Yaqin Wang

Grafting of β-cyclodextrin to magnetic graphene oxide via ethylenediamine and application for Cr(VI) removal.

A novel β-cyclodextrin (β-CD) polymer adsorbent named β-cyclodextrin/ethylenediamine/magnetic graphene oxide (CD-E-MGO) was synthesized for decontamination of Cr(VI) from aqueous solution. The sorption kinetics, isotherms and thermodynamics, as well as the effects of pH, aniline and ionic strength on the sorption process were investigated. The results indicated that CD-E-MGO could effectively remove Cr(VI) from aqueous solution and the sorption data could be well described by pseudo-second-order and Langmuir models. The intraparticle diffusion study indicated that intraparticle diffusion was not the only rate-limiting step. Thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The decontamination of Cr(VI) was influenced by solution pH and ionic strength. In the system with aniline, the Cr(VI) sorption was improved at low pH values but reduced at high pH values. These results are important for estimating and optimizing the removal of metal ions by CD-E-MGO composite.

Effect of aniline on cadmium adsorption by sulfanilic acid-grafted magnetic graphene oxide sheets

Cd(II) has posed severe health risks worldwide. To remove this contaminant from aqueous solution, the sulfanilic acid-grafted magnetic graphene oxide sheets (MGOs/SA) were prepared and characterized. The mutual effects of Cd(II) and aniline adsorption on MGOs/SA were studied. The effects of operating parameters such as pH, ionic strength, contact time and temperature on the Cd(II) enrichment, as well as the adsorption kinetics and isotherm were also investigated. The results demonstrated that MGOs/SA could effectively remove Cd(II) and aniline from the aqueous solution and the two adsorption processes were strongly dependent on solution pH. The Cd(II) adsorption was reduced by the presence of aniline at pH<5.4 but was improved at pH>5.4. The presence of Cd(II) diminished the adsorption capacity for aniline at pH<7.8 but enhanced the aniline adsorption at pH>7.8. The decontamination of Cd(II) by MGOs/SA was influenced by ionic strength. Besides, the adsorption process could be well described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that the intraparticle diffusion was not the only rate-limiting step for the adsorption process. Moreover, the experimental data of isotherm followed the Freundlich isotherm model.

Enhanced efficiency of cadmium removal by Boehmeria nivea (L.) Gaud. in the presence of exogenous citric and oxalic acids

Boehmeria nivea (L.) Gaud. is a potential candidate for the remediation of Cd contaminated sites. The present investigation aims to explore Cd tolerance threshold and to quickly identify the role of exogenous organic acids in Cd uptake and abiotic metal stress damage. Elevated Cd levels (0-10mg/L) resulted in an obvious rise in Cd accumulation, ranging from 268.0 to 374.4 in root and 25.2 to 41.2mg/kg dry weight in shoot, respectively. Citric acid at 1.5 mmol/L significantly facilitated Cd uptake by 26.7% in root and by 1-fold in shoot, respectively. Cd translocation efficiency from root to shoot was improved by a maximum of 66.4% under 3 mmol/L of oxalic acid. Citric acid exhibited more prominent mitigating effect than oxalic acid due to its stronger ligand affinity for chelating with metal and avoiding the toxicity injury of free Cd ions more efficiently. The present work provides a potential strategy for efficient Cd remediation with B. nivea.

Mechanism of exogenous selenium alleviates cadmium induced toxicity in Bechmeria nivea (L.) Gaud (Ramie)

Abstract The protective role of exogenously supplied selenium (Se 6+ ) on Bechmeria nivea ( L .) Gaud (Ramie) subjected to cadmium (Cd) stress was studied in vitro, and the mechanism was discussed by investigating plant growth, malondialdehyde (MDA), activity of antioxidative enzymes and DNA methylation pattern. Plants grown in hydroponic culture were supplied with spraying Se (selenate, 1.2 μmol/L) and cadmium (Cd(NO 3 ) 2 , 0, 3, 6 and 9 mg/L), individually or simultaneously. At low Se spraying levels, SOD activity was increased by 35.34%, 43.18%, 3.63% under 3, 6 or 9 mg/L cadmium contents, POD was increased by 12.45%, 14.14%, 3.27%, and the level of DNA methylation was decreased by 10.70%, 18.18% and 15.59%, respectively. The results confirmed that spraying low Se on ramie leaves could enhance the activity of SOD and POD, and regulate DNA methylation in ramie leaves.

Effects of limonene stress on the growth of and microcystin release by the freshwater cyanobacterium Microcystis aeruginosa FACHB-905.

The effects of limonene exposure on the growth of Microcystisaeruginosa and the release of toxic intracellular microcystin (MCY) were tested by evaluating the results obtained from the batch culture experiments with M. aeruginosa FACHB-905. The time series of cell as well as intracellular and extracellular MCY concentrations were evaluated during 5d of the incubation. After exposure to limonene, the number of cells gradually diminished; the net log cell reduction after 5d of the exposure was 3.0, 3.6, and 3.8log when the initial cell densities were set at 1.6×10(7), 1.1×10(6) and 4.1×10(5)cell/mL, respectively. Limonene was found to significantly influence the production and release of MCY. As the limonene exposure could inhibit the increase in the number of cells, the increase in the total MCY concentration in the medium was also inhibited. In the presence of limonene, the intracellular MCY was gradually released into the medium through a gradual reduction in the number of cells. The extracellular MCY concentration in the medium was significantly higher in the limonene-exposed samples than in the control samples, which confirmed that limonene cannot decompose the extracellular MCY.

Cadmium accumulation and apoplastic and symplastic transport in Boehmeria nivea (L.) Gaudich on cadmium-contaminated soil with the addition of EDTA or NTA

A Cd-tolerant plant species named Boehmeria nivea (L.) Gaudich (ramie) was applied to study its Cd accumulation and translocation mechanisms with the addition of ethylene diamine tetracetic acid (EDTA) or nitrilotriacetic acid (NTA). A pot experiment was designed to systematically investigate the Cd accumulation and subcellular compartmentation in different ramie tissues as well as soil Cd solubility and its physiological response. Results showed that soil EDTA- and NTA-extractable Cd concentrations were remarkably higher than the control, and Cd content in each tissue with Cd translocation factor (TF) after EDTA and NTA addition were significantly increased with elevated chelant concentration. In spite of the decreased cytoderm Cd contents in different tissues, extracellular and intracellular Cd content were increased dramatically under chelant treatment, particularly in ramie leaves with EDTA addition from 2 mmol kg−1 to 10 mmol kg−1 (increased by 98% for extracellular Cd and by 29% for intracellular Cd, respectively). Furthermore, the addition of chelant also resulted in an apparent increase of malondialdehyde (MDA) content and decrease of chlorophyll level in ramie leaves. These results revealed that EDTA and NTA could enhance Cd phytoavailability in soil, facilitate apoplastic and symplastic transport of Cd from root to the aboveground tissues and improve leaf Cd accumulation, which may because of the extracellular loading among spongy tissues and intracellular sequestration in mesophyll vacuoles. This study contributes to the control of Cd accumulation by plants.

Effects of d-menthol stress on the growth of and microcystin release by the freshwater cyanobacterium Microcystis aeruginosa FACHB-905

The effects of d-menthol on the growth of Microcystis aeruginosa FACHB-905 and microcystin (MCY) concentration were evaluated by batch culture experiments. The algal biomass and the intracellular and extracellular MCY concentrations were evaluated during 5d incubation. After the d-menthol exposure, the dry weight of the cells gradually decreased; the decrease in the dry weight after 5d exposure was 29, 12, and 2mgL(-1) when the initial cell densities were 1.4×10(7), 1.2×10(6), and 2.9×10(5)cellmL(-1), respectively. The results indicate that the d-menthol exposure inhibited the cellular growth, thus also inhibiting the increase of the total MCY concentration. In the presence of d-menthol, the intracellular MCY was gradually released into the medium after the cell lysis. The extracellular MCY concentration in the medium was significantly higher in the d-menthol-exposed samples than in the control samples, confirming that d-menthol cannot decompose the extracellular MCY.

Time-dependent antioxidative responses of ramie (Boehmeria nivea (L.) Gaudich) to moderate cadmium stress and its up-regulation mechanism by spermidine antioxidant

Cadmium (Cd) is present in soil and water at low concentrations that can be harmful to the biota. A Cd-tolerant plant species named ramie (Boehmeria nivea (L.) Gaudich) was applied to probe the precise Cd tolerance mechanism with different treatment duration and the up-regulation effect for antioxidant capacity by spermidine (Spd) pretreatment. The results showed that short-term (0–7 d) Cd stress resulted in the enhancement of pigment content, the accumulation of soluble sugar and the activation of partial antioxidants, meanwhile reducing the level of malondialdehyde (MDA), which is the indicator of oxidative stress. Spd pretreatment markedly increased the soluble protein, soluble sugar and reduced glutathione (GSH) content in ramie leaves under short-term Cd stress, whereas, it showed no significantly beneficial effects on photosynthesis and other antioxidants. Long-term (0–15 d) Cd stress may lead to growth inhibition which is associated with Cd accumulation, protein oxidation, sugar degradation, MDA surge and antioxidant inactivation. Spd application markedly alleviated long-term Cd toxicity by decreasing Cd accumulation, stabilizing cellular macromolecules such as pigments, soluble protein and sugar and inhibiting peroxidase (POD), catalase (CAT) and malate dehydrogenase (MDH) inactivation and GSH degradation. Our present work concluded that ramie could tolerate moderate Cd stress during a certain time span. Spd application could play a vital role in the promotion of Cd tolerance by adjusting different kinds of parameters.