylene Blue

The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biochar sam-ples were synthesized form kenaf to adsorb methylene blue(MB),which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aroma tic heterocyclic ring.By tuning the raw materials and pyrolysis temperature,a super adsorption capacity about 164.21 mg·g^(-1) was obtained over the biochar that pyrolyzed at 700℃ with the kenaf fiber as raw material Through the physical adsorption,elemental analysis,FTIR spectra and NH_(3)-TPD,it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB,and the acidic sites would also assist the adsorption process.Besides,the adsorption kinetic model was ftted and calculated,implying the MB physically adsorbed on the bio-char rapidly and then occurred chemical adsorption on the acidic sites.In addition,through KBC700 recycling experiments,it was found that kenaf biochar had a good binding force to MB,which effectively avoided secondary pollution.This work provides important insights for the adsorption mechanism of MB by biochar,also offers some guidance for the further synthesis of biochar from various biomass.

Biochar as a Soil Ameliorant: How Biochar Properties Benefit Soil Fertility—A Review

In recent years, biochar has received great attention among researchers worldwide. This carbon-rich material, mainly produced from residues from agriculture and forestry, holds a wide range of properties, e.g. large specific surface area, high cation exchange capacity, and substantial nutrient contents, that can have beneficial effects when added to soils. This review is giving a brief introduction to biochar properties and how feedstock, pyrolysis temperature, and time influence these properties. As the majority of studies concentrate on the soil amending effects of biochar, this review also provides an overview of how biochar affects the chemical, physical, hydrological, and biological properties of soils. For example, biochar addition to soils can raise the pH, increase the organic carbon content, enhance nutrient retention, foster porosity, augment the water-holding capacity, and increase microbial biomass. Consequently, biochar can contribute to soil fertility, increase yields, help closing nutrient cycles, and thus help secure food safety in a region. However, the knowledge about the long-term effects is still limited and should be broadened by a more systematic testing of biochar effects in the future to help bring the benefits of biochar into practice.

Biochar pyrolyzed at low temperature enhanced acidophilous plant growth by promoting rhizospheric microbes in a slightly alkaline urban soil

Biochar has been considered as a potential way to enhance acidophilous plant growth in alkaline soils.However,whether such enhancements are closely linked with biochar pyrolysis temperature and its improvements in rhizospheric soil fertility and microbial activities remains largely unknown.We performed a pot experiment to investigate changes in azalea(Rhodo-dendron)morphology and physiology,as well as its rhizosphere soil chemical and biological properties in a slightly alkaline urban soil under the amendment of biochars that pyrolyzed at three temperatures(i.e.,350,550 and 700°C).Our results showed that the effects of biochars on plant growth and soil properties depended on pyrolysis temperature.In comparison with the non-amended control,350 and 550°C biochars showed significant promotions on the azalea growth in terms of photosynthetic characteristics,biomass,root morphology,and N and P uptake.Whereas,700°C biochar showed an inhibi-tion effect on them.350°C biochar decreased soil pH and increased soil available P and K contents and the activities ofα-glucosidase,N-β-glucosaminidase,phosphatase and sulfatase.In addition,350°C biochar significantly enhanced bacterial 16S rRNA and fungal 18S rRNA gene abundances in the rhizosphere soil of azalea and mycorrhizal infection.Correlation analysis indicated that soil pH,available nutrients and fungal abundance had positive associations with the enhanced plant growth parameters.Therefore,our findings suggest that biochar produced at low temperature could be a feasible strategy for enhancing acidophilous azalea growth and improving urban soil quality.

Use of Biochar as an Amendment for Remediation of Heavy Metal-Contaminated Soils:Prospects and Challenges

Biochar(BC), known as the new black gold, is a stable, novel carbonaceous by-product that is synthesized through pyrolysis of biological materials in the absence of O_2.Recently, an emerging interest in the application of BC as a robust soil amendment has given rise to a broad research area in science and technology.It is considered a promising remediation option for heavy metal(HM)-contaminated soils to reduce HM bioavailability to plants.Remediation efficacy of BC depends on the porosity, composition,pyrolysis temperature, feedstock, and residence time of pyrolysis.This review article aimed to present an overview of BC use in the immobilization of HMs, i.e., Cd, As, Pb, Zn, Ni, Cu, Mn, Cr, and Sb, in contaminated soils.The remaining uncertain factors, including the specific soil HM immobilization mechanisms, long-term beneficial effects, and potential environmental risks associated with BC application are analyzed.Future research must be conducted to ensure that the management of environmental pollution is in accord with ecological sustainability and adaptation of the black gold biotechnology on a commercial basis for immobilization of HMs in contaminated soils.

Sorption of ammonium and phosphate from aqueous solution by biochar derived from phytoremediation plants

The study on biochar derived from plant biomass for environmental applications is attracting more and more attention. Twelve sets of biochar were obtained by treating four phytoremediation plants, Salix rosthornii Seemen, Thalia dealbata, Vetiveria zizanioides, and Phragmites sp., sequentially through pyrolysis at 500 °C in a N2 environment, and under different temperatures(500, 600, and 700 °C) in a CO2 environment. The cation exchange capacity and specific surface area of biochar varied with both plant species and pyrolysis temperature. The magnesium(Mg) content of biochar derived from T. dealbata(TC) was obviously higher than that of the other plant biochars. This biochar also had the highest sorption capacity for phosphate and ammonium. In terms of biomass yields, adsorption capacity, and energy cost, T. dealbata biochar produced at 600 °C(TC600) is the most promising sorbent for removing contaminants(N and P) from aqueous solution. Therefore, T. dealbata appears to be the best candidate for phytoremediation application as its biomass can make a good biochar for environmental cleaning.

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

Nowadays,iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water.In this study,boron-doped biochar(B-BC)was successfully prepared at various preparation conditions with the addition of boric acid.The as-prepared material has a more developed pore structure and a larger specific surface area(up to 897.97 m2/g).A series of characterization results shows that boric acid effectively activates biochar,and boron atoms are successfully doped on biochar.Compared with the ratio of raw materials,the pyrolysis temperature has a greater influence on the amount of boron doping.Based on Langmuir model,the maximum adsorption capacity of 800 B-BC1:2 at25℃,40℃,55℃ are 50.02 mg/g,95.09 mg/g,132.78 mg/g,respectively.Pseudo-second-order kinetic model can better describe the adsorption process,the adsorption process is mainly chemical adsorption.Chemical complexation,ions exchange,and co-precipitation may be the main mechanisms for Fe2+removal.

Adsorption Kinetics of 2,2′,4,4′-Tetrabromodiphenyl Ether(BDE-47) on Maize Straw-Derived Biochars

The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.

Analytical study on pyrolyzed products of Desmodesmus sp.cultivated in BG11

Pyrolysis-Gas Chromatography-Mass Spectrometry(Py-GC/MS)was adopted to determine the changes in component of BG11-cultivated Desmodesmus sp.(BG11/8-10)pyrolyzed products at different temperatures(300℃-800℃).The results of analysis on a series of total ions chromatogram(TIC)showed that pyrolyzed products of BG11/8-10 at different temperature mainly included aliphatic hydrocarbons,nitrogen compounds,aromatic hydrocarbons,fatty acids,ketones,alcohols,aldehydes and furan compounds.Compared to the bio-oil(42.36%)generated by pyrolysis at 700℃,the relative content of bio-oil generated at 800℃was the highest up to 56.96%.However,higher temperature could easily cause the generation of large quantities of such pollutants as nitrogen compounds and polycyclic aromatic hydrocarbons(PAHs).Therefore,based on lower pollutant discharge and higher bio-oil yield,the optimal pyrolysis temperature of BG11/8-10 was around 700℃.

Enhanced microbial reduction of aqueous hexavalent chromium by Shewanella oneidensis MR-1 with biochar as electron shuttle

Biochar, carbonaceous material produced from biomass pyrolysis, has been demonstrated to have electron transfer property(associated with redox active groups and multi condensed aromatic moiety), and to be also involved in biogeochemical redox reactions. In this study, the enhanced removal of Cr(VI) by Shewanella oneidensis MR-1(MR-1) in the presence of biochars with different pyrolysis temperatures(300 to 800 ℃) was investigated to understand how biochar interacts with Cr(VI) reducing bacteria under anaerobic condition. The promotion effects of biochar(as high as 1.07~1.47 fold) were discovered in this process, of which the synergistic effect of BMBC700(ball milled biochar) and BMBC800 with MR-1 was noticeable, in contrast, the synergistic effect of BMBCs(300–600 ℃) with MR-1 was not recognized. The more enhanced removal effect was observed with the increase of BMBC dosage for BMBC700 + MR-1 group. The conductivity and conjugated O-containing functional groups of BMBC700 particles themselves has been proposed to become a dominant factor for the synergistic action with this strain. And, the smallest negative Zeta potential of BMBC700 and BMBC800 is thought to favor decreasing the distance from microbe than other BMBCs. The results are expected to provide some technical considerations and scientific insight for the optimization of bioreduction by useful microbes combining with biochar composites to be newly developed.

Preparation of high water-retaining biochar and its mechanism of alleviating drought stress in the soil and plant system

To explore the effect of biochar on alleviating plant drought stress after being applied to soil,we prepared biochar using rice straw as raw material according to different pyrolysis temperatures(400,600 and 800°C)and reaction atmosphere(CO_(2)and N_(2)).The effect of different pyrolysis conditions on the water retention performance of biochar was studied.The early high water-retaining biochar materials were selected and wheat seeds were selected for the verification experiment of returning to the field in pots.Biochar with high porosity(specific surface area and total pore volume)and more surface hydrophilic functional groups(mainly-OH and-COOH)can indeed improve soil water retention performance.It is mainly reflected in the increase in the dry weight and fresh weight of wheat and the soil moisture content in the treatment group with the addition of biochar water retention agent.Among them,the growth rates of fresh weight and dry weight of wheat in the C800 treatment group were 11.51%and 10.64%,and the soil moisture content increased by 1.89%.It is worth noting that the application of biochar cannot completely alleviate the impact of drought stress on plants,but it can reduce the amount of water irrigation to a certain extent.Considering the quality of biochar,the biochar material(C800)prepared under the pyrolysis temperature of 800°C and the reaction atmosphere of CO_(2)has high water retention performance.

Carbon potentials of different biochars derived from municipal solid waste in a saline soil

There are numerous studies conducted on biochar for its carbon (C) sequestration potential;however,there are limited studies available on the behavior of salt-affected soils related to biochar application.Therefore,more studies are needed to elucidate the mechanisms through which biochar affects saline soil properties.In this study,biochars were produced from solid waste at pyrolysis temperatures of 300,500,and 700?C (BC300,BC500,and BC700,respectively)and applied to a saline soil to evaluate their impacts on soil carbon dioxide (CO_(2)) efflux,C sequestration,and soil quality.A soil incubation experiment lasting for 107 d was conducted.The results showed that soil CO_(2) efflux rate,cumulative CO_(2) emission,active organic C (AOC),and organic matter (OM)significantly increased with BC300 application to a greater extent than those with BC500 and BC700 as compared to those in the no-biochar control (CK).However,soil C non-lability did not significantly increase in the treatments with biochars,except BC700,as compared to that in CK.Besides improving the soil quality by increasing the soil AOC and OM,BC300 showed positive impacts in terms of increasing CO_(2) emission from the saline soil,while BC500 and BC700 showed greater potentials of sequestering C in the saline soil by increasing the soil non-labile C fraction.The recalcitrance index (R50) values of BC500 and BC700 were>0.8,indicating their high stability in the saline soil.It could be concluded that biochars pyrolyzed at high temperatures (?500?C)could be suitable in terms of C sequestration,while biochars pyrolyzed at low temperatures (?300?C) could be suitable for improving saline soil quality.

Enhanced ferroelectric properties of highly(100)oriented Pb(Zr_(0.52)Ti_(0.48))O_(3) thick films prepared by chemical solution deposition

Ferroelectric Pb(Zr_(0.52)Ti_(0.48))O_(3)(PZT)thick films with highly(100)preferential orientation have been prepared by chemical solution deposition process on Pt/Ti/SiO_(2)/(100)Si substrates and pyrolyzed at 350℃-450℃,then annealed at 650℃.The typical thickness of the films is 3.9
m.Effects of the pyrolysis temperature and excess PbO on the orientation,dielectric and ferroelectric properties of PZT thick films have been discussed.Domain switching and depoling process were studied by piezoelectric force microscopy.(100)oriented PZT films exhibit enhanced electrical properties.The dielectric constant and loss tangent of the films are 1444 and 0.022 at 1 kHz,respectively.The remnant polarization increases from 27.6 to 34.6μC/cm^(2),and the coercive field decreases from 61.4 to 43.5 kV/cm,when the orientation of the films changes from the random orientation to the preferential(100)orientation.The leakage current density is 10^(-8)A/cm^(2) at dc field of 0.25 kV/cm,and then increases to 10^(-6) A/cm^(2) at 40 kV/cm.The piezoelectric response of the oriented films is investigated by Piezoelecric Force Microscopy(PFM).

Blue-coke production technology and the current state-of-the-art in China

Blue-coke is a kind of char obtained by the low temperature pyrolysis of non-caking or weakly-caking coal with high volatile matter.It is generally granular with high reactivity,high electrical resistivity and high in fixed carbon but low in ash,sulfur,aluminum and phosphorus content.It has low price and extensive application decided by the raw coal and the production technology.This paper reviews pyrolysis reactor,process principle,technology characteristic and application state of blue-coke production technology in China.It includes vertical oven technology,rotary kiln technology and rotary-hearth furnace technology with external-heating,and vertical oven technology,rotary-disc furnace technology and conveyor-belt furnace technology with internal-heating.According to the existing problems in industrial blue-coke production technology,perspectives in terms of dust removal from volatiles,coke quenching and breakthrough of pyrolysis technology are given.

Interfacial engineering of metallic rhodium by thiol modification approach for ambient electrosynthesis of ammonia

Here we report a vapor-phase reaction approach to fabricate rhodium(I)-dodecanethiol complex coated on carbon fiber cloth(Rh(I)-SC_(12)H_(25)/CFC),followed by low-temperature pyrolysis to achieve dodecanethiol modified Rh(Rh@SC_(12)H_(2)5/CFC)for electrocatalytic nitrogen reduction reaction(NRR).The results demonstrate that after pyrolysis for 0.5 h at 150℃,the obtained Rh@SC_(12)H_(2)5/CFC-0.5 exhibits excellent NRR activity with an NH3 yield rate of 121.2±6.6μg∙h^(−1)∙cm^(−2)(or 137.7±7.5μg∙h^(−1)∙mgRh^(−1))and a faradaic efficiency(FE)of 51.6%±3.8%at−0.2 V(vs.RHE)in 0.1 M Na_(2)SO_(4).The theoretical calculations unveil that the adsorption of dodecanethiol on the hollow sites of Rh(111)plane is thermodynamically favorable,effectively regulating the electronic structure and surface wettability of metallic Rh.Importantly,the dodecanethiol modification on Rh(111)obviously decreases the surface H*coverage,thus inhibiting the competitive hydrogen evolution reaction and concurrently reducing the electrocatalytic NRR energy barrier.

Electromagnetic wave absorbing ceramics composites made of polymer-derived SiC with BN@CNTs pyrolyzed higher than 1200℃

Polymer-derived ceramics(PDCs)pyrolyzed at high temperatures are promising electromagnetic wave(EMW)absorption materials for aerodynamically heated parts of aircraft under harsh environments.Nev-ertheless,high-temperature pyrolysis results in a significant increase of electrical and dielectric proper-ties of the ceramics,causing extensive reflection of EMW.To address this challenge,boron nitride-coated carbon nanotubes(BN@CNTs)were fabricated and introduced into polymer-derived SiC(PDC-SiC)by py-rolyzing its precursor higher than 1200℃to form SiC-BN@CNT ceramic composites.The fabricated com-posites with 3 wt.%BN@CNTs pyrolyzed at 1200℃have an effective absorption bandwidth(EAB)of 4.2 GHz(8.2-12.4 GHz)at a thickness of 3.4 mm and the minimum reflection loss(RL min)of-57.20 dB.The ultra-broad EAB of 12.62 GHz(5.38-18 GHz)is obtained by simulation through periodic structure design-ing.The RL of the metamaterials was also measured using an arch testing method at a frequency range of 2-18 GHz and an EAB of 11.52 GHz(6.48-18 GHz)is obtained.The excellent absorption is attributed to the BN layer that limits the electrical conduction of the ceramic composites while retaining the high loss of CNTs.The introduction of BN@CNTs causes the refinement of SiC grains,which provides plenty of interfaces and enhances the interface polarization loss.This work successfully solves the problem that PDCs pyrolyzed at elevated temperatures cannot be used as EMW absorption materials by applying BN coating on CNTs served as absorbers for PDC-SiC.The results of this work greatly broaden the application scope of the PDC systems for EMW absorption.