Jingchun Tang

Preparation and characterization of a novel graphene/biochar composite for aqueous phenanthrene and mercury removal.

A graphene/biochar composite (G/BC) was synthesized via slow pyrolysis of graphene (G) pretreated wheat straw, and tested for the sorption characteristics and mechanisms of representative aqueous contaminants (phenanthrene and mercury). Structure and morphology analysis showed that G was coated on the surface of biochar (BC) mainly through π-π interactions, resulting in a larger surface area, more functional groups, greater thermal stability, and higher removal efficiency of phenanthrene and mercury compared to BC. Pseudo second-order model adequately simulated sorption kinetics, and sorption isotherms of phenanthrene and mercury were simulated well by dual-mode and BET models, respectively. FTIR and SEM analysis suggested that partitioning and surface sorption were dominant mechanisms for phenanthrene sorption, and that surface complexation between mercury and C-O, CC, -OH, and OC-O functional groups was responsible for mercury removal. The results suggested that the G/BC composite is an efficient, economic, and environmentally friendly multifunctional adsorbent for environmental remediation.

Application of iron sulfide particles for groundwater and soil remediation: A review.

Rapid industrialization and urbanization have resulted in elevated concentrations of hazardous inorganic and organic contaminants in groundwater and soil, which has become a paramount concern to the environment and the public health. In recent years, iron sulfide (FeS), a major constituent of acid-volatile sulfides, has elicited extensive interests in environmental remediation due to its ubiquitous presence and high treatment efficiency in anoxic environment. This paper provides a comprehensive review on recent advances in: (1) synthesis of FeS particles (including nanoscale FeS); and (2) reactivity of FeS towards a variety of common environmental contaminants in groundwater and soil over extended periods of time, namely, heavy metals (Hg(II), Cu(II), Pb(II), and Cr(VI)), oxyanions (arsenite, arsenate, selenite, and selenate), radionuclides (e.g., uranium (U) and neptunium (Np)), chlorinated organic compounds (e.g., trichloroethane, trichloroethylene, and p-chloroaniline), nitroaromatic compounds, and polychlorinated biphenyls. Different physiochemical and biological methods for preparing FeS with desired particle size, structure, and surface properties are discussed. Reaction principles and removal effectiveness/constraints are discussed in details. Special attention is placed to the application of nanoscale FeS particles because of their unique properties, such as small particle size, large specific surface area, high surface reactivity, and soil deliverability in the subsurface. Moreover, current knowledge gaps and further research needs are identified.

Isolation and characterization of alginate‐degrading bacteria for disposal of seaweed wastes

Aims:  Isolation of novel alginate degrading bacteria for the disposal of seaweed waste in composting process.

Effect of salinity on the bioremediation of petroleum hydrocarbons in a saline‐alkaline soil

Aims:  The aim of this paper is to check the effect of salinity on the bioremediation process of petroleum hydrocarbons in the saline‐alkaline soil.

Improved composting of Undaria pinnatifida seaweed by inoculation with Halomonas and Gracilibacillus sp. isolated from marine environments

Composting of the Undaria pinnatifida (wakame) seaweed was conducted after inoculation with 6×10(8) CFU g(-1)Halomonas sp. AW4 and the alginate-degrading bacterium Gracilibacillus sp. A7. Inoculation with strains A7 and AW4 resulted in 27.8% and 24.7% degradation of U. pinnatifida dry mass after 168 h, whereas only 17.5% degradation occurred in the uninoculated control. The C/N ratio decreased in the A7 and AW4 inoculated compost by 7.0% and 9.2% after 72 h, but increased by 11.5% in the control. Inoculation with A7 resulted in 2.8 times faster degradation of alginate and 1.2 and 1.6 times higher levels of reducing sugars and unsaturated sugars than inoculation with AW4. The compost produced from the inoculation with A7 had low plant toxicity as measured by germination experiment. The results suggest that inoculation of wakame with alginate-degrading bacteria not only shortened the length of composting but also created seaweed compost with good fertilizer qualities.

Photocatalytic degradation of commercially sourced naphthenic acids by TiO2-graphene composite nanomaterial

Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO2-graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17-22, z value -2) were easy to be degraded than the micromolecular ones (carbon number 11-16, z value -2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method.

Synthesis and characterization of an iron-impregnated biochar for aqueous arsenic removal

The iron (Fe)-impregnated biochar (FBC), fabricated via thermal pyrolysis of corn straw treated with FeCl3, was investigated for the sorption characteristics and mechanisms of aqueous arsenate removal. Structural and morphological analysis showed that large quantity of iron oxide particles tightly grew within the porous matrix of biochar (BC) through iron-impregnation. Batch sorption experimental results showed that the composite, with larger surface area, more functional groups, and greater thermal stability, exhibited excellent As(V) adsorption efficiency of 6.80mg/g compared to 0.017mg/g for unmodified BC (a 400-fold increase). The adsorption kinetics data were fitted well by pseudo second-order model, and sorption isotherms of As(V) were simulated well by both Freundlich and Langmuir models. XRD and FTIR analysis suggested that electrostatic attraction and precipitation were dominant mechanisms for As(V) sorption. The As(V)-loaded FBC could be easily separated from the solution by a magnet at the end of the sorption experiment. The FBC showed excellent re-sorption capacity, which account for about 70% removal efficiency for the second and third reuse in As(V) sorption. Results from this study demonstrated the promise of FBC composite as an efficient, low-cost, environmentally friendly, and regenerable adsorbent for As(V) remediation. CAPSULE FBC showed enhanced As(V) sorption capacity, excellent re-sorption capacity, and could be easily separated by a magnet.

Characterization of Alginase and Elicitor-Active Oligosaccharides from Gracilibacillus A7 in Alleviating Salt Stress for Brassica campestris L.

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 Mg(2+) 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.

Disposal of seaweed wakame (Undaria pinnatifida) in composting process by marine bacterium Halomonas sp. AW4

A novel marine bacterium, identified as Halomonas sp. AW4 by partial 16S rDNA analysis, was isolated from the seaweeds in Awaji Island, Japan. Strain AW4 grew well even in the wide NaCl concentration ranges of 0-3 mol/L, where it showed an optimal growth in the presence of 0.5 mol/L NaCl. The organic components were reduced to 73.6% of initial dry weight after 168 h of composting by inoculation of AW4. The microbial community structure became complex after 72 h of composting. The initial content of alginate was 35.6%, which decreased to 15.6% after 168 h of composting. The decomposition of alginate mainly occurred at the late stage of composting, suggesting that the microbial community consisting of various types of microorganisms is effective in degrading alginate. The germination of plant Brassica campestris L. indicated the promotion effect of composted wakame.

Recycling of the Seaweed Wakame Through Degradation by Halotolerant Bacteria

A review on the recycling of seaweed by halotolerant bacteria was conducted for the cleaning of the marine environment. Planting of seaweed is effective in dealing with organic pollutants, especially N and P. Thus, the composting through recycling of seaweeds is supposed to be suitable, although their salinity is awkward in the composting process. The activity of inoculated bacteria decreased with the increase of salinity in wakame composting with Bacillus sp. HR6. On the contrary, halotolerant bacterium AW4, isolated, showed better degradation of wakame during composting than others that were examined. Degradation of alginate, which is the central component in wakame, is a key point in the recycling of seaweed. Thus, alginate-degrading bacterium A7 was isolated from the compost, by which alginate was successfully decomposed to 14.3% after 72 h of composting. The decomposition product of wakame by A7 sufficiently enhanced the relative root length of Komatsuna to 263.2%, suggesting that the applications of A7 to produce special fertilizer using seaweeds might be a meaningful way for preserving the seashore environment.