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Chromium(VI) was removed from aqueous solution using sulfuric- and phosphoric-acid-activated Strychnine tree fruit shells (SSTFS and PSTFS) as biosorbents. Effects of various parameters such as adsorbent dose (0.02–0.1 g/L), temperature (303–333 K), agitation speed, solution pH (2–9), contact time, and initial Cr(VI) concentration (50–250 mg/L) were studied for a batch adsorption system. The optimum pH range for Cr(VI) adsorption was determined as 2. Equilibrium adsorption data were analyzed with isotherm models and the Langmuir and Freundlich models got best fitted values for SSTFS (R2 value – 0.994) and PSTFS (R2 value – 0.996), respectively. The maximum adsorption capacities of SSTFS and PSTFS were 100 and 142.85 mg/g, respectively. The biosorption process was well explained by pseudo-second-order kinetic model with higher R2 value (SSTFS – 0.996, PSTFS – 0.990) for both biosorbents. Characterization of biosorbents was done using Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analysis, energy-dispersive X-ray analysis, and thermogravimetric analysis. Thermodynamic studies revealed the spontaneous, endothermic, and randomness in nature of the Cr(VI) adsorption process. Different concentrations of NaOH solutions were used to perform the desorption studies. The results demonstrated that both SSTFS and PSTFS can be used as an effective and low-cost biosorbent for removal of Cr(VI) from aqueous solutions. [ABSTRACT FROM AUTHOR]

Interest in employing metal oxide nanoparticles as antimicrobial agents is growing. Among various nanoparticles, CuO nanoparticles (NP) has gained vast attention among researchers due to their unusual properties. Various studies has been reported on the antimicrobial activity of CuO NP on microbes. But, no studies can be found on designing suitable reactor for this system. In this study, conventional batch, continuous tubular reactor (CTR), and advanced microfluidic (MF) reactor systems were employed to carry out antimicrobial activity of CuO NP on E Coli..From the experimental results, we observe that minimum cell viability obtained in the batch reactor was about 48.6 %. CTR provided better contact between CuO NPs and E-Coli cells, hence cell viability of 45.3 % was obtained which is lesser than that of batch system. While, in the microfluidic system, when the contact between CuO NPs and E-Coli cells were increased by scaling down the diameter of the channels from 1,200 μm to 600 μm the efficiency of the cell lysis by CuO NP increased from 68.77 % to 95 %. This drastic improvement in cell lysis rates from batch to microchannel is attributed to high surface area to volume ratio and active internal circulation in microfluidic flows. Hence, microfluidic system, which operates at negligible gravity was found to be more efficient in carrying out microbial cell lysis using CuO NP nanoparticles. [ABSTRACT FROM AUTHOR]

Optimization experiments were carried using three-level Box–Behnken design for the adsorption of chromium onto immobilized macroalgae. The influence of independent parameters such as pH (2−8), temperature (303−333 K), and initial chromium concentration (20−100 mg/L) towards chromium ions removal has been performed. Second-order polynomial models were developed for the responses. The significance of the independent parameters and their interactions were investigated using the analysis of variance. The three-dimensional (3-D) response surface plots were used to study the interactive effects of the independent parameters on the chromium removal efficiency. The maximum Cr(VI) removal efficiency of 90.52, 90.86 was observed forEnteromorphasp. immobilized in sodium alginate (ESA),Enteromorphasp. immobilized in polysulfone (EPS), and maximum observed total chromium removal efficiency of 81.14, 79.90 was obtained for ESA, EPS, respectively. The observed value was in good agreement with the predicted values. These results indicated that immobilized macroalgae could be used for the removal of chromium from aqueous solution. [ABSTRACT FROM AUTHOR]

In the present study, the removal of Cr(VI) from aqueous solution by aStrychnos nux-vomicashell was examined in a batch study. The main process parameters such as adsorbent dose, pH, initial concentration, temperature, agitation speed and contact time were studied. The result shows that the maximum removal of Cr(VI) was observed at pH 2. The progressive changes on surface texture and the confirmation of chromium binding on adsorbent surface at different stages were obtained by the scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectrometer analysis. The equilibrium data from the biosorption study was evaluated by the use of two parameter isotherm models. Langmuir isotherm model seems to fit better with the equilibrium data. Kinetic studies were performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The biosorption data were found to best fitted for pseudo-second-order kinetic model. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the adsorption of Cr(VI) ions onto adsorbents was spontaneous, endothermic and increased randomness in nature. The results indicate that STFS can be an effective adsorbent for the removal of Cr(VI) from aqueous solutions. [ABSTRACT FROM PUBLISHER]

In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudosecond- order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: A mutant Aspergillus carbonarius produces partially saturated canthaxanthin (PSC; C40H62O2) during submerged fermentation. The pigment was extracted from dried biomass using various organic solvents and purified using nanofiltration (NF) and nonporous membranes. Particle size had a great influence; PSC extractability from fines fraction of biomass (75–105μm) was 1.5-fold higher compared to the coarse fraction (850–920μm) in ethanol. Among the four solvents, hexane exhibited the highest PSC extractability of 5.83mg/g and purity of 32mg/g. On a relative scale, the extraction performance of hexane, acetone, methanol and ethanol were in the order 100, 16.1, 7.5 and 5.4. An assessment based on enrichment factor and permeate flux revealed notable performance with NF-250 membrane in ethanol extract followed by NF-200 and NF-GKSS membranes in methanol extract. These results suggested the suitability of hexane for extraction followed by alcohol phase purification and concentration employing NF. Accordingly, a PSC purity of 206mg/g was achieved. [Copyright &y& Elsevier]