Biochar-mediated regulation of greenhouse gas emission and toxicity reduction in bioremediation of organophosphorus pesticide-contaminated soils

Organophosphorus pesticides(OPPs) are a set of toxic persistent organic pollutants(POPs) present in the environment. Recently, biochar-mediated bioremediation has exhibited many advantages over conventional methods for the remediation of pesticide-contaminated soil. In the present study, biochar and nitrogen fertilizer(NH_4NO_3)were employed to remediate OPP-contaminated soil and the greenhouse gas(GHG) emission during 90 days of incubation was investigated. After thermal desorption treatment, the content of organophosphorus pesticides reduced from 175.61 μg·kg^(-1) to 62.68 μg·kg^(-1). The addition of NH_4NO_3 in the following bioremediation led to larger reduction(34.35%) of the pesticide concentration than that of biochar(31.90%) for the contaminated soils with thermal desorption treatment, while the simultaneous addition of biochar and NH_4NO_3 led to the largest reduction of pesticide concentration(11.07%) for the soil without thermal desorption treatment. The addition of biochar and NH_4NO_3 only slightly increased the emission rate of GHGs from the soil without thermal treatment,but remarkably increased the emission rate of GHGs from the soil after thermal treatment. In most cases, the addition of NH_4NO_3 is more effective than biochar to promote the degradation of pesticide, but also exhibited higher GHG emission. The microbial community analysis suggests that the enhanced degradation of pesticide is mainly owing to the increased activity of microorganism.

Sustainable biochar as an electrocatalysts for the oxygen reduction reaction in microbial fuel cells

Microbial fuel cells(MFCs)have gained remarkable attention as a novel wastewater treatment that simultaneously generates electricity.The low activity of the oxygen reduction reaction(ORR)remains one of the most critical bottlenecks limiting the development of MFCs.To date,although research on biochar as an electrocatalyst in MFCs has made tremendous progress,further improvements are needed to make it economically practical.Recently,biochars have been considered to be ORR electrocatalysts with developmental potential.In this review,the ORR mechanism and the essential requirements of ORR catalysts in MFC applications are introduced.Moreover,the focus is to highlight the material selection,properties,and preparation of biochar electrocatalysts,as well as the evaluation and measurement of biochar electrodes.Additionally,in order to provide comprehensive information on the specific applications of biochars in the field of MFCs,their applications as electrocatalysts,are then discussed in detail,including the uses of nitrogen-doped biochar and other heteroatom-doped biochars as electrocatalysts,poisoning tests for biochar catalysts,and the cost estimation of biochar catalysts.Finally,profound insights into the current challenges and clear directions for future perspectives and research are concluded.

Carbon Fibers for Bioelectrochemical:Precursors,Bioelectrochemical System,and Biosensors

Carbon fibers(CFs)demonstrate a range of excellent properties including(but not limited to)microscale diameter,high hardness,high strength,light weight,high chemical resistance,and high temperature resistance.Therefore,it is necessary to summarize the application market of CFs.CFs with good physical and chemical properties stand out among many materials.It is believed that highly fibrotic CFs will play a crucial role.This review first introduces the precursors of CFs,such as polyacrylonitrile,bitumen,and lignin.Then this review introduces CFs used in BESs,such as electrode materials and modification strategies of MFC,MEC,MDC,and other cells in a large space.Then,CFs in biosensors including enzyme sensor,DNA sensor,immune sensor and implantable sensor are summarized.Finally,we discuss briefly the challenges and research directions of CFs application in BESs,biosensors and more fields.

Combination of rhamnolipid and biochar in assisting phytoremediation of petroleum hydrocarbon contaminated soil using Spartina anglica

Biochar (BC) and rhamnolipid (RL) is used in bioremediation of petroleum hydrocarbons,however,the combined effect of BC and RL in phytoremediation has not been studied until now.In this paper,the phytoremediation of petroleum hydrocarbon-contaminated soil using novel plant Spartina anglica was enhanced by the combination of biochar (BC) and rhamnolipid (RL).Samples of petroleum-contaminated soil (10,30 and 50 g/kg) were amended by BC,BC+ RL and rhamnolipid modified biochar (RMB),respectively.After 60 day's cultivation,the removal rate of total petroleum hydrocarbons (TPHs) for unplanted soil (UP),planted soil (P),planted soil with BC addition (P-BC),planted soil with BC and RL addition (P-BC + RL) and planted soil with addition ofRMB (P-RMB) were 8.6%,19.1%,27.7%,32.4% and 35.1% in soil with TPHs concentration of 30 g/kg,respectively.Compared with UP,the plantation of Spartina anglica significantly decreased the concentration of C8-14 and tricyclic PAHs.Furthermore,the application of BC and RMB alleviated the toxicity of petroleum hydrocarbons to Spartina anglica via improving plant growth with increasing plant height,root vitality and total chlorophyll content.High-throughput sequencing result indicated that rhizosphere microbial community of Spartina anglica was regulated by the application of BC and RMB,with increase of bacteria and plant mycorrhizal symbiotic fungus in biochar and RMB amended soil.

Vertical response of microbial community and degrading genes to petroleum hydrocarbon contamination in saline alkaline soil

A column microcosm was conducted by amending crude oil into Dagang Oilfield soil to simulate the bioremediation process. The dynamic change of microbial communities and metabolic genes in vertical depth soil from 0 to 80 cm were characterized to evaluate the petroleum degradation potential of indigenous microorganism. The influence of environmental variables on the microbial responds to petroleum contamination were analyzed. Degradation extent of 42.45% of n-alkanes(C8–C40) and 34.61% of 16ΣPAH were reached after 22 weeks. Relative abundance of alkB, nah, and phe gene showed about 10-fold increment in different depth of soil layers. Result of HTS profiles demonstrated that Pseudomonas, Marinobacter and Lactococcus were the major petroleum-degrading bacteria in0–30 and 30–60 cm depth of soils. Fusarium and Aspergillus were the dominant oil-degrading fungi in the 0–60 cm depth of soils. In 60–80 cm deep soil, anaerobic bacteria such as Bacteroidetes, Lactococcus, and Alcanivorax played important roles in petroleum degradation.Redundancy analysis(RDA) and correlation analysis demonstrated that petroleum hydrocarbons(PHs) as well as soil salinity, clay content, and anaerobic conditions were the dominant effect factors on microbial community compositions in 0–30, 30–60, and 60–80 cm depth of soils, respectively.

Graphitic carbon nitride/biochar composite synthesized by a facile ball-milling method for the adsorption and photocatalytic degradation of enrofloxacin

In order to enhance the removal performance of graphitic carbon nitride(g-C_(3)N_(4)) on organic pollutant, a simultaneous process of adsorption and photocatalysis was achieved via the compounding of biochar and g-C_(3)N_(4). In this study, g-C_(3)N_(4) was obtained by a condensation reaction of melamine at 550 °C. Then the g-C_(3)N_(4)/biochar composites were synthesized by ball milling biochar and g-C_(3)N_(4) together, which was considered as a simple, economical, and green strategy. The characterization of resulting g-C_(3)N_(4)/biochar suggested that biochar and g-C_(3)N_(4) achieved effective linkage. The adsorption and photocatalytic performance of the composites were evaluated with enrofloxacin(EFA) as a model pollutant. The result showed that all the g-C_(3)N_(4)/biochar composites displayed higher adsorption and photocatalytic performance to EFA than that of pure g-C_(3)N_(4). The 50% g-C_(3)N_(4)/biochar performed best and removed 45.2% and 81.1% of EFA(10 mg/L) under darkness and light with a dosage of 1 mg/mL, while g-C_(3)N_(4) were 19.0% and 27.3%, respectively. Besides, 50% g-C_(3)N_(4)/biochar showed the highest total organic carbon(TOC) removal efficiency(65.9%). Radical trapping experiments suggested that superoxide radical( ·O_(2)^(-)) and hole(h~+) were the main active species in the photocatalytic process. After 4 cycles, the composite still exhibited activity for catalytic removal of EFA.

Archaeal community structure along a gradient of petroleum contamination in saline-alkali soil

The response of archaeal communities to petroleum contamination in saline-alkali soil was characterized by analyses of three soil samples with different total petroleum hydrocarbon concentrations.Through the construction and screening of 16S rRNA gene clone libraries based on DNA extracts from these soils,nine distinct phylogenetic groups were identified.Statistical analyses showed that the distribution of archaeal community structures differ significantly along the gradient of petroleum contamination in these three saline- alkali soils.Five phylogenetic groups were dominant in the control soil,two of which were also abundant in the lightly contaminated soil.Four phylogenetic groups were dominant in heavily contaminated soil,one of which was also abundant in the lightly contaminated soil.The halophilic genus of Haloferax and the haloalkaliphilic genus of Natronomonas were more abundant in heavily contaminated soil.These results suggested that the genera of Haloferax and Natronomonas may have a role in the natural attenuation of petroleum- contaminated saline-alkali soil.

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.

A novel bioremediation strategy for petroleum hydrocarbon pollutants using salt tolerant Corynebacterium variabile HRJ4 and biochar

The present work aimed to develop a novel strategy to bioremediate the petroleum hydrocarbon contaminants in the environment.Salt tolerant bacterium was isolated from Dagang oilfield,China and identified as Corynebacterium variabile HRJ4 based on 16 S r RNA gene sequence analysis.The bacterium had a high salt tolerant capability and biochar was developed as carrier for the bacterium.The bacteria with biochar were most effective in degradation of n-alkanes（C16,C18,C19,C26,C28） and polycyclic aromatic hydrocarbons（NAP,PYR） mixture.The result demonstrated that immobilization of C.variabile HRJ4 with biochar showed higher degradation of total petroleum hydrocarbons（THPs） up to 78.9%after 7-day of incubation as compared to the free leaving bacteria.The approach of this study will be helpful in clean-up of petroleum-contamination in the environments through bioremediation process using eco-friendly and cost effective materials like biochar.

High pyrolysis temperature biochar reduced the transport of petroleum degradation bacteria Corynebacterium variabile HRJ4 in porous media

Biochar has been widely applied for the remediation of petroleum-contaminated soil.However,the effect of biochar on the transport of petroleum degradation bacteria has not been studied.A typical Gram-positive petroleum degradation bacteria-Corynebacterium variabile HRJ4 was used to study the effect of different biochars on bacterial transport and retention.Results indicated that the addition of biochar in sand was effective for reducing the transport of bacteria and poplar sawdust biochar(PSBC)had a stronger hinder effect than corn straw biochar(CSBC).The hindrance was more evident with pyrolysis temperature of biochar raised from 300℃ to 600℃,which was attributed to the increase of specific surface area(309 times).The hindrance effect also enhanced with higher application rate of biochar.Furthermore,the reduction of HRJ4 transport was more obvious in higher(25 mmol/L)concentration of Na Cl solution owing to electrostatic attraction enhancement.The adsorption of biochar to HRJ4 was defined to contribute to the hindrance of HRJ4 transport mainly.Combining the influence of feedstocks and pyrolysis temperature on HRJ4 transport,it suggested that specific surface area had the greatest effect on HRJ4 transport,and pore-filling,electrostatic force also contributed to HRJ4 retained in quartz sand column.At last,phenol transportation experiment indicated that the restriction of biochar on HRJ4 enhanced the phenol removal rate in the column.This study provides a theoretical basis for the interaction of biochar and bacteria,which is vital for the remediation of oil-contaminated soil and groundwater in the field.

Sorption and degradation of imidacloprid and clothianidin in Chinese paddy soil and red soil amended with biochars

Application of biochar technology in the remediation of organic contaminated soils has drawn growing interest in recent years.In this study,sorption and degradation of two typical neonicotinoid insecticides,imidacloprid(IMI)and clothianidin(CLO)in Chinese typical paddy soil and red soil amended with six kinds of biochars were investigated.The results showed that surface area(SA),pH,total organic carbon and dissolved organic carbon(DOC)of the two soils all increased after biochar amendment,while H/C decreased.With biochar pyrolyzing temperature(PT)increasing from 300℃ to 700℃,the sorption of the two insecticides on biochar-soil mixtures increased by more than 4.3-fold,due to the increasing SA and decreasing H/C.The acidic pH of the two tested soils also favored the enhanced sorption of the insecticides by removing the ash on biochar.The amendment of low-PT(300℃)biochar promoted the biodegradation of IMI and CLO by 11.3-41.9%via providing more DOC and available N for microorganisms,while inhibiting the chemical degradation.Oppositely,the high-PT(500-700℃)biochars inhibited the biodegradation of the insecticides by decreasing their bioavailability and promoted the chemical degradation by providing mineral active groups,and generating·OH and other free radicals.In addition,soil type also affected the effects of biochar remediation.The highest 60-day degradation extent was achieved for CLO(90.5%)and IMI(81.4%)in paddy soil by adding biochar derived from pig manure at 700℃ PT.In summary,the effect of biochar on the fate of organic contaminants in soil is a comprehensive result involving several processes and a systematic study considering the type and property of biochar and soil is needed to optimize biochar technology.