Phytoextraction Potential of Sunn Hemp, Sunflower, and Marigold for Carbaryl Contamination: Hydroponic Experiment.

The phytoextraction ability and responses of sunn hemp, sunflower, and marigold plants were investigated toward carbaryl insecticide at 10 mg L-1 and its degradative product (1-naphthol). All test plants exhibited significant carbaryl removal capability (65-93%) with different mechanisms. Marigold had the highest translocation factor, with carbaryl taken up, translocated and accumulated in the shoots, where it was biotransformed into 1-naphthol. Consequently, marigold had the least observable toxicity symptoms caused by carbaryl and the highest bioconcentration factor (1848), indicating its hyperaccumulating capability. Sunflower responded to carbaryl exposure differently, with the highest carbaryl accumulation (8.7 mg kg-1) in roots within 4 days of cultivation, leading to a partial toxicity effect. Sunn hemp exhibited severe toxicity, having the highest carbaryl accumulation (91.7 mg kg-1) that was biotransformed to 1-naphthol in the sunn hemp shoots. In addition, the different models were discussed on plant hormone formation in response to carbaryl exposure.

Recycling rice husk for removal of phosphate and nitrate from synthetic and swine wastewater: Adsorption study and nutrient analysis of modified rice husk.

The objective of this study was to determine the adsorbent potential of rice husk and its modified form for phosphate and nitrate removal from synthetic and swine-farm wastewater. The mechanism of adsorption as well as the potential of phosphate-/nitrate- adsorbed rice husk as nutrient rich residue was also investigated. Two-step modification of RH (using base-washing (BW) and chemical modification (CM) was conducted to compare the phosphate and nitrate removal. The effects of several factors (pH, sorbent dosage, contact time, initial concentration, and coexistence of both ions) were investigated to gain insight into the adsorption rate, behavior, and mechanism of the modified RH regarding phosphate and nitrate removal. The results of Fourier-transform infrared spectroscopy showed that the modification was successful by crosslinking with the amine group of the chemical agent. Fitting the adsorption kinetic data of phosphate showed physical adsorption, intraparticle diffusion, and chemisorption, whereas for nitrate, the data indicated mainly chemisorption. Fitting the adsorption isotherm data of phosphate and nitrate together showed adsorption on a monolayer coating of anions on the homogeneous sorbent's surface. The maximum phosphate and nitrate adsorption capacities were 6.94 and 2.46 mg/g, respectively, for a single adsorbate and 11.14 and 1.76 mg/g, respectively, for the binary solution. In real swine wastewater, removal efficiencies of phosphate, nitrite, nitrate, sulfate, and ammonia were 83.8%, 65.0%, >45.0%, 36.6%, and 2.6%, respectively, indicating that the modified RH would be effective for phosphate and nitrate removal from real wastewater. Finally, nutrient analysis of the phosphate- and nitrate-sorbed RH showed increases in nitrogen and phosphorus, which would be beneficial for further use of the RH as nutrient or fertilizer after adsorption.

Performance of packed bed column using Chara aculeolata biomass for removal of Pb and Cd ions from wastewater.

Biosorption of Pb and Cd from aqueous solution by biomass of Chara aculeolata was studied in a continuous packed bed column. C. aculeolata in the fixed bed column is capable of decreasing Pb and Cd concentrations from 10 mg/L to a value below the detection limit of 0.02 mg/L. Selective uptake of Pb and Cd in a binary solution resulted in Pb having much higher relative affinity than Cd. The experiments were conducted to study the effects of column design parameters, bed depth, and flow rate on the metal biosorption. Pb uptake capacity of C. aculeolata increased with increased bed depth and decreased flow rate, while Cd uptake capacity increased with increased bed depth but remained constant at any flow rate. The Thomas model was found in a suitable fitness with the experiment data for Pb and Cd (R2 > 0.90). The efficiency of biosorbent regeneration achieved by 0.1 M HCl was very high, that was, 98% for Pb and 100% for Cd in the third reused cycle. It can be concluded that C. aculeolata is a good biosorbent for treating wastewater having low concentrations of Pb and Cd contamination.

Exceptional hexose-fermenting ability of the xylitol-producing yeast Candida guilliermondii FTI 20037.

The yeast Candida guilliermondii FTI 20037 is well-known for its ability to produce xylitol from xylose. Recently, this strain was found to produce greater than 5% (w/v) ethanol from glucose. This level of ethanol is typically not exceeded by wild-type strains of other native pentose-fermenting yeasts. This prompted the current study to examine the ability of C. guilliermondii FTI 20037 to utilize and ferment high concentrations of each of the hexoses commonly found in lignocellulosic hydrolysates. In defined media, FTI 20037 fermented 14.4%-25.9% (w/v) of glucose, mannose or galactose individually to ethanol in concentrations ranging from 6% to 9.3% (w/v). Fermentation was completed within 36 h (for glucose) to 100 h (for galactose). In 25.9% (w/v) glucose, FTI 20037 produced 9.3% (w/v) ethanol within 40 h. FTI 20037 produced xylitol exclusively when xylose was given as the sole carbon source. The strain utilized arabinose poorly. Under the same fermentation conditions, an industrial Saccharomyces cerevisiae strain produced slightly higher levels of ethanol [9.9% (w/v)] from 25.0% (w/v) glucose. Another pentose-fermenting yeast Pachysolen tannophilus also fermented high concentrations of glucose and mannose to produce relatively high peak ethanol concentrations; however, this yeast required considerably longer to completely consume these hexoses. The ability of FTI 20037 to produce high level of ethanol rapidly from glucose is remarkable. To our knowledge, this is the first known instance of a non-modified native xylose-fermenting yeast strain able to produce such high levels of ethanol from glucose as rapidly as S. cerevisiae in a defined medium.

Bioaccumulation and biosorption of Cd(2+) and Zn(2+) by bacteria isolated from a zinc mine in Thailand.

The three bacteria, Tsukamurella paurometabola A155, Pseudomonas aeruginosa B237, and Cupriavidus taiwanensis E324, were isolated from soils collected from a zinc mine in Tak Province, Thailand. Among these bacteria, P. aeruginosa B237 and C. taiwanensis E324 were tolerant of both cadmium and zinc, while T. paurometabola A155 was highly tolerant of zinc only. Bioaccumulation experiment revealed that Cd(2+) and Zn(2+) were mainly adsorbed on the cell walls of these bacteria rather than accumulated inside the cells. During Cd(2+) and Zn(2+) biosorption, P. aeruginosa B237 and T. paurometabola A155 showed the highest removal efficiencies for Cd(2+) and Zn(2+), respectively. The maximum biosorption capacities of P. aeruginosa B237 and T. paurometabola A155 biomasses for Cd(2+) and Zn(2+) biosorptions were 16.89 and 16.75 mg g(-1), respectively, under optimal conditions. The experimental data of Cd(2+) and Zn(2+) biosorptions fitted well with Langmuir isotherm model, suggesting that Cd(2+) and Zn(2+) adsorptions occurred in a monolayer pattern on a homogeneous surface. Furthermore, the pseudo-second order and pseudo-first order kinetic models best described the biosorption kinetics of Cd(2+) and Zn(2+) adsorptions, respectively, suggesting that the Cd(2+) and Zn(2+) adsorptions took place mainly by chemisorption (Cd(2+)) and physisorption (Zn(2+)).

Phytoremediation potential of charophytes: bioaccumulation and toxicity studies of cadmium, lead and zinc.

The ability for usage of common freshwater charophytes, Chara aculeolata and Nitella opaca in removal of cadmium (Cd), lead (Pb) and zinc (Zn) from wastewater was examined. C. aculeolata and N. opaca were exposed to various concentrations of Cd (0.25 and 0.5 mg/L), Pb (5 and 10 mg/L) and Zn (5 and 10 mg/L) solutions under hydroponic conditions for 6 days. C. aculeolata was more tolerant of Cd and Pb than N. opaca. The relative growth rate of N. opaca was drastically reduced at high concentrations of Cd and Pb although both were tolerant of Zn. Both macroalgae showed a reduction in chloroplast, chlorophyll and carotenoid content after Cd and Pb exposure, while Zn exposure had little effects. The bioaccumulation of both Cd and Pb was higher in N. opaca (1544.3 microg/g at 0.5 mg/L Cd, 21657.0 microg/g at 10 mg/L Pb) whereas higher Zn accumulation was observed in C. aculeolata (6703.5 microg/g at 10 mg/L Zn). In addition, high bioconcentration factor values (> 1000) for Cd and Pb were observed in both species. C. aculeolata showed higher percentage of Cd and Pb removal (> 95%) than N. opaca and seemed to be a better choice for Cd and Pb removal from wastewater due to its tolerance to these metals.