Assessing the bioavailability of phenanthrene to soil microorganisms using the Tenax extraction method

The Tenax TA extraction technique followed by gas chromatography mass spectrometry (GC-MS) determinations was used to assess the actually bioavailable fraction of phenanthrene (ABF-Phe) in three different soils freshly contaminated with this compound at levels of 10, 100, and 1,000 mg kg⁻¹. The results were related to the ecotoxic effect of phenanthrene on soil nitrifying bacteria. Nitrification potential measurements were applied as an ecotoxicity end point. A strong positive linear relationship (r ² = 0.95) was obtained between the content of the actually bioavailable phenanthrene fraction and the inhibition of nitrifying bacteria activity.     

Electrochemical remediation of phenanthrene from contaminated kaolinite

In this work a two-stage process combining soil electrokinetic remediation and liquid electrochemical oxidation for the remediation of polluted soil with organic compounds has been developed and evaluated using phenanthrene-spiked kaolinite. Application of an unenhanced electrokinetic process resulted in negligible removal of phenanthrene from the kaolinite sample. Addition of co-solvents and electrolyte to the processing fluid used in the electrode chambers enhanced phenanthrene desorption from the kaolinite matrix and favoured electro-osmotic flow. Near-complete removal of phenanthrene was achieved using Na₂SO₄ and ethanol in the processing fluid. Phenanthrene was transported towards the cathode chamber where it was collected. The cathodic solution containing the pollutant was treated by electrochemical oxidation; complete degradation of phenanthrene occurred after 9 h using Na₂SO₄ as electrolyte.     

Enhancing the adsorption function of biochar by mechanochemical graphitization for organic pollutant removal

• Mechanochemical treatment reduced the calcination temperature for biochar synthesis. • Biochar is converted to graphite after mechanochemical treatment. • Biochar was reduced to nanoscale after mechanochemical treatment. Biochar (BC) has been extensively studied as adsorbent for the treatment of water pollution. Despite the distinct advantages, the high calcination temperature and low adsorption capacity of pristine BC limit its practical applications. Most of the former studies focused on the structure and/or surface modification to improve the adsorption capacity of BC. However, the harsh experiment conditions involved in the biochar modification limited the application in industrial level. Herein, we introduced mechanical treatment into BC preparation to reduce the calcination temperature and improve the adsorption capacity simultaneously. The results indicated that the calcination temperature was reduced and the adsorption capacity of the treated BC was improved after mechanochemical treatment. Characterization of the samples disclosed that BCs were graphitized with the particle size reduced to nanoscale after treatment. Adsorption tests indicated that the mechanochemically treated BCs showed much better removal performance of organic contaminants than that of pristine BCs. For instance, among four pristine BCs (BC600, BC700, BC800, and BC900), only BC900 has strong adsorption capacity for MB, while BC600 has low adsorption capacity (1.2 mg/g). By comparison, the adsorption capacity of MB increased greatly to 173.96 mg/g by BC600-500/1 (treated at 500 r/min for 1 hour). To optimize the mechanochemical treatment, the effects of rotation speed and agitation duration were also investigated.     

Synthesis of vinasse-dolomite nanocomposite biochar via a novel developed functionalization method to recover phosphate as a potential fertilizer substitute

• Nanocomposites were prepared by adding dolomite to vinasse at different ratio. • Textural and morphological features of adsorbents were studied in detail. • CCD based RSM was used for investigation of P ion removal by nanocomposite. • The q_m based on Langmuir model for modified vinasse biochar was 178.57 mg/g. • P loaded nanocomposite improved plant growth and could be utilized as P-fertilizer. The effectiveness of phosphate (P) removal from aqueous solutions was investigated by novel low-cost biochars synthesized from vinasse and functionalized with calcined dolomite. The vinasse-derived biochar, synthesized via pyrolysis at different temperatures, showed easy preparation and a large surface area. The novel vinasse biochar nanocomposites were prepared by adding dolomite to the vinasse biochars with different weight percentages (10, 20 and 30%). The characteristics of the prepared materials were identified for further understanding of the inherent adsorption mechanism between P ions and vinasse biochars. Vinasse-dolomite nanocomposite was very effective in the adsorption of P species from aqueous media. The effect of the operational factors on Vinasse-dolomite nanocomposite was explored by applying response surface methodology (RSM). According to RSM results, the optimum condition was achieved to be contact time 90 (min), 250 (mg/L) of P concentration and pH 7. Thermodynamic isotherm and kinetic studies were applied on experimental data to understand the adsorption behavior. The Vinasse-dolomite nanocomposite revealed preferential P species adsorption in the presence of co-existing anions. The P species could be recovered by 1.0 M HCl where the efficiency was not affected up to the fifth cycle. The P-loaded Vinasse-dolomite nanocomposite was successfully tested on a plant; it significantly improved its growth and proved its potency as a P-based fertilizer substitute.     

Immobilization of NZVI in polydopamine surface-modified biochar for adsorption and degradation of tetracycline in aqueous solution

Polydopamine/NZVI@biochar composite (PDA/NZVI@BC) with high removal efficiency of tetracycline (TC) in aqueous solutions was successfully synthesized. The resultant composite demonstrated high reactivity, excellent stability and reusability over the reaction course. Such excellent performance can be attributed to the presence of the huge surface area on biochar (BC), which could enhance NZVI dispersion and prolong its longevity. The carbonyl group contained on the surface of biochar could combine with the amino group on polydopamine(PDA). The hydroxyl groups in PDA is able to enhance the dispersion and loading of NZVI on BC. Being modified by PDA, the hydrophilicity of biochar was improved. Among BC, pristine NZVI and PDA/NZVI@BC, PDA/ NZVI@BC exhibited the highest activity for removal of TC. Compared with NZVI, the removal efficiency of TC could be increased by 55.9% by using PDA/NZVI@BC under the same conditions. The optimal modification time of PDA was 8h, and the ratio of NZVI to BC was 1:2. In addition, the possible degradation mechanism of TC was proposed, which was based on the analysis of degraded products by LC-MS. Different important factors impacting on TC removal (including mass ratio of NZVI to BC/PDA, initial concentration, pH value and the initial temperature of the solution) were investigated as well. Overall, this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.

Open image in new window

     

The factors affecting biochar application in restoring heavy metal-polluted soil and its potential applications

Heavy metal soil contamination is being given more and more attention due to increasing threats of heavy metals to soil quality, ecological function and human health. Biochar application is an effective way to remove toxic metals due to its high efficiency and low price. Electrostatic adsorption is the primary adsorption mechanism. The absorption ability and stability of biochar is the key to its adsorption performance. The extent of the restoration efficiency is dependent on many factors. The biomass, pyrolysis temperature and application rate affect the number of binding sites. The ageing process and soil properties significantly affect the biochar stability. For long-term purposes, biochar derived from woody residues and pyrolysed at high temperatures is the best available material. In addition, the application of alkaline and electronegative biochar to clay-rich, acidic and As- or Cr-contaminated soil should to be treated with caution.     

Adsorption characteristics of ciprofloxacin onto g-MoS2 coated biochar nanocomposites

• The g-MoS₂ coated composites (g-MoS₂-BC) were synthesized. • The coated g-MoS₂ greatly increased the adsorption ability of biochar. • The synergistic effect was observed for CIP adsorption on g-MoS₂-RC700. • The adsorption mechanisms of CIP on g-MoS₂-BC were proposed. The g-MoS₂ coated biochar (g-MoS₂-BC) composites were synthesized by coating original biochar with g-MoS₂ nanosheets at 300°C(BC300)/700°C (BC700). The adsorption properties of the g-MoS₂-BC composites for ciprofloxacin (CIP) were investigated with an aim to exploit its high efficiency toward soil amendment. The specific surface area and the pore structures of biochar coated g-MoS₂ nanosheets were significantly increased. The g-MoS₂-BC composites provided more π electrons, which was favorable in enhancing the π-π electron donor-acceptor (EDA) interactions between CIP and biochar. As a result, the g-MoS₂-BC composites showed faster adsorption rate and greater adsorption capacity for CIP than the original biochar. The coated g-MoS₂ nanosheets contributed more to CIP adsorption on the g-MoS₂-BC composites due to their greater CIP adsorption capacity than the original biochar. Moreover, the synergistic effect was observed for CIP adsorption on g-MoS₂-BC700, and suppression effect on g-MoS₂-BC300. In addition, the adsorption of CIP onto g-MoS₂-BC composites also exhibited strong dependence on the solution pH, since it can affect both the adsorbent surface charge and the speciation of contaminants. It was reasonably suggested that the mechanisms of CIP adsorption on g-MoS₂-BC composites involved pore-filling effects, π-π EDA interaction, electrostatic interaction, and ion exchange interaction. These results are useful for the modification of biochar in exploiting the novel amendment for contaminated soils.     

Anaerobic phenanthrene biodegradation with four kinds of electron acceptors enriched from the same mixed inoculum and exploration of metabolic pathways

Anaerobic phenanthrene biodegradation enriched process was described in detail. The enriched bacterial communities were characterized under four redox conditions. The enriched archaeal communities were stated under high percentage conditions. Relatively intact pathways of anaerobic phenanthrene biodegradation were proposed. Polycyclic aromatic hydrocarbons (PAHs) are widespread and persistent contaminants worldwide, especially in environments devoid of molecular oxygen. For lack of molecular oxygen, researchers enhanced anaerobic zones PAHs biodegradation by adding sulfate, bicarbonate, nitrate, and iron. However, microbial community reports of them were limited, and information of metabolites was poor except two-ring PAH, naphthalene. Here, we reported on four phenanthrene-degrading enrichment cultures with sulfate, bicarbonate, nitrate, and iron as electron acceptors from the same initial inoculum. The high-to-low order of the anaerobic phenanthrene biodegradation rate was the nitrate-reducing conditions>sulfate-reducing conditions>methanogenic conditions>iron-reducing conditions. The dominant bacteria populations were Desulfobacteraceae, Anaerolinaceae, and Thermodesulfobiaceae under sulfate-reducing conditions; Moraxellaceae, Clostridiaceae, and Comamonadaceae under methanogenic conditions; Rhodobacteraceae, Planococcaceae, and Xanthomonadaceae under nitrate-reducing conditions; and Geobacteraceae, Carnobacteriaceae, and Anaerolinaceae under iron-reducing conditions, respectively. Principal component analysis (PCA) indicated that bacteria populations of longtime enriched cultures with four electron acceptors all obtained significant changes from original inoculum, and bacterial communities were similar under nitrate-reducing and iron-reducing conditions. Archaea accounted for a high percentage under iron-reducing and methanogenic conditions, and Methanosarcinaceae and Methanobacteriaceae, as well as Methanobacteriaceae, were the dominant archaea populations under iron-reducing and methanogenic conditions. The key steps of phenanthrene biodegradation under four reducing conditions were carboxylation, further ring system reduction, and ring cleavage.     

改性生物炭对水体中抗生素的去除研究进展

随着社会经济的不断发展,抗生素造成的水体环境污染问题已不容忽视.利用生物炭去除水体中的抗生素是解决这一问题的有效手段之一.然而,原始生物炭对水体中抗生素等有机污染物的去除存在一定局限性,因此对生物炭进行改性以提升其吸附能力尤为必要.生物炭的吸附性能受生物质类型、碳化条件和改性方法等因素影响较大,导致目前虽然开展了许多相...     

Nanoscale zero-valent iron supported on biochar for the highly efficient removal of nitrobenzene

• Biochar supported nanoscale zero-valent iron composite (nZVI/BC) was synthesized. • nZVI/BC quickly and efficiently removed nitrobenzene (NB) in solution. • NB removal by nZVI/BC involves simultaneous adsorption and reduction mechanism. • nZVI/BC exhibited better catalytic activity, stability and durability than nZVI. The application of nanoscale zero-valent iron (nZVI) in the remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation and iron leaching. To address this issue, nZVI was distributed on oak sawdust-derived biochar (BC) to obtain the nZVI/BC composite for the highly efficient reduction of nitrobenzene (NB). nZVI, BC and nZVI/BC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For nZVI/BC, nZVI particles were uniformly dispersed on BC. nZVI/BC exhibited higher removal efficiency for NB than the simple summation of bare nZVI and BC. The removal mechanism was investigated through the analyses of UV-Visible spectra, mass balance and XPS. NB was quickly adsorbed on the surface of nZVI/BC, and then gradually reduced to aniline (AN), accompanied by the oxidation of nZVI to magnetite. The effects of several reaction parameters, e.g., NB concentration, reaction pH and nZVI/BC aging time, on the removal of NB were also studied. In addition to high reactivity, the loading of nZVI on biochar significantly alleviated Fe leaching and enhanced the durability of nZVI.     

Adsorption of herring sperm DNA onto pine sawdust biochar: Thermodynamics and site energy distribution

● Adsorption of environmental deoxyribonucleic acid on biochar was studied. ● π−π interaction and electrostatic repulsion worked in the adsorption. ● Thermodynamics indicated the adsorption was spontaneous and endothermic. Environmental deoxyribonucleic acid (eDNA), which includes antibiotic resistance genes, is ubiquitous in the environment. The interactions between eDNA and biochar, a promising material widely used in soil amendment and water treatment, greatly affect the environmental behavior of eDNA. Hitherto few experimental evidences are available yet, especially on the information of thermodynamics and energy distribution to explains the interactions between biochar and eDNA. This study investigated the adsorption of herring sperm DNA (hsDNA) on pine sawdust biochar, with a specific emphasis on the adsorption thermodynamics and site energy distribution. The adsorption of hsDNA on biochar was enhanced by an increase in the pyrolysis and adsorption temperatures. The higher surface area, stronger π−π interaction, and weaker electrostatic repulsion between hsDNA and biochars prepared at high pyrolysis temperatures facilitated the adsorption of hsDNA. The thermodynamics indicated that the adsorption of hsDNA on biochar was spontaneous and endothermic. Therefore, higher temperature was beneficial for the adsorption of hsDNA on biochar; this was well explained by the increase in E^* and F(E^*) with the adsorption temperature. These results are useful for evaluating the migration and transformation of eDNA in the presence of biochar.     

Sorption of aromatic organophosphate flame retardants on thermally and hydrothermally produced biochars

• TPhP showed faster and higher sorption on biochars than TPPO. • Pyrochars had higher sorption capacity for TPPO than hydrochar. • Hydrophobic interactions dominated TPhP sorption by biochars. • The π-π EDA and electrostatic interactions are involved in sorption. Aromatic organophosphate flame retardant (OPFR) pollutants and biochars are commonly present and continually released into soils due to their increasingly wide applications. In this study, for the first time, the sorption of OPFRs on biochars was investigated. Although triphenyl phosphate (TPhP) and triphenylphosphine oxide (TPPO) have similar molecular structures and sizes, TPhP exhibited much faster and higher sorption than TPPO due to its stronger hydrophobicity, suggesting the dominant role of hydrophobic interactions in TPhP sorption. The π-π electron donor–acceptor (EDA) interactions also contributed to the sorption process, as suggested by the negative correlation between the sorption capacity of the aromatic OPFRs and the aromatic index (H/C atomic ratios) of biochar. Density functional theory calculations further showed that one benzene ring of aromatic OPFRs has no electrons, which may interact with biochar via π-π EDA interactions. The electrostatic attraction between the protonated P = O in OPFRs and the negatively charged biochar was found to occur at pH below 7. This work provides insights into the sorption behaviors and mechanisms of aromatic OPFRs by biochars.     

Effects of different types of biochar on the properties and reactivity of nano zero-valent iron in soil remediation

• Biochar enhanced the mobility and stability of zero-valent iron nanoparticles. • Particle performance was best when the BC:nZVI mass ratio was 1:1. • Bagasse-BC@nZVI removed 66.8% of BDE209. The addition of nano zero-valent iron (nZVI) is a promising technology for the in situ remediation of soil. Unfortunately, the mobility and, consequently, the reactivity of nZVI particles in contaminated areas decrease due to their rapid aggregation. In this study, we determined how nZVI particles can be stabilized using different types of biochar (BC) as a support (BC@nZVI). In addition, we investigated the transport behavior of the synthesized BC@nZVI particles in a column filled with porous media and their effectiveness in the removal of BDE209 (decabromodiphenyl ether) from soil. The characterization results of N₂ Brunauer–Emmett–Teller (BET) surface area analyses, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) indicated that nZVI was successfully loaded into the BC. The sedimentation test results and the experimental breakthrough curves indicated that all of the BC@nZVI composites manifested better stability and mobility than did the bare-nZVI particles, and the transport capacity of the particles increased with increasing flow velocity and porous medium size. Furthermore, the maximum concentrations of the column effluent for bagasse–BC@nZVI (B–BC@nZVI) were 19%, 37% and 48% higher than those for rice straw–BC@nZVI (R–BC@nZVI), wood chips–BC@nZVI (W–BC@nZVI) and corn stalks–BC@nZVI (C–BC@nZVI), respectively. A similar order was found for the removal and debromination efficiency of decabromodiphenyl ether (BDE209) by the aforementioned particles. Overall, the attachment of nZVI particles to BC significantly increased the reactivity, stability and mobility of B–BC@nZVI yielded, and nZVI the best performance.     

A “Seawater-in-Sludge” approach for capacitive biochar production via the alkaline and alkaline earth metals activation

• Capacitive biochar was produced from sewage sludge. • Seawater was proved to be an alternative activation agent. • Minerals vaporization increased the surface area of biochar. • Molten salts acted as natural templates for the development of porous structure. Sewage sludge is a potential precursor for biochar production, but its effective utilization involves costly activation steps. To modify biochar properties while ensuring cost-effectiveness, we examined the feasibility of using seawater as an agent to activate biochar produced from sewage sludge. In our proof-of-concept study, seawater was proven to be an effective activation agent for biochar production, achieving a surface area of 480.3 m²/g with hierarchical porosity distribution. Benefited from our design, the catalytic effect of seawater increased not only the surface area but also the graphitization degree of biochar when comparing the pyrolysis of sewage sludge without seawater. This leads to seawater activated biochar electrodes with lower resistance, higher capacitance of 113.9 F/g comparing with control groups without seawater. Leveraging the global increase in the salinity of groundwater, especially in coastal areas, these findings provide an opportunity for recovering a valuable carbon resource from sludge.     

Decontamination of Cr(VI) facilitated formation of persistent free radicals on rice husk derived biochar

PFRs were produced on biochar during Cr(VI) decontamination. PFRs formation on biochar was owing to the oxidization of phenolic-OH by Cr(VI). Appearance of excessive oxidant led to the consumption of PFRs on biochar. Biochar charred at high temperature possessed great performance to Cr(VI) removal. This study investigated the facilitation of Cr(VI) decontamination to the formation of persistent free radicals (PFRs) on rice husk derived biochar. It was found that Cr(VI) remediation by biochar facilitated the production of PFRs, which increased with the concentration of treated Cr(VI). However, excessive Cr(VI) would induce their decay. Biochar with high pyrolysis temperature possessed great performance to Cr(VI) removal, which was mainly originated from its reduction by biochar from Inductively Coupled Plasma Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy. And the corresponding generation of PFRs on biochar was primarily ascribed to the oxidization of phenolic hydroxyl groups by Cr(VI) from Fourier Transform Infrared Spectroscopy analysis, which was further verified by the H₂O₂ treatment experiments. The findings of this study will help to illustrate the transformation of reactive functional groups on biochar and provide a new insight into the role of biochar in environmental remediation.     

Sorption and reduction of hexavalent uranium by natural and modified silicate minerals: A review

Environmental Chemistry Letters - In the context of rising anthropogenic activities and world conflicts, there is an urgent need for energy supply, such as nuclear power from uranium minerals....     

Simultaneous sorption of aqueous phenanthrene and phosphate onto bentonites modified with AlCl3 and CTMAB

The purpose of this work is to synthesize a new type of bentonite sorbent that can simultaneously remove both organic compounds and phosphate from water. Inorganic-organic bentonites (Al-CTMAB-Bent) were synthesized by modifying bentonites with both AlCl₃ and cetyltrimethyl ammonium bromide (CTMAB). Simultaneous sorption of aqueous phenanthrene and phosphate onto Al-CTMAB-Bent was examined. Removal rates of phenanthrene and phosphate from water reached 96.3% and 90.2%, respectively, at their respective initial concentrations of 1 mg/L and 5 mg/L and the added amount of Al-CTMAB-Bent was 1.25 g/L. The residual turbidity of the Al-CTMAB-Bent suspension decreased 81.4% compared to that of organobentonite suspension after a 1 h settling time. Thus, inorganic-organic bentonite can be used to treat wastewater containing both organic pollutants and phosphate.     

秸秆生物质炭土地利用的环境效益研究

农田土壤有机碳矿化释放CO2是农业温室气体排放的重要途径,促进土壤碳截获对于减缓全球温室效应具有重要意义。生物质炭具有改良土壤性质、促进土壤团聚体的形成、对土壤微生物生态具有调控作用等特性。因此,生物质炭对增强土壤碳截获能力及减少土壤CO2气体排放可能具有重要作用。采用实验室盆栽的方式,以黑麦草为目标植物,对农业秸秆生物质炭土地利用的环境效益进行了研究。实验结果表明：农业秸秆制生物质炭应用于农田土壤能产生多方面的环境效益。与对照相比,添加1%~4%生物质炭处理的土壤活性有机质质量分数均增加了25%以上,土壤呼吸度降低了23%~50%,同时,添加生物质炭对植物的生长也有促进作用。添加4%秸秆炭的处理的黑麦草生物量增加了68%。此外,秸秆生物质炭的添加对土壤中的养分具有较好的持留功能,与比照相比,添加生物质炭处理的土壤淋出液中氮和磷质量浓度显著降低,说明生物质炭能够有效减少水冲刷造成的氮磷流失,降低农业面源污染。     

改性天然磷灰石促进Pb/Zn复合污染土壤的稳定化修复

采用草酸和柠檬酸分别与天然磷灰石共培养以对其改性,并将改性磷灰石用于Pb/Zn复合污染土壤的稳定化修复,借助XRD、FTIR等仪器方法表征改性磷灰石的物相组成及其P结合形态的转变,采用TCLP方法评价改性天然磷灰石对土壤重金属的修复效果.研究表明,草酸改性磷灰石诱导了草酸钙生成,并且32.4%的P由稳定形态转化为水溶态,而柠檬酸改性未能使磷灰石主要成分发生显著变化,仅有0.28%的P转化为水溶态P.与天然磷灰石相比,改性磷灰石提高了对Pb和Zn的稳定性.草酸改性磷灰石可同时有效地稳定土壤中的Pb和Zn,稳定化效率分别为68%—100%和64%—73%,其固定机制主要是形成难溶的磷酸盐沉淀;柠檬酸改性磷灰石对Pb和Zn的稳定化效率分别为20%和62%—69%,对Pb和Zn的稳定性主要是通过吸附作用.总之,草酸改性磷灰石对Pb和Zn的稳定化优于柠檬酸改性磷灰石,是一种高效经济的土壤重金属稳定化修复材料.