Li Gan

Biodegradation of naphthalene by strain Bacillus fusiformis (BFN)

Bacterial strains isolated from oil refining wastewater sludge (Fuzhou, China) were used to biodegrade naphthalene in cultured medium. Bacillus fusiformis (BFN) strain was identified using 16S rDNA gene sequence analysis. Optimal conditions for the biodegradation of naphthalene included: temperature of 30 degrees C, pH 7.0, 0.2% inoculum size and a C/N ratio of 1.0. Under these conditions and initial naphthalene concentration of 50 mg/L, more than 99.1% was removed within 96 h. Of those factors influencing the biodegradation of naphthalene, salinity and inoculum concentration were of greatest importance. Furthermore, the biodegradation kinetics of naphthalene corresponded with the first-order rate model. Degradation metabolites identified using GC-MS, included o-phthalic acid and benzoic acid, suggesting possible metabolic pathways. Finally, given these metabolites are water-soluble and non-toxic, the findings suggest a potential bioremediation role of Bacillus fusiformis (BFN) in the removal of naphthalene from wastewaters.

Removal of nitrate using Paracoccus sp. YF1 immobilized on bamboo carbon

Paracoccus sp. strain YF1 immobilized on bamboo carbon was developed for the denitrification. The results show that denitrification was significantly improved using immobilized cells compared to that of free cells, where denitrification time decreased from 24h (free cells) to 15 h (immobilized cells). The efficiency of denitrification increased from 4.57 mg/(Lh) (free cells) to 6.82 mg/(Lh) (immobilized cells). Kinetics studies suggest that denitrification by immobilized YF1 cells fitted well to the zero-order model. Scanning electron microscopy (SEM) demonstrated that firstly, the bacteria became stable on the inside and exterior of the bamboo carbon particles and secondly, they formed biofilm after adhesion. Various factors and their influences on biological denitrification were investigated, namely temperature, pH, initial nitrate concentrations and carbon sources. The immobilized cells exhibited more nitrate removal at various conditions compared to free cells since bamboo carbon as a carrier protects cells against changes in environmental conditions. Denitrification using the YF1 immobilized in bamboo carbon was also maintained 99.8% after the tenth cycle reuse, thus demonstrating excellent reusability. Finally, wastewater was treated using the immobilized cells and the outcome was that nitrogen was completely removed by bamboo-immobilized YF1.

Removal of phosphate using iron oxide nanoparticles synthesized by eucalyptus leaf extract in the presence of CTAB surfactant

This study investigated the use of cetyltrimethylammonium bromide (CTAB) as a stabilizer in green synthesis to improve the reactivity of iron oxide nanoparticles (IONP). Results show that efficiency in removing phosphate increased from 71.0% to 97.3%. To understand how to improve the reactivity of IONP by CTAB: firstly, characterizations of IONP before and after phosphate removal by SEM, EDS, FTIR, XPS show the adsorption of P onto the IONP; secondly, batch experiments indicate that the adsorption capacity of phosphate increased when temperature or initial phosphate concentration increased and decreased with an increase in both adsorbent dose and pH. Adsorption followed the pseudo-second-order kinetics model and the equilibrium data fitted well to the Langmuir isotherm. Thermodynamic data confirmed the spontaneous and endothermic nature of the adsorption process. Finally, it was proposed that the adsorption of phosphate using CTAB-modified IONP was mainly associated with inner-sphere complexing mechanism and electrostatic attraction.

Burkholderia vietnamiensis C09V as the functional biomaterial used to remove crystal violet and Cu(II).

Burkholderia vietnamiensis C09V (B.V. C09V) was used to remove both crystal violet (CV) and Cu(II) because dye effluents often contain dyes and metal ions. Inhibiting the strain׳s growth through the biosorption of Cu(II) on B.V. C09V and promoting its growth by using CV as a carbon source led to the degradation of CV (30mg/L). It fell to 36.9 percent and the amount of Cu(II) (50mg/L) removed rose to 34.9 percent in the presence of both CV and Cu(II). This outcome is comparable to the single presence of CV and Cu(II). EDS analysis showed that Cu(II) was adsorbed onto the strain (the atomic percentage of Cu(II) was 1.9 percent), while kinetic studies indicated that firstly, the decolorization of CV fitted well to the pseudo first-order degradation kinetic model and secondly, the biosorption of Cu(II) fitted well to the pseudo second-order kinetic model. The degradation rate constants of CV were stable in the 0.101-0.0068/h range and R(2) was both higher than 0.981 when Cu(II) concentrations were present. Furthermore, the biosorption capacity of Cu(II) ranged from 38.8 to 20.3mg/g at the CV concentration of 30mg/L (both R(2)>0.96). This suggests that the strain has the potential to degrade CV and facilitate the biosorption of Cu(II) in dye effluent.

Effects of cetyltrimethylammonium bromide on the morphology of green synthesized Fe3O4 nanoparticles used to remove phosphate

In this paper, iron oxide nanoparticles (IONPs) are successfully synthesized using Eucalyptus leaf extract in the presence of cetyltrimethylammonium bromide (CTAB) to enhance the dispersion and reduce aggregation of IONPs. CTAB was used as a stabilizing and capping agent in biosynthesis of IONP was observed. The particle size decreased from 183.9±30.1nm to 89.8±17.1nm as the concentration of CTAB increased from 0 to 0.4mM CTAB, indicating that CTAB reduce the aggregation of IONPs and enhance the reactivity. In addition, the removal efficiency of phosphate declined from 95.13% to 89.58% when the CTAB concentration increased from 0.4 to 10mM, indicating that a CTAB impacted on micelles and lipophilic biomolecules in Eucalyptus leaf extract, and hence affected the formation of IONPs. Furthermore, SEM image showed that the smaller spherical with some irregularly shaped CTAB-IONPs having a diameter of 80-90nm in the presence of 0.4mM CTAB were observed. The date from EDS, FTIR and TGA suggested that the CTAB capped on the surface of CTAB-IONPs, while XRD showed that zero-valent iron and iron oxide were formed. Finally, the formation mechanism of IONPs was proposed.

New nano-biomaterials for the removal of malachite green from aqueous solution via a response surface methodology

The development of new biomaterials for the remove of organic contaminants from wastewater has attracted much attention over the few past years. One of the most cost-effective approaches is to produce new high value biomaterials from low value solid agricultural biowastes. In this work, sugarcane bagasse and agricultural waste rich in reducing sugars, acted as both a green bioreductant for graphene oxide (GO) and a sustainable supporter for the immobilization of Burkholderia cepacia. Therefore, this new biomaterial which contained both reduced graphene oxide (RGO) and Burkholderia cepacia, was cable of initial adsorption of malachite green (MG) and its subsequent biodegradation. After 60 h, immobilized Burkholderia cepacia degraded more MG (98.5%) than a cell cultured Burkholderia cepacia (87.7%) alone. Raman spectroscopy confirmed that GO was successfully reduced by bagasse and that consequently a composite (B-RGO) was prepared. SEM indicated that Burkholderia cepacia was well immobilized and kinetics studies showed that the adsorption of MG onto the developed composite fitted a pseudo-second order kinetics model (R2 > 0.99). Biodegradation of MG, was confirmed by the detection of appropriate degradation products such as N, N-dimethylaniline and 4-(Dimethylamino) benzophenone using GC-MS, UV and FT-IR, and via best fit first-order biodegration kinetics. Furthermore, a response surface methodology (RSM) was applied to the removal process by varying four independent parameters using a Box-Behnken design (BBD). Optimum MG removal (99.3%) was achieved at 31.5 °C, with an initial MG concentration of 114.5 mg L-1, initial pH of 5.85, and an adsorbent dosage of 0.11 g L -1. The excellent removal efficiency indicated that agricultural waste derived reduced graphene oxide bio-adsorbents have significant potential for the removal of dyes such as MG from industrial wastewaters.

Burkholderia cepacia immobilized on eucalyptus leaves used to simultaneously remove malachite green (MG) and Cr(VI)

A multifunctional biomaterial capable of simultaneously removing malachite green (MG) and Cr(VI) was prepared by immobilizing Burkholderia cepacia (B. cepacia) on eucalyptus leaves (EL). The maximum uptake of MG (60 mg/L) and Cr(VI) (20 mg/L) were 94.8% and 71.9% respectively, which was more efficient than when using EL or free cells alone. SEM-EDS demonstrated that B. cepacia was attached to EL and that Cr(VI) was biosorbed into the immobilized cells. FTIR showed that the degradation by functional groups of immobilized cells was in keeping with the products, detected by GC-MS, which suggested that MG could be degraded to 4-dimethylamino benzophenone and 4-dimethylamino phenol. The removal of both MG and Cr(VI) by EL immobilized cells fit the pseudo-second order adsorption kinetic model well (with both R2>0.983). The equilibrium adsorption capacity of MG was 9.59, 18.67 and 28.64 mg/g for initial MG concentrations of from 30, 60, 90 mg/L, respectively when the concentration of Cr(VI) was held constant at 20 mg/L. The adsorption capacity of Cr(VI) increased from 3.49, 7.68 to 9.79 mg/g as the initial Cr(VI) concentrations increased (10, 20, 30 mg/L) while the MG concentration was kept constant at 60 mg/L. The results showed that eucalyptus leaves as a low cost and eco-friendly material have some potential to be an effective immobilization for environmental applications.

Mechanism for removing 2,4-dichlorophenol via adsorption and Fenton-like oxidation using iron-based nanoparticles

In this paper, iron-based nanoparticles (Fe NPs) synthesized by Euphorbia cochinchensis leaf extract were used to remove 2,4-dichlorophenol (2,4-DCP). The possible mechanism for removing the adsorption and heterogeneous Fenton-like oxidation of 2,4-DCP was investigated. Various parameters affecting removal efficiency were tested, and the results showed that more than 83.5% of 2,4-DCP was removed with the addition of 10 mM H2O2 and the initial concentration of 2,4-DCP of 30 mg/L at pH 6.26 under 303 K. To understand the suggested removal mechanism, SEM and FTIR were used to characterize the surface change of Fe NPs before and after the adsorption and oxidation. This process confirmed that the removal of 2,4-DCP by Fe NPs was based on pre-adsorption and Fenton-like oxidation. Furthermore, GC-MS served to identify the intermediate and final products of 2,4-DCP to understand the possible pathway. Finally, Fe NPs were used in the treatment of wastewater and the removal efficiency of 2,4-DCP reached as high as 67.5%. Subsequently, a potentially efficient option for in situ organic pollutants remediation was demonstrated.

Identification of Fe-polycarboxylic complexes by electrospray ionization mass spectrometry and reduction of interferences by ion chromatography/inductively coupled plasma mass spectrometry with an octopole reaction system

Stable complexes are required during the ion chromatographic (IC) separation of Fe-polycarboxylic acid complexes. Electrospray ionization mass spectrometry (ESI-MS) was used to identify 1:1 stoichiometric complexes of Fe[HEDTA], Fe[EDTA](1-) and Fe[DTPA](2-), and the spectra showed that these Fe complexes were stable in solution. Furthermore, inductively coupled plasma mass spectrometry (ICP-MS) using an octopole reaction system (ORS) reduced polyatomic ion (40)Ar(16)O(+) interference in the detection of (56)Fe via the addition of either H(2) or He to the ORS, with He at a flow rate 3.5 mL min(-1) being the optimum collision gas. Finally, IC/ICP-MS was used for the separation and detection of Fe complexes with an eluent containing 30 mM (NH(4))(2)HPO(4) at pH 8.0, but only Fe[HEDTA], Fe[EDTA](1-) and Fe[DTPA](2-) were observed within 10 min with reasonable resolution. Detection limits in the range of 10-13 µg L(-1) were achieved using He as the collision gas. The proposed method was used for the determination of Fe species in soil solutions.