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Classic methods of biosurfactant separation are difficult and require large amounts of organic solvents, thus generate high amounts of waste. This work presents and discusses in detail an original procedure to separate rhamnolipid from fermentation broth using high performance membrane techniques. Due to the unique properties of surface active agents, such as capability of forming aggregates above the critical micelle concentration, it is possible to easily purify the biosurfactant with high efficacy using inexpensive and commonly used membranes. In this article, two-stage ultrafiltration is proposed as a method for separating and purifying rhamnolipid from the culture medium. The obtained purified rhamnolipid solution was capable of reducing surface tension of water down to 28.6 mN/m at critical micelle concentration of 40 mg/l. Separation of rhamnolipid was confirmed by HPLC; three types of rhamnolipids were identified (RL1, RL2, RL4), with considerable predominance of RL2.

BSTRACT: Batch sorption experiments were carried out for the removal of cationic dyes (méthylène blue and malachite green) from their aqueous solutions using sorbent made from fly ash-a waste material. Effects of various experimental parameters: initial dye concentration, contact time, pH, adsorbent dosage, solution temperature, surfactant addition and ionic strength on the fly ash sorption of dyes were evaluated. The isothermal data for sorption followed the Langmuir model. The maximum sorption capacity obtained for méthylène blue and malachite green was 36.05 mg/g and 40.65 mg/g, respectively. Kinetic studies indicate that sorption on fly ash follows the pseudo-second order kinetics. Present research suggests that fly ash couid be an appropriate adsorbent for the removal of basic dyes from aqueous solutions. Water Environ. Res., 84, 162 (2012).

This report demonstrates the application of the membrane contactor for carbon dioxide removal. The investigations were performed with the use of a single polypropylene capillary membrane. Two primary amines (monoethanolamine MEA, diglycolamine DGA), one secondary amine (diethanolamine DEA), one tertiary amine (methyldiethanolamine MDEA) were used to prepare absorbate solutions. Batch experiments were conducted for the counter-current flow with liquid on the tube side of the module. The system was investigated for aqueous solutions of amines and for the solutions with piperazine addition. The absorption kinetics with the use of primary amines appeared to be much faster than those of secondary and tertiary amines. The amine efficiency can be stated as follows: MEA>DGA>DEA>MDEA. Further investigations have shown/show that the presence of an activator improves the reaction and process kinetics and brings the DEA and MDEA efficiency to the level of primary amines. The influence of different types of amine solutions used as liquid absorbents on the stability of the membrane shows that these solutions do not wet PP (polypropylene) membranes even after 150 days' immersion in different absorbents.

The knowledge about membrane contactors is growing rapidly but is still insufficient for a reliable designing. This paper presents a new type of membrane contactors that are integrated with one of the following ways of separation by using absorbents, micelles, flocculants, functionalized polymers, molecular imprints, or other methods that are based on aggregation. The article discusses methods for designing multi-stage cascade, usually counter-current. At every stage of this cascade, relevant aggregates are retained by the membrane, while the permeate passes freely through membrane. The process takes place in the membrane boundary layer with a local cross-flow of the permeate and the retentate. So the whole system can be called a cross-counter-current. The process kinetics, k, must be coordinated with the permeate flux, J, and the rate of surface renewal of the sorbent on the membrane surface, s. This can be done by using ordinary back-flushing or relevant hydrodynamic method of sweeping, such as: turbulences, shear stresses or lifting forces. A surface renewal model has been applied to adjust the optimal process conditions to sorbent kinetics. The experimental results confirmed the correctness of the model and its suitability for design of the new type of contactors.