Weihua Xu

Biosorption of copper(II) by immobilizing Saccharomyces cerevisiae on the surface of chitosan-coated magnetic nanoparticles from aqueous solution.

Immobilized Saccharomyces cerevisiae on the surface of chitosan-coated magnetic nanoparticles (SICCM) was applied as a new magnetic adsorbent for the adsorption of Cu(II) from aqueous solution. The prepared magnetic adsorbent was characterized by TEM, XRD and FTIR. TEM images indicated that S. cerevisiae was immobilized on the surface of chitosan-coated magnetic nanoparticles (CCM) successfully, and conglobation was not observed. The XRD pictures suggested that the Fe(3)O(4) nanoparticles were pure Fe(3)O(4) with a spinel structure and that the immobilizing process did not result in the phase change of Fe(3)O(4). Factors that influence the adsorption of Cu(II) were investigated, which included the initial pH of Cu(II) solution, initial concentration of Cu(II) solution and contact time. The optimum pH for Cu(II) absorption was 4.5. The highest removal efficiency of 96.8% was reached when the initial Cu(II) concentration was 60 mg L(-1), and the adsorption capacity was increased with the increase of initial concentration of Cu(II). In particular, SICCM was highly efficient for the fast adsorption of Cu(II) within the first 10 min, and adsorption equilibrium could be achieved in 1h. Equilibrium studies show that the data of Cu(II) adsorption follow the Langmuir model. The maximum adsorption capacity for Cu(II) was estimated to be 144.9 mg g(-1) with a Langmuir adsorption equilibrium constant of 0.0719 L mg(-1) at 301 K.

Simultaneous Cr(VI) reduction and phenol degradation in pure cultures of Pseudomonas aeruginosa CCTCC AB91095.

Simultaneous Cr(VI) reduction and phenol degradation were investigated in a reactor containing Pseudomonas aeruginosa CCTCC AB91095. Phenol was used as carbon source. P.aeruginosa utilized metabolites formed during phenol degradation as energy source for Cr(VI) reduction. Cr(VI) inhibited both Cr(VI) reduction and phenol degradation when Cr(VI) concentration exceeded the optimum value (20 mg/L), whereas phenol enhanced both Cr(VI) reduction and phenol degradation below the optimum initial concentration of 100 mg/L. Cr(III) was the predominant product of Cr(VI) reduction in cultures after incubation for 24 h. Both Cr(VI) reduction and phenol degradation were influenced by the amount of inocula. The concentration of Cr(VI) and phenol declined quickly from 20, 100 to 3.36, 29.51 mg/L in cultures containing of 5% (v/v) inoculum after incubation for 12 h, respectively. The whole study showed that P. aeruginosa is promising for the reduction of toxic Cr(VI) and degradation of organic pollutants simultaneously in the mineral liquid medium.

Chitosan modification of magnetic biochar produced from Eichhornia crassipes for enhanced sorption of Cr(VI) from aqueous solution

In this research, chitosan modification of magnetic biochar (CMB) was successfully prepared for effective removal of Cr(VI). Moreover, this study highlighted that the conversion of Eichhornia crassipes into biochar was a promising method for improved management of this highly problematic invasive species. The sorption kinetics, isotherms, thermodynamics, the effects of pH, and background electrolyte on the sorption process were investigated. The results indicated that CMB adsorbed more Cr(VI) (120 mg g−1) than that of pristine biochar (30 mg g−1). The sorption data could be well illustrated by pseudo-second-order and Langmuir models. Furthermore, thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The adsorption of Cr(VI) was influenced by solution pH and the maximum sorption capacity was achieved at pH 2. The background electrolyte PO43− and SO42− restricted the Cr(VI) sorption. These results are significant for exploring and optimizing the removal of metal ions by the CMB composite.

Facile synthesis of Cu(II) impregnated biochar with enhanced adsorption activity for the removal of doxycycline hydrochloride from water

In this study, the effect factors and mechanisms of doxycycline hydrochloride (DOX) adsorption on copper nitrate modified biochar (Cu-BC) was investigated. Cu-BC absorbent was synthesized through calcination of peanut shells biomass at 450°C and then impregnation with copper nitrate. The Cu-BC has exhibited excellent sorption efficiency about 93.22% of doxycycline hydrochloride from aqueous solution, which was double higher than that of the unmodified biochar. The experimental results suggest that the adsorption efficiency of DOX on the Cu-BC is dominated by the strong complexation, electrostatic interactions between DOX molecules and the Cu-BC samples. Comprehensively considering the cost, efficiency and the application to realistic water, the Cu-BC hold the significant potential for enhancing the effectiveness to remove DOX from water.

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.

Adsorption of hexavalent chromium by polyacrylonitrile (PAN)-based activated carbon fibers from aqueous solution

Polyacrylonitrile (PAN)-based activated carbon fibers (PAC400 and PAC600) were prepared by heating Zn(NO3)2 pretreated-PAN at 400 °C and 600 °C for the removal of Cr(VI) from aqueous solution. Formation of PAC400 and PAC600 was confirmed by FTIR and XPS. Field Emission Scanning Electron Microscopy (FESEM) imaging of PAC400 and PAC600 revealed the formation of nearly spherical agglomerated particles. The conditions for adsorption of Cr(VI) onto PAC400 and PAC600 had been optimized and kinetics and isotherm studies were performed. Although the adsorption took place in the range of pH (2–6), pH 3 was found to be most suitable. The adsorption data fitted well with the pseudo-second-order rate model and Langmuir isotherm model. PAC600 showed much greater ability in the adsorption of Cr(VI) than PAC400, and Qmax were calculated to be 187.79 mg g−1 and 136.87 mg g−1 based on the Langmuir model, respectively. Desorption experiments showed PAC600 and PAC400 can be regenerated and reused. The adsorption process for the removal of Cr(VI) was governed by the ionic interaction between protonated amine groups of PAC and HCrO4− ions.

Direct current stimulation of Thiobacillus ferrooxidans bacterial metabolism in a bioelectrical reactor without cation-specific membrane.

A bioelectrical reactor without cation-specific membrane was designed to test effects of direct electrical current on growth of Thiobacillus ferrooxidans bacterium. The results indicated that the cell significantly enhanced the growth of T. ferrooxidans. At a current of 30 mA, the maximum cells density reached 1.39 x 10(9)cells/mL within 84 h, which was 10 times faster than under a conventional cultivation method, in which electrical current is not used. A lag phase during the growth of T. ferrooxidans was observed when direct electrical current was applied, and the lag phase became longer under higher current intensity.

Enhanced biological stabilization of heavy metals in sediment using immobilized sulfate reducing bacteria beads with inner cohesive nutrient

A series of experiments were conducted for treating heavy metals contaminated sediments sampled from Xiangjiang River, which combined polyvinyl alcohol (PVA) and immobilized sulfate reducing bacteria (SRB) into beads. The sodium lactate was served as the inner cohesive nutrient. Coupling the activity of the SRB with PVA, along with the porous structure and huge specific surface area, provided a convenient channel for the transmission of matter and protected the cells against the toxicity of metals. This paper systematically investigated the stability of Cu, Zn, Pb and Cd and its mechanisms. The results revealed the performance of leaching toxicity was lower and the removal efficiencies of Cu, Zn, Pb and Cd were 76.3%, 95.6%, 100% and 91.2%, respectively. Recycling experiments showed the beads could be reused 5 times with superbly efficiency. These results were also confirmed by continuous extraction at the optimal conditions. Furthermore, X-ray diffraction (XRD) and energy-dispersive spectra (EDS) analysis indicated the heavy metals could be transformed into stable crystal texture. The stabilization of heavy metals was attributed to the carbonyl and acyl amino groups. Results presented that immobilized bacteria with inner nutrient were potentially and practically applied to multi-heavy-metal-contamination sediment.

Tartaric acid modified Pleurotus ostreatus for enhanced removal of Cr( vi ) ions from aqueous solution: characteristics and mechanisms

Pleurotus ostreatus was modified by tartaric acid and used as a biosorbent for the removal of Cr(VI) from aqueous solution. The removal efficiency of Cr(VI) by the modified P. ostreatus was 2 to 2.5 times higher than by pristine P. ostreatus. FTIR and XPS analysis indicated that carboxyl and amino groups were the major functional groups for Cr(VI) sorption. Batch sorption experiments were carried out to investigate the characteristic adsorption behavior of MPOD. Experimental data fitted a pseudo-second order equation and the Freundlich isotherm. The optimum biosorption was observed at pH 2.0 with the biosorption capacity was 99.66 mg g−1. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. The present results confirmed that electrostatic attraction and complexation were involved in Cr(VI) removal. Modified P. ostreatus has the characteristics of simplicity and obvious effects for the removal of Cr(VI) ions from aqueous solution.

The effects of P. aeruginosa ATCC 9027 and NTA on phytoextraction of Cd by ramie (Boehmeria nivea (L.) Gaud)

In pot experiments, the effects of Pseudomonas aeruginosa ATCC 9027 and nitrilotriacetic acid (NTA) on Cd phytoextraction from contaminated soil by Boehmeria nivea (L.) Gaud (ramie) was investigated. Ramie was grown in a sandy soil in the presence of 30 mg kg−1 Cd and 50 mg kg−1 Cd, respectively. The experimental pots were amended with P. aeruginosa ATCC 9027 or NTA at different levels (5, 10 and 20 mmol kg−1) weekly. The results showed that the inoculation of P. aeruginosa ATCC 9027 alleviated the Cd-induced damages, resulting in promotion of ramie growth, improvement of antioxidative enzymes activities and increase of total Cd-uptake by ramie. By contrasting 30 and 50 mg kg−1 Cd treatments, the inoculation of P. aeruginosa ATCC 9027 increased accumulation in the roots ranging from 54% to 96% and 13% to 104% in 30 and 50 mg kg−1 Cd soils, respectively. The average accumulation of Cd with P. aeruginosa ATCC 9027 was about 1.95-fold (30 mg kg−1 Cd) and 1.54-fold (50 mg kg−1 Cd) compared to the corresponding NTA treatments. When added with NTA, the accumulation of Cd in the shoots of ramie was higher than the controls, but inhibition of plant growth and related enzyme activities were observed. The experimental results demonstrated that P. aeruginosa ATCC 9027 can greatly enhance phytoremediation efficiency. Besides, the results also indicated that P. aeruginosa ATCC 9027 was more effective than NTA to improve the efficiency of ramie under cadmium stress in practical applications.