Poplar biochars from pyrolysis at temperatures of 300, 500 and 700 °C were modified with KOH and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and nitrogen adsorption–desorption isotherm studies. Adsorption experiments were carried out on the modified biochars to remove tetracycline (TC) from aqueous solution. The results showed that KOH modification could increase or decrease TC adsorption onto biochars depending on the different pyrolysis temperatures. Maximum adsorption capacities (qe,m) of TC in modified biochar from a low pyrolysis temperature of 300 °C increased up to 21.17 mg g−1 relative to 4.30 mg g−1 in unmodified biochar of 300 °C (final TC concentrations were 8.83 and 25.70 mg L−1, respectively). In contrast, qe,m decreased from 7.37 and 11.63 mg L−1 to 4.97 and 7.13 mg L−1 in biochars from higher pyrolysis temperatures of 500 and 700 °C with and without modification, respectively, even with an increase in SBET. The adsorption ability of biochar can remain over a wider range of pH in modified biochar relative to unmodified biochar. Further analysis indicated that there was a strong linear regression relationship between qe,m and total functional oxygen groups using Bohem titration (n = 6, R2 = 0.84), whereas no significant relationship was observed between qe,m and SBET in this experiment. The result suggested that KOH modification of biochar from a low pyrolysis temperature can enhance TC adsorption and can be used over a wide range of pH, which may be a good choice for disposal of organic pollutants in aqueous solution.

In the present study, salt-tolerant strains, Dietzia sp. HRJ2, Corynebacterium variabile HRJ4, Dietzia cinnamea HRJ5 and Bacillus tequilensis HRJ6 were isolated from the Dagang oil field, China. These strains degraded n-alkanes and polycyclic aromatic hydrocarbons (PAHs) aerobically from heavy crude oil (HCO) in an experiment at 37 °C and 140 rpm. The GC/MS investigation for degradation of different chain lengths of n-alkanes (C8–C40) by individual strains showed the highest degradation of C8–C19 (HRJ5), C20–C30 (HRJ4) and C31–C40 (HRJ5), respectively. Moreover, degradation of 16 PAHs with individual strains demonstrated that the bicyclic and pentacyclic aromatic hydrocarbons (AHs) were mostly degraded by HRJ5, tricyclic and tetracyclic AHs by HRJ6 and hexacyclic AHs by HRJ2. However, the highest degradation of total petroleum hydrocarbons (TPHs), total saturated hydrocarbons (TSH), total aromatic hydrocarbons (TAH), n-alkanes (C8–C40) and 16 PAHs was achieved by a four-membered consortium (HRJ2 + 4 + 5 + 6) within 12 days, with the predominance of HRJ4 and HRJ6 strains which was confirmed by denaturing gradient gel electrophoresis. The abundance of alkB and nah genes responsible for catabolism of n-alkanes and PAHs was quantified using the qPCR. Maximum copy numbers of genes were observed in HRJ2 + 4 + 5 + 6 consortium (gene copies l−1) 2.53 × 104 (alkB) and 3.47 × 103 (nah) at 12 days, which corresponded to higher degradation rates of petroleum hydrocarbons. The superoxide dismutase (SOD) (total SOD (T-SOD), Cu2+Zn2+-SOD), catalase (CAT) and ascorbate peroxidase (APX) activities in Allium sativum and Triticum aestivum were lower in the HRJ2 + 4 + 5 + 6-treated HCO as compared to the plantlets exposed directly to HCO. The present results revealed the effective degradation of HCO-contaminated saline medium using the microbial consortium having greater metabolic diversity.

•Thiol-functionalized graphene oxide/Fe-Mn composite synthesized via three methods.•Composite formed via interaction between 3-MPTS and GO/Fe-Mn and self-polymerization.•Ammonium hydroxide method obtains the composite with highest sorption capacity.•CH3Hg+ removed by electrostatic attraction, ligand exchange and surface complexation.A novel thiol-functionalized graphene oxide/Fe-Mn composite (SGO/Fe-Mn) was synthesized via three different methods, i.e., acetic acid method (SGO/Fe-Mn-ac), neutral method (SGO/Fe-Mn-ne), and ammonium hydroxide method (SGO/Fe-Mn-am). The composites were characterized and tested for aqueous methylmercury removal. SGO/Fe-Mn was prepared using 3-mercaptopropyltrimethoxysilane (3-MPTS) as a silanizing reagent, and hydrolyzed 3-MPTS mainly interacted with GO/Fe-Mn through surface oxygen-containing groups (i.e., OH, CO, epoxy COC, carboxyl OCO, and CO) and π-π interactions, partially through self-polymerization. SGO/Fe-Mn-am showed the largest hydrodynamic diameter, strongest π-π bond, fewest S oxidation products, most thiol groups, negative charge, sp3 defects, and FeOOH. Pseudo-second-order kinetic model and Langmuir and Freundlich isotherm models fitted well with methylmercury sorption kinetic and isotherm data, respectively, resulting in a CH3Hg+ maximum sorption capacity of 43.88 mg/g for SGO/Fe-Mn-am, 36.33 mg/g for SGO/Fe-Mn-ac, and 28.00 mg/g for SGO/Fe-Mn-ne. The removal mechanism was described by electrostatic attraction, ligand exchange, and surface complexation. This study demonstrates potential and viability of SGO/Fe-Mn for enhanced immobilization of CH3Hg+ in surface water, groundwater, and soil/sediments.Download high-res image (255KB)Download full-size image

Bi2O2CO3 nanosheets were synthesized via a facile sodium dodecyl sulfate (SDS)-assisted hydrothermal process. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis and UV-Vis diffuse reflectance spectroscopy techniques were used to investigate the phase structure, morphology and optical properties of the Bi2O2CO3 products. The SDS surfactant played an important role in the formation of Bi2O2CO3 nanosheets. As-synthesized Bi2O2CO3 nanosheets exhibited excellent photocatalytic activity for RhB degradation under irradiation with simulated sunlight. O2− radicals are considered to be the dominant active oxygen species in the photodegradation process.

Alginase was purified from Gracilibacillus A7 and evaluated for its ability to produce elicitor-active oligosaccharides. The optimum conditions for the alginase reaction are as follows: temperature, 40 °C; pH, 8.0; alginate content, 0.3–0.7%; and the presence of Na+ and Mg2+ metal ions. The degree of polymerization (DP) decreased as the reaction time of the alginase progressed, achieving values of 5.4 and 3.3 after 240 and 300 min, respectively. The relative root length (RRL) of the Brassica campestris L. increased with the addition of oligosaccharides with reduced DP values. The oligosaccharides with lower DP values are effective in reducing the effect of salt stress on the activity of the superoxide dismutase (SOD) and guaiacol peroxidase (POD), and oligosaccharides with moderate DP values can reduce the increase in lipid peroxidation activities (as malondialdehyde content) induced by salt stress. These results suggest that oligosaccharides may act as osmoprotective agents during the plant germination process.

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 16S rRNA 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.Download high-res image (132KB)Download full-size image

Biochar is produced by thermal decomposition of biomass under oxygen-limited conditions (pyrolysis), and it has received attention in soil remediation and waste disposal in recent years. The characteristics of biochar are influenced mainly by the preparation temperature and biomass. Higher pyrolysis temperature often results in the increased surface area and carbonized fraction of biochar leading to high sorption capability for pollutants. Biochars derived from various source materials show different properties of surface area, porosity and the amount of functional groups which are important concerning on the effect of biochar. Biochar has been proved to be effective in improving soil properties and increasing crop biomass. It has also been suggested that it can even enhance crop resistance to disease. Biochar has recently been used to remediate soil with both heavy metal and organic pollutants. The mechanism is electrostatic interaction and precipitation in the case of heavy metal, and the surface adsorption, partition and sequestration in the case of organic contaminants. However, application of biochar in soil has been shown to result in decreased efficacy of pesticides, which indicates a trade-off between the potentially promising effect of biochar on pesticide remediation and its negative effect on pesticide efficacy. While arguments on the effectiveness of biochar appear sound, further research is needed prior to widespread application of biochar in soil remediation.

Urban environmental pressure is increasing with acceleration of urbanization and urban ecological situation is not optimistic any more. It's very necessary to conduct ecological security assessment on cities. This paper employed the PSR (pressure-state-response) model and determined the weight of index based on improved analytic hierarchy process (IAHP) and entropy method. Index system of ecological security assessment of Tianjin with time scale from the year 2001 to 2007 was also established. From the evaluation result, the urban ecological security state in Tianjin from 2001 to 2007 was getting better, which can measure situation of ecological security in Tianjin in the past seven years and in order to assist early-warning, management and decision-making of city ecological safety.

•FeS coated on Fe0 surface, effectively inhibited Fe0 aggregation, and formed Fe/FeS•Increasing S/Fe molar ratio from 0.138 to 0.207 enhanced Cr(VI) removal by 63%•Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles•Fe/FeS removed aqueous Cr(VI) mainly by adsorption, reduction, and precipitation•Fe/FeS effectively removed Cr(VI) through batch and column testsFeS-coated iron (Fe/FeS) magnetic nanoparticles were easily prepared, characterized, and applied for Cr(VI) removal in simulated groundwater. TEM, XRD, and BET characterization tests showed that FeS coating on the surface of Fe0 inhibited the aggregation of Fe0 and that Fe/FeS at a S/Fe molar ratio of 0.207 possessed a large surface area of 62.1 m2/g. Increasing the S/Fe molar ratio from 0 to 0.138 decreased Cr(VI) removal by 42.8%, and a further increase to 0.207 enhanced Cr(VI) removal by 63% within 72 h. Moreover, Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles. Mechanistic analysis indicated that Fe0, Fe2 +, and S2 − were synergistically involved in the reduction of Cr(VI) to nontoxic Cr(III), which further precipitated as (CrxFe1-x)(OH)3 and Cr(III)-Fe-S. The process of Cr(VI) sorption by Fe/FeS (S/Fe = 0.207) was fitted well with a pseudo-second-order kinetic model, and the isotherm data were simulated by Langmuir isotherm model with a maximum sorption capacity of 69.7 mg/g compared to 48.9 mg/g for Fe0. Low pH and initial Cr(VI) concentration favored Cr(VI) removal. Continuous fixed bed column studies showed that simulated permeable reactive barriers (PRB) with Fe/FeS was considerably effective for in situ removal of Cr(VI) from groundwater. This study demonstrated the high potential of Fe/FeS for Cr(VI) immobilization in water, groundwater, and soil.Download high-res image (243KB)Download full-size image

•FeS coated on Fe0 surface, effectively inhibited Fe0 aggregation, and formed Fe/FeS•Increasing S/Fe molar ratio from 0.138 to 0.207 enhanced Cr(VI) removal by 63%•Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles•Fe/FeS removed aqueous Cr(VI) mainly by adsorption, reduction, and precipitation•Fe/FeS effectively removed Cr(VI) through batch and column testsFeS-coated iron (Fe/FeS) magnetic nanoparticles were easily prepared, characterized, and applied for Cr(VI) removal in simulated groundwater. TEM, XRD, and BET characterization tests showed that FeS coating on the surface of Fe0 inhibited the aggregation of Fe0 and that Fe/FeS at a S/Fe molar ratio of 0.207 possessed a large surface area of 62.1 m2/g. Increasing the S/Fe molar ratio from 0 to 0.138 decreased Cr(VI) removal by 42.8%, and a further increase to 0.207 enhanced Cr(VI) removal by 63% within 72 h. Moreover, Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles. Mechanistic analysis indicated that Fe0, Fe2 +, and S2 − were synergistically involved in the reduction of Cr(VI) to nontoxic Cr(III), which further precipitated as (CrxFe1-x)(OH)3 and Cr(III)-Fe-S. The process of Cr(VI) sorption by Fe/FeS (S/Fe = 0.207) was fitted well with a pseudo-second-order kinetic model, and the isotherm data were simulated by Langmuir isotherm model with a maximum sorption capacity of 69.7 mg/g compared to 48.9 mg/g for Fe0. Low pH and initial Cr(VI) concentration favored Cr(VI) removal. Continuous fixed bed column studies showed that simulated permeable reactive barriers (PRB) with Fe/FeS was considerably effective for in situ removal of Cr(VI) from groundwater. This study demonstrated the high potential of Fe/FeS for Cr(VI) immobilization in water, groundwater, and soil.Download high-res image (243KB)Download full-size image