Efficiency of membrane-sorption integrated processes

The paper presents the characteristics of membrane-sorption integrated process, which comprise sorption of the solute with membrane separation of the sorbent. The main advantage of this separation method is the high efficiency and lower costs of the process comparing with classical sorption in fixed beds. The variety of sorbents and binding materials in form of very fine particles may be applied in this system. This increases the specific surface of the sorbent and consequently rise the uptake of the sorbate and enhances kinetics. Moreover, the high intensity of the process may be achieved due to synergetic effects of sorbent concentrating at membrane vicinity. The best results may be accomplished when flux is maintained below critical value and when the permeate flux is fully synchronized with the sorption kinetics and rate of sorbent renewal on membrane surface. Sorbent's residence time at membrane surface may be controlled by various means such as backflushing, cross-flow, reverse flow, pulsations, gas sparking, etc. The experimental results on membrane biosorption of heavy metals fully support this idea. The mathematical model enables to attain the optimum process conditions. A new factor, i.e. biosorption efficiency has been introduced as a criterion to evaluate the process performance, which comprised yield and selectivity of separation simultaneously. (C) 2004 Elsevier B.V. All rights reserved.