Supercritical water gasification of microalgae: The impact of the algal growth water

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Investigation into the supercritical water gasification (SCWG) of microalgae has largely used deionized water as the reaction medium. However, real systems would use the algal growth water directly, containing ions that have been known to catalyse SCWG (K+, Na+, OH-, Fe3+, Cl-). Investigation into the effect of the growth water on SCWG was carried out for a range of temperatures (450–550), biomass concentrations (1–3wt%) and catalysts (KOH, Ru/C), using glucose or Chlorella vulgaris as the feedstock was performed. A significant increase in CO2 and reduction in CO content in the gas was observed without a catalyst and with a Ru/C catalyst. An increase in char/tar was also observed without a catalyst. As a result, the impact of the growth water should be considered for the SCWG of microalgae, in laboratory experiments and the selection of algal growth media in industrial applications.Engineering and Physical Sciences Research Council (EPSRC

Enhancement of lipase activity in non-aqueous media upon immobilization on multi-walled carbon nanotubes

<p>Abstract</p> <p>Background</p> <p>Immobilization of biologically active proteins on nanosized surfaces is a key process in bionanofabrication. Carbon nanotubes with their high surface areas, as well as useful electronic, thermal and mechanical properties, constitute important building blocks in the fabrication of novel functional materials.</p> <p>Results</p> <p>Lipases from <it>Candida rugosa </it>(CRL) were found to be adsorbed on the multiwalled carbon nanotubes with very high retention of their biological activity (97%). The immobilized biocatalyst showed 2.2- and 14-fold increases in the initial rates of transesterification activity in nearly anhydrous hexane and water immiscible ionic liquid [Bmim] [PF6] respectively, as compared to the lyophilized powdered enzyme. It is presumed that the interaction with the hydrophobic surface of the nanotubes resulted in conformational changes leading to the 'open lid' structure of CRL. The immobilized enzyme was found to give 64% conversion over 24 h (as opposed to 14% with free enzyme) in the formation of butylbutyrate in nearly anhydrous hexane. Similarly, with ionic liquid [Bmim] [PF6], the immobilized enzyme allowed 71% conversion as compared to 16% with the free enzyme. The immobilized lipase also showed high enantioselectivity as determined by kinetic resolution of (±) 1-phenylethanol in [Bmim] [PF6]. While free CRL gave only 5% conversion after 36 h, the immobilized enzyme resulted in 37% conversion with > 99% enantiomeric excess. TEM studies on the immobilized biocatalyst showed that the enzyme is attached to the multiwalled nanotubes.</p> <p>Conclusion</p> <p>Successful immobilization of enzymes on nanosized carriers could pave the way for reduced reactor volumes required for biotransformations, as well as having a use in the construction of miniaturized biosensensor devices.</p

Prediction of Bisolute Adsorption Isotherms using Single Component Data for Dye Adsorption onto Carbon

Equilibrium isotherms have been determined for the adsorption of dyes in solution onto activated carbon. Single-component isotherms were measured for three basic dyes and then the three possible bisolute isotherms from the dyes were determined. Methods of predicting multicomponent dye isotherms were developed and applied using the single-component dye adsorption data to predict the bisolute equilibrium data. A comparison was made between predicted and experimental results. A simplified proximate method and a more rigorous method incorporating a Langmuir isotherm approach failed to give accurate predictions. However, the same rigorous method using a modified Freundlich isotherm proved successful in predicting bisolute isotherm data for a number of two-component dye mixtures adsorbing onto activated carbon. © 1988

Branched Pore Model Applied to the Adsorption of Basic Dyes on Carbon

The branched-pore adsorption model, expressed by an external mass transfer coefficient kf, a solid diffusivity Ds, a lumped micropore diffusion rate parameter kb, and the fraction of macropores f, describes kinetic data from initial contact of adsorbent-adsorbate to the long-term ( > 24 hours) adsorption stages with reasonable accuracy. In this work the model is applied for three basic dye systems, namely Basic Red 22, Basic Yellow 21 and Basic Blue 69, all on carbon. A single value of each parameter describes each dye system. The kf values are 0.18 × 10-2±28%, 0.3 × 10-2±17% and 0.2 × 10-2 ± 20% cm s-1, the Ds values are 0.33 × 10-9 21%, 0.72 × 10-9 ± 9% and 0.72 × 10-9 ± 9% cm2 s-1, the kb values are 0.65 × 10-6 ± 7.7%, 1.8 × 10-6 0.2 × 10-6 1% s-1, while the f values are 0.55 ± 9%, 0.60 ± 10 % and 0.18 ± 11%, each for Basic Red 22, Basic Yellow 21 and Basic Blue 69 respectively. The model is based on the internal structure of the carbon particle being divided into a macropore and a micropore region. The latter has an upper-bound capacity of 241, 245 and 656 mg g-1 for Basic Red 22, Basic Yellow 21 and Basic Blue 69 respectively. A sensitivity analysis for each parameter has been carried out. © 1988

Prediction of Multicomponent Adsorption Equilibrium Data using Empirical Correlations

In this study, extended empirical Langmuir, Freundlich and Redlich-Peterson formulate have been applied for the calculation of multicomponent adsorption equilibrium data for all combinations of three basic dye systems: Basic Blue 69 (B), Basic Red 22 (R) and Basic Yellow 21 (Y) on Activated Carbon (F400). Extended Langmuir application yielded average variances (σ2) of 3.3%, 589%, 51% and 47% for RY, RB, YB and RYB system components respectively. The Redlich-Peterson relationship gave σ2 of 8%, 62%, 50% and 44% respectively. Introducing an interaction term (η) lowered σ2 to 0.5%, 23%, 16% and 11% for RY, RB, YB and RYB system components respectively for the Langmuir formula and to 0.4%, 21.3%, 15% and 11% respectively for the Redlich-Peterson equation. The Freundlich empirical extended formula for bisolute systems produced variances of 0.69%, 9.1% and 8.8% for RY, RB and YB system components respectively. The latter formula is the most accurate for bisolute systems as it is obtained by single and multisolute correlation of all constants in the formula. © 1989