**9.3 Waste treatment**

562 Mass Transfer - Advanced Aspects

appropriate by hydrolases (Giebauf et al., 1999). In continuous reaction of acidolysis of triolein with stearic acid, the constants of the reaction and mass transfer such as rate constant, solubility, effective diffusivity, mixing diffusivity and mass transfer coefficient

Immobilized *Candida antarctica* lipase B was successfully used as catalyst to synthesize butyl butyrate from butyl vinyl ester and 1-butanol in SC-CO2) with excellent results. A clear enhancement in the synthetic activity and selectivity was observed with the decrease in fluid density for both liquids and SC-CO2 media (Lozano et al., 2004). Also a commercial solution of free *Candida antarctica* lipase B (Novozyme 525L) was immobilized by adsorption onto 12 different silica supports modified with specific side chains (e.g. alkyl, amino, carboxylic, nitrile, etc.). The best results were obtained for the supports modified with non-functionalized alkyl chains and when the in water activity increased from 0.33 to 0.90. Immobilized derivatives coated with ionic liquids clearly improved their synthetic activity in SC-CO2 by up to six times with respect to the hexane medium (Lozano et al.,

*Pseudomonas cepacea* lipase (PCL) was used to catalyze the trans-esterification reaction between 1-phenylethanol and vinyl acetate in SC-CO2. The catalytic efficiency of enzyme enhances by increasing pressure. Moreover SC sulphur hexafluoride (SCSF6) was used as reaction medium. Results showed high stability of the enzyme in this SC medium in

Thermal stability of proteinase of *Carica papaya* was tested at atmospheric pressure, SC-CO2, nearcritical propane and dimethyl-ether. In SC-CO2 at 300 bar thermal activation of the enzyme was improved in the comparison to ambient pressure. Activity of the enzyme decreased in propane and dimethyl-ether (300 bar). Addition of water in the system

Isoamyl acetate was synthesized from isoamyl alcohol in SC-CO2 by enzymatic catalysis. Among several reactants, including acetic acid and two different acetates, acetic anhydride gave best yields. An esterification extent of 100% was obtained in continuous operation using acetic anhydride (acyl donor) and Novozyme 435 (enzyme) (Romero et al. 2005). Cocoa beans had been subjected to various pod storage periods prior to fermentation were

The use of SCFs media for polymer modification has been demonstrated (Yalpani 1993). Treatment of chitosan mixtures with glucose or malto-oligosaccharides in SC-CO2 afforded the corresponding water soluble imine-linked, branched chitosan derivatives with high degrees of conversion. Treatment of starch, maltodextrins, cellulose acetate, poly(vinyl alcohol) and paper in SC-CO2 and O2 (19:1 v/v) led to the corresponding

Bioconversion of lignocellulosics consists of substrate pretreatment by high pressure steam (for fractionation into cellulose, hemicellulose and lignin components), enzymatic hydrolyze, followed by fermentation of the liberated sugars to ethanol. The various technoeconomic models developed by network members were used to identify probable

increased activity, which was incubated in SC-CO2 for 24 h (Habulin et al. 2005).

depend on temperature, pressure and flow velocity (Nakamura, 1990).

comparison to those achieved in SC-CO2 (Celia et al. 2005).

analysed for pyrazines and SCE (Sanagi et al. 1997).

**9.1 SCFs: puissant media for the modification of biopolymers** 

process schemes and determine technical "bottlenecks" (Saddler 1992).

2007).

oxidized materials.

**9.2 Gasification of straw** 

Waste treatment is one of the most important and urgent problems in environmental management around the world. SC-water oxidation has attracted attention for the treatment of industrial waste, especially toxic and refractory waste. In a study, SC-water oxidation with H2O2 was applied as the oxidant to the treatment of a model municipal solid waste containing proteins, fats, vitamins, fiber, and inorganic minerals. The effects of temperature, oxidant concentration, and reaction time on the decomposition of solid waste were investigated in a batch reactor with hydrogen peroxide over the temperature range of 673-823 K. (Mizuno et al. 2000). SC-water is very reactive, corrosive, and miscible with air and oxygen. An industrial process was describes the use of SC water to treat aqueous solutions containing organic compounds (Haas et al. 1989). The operation of a process based on SCF technology was described to treat waste of recombinant fermentation (Krishna et al.1986).
